CHAPTER 4 ~ GLOBAL SOIL EROSION (Continued) ~
Edition 9 of March 2010 (Updated Sept. 2011)

The top portion of Chapter 4 (Sections (4-A) through (4-F)) is in another file (se4.html) 

(4-A) ~ Specific Cropland Soil Erosion Data ~ [A1]~General, [A2]~Table of Specific Erosion Data by Continent, [A3]~Table of Specific Erosion Data for Various Land-Uses, [A4]~Canada, [A5]~China, [A6]~US, ~
(4-B) ~ Gross Soil-Loss and Soil-Organic-Matter Loss Data ~ [B1]~Gross Erosion Data, [B2]~Africa, [B3]~Anthropogenic Effects, [B4]~Canada, [B5]~US, ~

(4-C) ~ Shifting Agriculture ~
[C1]~Table of Cycle Times, [C2]~Carrying Capacity under Shifting Cultivation, [C3]~Tropical Cropland Lifetimes, ~
(4-D) ~ Wind Erosion Data ~
[D1]~Africa, [D2]~Australia, [D3]~Asian Sub-Continent, [D4]~Central Asia, [D5]~US, [D6]~Far East, [D7]~Mid-East, ~
(4-E) ~ Cropland Loss to Urbanization, Chemical Contamination and Erosion ~
(4-F) ~ Cropland Loss to Salinization and Water-Logging ~
[F1]~Global, [F2]~North America, [F3]~Latin America, [F4]~Middle East, ~
~ Table of Contents of Second Half of Chapter 4:

(4-G) ~ Sediment Delivery ~
~ (4-G-a) ~
Sediment Chemistry ~
~ (4-G-b) ~
The Upper End of Sediment Delivery ~ [Gb1]~Fraction of Erosion not entering a Waterway, [Gb2]~The Dependence of Sediment Delivery Ratio on Sediment Load, [Gb3]~Extremes in the Time-Variation of Sediment Delivery, [Gb4]~Dependence of Sediment Delivery on Drainage Basin Size, [Gb5]~Dependence of Sediment Load on Runoff, [Gb6]~Asian Sub-Continent, [Gb7]~Far East, [Gb8]~US, ~
~ (4-G-c) ~
Sediment Trapping in Reservoirs ~ [Gc1]~General, [Gc2]~Rates (%/year) of Depletion of Reservoir Capacity due to Siltation (table), [Gc3]~Capacities of Major Reservoirs (table), [Gc4]~Reservoir areas of hydroelectric dams (table), [Gc5]~Africa (North), [Gc6]~Southeast Asia, [Gc7]~Canada, [Gc8]~China, [Gc9]~Latin America, [Gc10]~Asian Sub-Continent, [Gc11]~US, [Gc12]~Sub-Saharan Africa, ~
~ (4-G-d) ~
Bed Load Contributions to Sediment Delivery ~
~ (4-G-e) ~
Sediment Transport to Oceans ~ [Ge1]~General, [Ge2]~Suspended Sediment Yields of Selected Rivers (table), [Ge3]~Data for Major Rivers of the World (table), [Ge4]~Major Sediment-Yielding Rivers of the World (table), [Ge5]~Average Sediment Discharge to Oceans (table), [Ge6]~Suspended Sediment Discharge from Continents (table), [Ge7]~Sediment Yields of Rivers to Oceans (table),
[Ge8]~
Estimates of Suspended Sediment Reaching the Oceans (table), [Ge9]~Yellow River, [Ge10]~Peruvian Rivers, [Ge11]~Great Lakes, [Ge12]~Southeastern US, [Ge13]~Sediment Deposited at River Mouths,
~ (4-G-f) ~
Dissolved-Solids Transport to Oceans ~

(4-H) ~ Grazing Land Erosion ~
(4-I) ~
Deforestation-caused Erosion ~ [I1]~General, [I2]~Europe, [I3]~US, [I4]~Southeast Asia, [I5]~Africa, [I6]~Asian Sub-Continent, [I7]~USSR,

NOTE 1: The notation (su1) means that the data is used in the document analyzing the sustainability of the productivity of the world's food, fiber and water supply systems. (See elsewhere in this website.)
NOTE 2: See one of the FAO's AQUASTAT databases described in Chapter 11, Section F of this soils- and croplands degradation review for a huge compilation of data on sediment delivery issues for the world's rivers.

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SECTION (4-G) ~ Sediment Delivery ~
This topic concerns what happens to erosion products (sediments) after they leave their point of origin. Some ends up lower down the slope, on flood plains, on river bottoms, on the bottoms of reservoirs, and on the bottom of oceans. Some dissolve in the waters of rivers and oceans. The problem of how much erosion sediment goes where is known as the "Sediment Delivery Problem". Much research has been done, but the state of knowledge is inadequate for most purposes.

"At present we are unable to predict within any acceptable limits of accuracy, or within any reasonable degree of certainty, the pathways and sinks of sediment particles in river systems" (90M1).

The sediment-delivery problem is discussed in depth in Ref. (89N1). As outlined in a summary by Walling (83W2), the problems of sediment delivery and long-term storage in river valleys are among the principal challenges for future studies of sediments (90M1).

Total length of river segments altered for shipping (globally): 9000 km in 1900; 498,000 km. in 1980 (Ref. 13 of (96A1)).

Part [Ga] ~ Sediment Delivery ~ Sediment Chemistry ~
Soil removed by either wind- or water erosion is 1.3-5 times richer in organic matter than the soils left behind (Refs. 34 and 70 of (95P1)).

Eroded soil typically contains about 3 times more nutrients per unit weight than the soil left behind (Refs. 63 and 65 of (95P1)).

Organic-matter content of erosion sediments is sometimes found to be 5 times the organic-matter content of soils from which the sediments came (p. 88 of (71R1)). Comments: The reason for this is that water runoff picks up soil surface litter (45% carbon by dry weight) in preference to denser soil particles (typically 3% carbon in temperate soils, 1% carbon in tropical soils). This is important because soil organic matter contributes strongly to soil fertility, tilth, and erosion resistance and soil creation. Other references (83W2) find enrichment factors less that 5, e.g. 1.5-3. As erosion becomes more severe, enrichment ratios tend to drop, as might be expected from the fundamentals. More information is found in my reviews of the Earth's carbon budget and sewage-sludge disposal on land.

Part [Gb] ~ The Upper End of Sediment Delivery ~ [Gb1]~Fraction of Erosion not getting into a Waterway, [Gb2]~The Dependence of Sediment Delivery Ratio on Sediment Load, [Gb3]~Extremes in the Time-Variation of Sediment Delivery, [Gb4]~Dependence of Sediment Delivery on Drainage Basin Size, [Gb5]~Dependence of Sediment Load on Runoff, [Gb6]~Asian Sub-Continent, [Gb7]~Far East, [Gb8]~US, ~

Sediment yields are plotted vs. % croplands in the watershed for 3 rivers in the Atlantic drainage of the US. These plots are consistent with the premise that cropland erosion is about 30 times the erosion rate from non-crop-lands (82M2).

Playfair's Law, one of the basic premises of stream morphology, states that, over a long time, a natural stream must transport essentially all sediment delivered to it (Ref. 7 of (89N1)). Schumm (Ref. 42 of (89N1)) assumes that, in 100 years, a stream will discharge essentially all sediment it receives. Comments: This concept is probably a limiting behavior. Huge increases in sediment loads from anthropogenic effects are likely to require changes in landform before Playfair's law returns to validity, and by that time, topsoil erosion may have caused enough abandonment to change sediment loads. While global soil erosion increased by about 30 times, sediment delivery to oceans increased only 3 times.

Sub-Part [Gb1] ~ Fraction of Total Erosion that doesn't make it into a Waterway ~
A high proportion of eroded soil is redeposited elsewhere in the catchment area, where it tends to boost productivity, but it may also silt up reservoirs and irrigation canals. In the US some 45% is redeposited locally, and some 46% in lakes, reservoirs and other impoundments (
01S1) (03N1). Comments: River bottoms are being neglected here - a major sink for soil sediments. Ocean bottoms are smaller sinks that are neglected.

Scientists at the US Department of Agriculture have estimated that 60% of water-eroded soil ends up in streams (Ref. 2 of (97P3)).

A model developed at Resources for the Future (Peshkin and Gianessi) shows that 40% of the 1.9 billion tons of sheet/rill erosion in 1977 in the US ended up in US waterways (p. 37 of (83C1)). Comments: Remainder presumably winds up on lower slopes and flood plains on land.

China's Yellow River (Huanghe) (5464 km long) carries 48,000 million cubic meters/ year of total runoff. About 1,200 million tonnes/ year of silt carried to mouth of Yellow River. About 400 million tonnes/ year are deposited on a 400-km long river-bed (across North China Plain) (93W3).

About 40% of total soil eroded (about 2 billion tonnes/ year) carried to mouths of rivers in China. The other 60% (3.5 billion tonnes/ year) is deposited along way (93W3).

About 25-40% of US soil moved as sheet/ rill erosion ends up in waterways (83C1). Similar arguments on wind erosion leads to the conclusion that erosion-data losses are greater than the amount of soil "lost to agriculture" (83C1). Comments: Check Sediment-Delivery-vs.-Drainage-Area plots to obtain other estimates of the fraction of total soil erosion that only gets down to lower slopes and not into streams and rivers.

About 60% of soil lost from US croplands is deposited in streams and rivers (Ref. 13 of (95P1)).

Total US sheet/ rill erosion = 4.92 Gt./ year. Total suspended solids in rivers from sheet/rill erosion = 2.72 Gt./ year. The difference, 2.2 Gt./ year (45%), presumably ends up on lower slopes and flood plains (86P2).

Hydrologists estimate than, on average, 25% of soil lost through erosion actually makes it to the ocean as sediment. The other 75% is deposited on foot slopes, in reservoirs, on river flood plains or other low-lying areas or in the river-bed itself (Ref. 15, p. 15 of (84B3)). Comment: Most sediment delivery data suggest delivery ratios are well under 25% for drainage-basin areas larger than 1000 km2.

In the Oka Basin (central European USSR), 60% of erosion sediments are deposited on the lower parts of the slopes (Golubev, 1982, in (83W2)).

A study in the southern Piedmont of the US found that, by the early 1970s, only about 5% of the soil eroded over the previous two centuries had been delivered to the fall line of the rivers in the region (Ref. 3 of (97C1)). A study of the Coon Creek basin in Wisconsin revealed that, during 1853-1975, only 6-7% of the soil eroded from upland areas was exported from the basin to the Mississippi River (Ref.4 of (97C1)). Comments: This data is incompatible with data on sediments delivered to river-bottoms and oceans.

Sub-Part [Gb2] ~ Dependence of Sediment Delivery Ratio on Sediment Load ~
Delivery ratios did not change over a period in which numerous soil conservation measures were instituted, and upland erosion dropped significantly (Ref. 30 of (89N1)).

The discussion in (90M1) of its Fig. 9 (C) (See table below) also gives evidence that sediment delivery ratios are quite independent of sediment loads.

Sub-Part [Gb3] ~ Extremes in the Time-Variation of Sediment Delivery ~
In 5 Atlantic drainages of the eastern US, nearly half of the sediment is discharged in 1% of the time, and 85-90% is discharged in 10% of the time (82M2).

Typically, 1-2 storms generate 80-90% of total sediment load for any given year (89N1).

In most rivers, 40-60% of total sediment load is discharged during 1% of the time, and 85-95% of sediment discharge happens during 10% of the time (90M1).

In Australia, New South Wales, most erosion associated with only a few rain events. In at least 30% of all years, one rain accounted for at least 75% of annual topsoil loss (85E1).

Sub-Part [Gb4] ~ Dependence of Sediment Delivery on Drainage Basin Size ~
Fig.2 of (83M2) plots sediment yield (tonnes/ km2/ year) vs. drainage area (km2) for all major sediment-discharging rivers (over 107 tonnes/ year). 46 points are plotted. A straight-line fit on a log-log plot yields the following results.
Area (km2) - - - - -|1000~ | ~2500|1*104|5*104|1*105|1*106|1*107
Yield (t/ km2/ year)|20,000|10,000|3,500|1000|600 |90 ~ |14
Comments: The world's largest drainage (Amazon) has an area of 6.15 million km2.

Sediment-loss data in major River systems that support the contention that Slopes of sediment-delivery-vs. drainage area curves become more negative as drainage areas increase, and can be less than (-1) (on a log-log plot) (from Table I of (83W2))
River - - - -| ~Station | Area~ ~ |Suspended Sediment
- - - - - - -| ~ ~ ~ ~ ~| (km2 ) ~ |(1000 t/ year)
Nile ~ ~ ~ ~ | Kajnarty |1,850,000| 133,700
(Sudan-Egypt)| Cairo~ ~ |3,000,000| 111,000
Wisla~ ~ ~ ~ | Zawichost| ~ 50,543| ~ 1,990
(Poland) ~ ~ | Plock~ ~ | ~168,857| ~ 1,180
Lech ~ ~ ~ ~ | Fussen ~ | ~ ~1,422| ~ ~ 329
(Fed.Rep.Ger.)| Feldheim| ~ ~2,124| ~ ~ 192
Po ~ ~ ~ ~ ~ | Becca~ ~ | ~ 30,170| ~ 4,375
(Italy)~ ~ ~ | Piacenza | ~ 35,430| ~ 3,791
MeNan~ ~ ~ ~ | Tha Pla~ | ~ 12,790| ~ 4,999
(Thailand)~ |Pitsannloke| ~ 25,491| ~ 3,252
Atrak~ ~ |Shirrin-Darrah| ~ ~1,500| ~ ~ ~93
(Iran) ~ ~ ~ | Reza-Abad| ~ ~5,430| ~ ~ ~31
Nazus~ ~ ~ ~ |El Palmito| ~ 18,321| ~ 2,451
(Mexico) ~ |Canon Fernad| ~ 33,468| ~ 1,813

Comments: Presumably these data predate dams between the two indicated stations.

River Bed Rise/ Shift Data
Ref.|Page | Place
84B3|30,31| Panama Canal and Mississippi River
76E1|31 ~ | Yellow River (China)
74C1|199~ | Yellow River
81H1| ~ ~ | Yellow River
81R1| ~ ~ | Yellow River
76E1|81 ~ | Nepal/India (Kosi River, Terai Rivers)
76E1|97 ~ | Eastern Tanzania
76E1|122~ | Pakistan
76E1|117~ | Tigris-Euphrates River
74C1|39-54| Mesopotamia
74C1|197~ | Indus River
74C1|153~ | Adria (Po River)
74C1|204~ | Mayans
74C1|228~ | Baltimore (US)
74C1|229~ | Mississippi, Colorado
74C1|256~ | an Oklahoma River (photo)

China's Yellow River-bed rises about 10 cm./ year in North China Plain. It is now 6-10 meters above surrounding plain (93W3). Comments: Much of this sediment is loess (wind-blown) soil with inherently low fertility and low organic matter.

Erosion is causing riverbed levels in Terai (Nepal) to rise by 6-12 inches/ year (15-30 cm./ year) (85K2).

The bed of the Bramaputra River rose 5.5 inches in past 5 decades (85J1).

Bed of the Ganges (Ganga) river is rising at a rate of 7-8 cm./ year (85J1).

Complete remobilization of flood plain deposits by lateral movement of the riverbed may require on the order of 1000 years (p. 271 of (90M1)).

Plots of debris yield (yd3/ mi2/ year) vs. drainage area (0.3-10 mi2) suggest that only a small fraction of erosion- and river sediments get to oceans (78S3). Comments: No good plots of sediment delivery vs. drainage area are in (78S3).

Sediment allocation among various sinks in Coon Creek Basin, Wisconsin is in (90M1).

Many plots of delivery ratio vs. drainage-basin area are shown and discussed in (83W2). Fig. 3 of (83W2) plots sediment yield vs. drainage area for about 15 studies (mainly US). This plot suggests a sediment yield at 0.1 km2 of roughly 2000 tonnes/ km2/ year.

Sediment delivery is plotted vs. drainage area (0.1-1000 km2) in (62R1). (Delivery ratio at 1000 km2 = 5% (62R1).)

A Summary of Sediment Delivery Ratio vs. Drainage Area Plots

Reference

Drainage Basin Area (km2)

0.1

1.0

10.

100

103

104

105

106

107

90M1 Fig.9C (1)

1100

950

630

500

250

90

-

-

-

90M1 Fig.9C (2)

-

630

500

400

250

125

63

20

-

90M1 Fig.9C (3)$

-

320

200

150

105

63

16

-

-

90M1 (Fig.16)(4)

-

0.63

0.25

0.11

.063

-

-

-

-

90M1 (Fig.19)(5)

-

-

-

#<0.10

-

-

-

-

-

89N1 (Fig. 1)(6)

0.54

0.35

0.22

0.13

0.06

-

-

-

-

83W2 (Fig. 1)(7)

0.50

0.32

0.20

0.11

0.05

-

-

-

-

83W2 (p.210)(8)

-

-

-

*0.09

-

-

-

-

-

83W2 (ASCE)(9)

1.0

0.76

0.53

0.34

0.20

0.1

.063

.036

.02

# 360 km2 * 125 km2

$ (Upper Mississippi R. basin; 58 data pts. (16 are reservoir sediment surveys)
Deliveries are expressed either in terms of fraction of total erosion or in terms of sediment yield (t/ km2/ year)

  1. 1948 Brune data, for land over 2/3 croplands.
  2. 1948 Brune data, for land 1/3-2/3 croplands.
  3. 1948 Brune data, for land under 1/3 croplands.
  4. Piedmont (in North Carolina, South Carolina, and Georgia), data of Roehl, 1962.
  5. Coon Creek, WI, data of Trimble and Lund, 1982.
  6. From Ref. 41
  7. USDA SCS data deemed applicable to central and eastern US.
  8. Northwest Colorado
  9. 1975 ASCE correlation; slope = -0.125 on log(delivery) vs. log(area) plot. (Numbers are relative to amount of sediment entering waterways, not amount of erosion on land.)

Decreases in sediment yield/acre with drainage area are attributed (76D1) to:

Comments: Other researchers do not consider these as the main reasons. In fact, the above appears to be a misconception. Sediment yields are being compared to calculated erosion rates, e.g. USLE, which take slopes into account.

Sediment yield/ unit-drainage-area is plotted vs. relief-to-length ratio in (90M1). Yields increase by about 10 times for each doubling of relief-to-length ratio (90M1).

Ave. sediment yield/ unit-drainage-area = C * drainage area -0.16 (Fig. 2 of (76D1)).

Sediment production rates are usually lower than erosion rate, and increasingly so the larger the drainage area, because of deposition of some of the eroded material on flood plains and in stream channels (Glymph, 1951, in (53B1)).

Sub-Part [Gb5] ~ Dependence of Sediment Load on Runoff
Fournier's Correlation for Denudation Rate vs Precipitation based on Worldwide Small Catchment Data gives
(Fig. 4 of (67D1))
(p2/P) (") |m3/km2 /year|t/ km2/year*
0.4(1.0 cm)| ~ ~25 ~ ~ | ~ 49
4.0(10. cm)| ~ 500 ~ ~ | ~980
40.(100 cm)| 11000 ~ ~ |21560
* Density of sediment = 1.96 tonnes/ m3 (68H1)
Comments:
Global mean precipitation over land = 86.4 cm./ year (87W1) or 67.3 cm./ year (68H1). Denudation rates in undisturbed forests are much smaller than these data indicate (See table in Section (4-A)), so Fournier's data must pertain to agricultural land. Small catchments usually have steeper slopes than large catchments, but large catchments have more land affected by runoff from land at the outer rim of the catchments.

Suspended sediment load (tonnes/ year) is plotted vs. runoff (km3/ year) and drainage area (km2) in (83M2).

Equations are given for sediment yield/ unit-drainage-area as a function of mean runoff (km3/ year) (76D1).

Sub-Part [Gb6] ~ Asian Sub-Continent ~

[Gb6a] ~ Asian Sub-Continent ~ Ceylon ~
Current silt loads in most streams of Ceylon are so great that it would be impractical to construct irrigation works that could supply water to the semi-arid plain on which the ancient Singhalese civilization was built (It was based on an advanced irrigation system) (p. 203 of (74C1)).

[Gb6b] ~ Upper End of Sediment Delivery ~ Asian Sub-Continent ~ Nepal ~
Beds of many Terai rivers in Nepal are rising at 6-12"/ year (75E1) (76E1). Nepal's rivers carry 0.24 km3 (0.47 Gt.)/ year of soil to India (Nepalese Government estimate) (p. 25 of (78B2)) (p. 35 of (78B1)). Comments: Area of Nepal= 141,000 km2, so sediment yield = 2255 tonnes/ km2/ year.

Sub-Part [Gb7] ~ Upper End of Sediment Delivery ~ Far East ~

[Gb7a] ~ Upper End of Sediment Delivery ~ Far East ~ China ~
Dikes along Yellow River must be raised about 10 cm./ year to offset aggradation of sediments in the river bed (81H1). China's Yellow River (680,000 km2 watershed area) has a river bottom on its aluvial plain that is 3 to 10 meters above the surrounding countryside (81R1). In Hevon Province near the beginning of the aluvial delta, the Yellow River bottom builds up 5-30 cm/ year (81R1).

Sub-Part [Gb8] ~ Upper End of Sediment Delivery ~ United States ~

[Gb8a] ~ Upper End of Sediment Delivery ~ US ~ Palouse Region ~
Of the 1 million tons/ year of soil lost from Palouse farm fields (in Washington and Idaho), 587,000 tons become sediments in the area's surface waters (Ref. 3, 8 of (81B5)). Comments: Something is wrong here. The Palouse region has 2 million acres (Journal of Soil and Water Conservation, 44 (1989) p. 303) and the erosion rate from the region is many times the erosion rate implied here (0.5 ton/ acre/ year).

[Gb8b] ~ Upper End of Sediment Delivery ~ US - Ohio ~

Suspended Sediment Discharge at 8 Ohio Stations (91H3)
Station - - |Area~ |Mean ~ ~ ~ |Mean Sediment
(River) - - |(km2 ) |Discharge* |(mg/ liter)
Muskingum ~ |15,522| 576 ( 524)| 110
Muskingum ~ |19,223|1081 ( 982)| 130
Hocking ~ ~ | 2,442| 166 ( 151)| 210
Scioto~ ~ ~ |13,290|1088 ( 989)| 260
(2 reservoirs were built upstream during the study)
Little Miami| 3,116| 434 ( 395)| 330
Maumee~ ~ ~ |16,395|1198 (1089)| 260
Sandusky~ ~ | 3,240| 315 ( 286)| 300
Cuyahoga~ ~ | 1,831| 217 ( 197)| 280
* in units of 1000 tons/ year and (1000 tonnes/ year).

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Part [Gc] ~ Sediment Trapping in Reservoirs ~
[Gc1]~
General, [Gc2]~Rates (%/year) of Depletion of Reservoir Capacity due to Siltation (table), [Gc3]~Capacities of Major Reservoirs (table), [Gc4]~Reservoir areas of hydroelectric dams (table), [Gc5]~Africa (North), [Gc6]~Southeast Asia (3), [Gc7]~Canada, [Gc8]~China, [Gc9]~Latin America, [Gc10]~Asian Sub-Continent, [Gc11]~US, [Gc12]~Africa (Sub-Saharan), ~

Sub-Part [Gc1] ~ Sediment Trapping in Reservoirs ~ General ~
The world's dams are losing 1%/ year of their capacity due to built up silt, the United Nations Environment Program reported on the International Conference on Freshwater. A capacity of 1500 km3 of a total of 7000 km3 could be lost by 2050 ("
Silt Behind Dams 'Worsens Water Shortage", BBC News (12/4/01) (See book, "Evacuation of Sediments from Reservoirs", by Rodney White.)). Comments: Earlier figures by the World Bank also claimed a loss of 1%/ year. Data on individual dams is given elsewhere in this review document.

Many of the world's reservoirs are suffering significant reductions in storage capacity as a result of sedimentation, experts said yesterday at the International Conference on Freshwater in Bonn. Unless action is taken, 20% of reservoir capacity will be lost over the coming decades, the UN Environment Program warned. Sedimentation rates are now 8 times higher than in the mid-1960s ("Sedimentation Threatens Dams' Water Capacity", UNEP release (12/4/01)).

Worldwide, reservoirs are estimated to be losing storage capacity at 1%/ year (i.e. 66 km3/ year). Replacing this lost storage by building new reservoirs could cost $10-$13 billion/ year, assuming enough new reservoir sites could be found. If sediments had to be dredged out of existing reservoirs, the cost would climb to $130-$200 billion/ year (K. Mahmood, "Reservoir Sedimentation: Impact, Extent and Mitigation", World Bank, Washington DC, 1987).

Large dams (over15 m. high) have increased 7-fold since the 1950s from about 5750 to over 41,000 (98I1) and now impound 14% of the World's runoff (p. 239 of (90L5)).

As of 1998 349 dams over 60 m. high were under construction globally ((98I2), pp.12-14).

More that 30,000 water storage basins have been built around the world; 75% of these have been built in the past 35 years. These basins have a total filled capacity of 6000 km3, and a total surface area of 400,000 km2 (p. 170 of (90W1)). Total volume of water currently stored in man-made reservoirs is 5,000 km3, or 11% of the annual runoff from land to oceans (87W1). Comments: Compare 6000 or 5000 km3 to global runoff (about 40,000 km3/ year), not global precipitation (about 100,000 km3/ year) to estimate what fraction of sediments gets trapped behind dams. If a dam were built at the mouth of every river draining into an ocean, and these dams had capacity/ inflow =0.11 year, these dams would collect 85% of sediment flowing into them.

Large dams (over 15 m. high): 5000 in 1950; 38,000 in 1995. Over 85% of large dams now standing were built in the last 35 years (S. Postel, State of the World 1996, Chapter 3).

Number of large (over 15 meters high) dams (global): 5270 in 1950 (2 in China); 36,562 in 1985 (18,820 of these were in China) (Ref. 13 of (96A1)).

Number/ volume of large reservoirs (global): 539/ 528 km3 in 1950; 1777/4982 km3 in 1985 (Ref. 13 of (96A1)).

World Bank financing of dams: 18/ year (1980-1985); 6/ year (1986-1993). As many as 843 large dams (those over 15 meters high) are under construction world-wide, 430 of them in Asia according to International Commission On Large Dams (ICOLD) (Wall Street Journal (3/12/96)).

Total length (km.) of rivers that have been altered for navigation: 8,750 in 1900; 498,000 in 1980 (96A1).

A global analysis by the World Bank puts losses to reservoir storage-capacity from sediments at an average rate of 1%/ year (Chapter 11, Ref. 10 of (94B4)).

About 25-75% of sediments normally carried downstream can be trapped in reservoirs (Ref. 12, Chapter 11 of (94B4)). Comments: This suggests 60 km2 (= 115 Gt./ year) of sediments trapped.

The share of runoff impounded by dams has been estimated at 20% in North American and Africa, 15% in Europe, 14% in Asia, 6% in South America, and 4% in Oceania (Ref. 40 of (93W2)). The useable man-made reservoir capacity is 9% of annual river runoff (globally) -10% in Europe, 22% in North America (Ref. 3 of (94D2)).

The number of large dams (over 100 million m3) has increased 7-fold during 1950-1986, up to 39,000 (Ref. 21 of (94D2)). The backwater area of these dams is comparable to the size of France (552,000 km2) (Ref. 3 of (94D2)). Construction begins on 170 dams/ year, globally, as compared to 360 dams/ year during 1951-74 (92P1).

Trap efficiencies of 17 small flood-water-retarding reservoirs ranged between 81 and 98%. Reservoirs with C/I (Capacity/ annual-input) greater than 0.1 will trap 80-95% of inflowing sediment (somewhat less than the 1953 Brune curve predicts - see below) (74D1). Trap efficiencies of reservoirs for sediments tend to fall into the range 80-98% (63C1) (US SCS and USGS data). Sediment trap efficiency is 85% or better when reservoir capacity is greater than 10% of annual inflow (Refs. 4, 5 of (76D1)). Trap efficiency (%) is plotted against reservoir-capacity/ annual-inflow for many reservoirs in (53B1). Trap efficiency is greater than 85% when capacity/ annual-inflow is greater than 0.1 year (53B1).

Reservoir-Sediment-trapping Efficiencies as a Function of Capacity-to-annual-Inflow (C/I) ratio from two studies
C/I (years) - - -|0.01|0.02|0.04|0.06|0.08|0.10|0.20|0.40|0.60
Efficiency (74D1)| 44%| 59 | 73 | 78 | 82 | 85 | 91 | 94 | 96
Efficiency (53B1)| 44%| 60 | 74 | 80 | 85 | 87 | 93 | 96 | 97
Comments: These data were picked off plots. Differences between the two data sets do not appear to be statistically significant.

Sub-Part [Gc2] ~ Rates of Depletion of Reservoir Capacity due to Siltation ~

Rates (%/ year) of Depletion of Reservoir Capacity due to Siltation
Reservoir (Country) - - - -|Rate |References
LOW-STRESS REGION
Lake Diefenbacher (Canada) | 0.1 |90M1 (Yuzyk, 1983)
Lake Mead (USA)~ ~ ~ ~ ~ ~ | 0.4 |56L1
Bassano (Canada) ~ ~ ~ ~ ~ | 1.0 |90M1 (Yuzyk, 1984)
Lake Aldred (PA) ~ ~ ~ ~ ~ |>1.1 |97L1
Conowingo (PA) ~ ~ ~ ~ ~ ~ |>1.1 |97L1
Tavares (USA)~ ~ ~ ~ ~ ~ ~ | 1.3 |87U2 (See below)
Lake Clark (PA)~ ~ ~ ~ ~ ~ |>1.5 |97L1
Lake Ballinger (Texas) ~ ~ | 4.5 |74C1
MEDIUM-STRESS REGION
Aswan High Dam ~ ~ ~ ~ ~ ~ | 1.0*|84B2, 84B3
74 dams (Zimbabwe) ~ ~ ~ ~ | 1-2+|92T1
21 dams (Zimbabwe) ~ ~ ~ ~ | 2-3+|92T1
Shongweni (Natal)~ ~ ~ ~ ~ | 1.6 |56A3
Matumbula (Tanzania) ~ ~ ~ | 3.3 |84B2
Roseires (Sudan, Blue Nile)| 3.7 |94B4
near Arusha (N. Tanzania)~ | 3.7 |EROS 1995 Land Deg. Rev.
Kisonga (Tanzania) ~ ~ ~ ~ | 6.7 |84B2
Anchicaya (Columbia) ~ ~ ~ |12.5 |84B2, 76E1
HIGH-STRESS REGION
Kedung Ombo (Indonesia)~ ~ | 0.4 | 87S2
Bakra (India)~ ~ ~ ~ ~ ~ ~ | 0.67| 77M1
Mangla (Pakistan)~ ~ ~ ~ ~ | 1.5 | 84B2
Nizamsagar (India) ~ ~ ~ ~ | 1.5 | (3)
Tonle Sap (Cambodia) ~ ~ ~ | 1.6 | 96G3
Tarbela *# (Pakistan)~ ~ ~ | 2.5 | 76E1
Lake Sukhna (India)~ ~ ~ ~ | 2.85| 90S5
Xiaolangdi Dam (China) ~ ~ | 3.3 | (1)
Ambuklao (Philippines) ~ ~ | 3.1 | 84B2
Sukna Lake (India) ~ ~ ~ ~ | 6.7 | 77M1
Shihmen (Taiwan) ~ ~ ~ ~ ~ | 8.5 | 76E1
Yangouxia Dam (China)~ ~ ~ |10.~ |(2) rough estimate
Sanmenxia (China)~ ~ ~ ~ ~ |25.~ | 95G1

8 dams (India) (Fill rate = 0.31 Gt./ year) (84B3)

  1. James Nickum, "Issue Paper on Water and Irrigation" prepared for the Strategy and Action Project for Chinese and Global Food Security, Millenium Institute, Arlington, VA 1997.
  2. Patrick McCully, "Silenced Rivers: the Ecology and Politics of Large Dams", Zed Books, London, 1996.
  3. Malcolm Newson, "Land, Water and Development: River Basin Systems and their Sustainable Management", Routledge, London, 1992.
  4. * 0.139 Gt./ year
    *# initial storage capacity = 12 km3 (13.5 km3 according to (86I1))
    Comments:
    These numbers would be more useful if data on reservoir volume/drainage area were available.
    Comments: The average lifetime of US dams appears to be 400-500 years (0.22%/ year (87C1)), although in the early 1940s 39% of US dams had estimated lifetimes of less than 50 years (76E1)?).).

    Taveras Dam (See table above), built 1973, 260 feet high, has 75 feet of silt in bottom (87U2). Comments: If the river bottom at the dam site is assumed to have a width of a third of the dam width at its top, the backwaters are being filled at 1.3%/ year. Guess that the Tavares dam is in the US (Sierra).

    Sub-Part [Gc3] ~ Sediment Trapping in Reservoirs ~ Capacity of Major Reservoirs ~

    Capacities of Major Reservoirs (km3) (p. 25 of (70P1))
    NOTE: Reference (70P1) also gives data on height and year of completion.
    Dam - - - - -| (Location) ~ ~ ~ ~ ~ |Capacity, km3
    Sunmen Gorge | Yellow R., China)~ ~ | 33.00 (81R1)
    Saf'd Rud~ ~ |(Iran)~ ~ ~ ~ ~ ~ ~ ~ | ~1.67
    Dez~ ~ ~ ~ ~ |(Iran)~ ~ ~ ~ ~ ~ ~ ~ | ~3.35
    Habbaniay~ ~ |(Euphrates, Iraq) ~ ~ | ~3.20
    Dokan~ ~ ~ ~ |(Lesser Zab, Iraq)~ ~ | ~3.20
    Derbendi Khan| (Diyala, Iraq) ~ ~ ~ | ~1.60
    Mangla ~ ~ ~ | (Jhelum, Pakistan) ~ | 10.25
    Tarbela~ ~ ~ | (Indus, Pakistan)~ ~ | 13.70
    Bhakra ~ ~ ~ | (Sutlej, India)~ ~ ~ | 13.60
    Beas ~ ~ ~ ~ | (Beas, India)~ ~ ~ ~ | ~6.18
    Aswan High ~ |(Nile, Egypt) ~ ~ ~ ~ |157.00
    Kajakai~ ~ ~ |(Helmand, Afghanistan)| ~1.85
    Flaming Gorge|(Colorado, USA) ~ ~ ~ | ~4.70
    Glen Canyon~ |(Colorado, USA) ~ ~ ~ | 33.30
    Hoover ~ ~ ~ |(Colorado, USA) ~ ~ ~ | 38.50
    Falcon ~ ~ ~ |Rio Grande, Mexico/USA| ~5.04
    Pte.A.Lopez Mateos|(Humayo, Mexico) | ~3.15
    Lazaro Cardenas|Nazas y Oro, Mexico)| ~3.00
    Alvaro Obregon |(Yaqui, Mexico) ~ ~ | ~3.00
    TOTAL (out of 6000 world-wide) 339.29

    Sub-Part [Gc4] ~ Sediment Trapping in Reservoirs ~ Reservoir Area of Dams ~

    Reservoir Areas of selected Hydroelectric Dams
    (Source: R. J. A. Goodland, Environment, 31(9) (Nov. 1989) p. 33)
    Dam - - - - - |(Country)~ | Area (km2)
    Paulo Afonso~ |(Brazil) ~ | ~ 16
    Pehuenche ~ ~ |(Chili)~ ~ | ~ ~4
    Guavio~ ~ ~ ~ |(Colombia) | ~ 15
    Rio Grande II |(Colombia) | ~ 11
    Itaipu~ ~ |Brazil,Paraguay| 1350
    Aguamilpa ~ ~ |(Mexico) ~ | ~120
    Sayanskaya~ ~ |(USSR) ~ ~ | ~800
    Churchill Falls|(Canada)~ | ~665
    Grand Coulee~ | (USA) ~ ~ | ~324
    Urra I~ ~ ~ ~ |(Colombia) | ~ 62
    Jupia ~ ~ ~ ~ |(Brazil) ~ | ~333
    Sao Simao ~ ~ |(Brazil) ~ | ~660
    Tucurui ~ ~ ~ |(Brazil) ~ | 2160
    Paredao ~ ~ ~ |(Brazil) ~ | ~ 23
    Ilha Solteira |(Brazil) ~ | 1200
    Guri~ ~ ~ ~ ~ |(Venezuela)| 3280
    Urra II ~ ~ ~ |(Colombia) | ~540
    Cabora Bassa~ |Mozambique | 3800
    Furnas~ ~ ~ ~ |(Brazil) ~ | 1440
    Aswan High~ ~ |(Egypt)~ ~ | 4000
    Curua-Una ~ ~ |(Brazil) ~ | ~ 86
    Tres Maria~ ~ |(Brazil) ~ | 1052
    Kariba ~ |Zimbabwe, Zambia| 5100
    Samuel~ ~ ~ ~ |(Brazil) ~ | ~790
    Sobradinho~ ~ |(Brazil) ~ | 4214
    Balbina ~ ~ ~ |(Brazil) ~ | 2360
    Akosombo~ ~ ~ |(Ghana)~ ~ | 8482
    Brokopondo~ ~ |(Suriname) | 1500

    Note: The table in the source publication also gives data on rated power capacity of the dams, permitting one to also gauge river flow rates and dam heights.

    Sub-Part [Gc5] ~ Sediment Trapping in Reservoirs ~ Africa (North) ~

    Capacity of Major Impoundments (in millions of acre-ft.) (Ref. 12 of (86S1))
    Facility - - - |Location Miles from sea|Capacity
    Aswan High ~ ~ |Egypt-Main Nile 750|136. (168 km3)
    Khashm el Girba|Sudan-Atbara 1700| ~1.0
    Jebel Aulia~ ~ |Sudan-White Nile 1920| ~4.5
    Sennar ~ ~ ~ ~ |Sudan-Blue Nile 2110| ~0.8
    Roseires ~ ~ ~ |Sudan-Blue Nile 2280| ~2.4
    Owens Falls~ ~ |Uganda-White Nile 3450| 97.2 (120 km3)

    1.234 km3 = 1 million acre-ft. Total = 241.9 (299 km3)

    Degradation of Reservoir Capacity in northern Tanzania (a grazing area west of Arusha where over-grazing is the cause of erosion gullies.) (Catchment area: 9.3 km2)
    Year - - - - - - -| 1960~ | 1969 | 1971
    Reservoir Capacity|121,000|83,600|71,700 m3
    (3.7% loss/ year) (Source: EROS Land Degradation Review of 1995)

    Shongweni Dam (Natal) completed in 1928. Capacity 2455 billion gallons. By 1951, estimated capacity 1.7 billion gallons. 37% loss due to silt in 23 years ~ 1.6%/ year (56A3).

    Data is given on percent-of-capacity lost by siltation of several dams in Zimbabwe. Five dams have 100% lost (86D2).

    [Gc5a] ~ Sediment Trapping in Reservoirs ~ Africa (North) ~ Egypt ~
    The Nile River transports 110 million tons of silt/ year. Virtually all of this winds up in the pool behind Aswan High Dam (Fred Pearce, "High and Dry in Aswan", New Scientist (5/7/94)).

    Aswan High Dam was completed in 1971. (It closed off Lake Nassar in 1965 (93W1 FI p.20). It bought 5300 km2 of new land into production and extended year-around cropping to another 2800 km2. When the High Dam was started, there were 24 million Egyptians. When it was finished there were 36 million (74C1). Comments: 12 million more Egyptians/ 8000 more km2 of cropland = 1500 Egyptians/ km2 = 6 more Egyptians for each added acre. This suggests that Aswan dams would need to be under construction forever to keep up with Egypt's 1971 population growth rate in terms of supplying food. Before impoundment of the High Aswan Dam, River Nile flow averaged 84 billion m3/ year and transported 0.124 Gt./ year of sediment to the coast (Ref.30 of (93S1)). In addition, 9.5 million tonnes/ year of suspended sediment were deposited on the Nile floodplain. Low Aswan Dam built in 1902 and modified in 1912 and 1934. High Aswan Dam closed in 1964 (93S1).

    [Gc5b] ~ Sediment Trapping in Reservoirs ~ Africa (North) ~ Sudan ~
    The capacity of Khashm El Girba Dam was reduced, by silting, from 1.3 km3 to 0.72 km3 in 1976 (Ref.19 of (87E2)). The dam's capacity is expected to reach 0.5 km3 by 1997 (87E2). For the Roseires Dam (Sudan, Blue Nile), the actual siltation rate exceeds design estimates by 2x (Ref. 19 of (87E2)).

    Sub-Part [Gc6] ~ Sediment Trapping in Reservoirs ~ Southeast Asia ~

    [Gc6a] ~ Sediment Trapping in Reservoirs ~ Southeast Asia ~ Cambodia ~
    Tonle Sap Lake is Cambodia's richest source of protein: it has been described as the largest inland fishery in the world, and as the "heart and soul of Cambodia". In January 1979 the water was 4-4.5 m. deep, in January 1994 Tonle Sap Lake was 3-3.5 m. deep (96G3). Comments: These data suggests a reservoir fill rate of 1.6%/ year. Cambodia is undergoing massive deforestation ~ the probable source of the sedimentation.

    [Gc6b] ~ Sediment Trapping in Reservoirs ~ Southeast Asia ~ Indonesia ~
    Kedung Ombo Reservoir, Serang River,Indonesia has dead storage capacity of 91 million m3, and a total storage capacity of 728 million m3. Estimate 2.4 million m3 of sediment in reservoir that displaces live storage (?). 1.4 million m3/ year loss of live storage (How do we reconcile this and above 2.4 million?). At this rate of sedimentation, total storage will be lost in 250 years (0.4%/ year) (87S2).

    [Gc6c] ~ Sediment Trapping in Reservoirs ~ Southeast Asia ~ Philippines ~
    Pantabangan Dam in Central Luzon region (Philippines). Completed in 1974. Had projected life of 100 years but siltation will shorten that due to accelerated erosion (83R1).

    Sedimentation Rates of some Philippine Reservoirs (Sedimentation Rates in Col. 2 are in units of m3/ km2/ year ) (Sedimentation rates in Col. 4 are in units of tonnes/ km2/ year)
    Reservoir| Rate |(Year)|Rate |Reference
    Ambuklao | 3647 |(1967)| 7148|88P1, p.91
    Ambuklao | 8071 |(1980)|15800|88P1, p.91
    Binga~ ~ | 2857 |(1967)| 5600|88P1, p.91
    Binga~ ~ | 5844 |(1980)|11450|88P1, p.91

    Comments: Sediment density is 1.96 g/cc. (68H1); multiply the above figures by 1.96 tonnes/ m3 to get tonnes/ km2/ year. To get total erosion rate, one must add the eroded material that landed on the lower slopes and on river bottoms upstream of the reservoirs. (This would probably increase the above sedimentation rates by a factor of at least 2.5.)

    Sub-Part [Gc7] ~ Sediment Trapping in Reservoirs ~ Canada ~
    Lake Diefenbaker (sp?) decreases the sediment load of the South Saskatchewan River downstream of the dam by 90%. Sediment discharge above the reservoir averaged 6 million tonnes/ year. Those at Saskatoon, 115 km. down-river averaged 0.7 million tonnes/ year (Rasid, 1979, in (90M1)). The 6 million tonnes/ year deposited in Lake Diefenbaker (sp?) reduces storage capacity by 0.1%/ year (Yuzyk, 1983, in (90M1)).

    Sub-Part [Gc8] ~ Sediment Trapping in Reservoirs ~ China ~
    Xiaolangdi Dam (China) on the Yellow River, to be completed in 2001, will store 12.6 km3 of water - 20% of the river's annual flow. It is expected to fill with silt in 30 years. (James Nickum, "Issue Paper on Water and Irrigation" prepared for the Strategy and Action Project for Chinese and Global Food Security, Millennium Institute, Arlington, VA 1997).

    Sunmen Gorge Dam (Yellow R.) has a sedimentation rate of 0.4 Gt./ year (81R1). (1.6 Gt./ year of sediment bypasses this dam.).

    The reservoir behind Yangouxia Dam on the upper Yellow River lost nearly 1/3 of its storage capacity before it even came into full operation. (Patrick McCully, "Silenced Rivers: the Ecology and Politics of Large Dams", Zed Books, London, 1996). Comments: Assume about 3 years are required to come to full operation.

    Turbines of China's Sanmenxia Dam were shut down in 1964 after 4 years of operation when the dam's reservoirs filled with sediment (95G1).

    Counting only larger reservoirs (over 0.001 km3 capacity), China has been adding 0.26 km3/ year of water capacity, but 0.08 km3/ year are lost to siltation (85X1). Comments: 0.08 km3/ year x 1.96 tonnes/ m3 x (1000 m/ km)3 = 0.157 Gt./ year.

    Sub-Part [Gc9] ~ Sediment Trapping in Reservoirs ~ Latin America ~
    In 1957, 20 months after Anchicaya Dam in Colombia was completed, nearly 25% of the reservoir's capacity had been lost to sediment (p. 129 of (76E1)) (p. 29 of (84B3)).

    If current rates of deforestation continue, 40% of the man-made reservoir feeding the Panama Canal will be silted in by the year 2000 (88U2).

    Sub-Part [Gc10] ~ Sediment Trapping in Reservoirs ~ Asian Sub-Continent ~
    India has about 4500 large reservoirs. Siltation studies of 27 dam-created reservoirs spanning India, indicate that all is not well. Studies over the years have shown that silt gets deposited in both the dead storage (the storage at the bottom, below the Minimum Draw Down Level (MDDL), which is not used under normal circumstances) and in the live storage (LS). Dams cannot be reconstructed at the same site once the reservoir has filled with sediment, and that the sediment must either be removed or the site abandoned. "The cost of sediment removal at a large reservoir can easily exceed the original dam construction cost by an order of magnitude (
    06T1).

    For 23 of the studied 27 reservoirs, the annual loss in live storage capacity is 214.2 million cubic meters (MCM), that is 0.912% (or nearly 1% per year) of the original live storage capacity. These 23 reservoirs have already lost 23.11% of LS by 2006. Some 13 of these reservoirs have already lost 20% or more of their capacities. (1 m3=1000 liters.) The annual loss figure arrived at by the Government of India's National Commission for Integrated Water Resources Development is 1.3 BCM. This may prove to be an underestimate. Considering that India now has about 214 billion cubic meters (BCM) of live storage capacity through large reservoirs, and if we apply the same loss rate (since the reservoirs in this sample are well distributed geographically and represent both small and large and also low and high siltation rate reservoirs, we may not be too much off the mark), we are losing about 1.95 BCM capacity annually (06T1). Comments: This is probably the total loss for India's 4500 large reservoirs.

    India has already lost about a quarter of the live storage capacities of just the 23 reservoirs, due to siltation. The proportion of capacity lost from reservoirs all over India could easily be of a similar order of magnitude. This implies a significant reduction in benefits from the reservoirs in terms of hydropower generation, irrigation, water supply and flood management (06T1).

    The Matatila reservoir (Betwa river, UP) lost 38% of gross capacity between 1956 and 1998-9. The dead storage up to the original Minimum Draw Down Level (MDDL) of 295.66 meters is completely filled with silt. Even further level up to 296.15 meters is now completely filled with silt. Total capacity loss by 1999 was 430.47 MCM (million cubic meters) (06T1).

    Gumti (Gumti river, Tripura) has lost 63.83 MCM, (20.4% of its live storage capacity) in 19 years (06T1).

    Maithon (Damodar river, Jharkhand) has lost 25.29% of its live storage capacity silted up in 46 years (06T1).

    Kadana (Mahi river, Gujarat) has lost 12.85% (278.6 MCM) in 11 years (06T1).

    Srisailam (Krishna river, AP) has lost 2013.33 MCM or 28.096% in 15 years (06T1).

    India is losing at least 1.95 BCM of reservoir storage capacity through siltation every year (06T1).

    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

    [Gc10a] ~ Sediment Trapping in Reservoirs ~ Asian Sub-Continent ~ India ~

    Sedimentation Rate (acre-ft/ year) of Some Indian Reservoirs ((84B3), p. 30), ((84B2) p. 66)
    Reservoir - - - - |Sed. Rate
    Bhakor -(India) ~ | 33,475
    Maithon -(India)~ | ~5,980
    Mavurakshi-(India)| ~2,000
    Nizam Sugar(India)| ~8,725
    Panchet -(India)~ | ~9,533
    Ramganga -(India) | ~4,366
    Tungabhadra(India)| 41,058
    Ukai -(India) ~ ~ | 21,758
    Total~ ~ ~ ~ ~ ~ |*126,895
    * = 0.1566 km3/ year = 0.307 Gt./ year

    1.234 km3 = 1 million acre-ft. Sediment density = 1.96 tonnes/ m3

    Nizamsagar Reservoir in Andhra Pradesh (India) lost over 60% of its capacity over 40 years. (Malcolm Newson, "Land, Water and Development: River Basin Systems and their Sustainable Management", Routledge, London, 1992).

    Sukna Lake (near Chandigarh India) may be silted up in 15 years (6.67%/ year) (77M1).

    Lake Sukhna in India's Shivalik (Siwalik) hills was 60% silted by 1976 (2.85%/ year) (built in 1950's) (90S5).

    Sardar Sarovar Dam being built in western India as part of the Narmoda Valley Development Project (30 large dams + 135 medium dams + 3000 small dams) will flood 370 km2 (Ref. 14 of (92P1)).

    Bakra Reservoir (Siwaliks (India)) may be silted up within 150 years (0.67%/ year) instead of estimated 600 years (77M1).

    [Gc10b] ~ Sediment Trapping in Reservoirs ~ Asian Sub-Continent ~ Pakistan ~
    Indus River is 2737 km. long, and has a drainage area of 966,000 km2. Its Tarbella Dam stores 13.5 km3. Its Manchar Lake stores about 0.7 km3 (86I1). In 1981 and 1983 the Indus carried 53.4 and 57.9 km3 of water and 91.9 and 37.2 million tonnes of sediment (Arain, 1985, in (86I1)). Milliman and Meade (1983, in (86I1)) estimate 0.1 Gt. sediment/ year (86I1).

    Sub-Part [Gc11] ~ Sediment Trapping in Reservoirs ~ US ~
    About 2 km3 of US reservoir storage capacity are lost to sediment retention annually. Cost: $819 million/ year (p. 217 of (97V1)).

    At least 10 million acres (40,000 km2) in the US have been covered by artificially impounded water (56G2) (unpublished USGS and US SCS estimates).

    Some 0.88 Gt./ year of agricultural soils are deposited into American reservoirs and aquatic systems (Ref. 4 of (95P1)).

    Sediment discharges to the Gulf of Mexico by the Mississippi River are less than half of what they were before 1953 (Keown et al, 1981 and 1986, in (90M1)).

    Some 25-30 million tonnes/ year of sediment have been deposited in the Great Lakes since 1850 (Kemp et al, 1976, 1977, 1978). 10-15 million of this is derived from rivers. Most of the remainder is derived from erosion of shoreline bluffs. The discharge from the St. Lawrence River is 1.3 million tonnes/ year of sediment (90M1).

    Between 0.3 and 0.4 Gt./ year are stored in reservoirs of the Colorado and Missouri Rivers. Another 0.1-0.2 Gt./ year are stored in reservoirs of the Rio Grande, Columbia and elsewhere (Meade and Parker, 1985 in (90M1)). This leaves 70-80% of the sediments eroded off the uplands of the conterminous US to be accounted for by other storage components (90M1).

    Over 1 billion yd3 (= 0.76 km3) (=1.5 Gt.) of sediment are deposited in the major reservoirs of the US annually ((71R1), p. 88). The US dredges 38 million yd3 (0.029 km3) of sediments from harbors and waterways annually (73O1). The US Army Corps of Engineers removes over 350 million yd3/ year (=0.266 km3/ year) (=0.52 Gt./ year) of dredged materials from navigation channels (p. 51 of (78H1)).

    New US reservoir capacity costs $300 to $700/ acre-foot (87C1). US dredging costs 3-8 times more than the cost of building replacement capacity, excluding disposal costs (87C1). US cropland sediment costs $197.2 million/ year in reservoir capacity (87C1). 0.22% of US water storage capacity (in reservoirs) is lost annually. Some 24% is due to cropland soil erosion (87C1). Total US water storage capacity is 728.3 million acre-ft. (898.7 km3). Of this amount, 472.1 million acre-ft. (582.6 km3) are useable (87C1).

    A 1941 survey found that 39% of US reservoirs had a useful life of less than 50 years due to sediment (76E1?).

    Dams on the Colorado River have reduced suspended sediment discharge to the ocean by at least 95% (Fig. 4 of (73C1)). Closure of Hoover Dam in the mid-1930s reduced suspended sediment discharge at Yuma AZ (500 km. downstream) by 0.17 Gt./ year (BUREC data) (90M1).

    A history of sediment yields and dam construction along the Missouri River is given in Fig.13 of (90M1).

    Lake Pepin, a widening of the Mississippi River in SE Minnesota has been the subject of a study of lake sediments documents how human activity has impacted the upper Mississippi watersheds. Pre-1830 is the baseline, and after 1830 the impacts parallel development and population growth in the area. Due to human activities, the life of this lake is being shortened about ten fold, becoming about one block shorter and 1/2-3/4 inch shallower every year (00A1).

    Reservoir Siltation Data ~ Pennsylvania (97L1)
    Lake Clark# (Pa.)~ |over 1.5%/ year (built 1931)
    Lake Aldred# (Pa.) |over 1.1%/ year (built 1910)
    Conowingo Res.(Pa.)|over 1.1%/ year (built 1928)

    # Now 100% filled

    [Gc12] ~ Sediment Trapping in Reservoirs ~ Africa (Sub-Saharan) ~

    In a 1983 survey of 16 dams in the Masvingo and Matebeleland Provinces of Zimbabwe, 5 dams were found to be 100% silt-filled, and 8 others were found to be over 50% silted (Ref. 12 of (92T1)). Another survey of 132 dams in Masvingo Province showed 16 dams to be 100% silted, and more than half to be 50% silted. Most of these dams were built in the past 30-50 years (Ref. 13 of (92T1)).

    Part [Gd] ~ Bed Load Contributions to Sediment Delivery ~
    Data on bed load/ total sediment load are given on p. 255-256 of (90M1). The maximum sand grain size carried in suspension by today's large rivers is about 0.5 mm. Since the geological column contains sandstones of alluvial origin and with particle sizes greater than 0.5 mm., fluvial bed load transport must have been important in older geochemical cycles (90M1). Bed load can be over 50% of total sediment load (90C3). Comments: Most workers in the field tend to take 10% as the average ratio of bed load to total sediment load.

    Global coarser bed load carried to the sea by rivers and streams is 1 Gt./ year (D. E. Walling (1987) in (89P2)).

    Ref. (89P2) estimates 0.9 Gt./ year of coarser bed load is discharged into the oceans. Based on estimate by D. E. Walling (87W1).

    Between 0.9 and 1.8 Gt./ year of bed load + flood-discharges enter the oceans (87W1).

    In general, the larger the river the smaller the proportion of total sediment load that is attributable to bed load (90M1). In glacier-fed streams draining small watersheds (200-400 km2, partly under glacier ice) on Baffin Island, bed load accounts for 80-90% of total sediment transport (Church (1972) in (90M1)).

    In a small stream draining 500 km2 of Wind River Range (Wyo.), bed load = 50% of total sediment load (Nordin, 1985 in (90M1)).

    Trinity River (7,700 km2) on the Northern California coast, bed load is 20% of total sediment load (Knott, 1974, in (90M1)).

    The Snake and Clearwater Rivers (Idaho), Fraser R. (Canada), and Tanana and Susitna Rivers (Alaska) have bed loads = 1-10% of load (Burrows and Harrold, 1983, in (90M1)).

    Mississippi River's bed loads = 5% of sediment load (Jordan, 1965, in (90M1)).

    Bed loads account for less than 10% of present-day transfers of sediment from continental uplands to continental margins (90M1). Comments: Note that this does not mean that bed load carry less than 10% of total erosion, because smaller rivers have a larger fraction of bed load, and total loads are much larger in smaller rivers.

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    Part [Ge] ~ Sediment Transport to Oceans ~ [Ge1]~General, [Ge2]~Suspended Sediment Yields of Selected Rivers (table), [Ge3]~Data for Major Rivers of the World(table), [Ge4]~Major Sediment-Yielding Rivers of the World (table), [Ge5]~Average Sediment Discharge to Oceans (table), [Ge6]~Suspended Sediment Discharge from Continents (table), [Ge7]~Sediment Yields of Rivers to Oceans (table), [Ge8]~Suspended Sediment Reaching the Oceans (table)), [Ge9]~Yellow River, [Ge10]~Peruvian Rivers, [Ge11]~Great Lakes, [Ge12]~Southeastern US, [Ge13]~Sediment Deposited at River Mouths,

    Sub-Part [Ge1] ~ Sediment Transport to Oceans ~ General ~
    Topsoil Content in River Sediments:

    Data on carbon contents of river sediments collected by Meybeck (82M1) permit an estimate of how the global rate of soil erosion should be broken down into rates of subsoil-, topsoil, and soil-surface-litter erosion. This breakdown is not without ambiguities. Bed rock (and, by inference, sub-soil) contains about 0.5 wt.% carbon, mainly in the form of kerogens. (All weight percentages here are in dry-wt.%.) Topsoil typically contains about 2 wt.% organic carbon (more in temperate soils, less in tropical soils). Soil surface litter typically contains about 45% (dry-weight basis) carbon. A conceptual problem arises as to how to treat soil organic compounds like humic acid, fulvic acid and humins, all of which contain about 50-60 wt.% carbon. Some of these compounds provide carbon-residence times in the soil of 1000 or more years (before mineralization to CO2, etc.) while others are characterized by carbon residence times in soil of only a few years to a few decades. Apparently a continuum in residence-times exists between these extremes, probably resulting from the degree to which these organic compounds become stabilized by formation of mineral-organic complexes on external- and internal-pore surfaces of soil minerals (clays, silts, sand). The highly stabilized organics are no doubt properly considered as part of the 2% topsoil-carbon content, while the much-less-stabilized organics are probably more properly considered as related to soil-surface litter which is typically characterized by carbon residence times of a few months to a few decades.

    Erosion-induced sediment deposition and burial may occur at a rate of 0.4-0.6 Gt. C/ year compared with perhaps 0.8 to 1.2 Gt. C/ year emitted into the atmosphere (R. Lal, Environ. Int. 29 (2003) p.437.) (04L1). Comments: Does this deposition and burial include both oceans and rivers or just oceans? Many authors neglect river-bottom sediments which account for much more deposition and burial than oceans in anthropogenically affected rivers.

    A table and map of rivers and their water discharges for several hundred rivers in the northern third of the world are given in (94D2).

    The world's 60 largest rivers discharge half of all river water entering the oceans. The world's 260 largest rivers discharge 60% of all river water entering the oceans (UNESCO in press (1981)) (82M1).

    A world map showing the global pattern of suspended sediment yields based on data from 1500 measuring stations is shown on p. 107 of (87W1).

    The Amazon River discharges 11-18% of water discharged into the oceans, but it transports only about 2% of the sediments reaching the oceans annually (1964). 82% of suspended sediment reaching the mouth of the Amazon comes from the Andes Mountains and highlands; only 12% of the drainage area (Gibbs, 1967, in (68H1)).

    Sub-Part [Ge2] ~ Sediment Transport to Oceans ~ Suspended Sediment Yields ~
    Suspended Sediment Yields of Selected Rivers
    (Tables 2-5 of (68H1))

    (NOTE: Most data neglect bed loads (about 10% of total load).)
    River (Location)- - - - - -|Drainage|Average Annual|Average
    - - - - - - - - - - - - - -| Area ~ |Suspended Load|Disch.
    - - - - - - - - - - - - - -|1000 mi2|million|tons/ |1000 cfs
    - - - - - - - - - - - - - -| ~ ~ ~ | tons ~ |mi2 ~ | ~ ~ ~.
    NORTH AMERICA
    Mississippi (Baton Rouge)~ | - - - |262.5 ~ |- - - |- - -
    Atchafalaya (Simmesport) ~ | - - - |121.4 ~ |- - - |- - -
    Mississippi (sum of above) |1244.0 |344.0 ~ | 277. |630.0
    Mississippi (73C1) ~ ~ ~ ~ |1262.0 |244.9 ~ | 259. |- - -
    Missouri -(Hermann MO) ~ ~ | 528.2 |239.6 ~ | 454. | 69.0
    St. Lawrence (mouth) ~ ~ ~ | 498.0 | ~4.0 ~ | ~ 8. |500.0
    Colorado (Grand Canyon AZ) | 137.8 |149.0 ~ |1082. | ~5.5
    Colorado River (73C1)~ ~ ~ | 245.0 | ~0.016 | ~ 0.0|- - -
    Saskatchewan (The Pas) ~ ~ | 125.1 | ~4.6 ~ | ~37. | 80.0
    Red -(Lockport Canada) ~ ~ | 110.8 | ~1.8 ~ | ~16. | 80.0
    Snake -(Cent.Ferry WA) ~ ~ | 103.5 | 13.1 ~ | 127. | 48.6
    Columbia (Pasco WA)~ ~ ~ ~ | 102.6 | 10.3 ~ | 100. |256.0
    Columbia R. (73C1) ~ ~ ~ ~ | 258.2 | 15.62~ | ~60.5|- - -
    Ohio -(Cincinnati OH)~ ~ ~ | ~76.6 | 15.0 ~ | 196. |258.0
    Yellowstone -(Glendive MT) | ~66.9 | 30.3 ~ | 455. |- - -
    Brazos -(Richmond TX)~ ~ ~ | ~34.8 | 34.8 ~ |1000. | ~5.2
    Rio Grande (San Acacia NM) | ~26.8 | ~9.4 ~ | 352. | ~2.7
    Susquehanna (73C1) ~ ~ ~ ~ | ~24.1 | ~1.95~ | ~81. |- - -
    Sacramento River (73C1)~ ~ | ~23.5 | ~2.72~ | 116. |- - -
    Alabama -(Claiborne AL)~ ~ | ~22.0 | ~2.1 ~ | ~97. | 31.9
    Alabama (73C1) ~ ~ ~ ~ ~ ~ | ~22.0 | ~2.53~ | 115. |- - -
    Tombigbee River (73C1) ~ ~ | ~19.2 | ~2.454 | 128. |- - -
    Apalachicola River (73C1)~ | ~17.2 | ~0.173 | ~10.1|- - -
    Potomac River (mouth)~ ~ ~ | ~14.6 | ~2.5 ~ | 170. | 11.1
    Potomac River (73C1) ~ ~ ~ | ~ 9.65| ~0.786 | ~81. |- - -
    San Joaquin (Vernalis CA)~ | ~14.0 | ~0.35~ | ~25. | ~4.7
    Rio San Juan (Santa Rosalia| ~12.0 | ~5.3 ~ | 445. | ~0.3
    Pee Dee (73C1) ~ ~ ~ ~ ~ ~ | ~ 8.83| ~0.442 | ~15.2|- - -
    Delaware -(Trenton NJ) ~ ~ | ~ 6.8 | ~1.0 ~ | 147. | 20.1
    Delaware (73C1)~ ~ ~ ~ ~ ~ | ~ 6.78| ~0.749 | 111. |- - -
    Pearl (73C1) ~ ~ ~ ~ ~ ~ ~ | ~ 6.6 | ~0.881 | 133. |- - -
    Sabine (Logansport LA) ~ ~ | ~ 4.9 | ~0.73~ | 150. | ~8.8
    Pecos (Puerto de Luna NM)~ | ~ 4.0 | ~2.7 ~ | 685. | ~0.6
    Eel (Scotia CA)~ ~ ~ ~ ~ ~ | ~ 3.1 | 18.2 ~ |5846. | ~7.0
    Eel (73C1) ~ ~ ~ ~ ~ ~ ~ ~ | ~ 3.11| 29.345 |9426. |- - -
    Trinity River (73C1) ~ ~ ~ | ~ 2.87| ~5.497 |1919. |- - -
    Ogeechee River (73C1)~ ~ ~ | ~ 2.65| ~0.062 | ~23.2|- - -
    Mad River (73C1) ~ ~ ~ ~ ~ | ~ 0.49| ~2.691 |5549. |- - -
    Totals (w/o Tributaries) ~ |2465.~ |604.0 ~ | 245. |- - -
    (Totals exclude data from Ref. (73C1))
    Comments:
    Compare 604 million tons/ year to total erosion in conterminous US of 5000 million tons/ year.

    SOUTH AMERICA (Same column titles as above)
    Amazon (mouth) ~ ~ ~ ~ ~ ~ |2368.0|400.0| ~170. |6400.
    Parana (mouth, Argent.)~ ~ | 890.0| 90.0| ~100. | 526.
    Orinoco (mouth, Venez.)~ ~ | 366.7| 95.3| ~260. | 800.
    Uruguay (Concordia, Argen.)| 150.0| 15.0| ~100. | 140.
    Negro (Primera Angustura ")| ~36.7| ~1.5| ~405. | ~36.
    Caroni (Orinoco Venez.)~ ~ | ~35.0| 52.5| 1500. |- - -
    Colorado (Pichi Mahuida) ~ | ~ 9.0| ~7.6| ~880. |- - -
    Totals (w/o tributaries) ~ |3820.0|609.4| ~160. |- - -
    AFRICA
    Congo (mouth, Congo) ~ ~ ~ |1550.0| 71.3| ~ 46. |1400.
    Nile (delta, Egypt)~ ~ ~ ~ |1150.0|121.9| ~100. | 100.
    Niger (Baro, Nigeria)~ ~ ~ | 430.0| ~5.0| ~ 12. | 215.
    Cheliff (mouth, Algeria) ~ | ~ 8.6| ~3.4| ~395. |- - -
    Medjerdah (mouth, Tunisia) | ~ 8.1| 14.8| 1825. |- - -
    Totals (w/o tributaries) ~ |3146.7|216.3| ~ 70. |- - -
    AUSTRALIA
    30 Streams (E. Australia) | - - - |- - -| ~ 85. |- - -
    Murray-Darling (mouth)~ ~ | 414.0 | 35.2|- - -~ |- - -
    Waipano (Kanakanaia N.Z.) | ~ 0.6 | 12.2|19930. | ~13.
    Totals (w/o tributaries)~ | 414.6 | 47.4| ~115. |- - -
    EUROPE
    Volga -(Dubovka USSR) ~ ~ ~ | 521.5| 20.8 | ~ 40.|283.
    Danube (mouth USSR) ~ ~ ~ ~ | 315.0| 21.4 | ~ 68.|218.
    Dnepr (Verkhnedneprovsk USSR| 167.5| ~1.2 | ~ ~7.|194.
    Don (Volga Trib.) ~ ~ ~ ~ ~ | 146.0| ~5.4 | ~ 37.|- -
    Ural (Topolinski USSR) ~ ~ | ~74.8| ~1.8 | ~ 24.|- -
    Vistula (Tczew, Poland) ~ ~ | ~74.6| ~1.7 | ~ 23.| 38.
    Tisza (Danube R. Hungary) ~ | ~60.3| 11.0 | ~180.|- -
    Rhine (mouth, Holland)~ ~ ~ | ~56.0| ~0.5 | ~ ~9.| 78.
    Rhine (Lake Constance Swtz.)| ~ 4.6| ~9.6 | 2094.|- -
    Loire (Nantes Fr.)~ ~ ~ ~ ~ | ~46.7| ~0.47| ~ 10.| 30.
    Oder (Gozdowice Poland) ~ ~ | ~42.2| ~0.15| ~ ~4.|- -
    Po (Pontelaguscuro Italy) ~ | ~21.0| 16.8 | ~800.| 51.
    Seine (Paris France)~ ~ ~ ~ | ~17.1| ~1.22| ~ 71.|- -
    Tiber (Rome Italy)~ ~ ~ ~ ~ | ~ 6.4| ~6.42| 1005.|- -
    Drin (Can Deje Albania) ~ ~ | ~ 4.8| 16.2 | 3400.|- -
    Garone (Toulouse Fr.) ~ ~ ~ | ~ 3.9| ~2.76| ~715.| 24.
    Inn (Reisach W. Germ.)~ ~ ~ | ~ 3.8| ~3.52| ~933.|- -
    Arno (San Giovanni alla Vena| ~ 3.2| ~2.43| ~770.|- -
    Semani (Urae Kucit Albania~ | ~ 2.0| 24.2 |11844.|- -
    Simento (Giarretta Sicily)~ | ~ 0.7| ~3.96| 5605.|- -
    Totals (w/o tributaries)~ ~ |1357.0|121.9 | ~ 90.|- -
    ASIA
    Yenisei (Igarka USSR) ~ ~ ~ | 954.2| ~11.6| ~ 12.| 614.
    Ob (Salekhard USSR) ~ ~ ~ ~ | 945.3| ~15.7| ~ 17.| 441.
    Ganges (delta, E.Paki.) ~ ~ | 409.2|1600.0| 4000.| 498.
    Yangtze (Chikiang China)~ ~ | 395.7| 552.0| 1400.| 770.
    Indus -(Kotri W.Paki.)~ ~ ~ | 370.0| 481.0| 1300.| 239.
    Indus (Kalabagh W.Paki.)~ ~ | 117.7| 751.0| 6370.|- - -
    Yellow (Shenhsien China)~ ~ | 276.0|2083.0| 7545.| ~53.
    Bramaputra (delta, E.Paki.) | 216.0| 800.0| 3700.| 706.
    Mekong (Mukdaham Thailand)~ | 151.0| 187.0| 1240.| 530.
    Irrawaddy (Prome Burma) ~ ~ | 141.7| 331.0| 2340.| 479.
    Pearl-West (Wuchow China) ~ | 120.8| ~30.8| ~250.| 277.
    Mahanadi-(Naraj India)~ ~ ~ | ~51.0| ~67.8| 1330.| 101.
    Euphrates -(Tabqa Syria)~ ~ | ~46.6| ~ 4.8| ~100.| ~51.
    Red (Hanoi N. Viet Nam) ~ ~ | ~46.3| 143.0| 3080.| 138.
    Chao Phya(Nakornsawan Thai.)| ~41.1| ~12.5| ~300.|- - -
    Kabul (Nowshera W. Paki.) ~ | ~34.9| ~26.0| ~745.| ~24.
    Tigris (Bagdad Iraq)~ ~ ~ ~ | ~30.8| ~57.6| 1870.| ~51.
    Kosi -(Chatra India)~ ~ ~ ~ | ~23.8| 190.0| 7980.| ~64.
    Ching (Changchiashan China) | ~22.0| 450.0|20500.| ~ 2.
    Chenab (Alexandria Br.W.Pak.| ~12.6| ~55.0| 4380.|- - -
    Lo -(Chuantou China)~ ~ ~ ~ | ~10.4| 210.0|20200.|- - -
    Damodar (Rhondia India) ~ ~ | ~ 7.7| ~31.3| 4050.| ~11.
    Ishikari (Ebestu Japan) ~ ~ | ~ 4.9| ~ 1.9| ~393.|- - -
    Tone (Matsudo Japan)~ ~ ~ ~ | ~ 4.6| ~ 3.2| ~778.|- - -
    Totals (w/o tributaries)~ ~ |4212.8|6414.6| 1530.|- - -
    1000 cfs. x 0.8936 gives km3/ year
    tons/ mi2 x 0.351 gives tonnes/ km2
    mi2 x 2.59 gives km2

    Sub-Part [Ge3] ~ Data for Major Rivers ~
    Data for Major Rivers of the World (Table 2 of (83M2))
    Col. 2 Drainage Area (1000 km2)
    Col. 3 Water Discharge (km3/ year)
    Col. 4,5,6,7 Sediment Discharge (million tonnes/ year)
    Col. 4 Strakhov (1961) and Lisitzin (1972)
    Col. 5 Holeman (1968) (See (68H1))
    Col. 6 Milliman and Meade ~ (83M2)
    Col. 7 (73C1) (Curtis. Culbertson, Chase) (North American data only)
    NORTH AMERICA - - - - | Col. |Col.|Col.|Col.|Col. |Col.
    River - - - - - - - - | (2)~ | (3)| (4)| (5)| (6) | (7)
    St. Lawrence (Canada) |1030. |447.| ~4.| ~4.| ~4~ |- - -
    Fraser -(Canada)~ ~ ~ | 220. |112.| - -|- - | 20~ |- - -
    MacKenzie (Canada)~ ~ |1810. |306.| 15.|- - | 100.|- - -
    Colorado (Mexico) ~ ~ | 640. | 20.|135.|135.| ~0.1|- - -
    Alabama -(US) ~ ~ ~ ~ | ~57.0|- - |- - |- - |2.293|- - -
    Apalachicola (US) ~ ~ | ~44.5|- - |- - |- - |- - -| 0.157
    Brazos -(US)~ ~ ~ ~ ~ | 110.0| ~7.| 32.| 32.| 16. |- - -
    Brazos -(US)~ ~ ~ ~ ~ | 114.0|- - |- - |- - |- - -|15.893
    Chehalis (US) ~ ~ ~ ~ | ~ 3.4|- - |- - |- - |- - -| 0.115
    Columbia (US) ~ ~ ~ ~ | 670.0|251.| 36.| ~9.| ~8~ |- - -
    Columbia (US) ~ ~ ~ ~ | 624.2|- - |- - |- - |- - -| 9.704
    Copper*# (Alaska) ~ ~ | ~60.0| 39.|- - |- - |70(glacier-fed)
    Delaware (US) ~ ~ ~ ~ | ~17.6|- - |- - |- - |- - -| 0.680
    Edisto -(US)~ ~ ~ ~ ~ | ~ 7.1|- - |- - |- - |- - -| 0.019
    Eel -(US) ~ ~ ~ ~ ~ ~ | ~ 8. |- - |- - | 16.| 14. |- - -
    Eel-(US)~ ~ ~ ~ ~ ~ ~ | ~ 8.1|- - |- - |- - |- - -|26.621
    Hudson -(US)~ ~ ~ ~ ~ | ~20. | 12.| 36.|- - | ~1. |- - -
    Klamath -(US) ~ ~ ~ ~ | ~22.0|- - |- - |- - |- - -| 2.389
    Mad -(US) ~ ~ ~ ~ ~ ~ | ~ 1.3|- - |- - |- - |- - -| 2.441
    Mississ.(+Atchafalaya)|3270~ |580.|500.|349.|210. |- - -
    Mississ.(Red R. L.) ~ |2924. |- - |- - |- - |- - -|222.2
    Nueces -(US)~ ~ ~ ~ ~ | ~40.4|- - |- - |- - |- - -| 0.445
    Ogeechee (US)(Ga.)~ ~ | ~ 6.9|- - |- - |- - |- - -| 0.056
    Pearl -(US) ~ ~ ~ ~ ~ | ~17.2|- - |- - |- - |- - -| 0.799
    Pee Dee -(US) ~ ~ ~ ~ | ~22.9|- - |- - |- - |- - -| 0.401
    Potomac -(US) ~ ~ ~ ~ | ~25.0|- - |- - |- - |- - -| 0.723
    Rogue -(US) ~ ~ ~ ~ ~ | ~ 5.3|- - |- - |- - |- - -| 0.059
    Russian -(US) ~ ~ ~ ~ | ~ 3.5|- - |- - |- - |- - -| 4.135
    Sacramento (US) ~ ~ ~ | ~60.9|- - |- - |- - |- - -| 2.464
    Salinas (US)~ ~ ~ ~ ~ | ~10.8|- - |- - |- - |- - -| 0.531
    San Joaquin (US)~ ~ ~ | ~35.1|- - |- - |- - |- - -| 0.350
    Santa Clara (US)~ ~ ~ | ~ 4.1|- - |- - |- - |- - -| 0.069
    Skagit (US) ~ ~ ~ ~ ~ | ~ 8.0|- - |- - |- - |- - -| 0.330
    Skyhkomish (US) ~ ~ ~ | ~ 2.2|- - |- - |- - |- - -| 0.244
    Snoqualmie (US) ~ ~ ~ | ~ 1.6|- - |- - |- - |- - -| 0.263
    Susitna (US)~ ~ ~ ~ ~ | ~50~ | 40.|- - |- - | 25. | - - -
    Susquehanna (US)~ ~ ~ | ~62.4|- - |- - |- - |- - -| 1.771
    Tar (US)~ ~ ~ ~ ~ ~ ~ | ~ 5.5|- - |- - |- - |- -~ | 0.105
    Tombigbee (US)~ ~ ~ ~ | ~49.7|- - |- - |- - |- - -| 2.226
    Trinity (US)~ ~ ~ ~ ~ | ~ 7.4|- - |- - |- - |- - -| 4.987
    Yukon (US)~ ~ ~ ~ ~ ~ | 840. |195.| 88.|- - | 60. | - - -
    Totals North America~ |9570. |- - |- - |- - |528. | - - -
    (Totals exclude input from (73C1).)
    *# Considerable effect of glaciers (90M1). A river of similar size with far fewer glaciers (Kushokwim of S.W. Alaska) carries 1/10 as much sediment (90M1).

    SOUTH AMERICA - - - -|Col. |Col. |Col. |Col. |Col.
    River - - - - - - - -| (2) | (3) | (4) |(5)~ | (6)
    Chira - - (Peru) ~ ~ | ~ 20| ~ ~5| - - | - - |4-75
    Magdalena (Colomb.)~ | ~240| ~237| - - | - - | 220
    Orinoco (Venez.) ~ ~ | ~990| 1100| ~86 | ~86 | 210
    Amazon (Brazil)~ ~ ~ | 6150| 6300| 498 | 364 | 900
    San Francisco(Brazil)| ~640| ~ 97| - - | - - | ~~6
    La Plata (Argentina) | 2830| ~470| 129 | ~82 | ~92
    Negro - -(Argentina) | ~100| ~ 30| - - | - - | ~13
    Totals South America |10850| - - | - - | - - |1420

    EUROPE - - - - -|Col. |Col. |Col. |Col. |Col.
    River- - - - - -| (2) | (3) | (4) | (5) | (6)
    Rhone -(France) | ~90 | ~49 | ~31 | - - | 10
    Po - -(Italy) ~ | ~70 | ~46 | ~18 | ~15 | 15
    Danube (Romania)| 810 | 206 | ~67 | ~19 | 67
    Semani (Albania)| - - | - - | - - | ~22 | ??
    Drini -(Albania)| ~10 | - - | - - | ~15 | ??
    Totals - -Europe| 970 | - - | - - | - - | 92

    EURASIAN ARCTIC - - - |Col. |Col. |Col.|Col. |Col.
    River - - - - - - - - | (2) | (3) | (4)| (5) | (6)
    Yana -(USSR)~ ~ ~ ~ ~ | ~220| ~29 | ~3 | - - | ~3
    Ob -(USSR)~ ~ ~ ~ ~ ~ | 2500| 385 | 16 | ~15 | 16
    Yenisei -(USSR) ~ ~ ~ | 2580| 560 | 13 | - - | 13
    Severnay Dvina (USSR) | ~350| 106 | 4.5| 4.5 | ~-
    Lena -(USSR)~ ~ ~ ~ ~ | 2500| 514 | 15 | - - | 12
    Kolyma -(USSR)~ ~ ~ ~ | ~640| ~71 | ~6 | - - | ~6
    Indigirka (USSR)~ ~ ~ | ~360| ~55 | 14 | - - | 14
    Total Eurasian Arctic | 9150| - - | - -| - - | 68

    ASIA - - - - - - - - - - |Col. |Col. |Col.|Col.|Col.
    River- - - - - - - - - - | (2) | (3) | (4)| (5)| (6)
    Amur -(USSR) ~ ~ ~ ~ ~ ~ | 1850| ~325| ~25| - -| ~52
    Liaohe (China) ~ ~ ~ ~ ~ | ~170| ~ ~6| - -| - -| ~41
    Daling (China) ~ ~ ~ ~ ~ | ~ 20| ~ ~1| - -| - -| ~36
    Haiho (China)~ ~ ~ ~ ~ ~ | ~ 50| ~ ~2| - -| - -| ~81
    Yellow (Huangho)(China)~ | ~770| ~ 49|1890|1890|1080
    Yangtze (China)~ ~ ~ ~ ~ | 1940| ~900| 500| 502| 478
    Huaihe (China) ~ ~ ~ ~ ~ | ~260|- - -| - -| - -| ~14
    Pearl(Zhu Jiang)(China)~ | ~440| ~302| - -| ~27| ~69
    Hungho (Vietnam) ~ ~ ~ ~ | ~120| ~123| 130| 130| 130
    Mekong (Vietnam) ~ ~ ~ ~ | ~790| ~470| 170| 170| 160
    Irrawaddy (Burma)~ ~ ~ ~ | ~430| ~428| 299| 300| 265
    Ganges/Brahmaputra(Bang.)| 1480| ~971|2180|2180|1670
    Mehandi (India)~ ~ ~ ~ ~ | ~130| ~ 67| - -| ~62| ~ 2
    Damodar (India)~ ~ ~ ~ ~ | ~ 20| ~ 10| - -| ~28| ~ ?
    Godavari (India) ~ ~ ~ ~ | ~310| ~ 84| - -| - -| ~96
    Indus (Pakistan) ~ ~ ~ ~ | ~970| ~238| 435| 440| 100
    Tigris-Euphrates (Iraq)~ | 1050| ~ 46| 105| ~53| ~ ?
    Totals ~ ASIA ~ ~ ~ ~ ~ | 9740| - - | - -| - -|4334

    Africa - - - - - - - |Col. |Col. |Col. |Col. |Col.
    River- - - - - - - - | (2) | (3) | (4) | (5) |(6)
    Nile (Egypt) ~ ~ ~ ~ |2960 | ~30 | 110 | 111 | ~0
    Niger (Nigeria)~ ~ ~ |1210 | 192 | ~67 | ~ 4 | 40
    Zaire (Zaire)~ ~ ~ ~ |3820 |1250 | ~65 | ~64 | 43
    Orange (S. Africa) ~ |1020 | ~11 | 153 | - - | 17
    Zambesi (Mozambique) |1200 | 223 | 100 | - - | 20
    Limpopo (Mozambique) | 410 | ~ 5 | - - | - - | 33
    Rufiji (Tanzania)~ ~ | 180 | ~ 9 | - - | - - | 17
    Tana (Kenya) ~ ~ ~ ~ | ~32 | - - | - - | - - | 32
    Total ~ Africa ## ~ |7480 | - - | - - | - - |175

    ## Not counting the Nile River

    Oceania - - - - - - -(Total excludes Murray River)
    River - - - - - - -|Col.|Col.|Col.|Col.|Col.
    - - - - - - - - - -| (2)| (3)| (4)| (5)|(6)
    Murray (Aust.) ~ ~ |1060| 22 | 32 | 32 | 30
    Waiapu (New Z.)~ ~ | - -|- - | - -|- - | 28
    Haast -(New Z.)~ ~ | ~ 1| ~6 | - -|- - | 13
    Fly - -(New Guinea)| ~61| 77 | - -|- - | 30
    Purari (New Guinea)| ~31| 77 | - -|- - | 80
    Choshui -(Taiwan)~ | ~ 3| ~6 | - -|- - | 66
    Kaoping -(Taiwan)~ | ~ 3| ~9 | - -|- - | 39
    Tsengwen (Taiwan)~ | ~ 1| ~2 | - -|- - | 28
    Hualien -(Taiwan)~ | ~ 2| ~4 | - -|- - | 19
    Peinan -(Taiwan) ~ | ~ 2| ~4 | - -|- - | 17
    Hsiukuluan (Taiwan)| ~ 2| ~4 | - -|- - | 16
    Totals - Oceania ~ |1074| 39 | - -|- - |336

    Sub-Part [Ge4] - Sediment Transport to Oceans ~ Major Sediment-Yielding Rivers

    Major Sediment-Yielding Rivers of the World (68H1)
    (Drainage Area (Col. 2) is in units of 1000 sq. miles.)
    Col. 3 gives tons/ mi2/ year; Col. 4 gives Gt./ year.
    River (Location)- - - -|Drainage|Ave. Annual|Discharge
    - - - - - - - - - - - -|Area~ ~ | Sediment~ |at mouth
    - - - - - - - - - - - -| ~ ~ ~ ~| Load~ ~ ~ |(1000 cfs.)
    Yellow -(China)~ ~ ~ ~ | ~ ~260 | 7540|2.080| ~53
    Ganges -(India)~ ~ ~ ~ | ~ ~369 | 4000|1.600| 415
    Bramaputra (E.Pakistan)| ~ ~257 | 3700|0.800| 430
    Yangtze -(China) ~ ~ ~ | ~ ~750 | 1400|0.550| 770
    Indus (W. Pakistan)~ ~ | ~ ~374 | 1300|0.480| 196
    Ching (Yellow trib.) ~ | ~ ~ 22 |20500|0.450| ~ 2
    Amazon - -(Brazil) ~ ~ | ~ 2230 | ~170|0.400|6400
    Mississippi (US) ~ ~ ~ | ~ 1244 | ~280|0.344| 630
    Irrawaddy-(Burma)~ ~ ~ | ~ ~166 | 2340|0.330| 479
    Missouri (Miss. trib.) | ~ ~529 | ~450|0.240| ~69
    Lo- -(Yellow trib.)~ ~ | ~ ~ 10 |20200|0.210| - -
    Kosi (Ganges trib.)~ ~ | ~ ~ 24 | 7980|0.190| ~64
    Mekong- -(Thailand)~ ~ | ~ ~307 | 1240|0.187| 390
    Colorado (US)~ ~ ~ ~ ~ | ~ ~246 | 1080|0.149| ~ 5.5
    Red - (North Viet Nam) | ~ ~ 46 | 3090|0.143| 138
    Nile -(Egypt)~ ~ ~ ~ ~ | ~ 1150 | ~100|0.122| 100
    1000 cfs. x 0.8936 gives km3/ year
    tons/ mi2 x 0.351 gives tonnes/ km2
    mi2 x 2.59 gives km2

    Sub-Part [Ge5] ~ Sediment Transport to Oceans ~ Average Sediment Discharge to Oceans ~

    Average Sediment Discharge to Oceans (in million tonnes/ year) (83M2)
    Ganges/Brahmaputra|1670
    Yellow (Huangho)~ |1080
    Amazon~ ~ ~ ~ ~ ~ | 900
    Yangtze ~ ~ ~ ~ ~ | 478
    Irrawaddy ~ ~ ~ ~ | 285
    Magdalena ~ ~ ~ ~ | 220
    Mississippi ~ ~ ~ | 210
    Orinoco ~ ~ ~ ~ ~ | 210
    Hungho (Red)~ ~ ~ | 160
    Mekong~ ~ ~ ~ ~ ~ | 160
    Indus ~ ~ ~ ~ ~ ~ | 100
    MacKenzie ~ ~ ~ ~ | 100
    Godavari~ ~ ~ ~ ~ | ~96
    La Plata~ ~ ~ ~ ~ | ~92
    Haiho ~ ~ ~ ~ ~ ~ | ~81
    Puran ~ ~ ~ ~ ~ ~ | ~80
    Zhu Jiang (Pearl) | ~69
    Copper~ ~ ~ ~ ~ ~ | ~70
    Danube~ ~ ~ ~ ~ ~ | ~67
    Choshui ~ ~ ~ ~ ~ | ~66
    Yukon ~ ~ ~ ~ ~ ~ | ~60

    Sub-Part [Ge6] ~ Sediment Transport to Oceans ~ Suspended Sediment Discharge from Continents ~

    Suspended Sediment Discharge from Continents (Table 3 of (83M2))
    Col.2 = Sediment Yield (tonnes/ km2/ year)
    Col.3 = Drainage Area (million km2)
    Col.4 = Sediment Discharge (millions of tonnes/ year)
    North America
    Region - - - - - - -| Col.2|Col.3|Col.4
    St. Lawrence~ ~ ~ ~ | ~ 4.0| 1.03| ~ 4.
    US Atlantic Coast ~ | ~17. | 0.74| ~13.
    Gulf Coast~ ~ ~ ~ ~ | ~59. | 4.50| 256.
    Colorado~ ~ ~ ~ ~ ~ | ~ 0.2| 0.63| ~ 0.1
    Columbia~ ~ ~ ~ ~ ~ | ~12. | 0.69| ~ 8.
    Rest of W. US ~ ~ ~ | 193. | 0.32| ~62.
    Canada West Coast ~ | ~91. | 0.67| ~61.
    S. Alaska(glacial)~ |1000. | 0.34| 340.
    S. Alaska(non-glac.)| ~76. | 1.37| 104.
    N. Alaska ~ ~ ~ ~ ~ | 120. | 0.35| ~42.
    MacKenzie ~ ~ ~ ~ ~ | ~55. | 1.81| 100.
    N. NE Canada~ ~ ~ ~ | ~ 8. | 3.73| ~30.
    Subtotals ~ ~ ~ ~ ~ | ~66. |15.42|1020.

    Central America
    Region ~ |Col.2 |Col.3|Col.4
    Mexico ~ | 140. | 1.50| 210.
    Remainder| 400. | 0.58| 323.
    Subtotals| 213. | 2.08| 442.

    South America
    Region - - - - - | Col.2|Col.3|Col.4
    Northwest~ ~ ~ ~ | 500. | 0.30| 150.
    Magdalena~ ~ ~ ~ | 900. | 0.24| 220.
    Northern ~ ~ ~ ~ | 150. | 7.79|1218.
    Eastern~ ~ ~ ~ ~ | ~ 9.4| 3.00| ~28.
    Southern ~ ~ ~ ~ | ~32. | 4.38| 154.
    Western and South| ~10. | 1.77| ~18.
    Subtotals~ ~ ~ ~ | 100. |17.90|1788.

    Europe
    Region - |Col.2|Col.3|Col.4
    Western~ | 12. | 2.60| ~31.
    Alpine ~ |120. | 0.55| ~66.
    Black Sea| 72. | 1.86| 133.
    Subtotals| 50. | 4.61| 230.

    Eurasian Arctic
    Region - - - -|Col.2|Col.3|Col.4
    West of 140o E| ~6. | 9.90| 59.
    East of 140o E| 20. | 1.27| 25.
    Subtotals ~ ~ | ~7.5|11.17| 84.

    Asia
    Region - - - - - - - |Col.2|Col.3|Col.4
    Northeast~ ~ ~ ~ ~ ~ | ~28.| 3.20| 100.
    NE China/ Korea~ ~ ~ | 658.| 1.00| 658.
    Yellow (Huangho) ~ ~ |1400.| 0.77|1080.
    Rest of China~ ~ ~ ~ | 250.| 3.72| 930.
    SE Asia and Himalayas| 796.| 3.93|3128.
    (exclusive of Indus) - -
    India~ ~ ~ ~ ~ ~ ~ ~ | 154.| 1.86| 286.
    Indus~ ~ ~ ~ ~ ~ ~ ~ | - - | - - | 100.
    Asia Minor ~ ~ ~ ~ ~ | ~50.| 1.35| ~67.
    Subtotals~ ~ ~ ~ ~ ~ | 376.|16.88|6349.

    Africa
    Region - - - - - - - - | Col.2|Col.3|Col.4
    Northwest~ ~ ~ ~ ~ ~ ~ | 100. | 1.10| ~110.
    West ~ ~ ~ ~ ~ ~ ~ ~ ~ | ~16.5| 6.86| ~113.
    Southwest~ ~ ~ ~ ~ ~ ~ | ~17. | 1.02| ~ 17.
    East ~ ~ ~ ~ ~ ~ ~ ~ ~ | ~80. | 3.00| ~240.
    Zambesi~ ~ ~ ~ ~ ~ ~ ~ | ~17. | 1.20| ~ 20.
    (Tana) ~ ~ ~ ~ ~ ~ ~ ~ |(1000)| - - | ~(30.)
    Nile ~ ~ ~ ~ ~ ~ ~ ~ ~ | ~ 0. | 2.16| ~ ~0.
    Subtotals~ ~ ~ ~ ~ ~ ~ | ~34.6|15.34| ~530.
    Australia (East, North)| ~28. | 2.20| ~ 62.
    Oceanic Islands~ ~ ~ ~ |1000. | 3.00| 3000.
    Totals ~ ~ ~ ~ ~ ~ ~ ~ | 116. |86.40|13505.

    Sub-Part [Ge7] ~ Sediment Yields of Rivers to Oceans ~

    Sediment Yields of Rivers to Oceans (Tables 6a and 6b of (68H1))
    (Drainage in millions of sq. mi.; area in millions of sq. miles/ million km2)
    (Measured and Extrapolated discharges are in millions of tons/ year.)
    (Specific discharges are in tons/ sq. mile)

    Continent |Measured|Total Area*| Discharge
    - - - - - |Drainage| to Oceans |Measured|Extrap.|Specific
    N. America| 2464.6 | 8.0/ 20.72| 604.0~ | 1960. | 245.
    S. America| 3820.4 | 7.5/ 19.43| 609.4~ | 1200. | 160.
    Africa~ ~ | 3146.7 | 7.7/ 19.99| 216.3~ | ~540. | ~70.
    Australia | ~414.6 | 2.0/ 5.18| ~47.4~ | ~230. | 115.
    Europe~ ~ | 1357.3 | 3.6/ 9.32| 121.9~ | ~320. | ~90.
    Asia~ ~ ~ | 4212.8 |10.4/ 26.94|6414.6~ |15910. |1530.
    TOTALS~ ~ |15416.5 |39.2/101.58|8013.5~ |20160. | 520.

    2.59 km2 = 1.0 mi2 * Ice-free area
    Not all rivers of the world were measured. Total drainage areas of measured rivers are shown in Col.2. By assuming specific discharges (Col. 7) on each continent are the same (on average) for both measured- and unmeasured rivers, one can extrapolate measured discharges (Col. 5) to total discharges (Col. 6) (that which would probably be measured if all rivers were measured).

    Comparison of Calculations of World Sediment Transport to Oceans by Milliman and Meade (83M2) and by Holeman (68H1) (See Table 4, (83M2))
    Area- - - - - -|Drainage Area ~ ~ |Sed. Yield | Sed. Disch.
    - - - - - - - -|million km2~ ~ ~ ~ ~ ~ |t/km2/ year| Gt. / year
    - - - - - - - -|(?)~ |(68H1|(83M2)|(68H1|(83M2|(68H1|(83M2)
    N. /C. America | 20.7| 20.5| 17.5 | 87. | ~84.| 1.78| 1.462
    S. America ~ ~ | 19.4| 19.2| 17.9 | 57. | ~97.| 1.09| 1.788
    Europe ~ ~ ~ ~ | ~9.3| ~9.2| ~4.6 | 32. | ~50.| ~.29| ~.230
    Eurasian Arctic| - - | - - | 11.2 | - - | ~ 8.| - - | ~.084
    Asia ~ ~ ~ ~ ~ | 26.9| 26.6| 16.9 |543. | 380.|14.48| 6.349
    Africa ~ ~ ~ ~ | 19.9| 19.7| 15.3 | 25. | ~35.| ~.49| ~.530
    Australia~ ~ ~ | ~5.2| ~5.1| ~2.2 | 41. | ~28.| ~.21| ~.062
    Large Pacif.Is.| - - |- - -| ~3.0 | - - |1000.| - - | 3.000
    Desert Areas*#*| - - |- - -| 11.4 | - - | ~ 0.| - - | - - -
    Totals ~ ~ ~ ~ |101.5|100.3|100.0 |183. | 150.|18.30|13.505

    *#* North Africa, Saudi Arabian peninsula and western Australia.

    Sub-Part [Ge8] ~ Suspended Sediments Reaching Waterways and Oceans ~

    Estimates of Global Rate of Soil Loss to Waterways and Oceans
    Reference (Year)|Denudation or Sediment Yield Equivalent*
    - - - - - - - - | (various ~ ~ | Gt./|tonnes/| Reference
    - - - - - - - - | ~units)~ ~ ~ |Year |km2/yr| ~ ~ ~ ~ ~ .
    Small-catchment data
    Fournier (1960) | - - - - - - -|58.~ |572. |68H1, 60F1(1)
    Kuenen (1950) ~ | - - - - - - -|32.5 |321. |68H1
    Gilluly(1955) ~ |12 km3 rock(2) |31.8 |314. |68H1
    Pechinov(1959)~ |0.090 mm/year |24.3 |239. |68H1
    Schumm(1963)~ ~ |0.076 mm/year |20.5 |202. |68H1, 63S1(3)
    Schumm(1963)~ ~ |0.152 mm/year |41.0 |404. |63S1(3)
    Sediment Delivery to Oceans + river bottoms:
    Brown/Wolf(1985)| - - - - - - -|37.3 |367. |85B3(4)
    Sediment Delivered to Oceans
    (neglects deposits in river bottoms and dam backwaters)
    Holeman(1968)~ ~ ~ ~ ~ | - - - -|18.4 |183. |68H1(5)
    Lopatin(1952)~ ~ ~ ~ ~ | - - - -|12.7 |125. |68H1
    Jansen/Painter(1974) ~ | - - - -|26.7 |263. |87W1
    Goldberg(1976) ~ ~ ~ ~ | - - - -|18.0 |177. |87W1
    USSR ##~ ~ ~ ~ ~ ~ ~ ~ | - - - -|15.7 |155. |87W1
    Milliman/Meade(1983) ~ | - - - -|13.5 |133. |87W1(7)
    M. Meybeck(1982) ~ ~ ~ | - - - -|17.5 |172. |82M1
    S. Postel(1989)~ ~ ~ ~ | - - - -|13.9 |137. |89P2(6)
    Judson(1968) ~ ~ ~ ~ ~ | - - - -|24.0 |236. |84B3
    Measurements useful for gaining perspective:
    Judson(1968) ~ ~ ~ ~ ~ | - - - -| 9.0 | 89. |84B3(ages past)
    Mackenzie/Garrels(1966)| - - - -| 8.3 | 82. |87W1(ages past)
    Whole-Earth Weathering Rate of Bed Rock:
    - Patric/Smith Ref.~ ~ | - - - -| 2.7 | 27. |75P1
    - Thomas Ref.___ ~ ~ ~ | - - - -| 2.1 | 21. |56T1
    - Garrels et al Ref.__ | - - - -| 5.9 | 58. |76G1
    ## USSR National Committee for IHD (1974)

    Adjusted to 39.2 million mi2 (101.5 million km2) contributing sediments to oceans.

  5. A refinement of Kuenen's 1950 estimate (68H1).
  6. Schumm data neglects bed load (about a 10% error) and spillage over the reservoirs (about 10% error). The first entry comes from catchments about 1500 mi2 in area; the second entry comes from catchments about 30 mi2 in area. All experiments were done in the US where erosion rates are typically significantly less than the global average.
  7. 25.4 billion tons of "excess" erosion + 15.7 billion tons of soil creation.
  8. Most data neglect bed load, so these figures should be increased by 5-10%. The same problem pertains to much of the other data in this table.
  9. Ref. (89P2) estimates an added 0.9 Gt. coarser bed load +3.6 Gt. dissolved material. Based on estimate by D. E. Walling, 1987 (87W1).
  10. Ref. (87W1) estimates an additional 0.9-1.8 Gt. of bed load + flood-discharges.
  11. Two methods have been used above to estimate the mass of river sediments entering the oceans:

  12. Estimate the mass being carried ocean-ward by rivers by measuring sediment loads where rivers enter the ocean (Kuenen, 1950); (Lopatin, 1950); (Holeman, 1968);
  13. Estimate denudation of the continents using small-catchment data (Gilluly, 1955); (Fournier, 1960); (Schumm, 1963).
  14. Sediment loads based on Method (2) significantly exceed those of Method (1) because they include large amounts of sediment that never reach the ocean (83M2). For example, gross erosion within the Potomac River Basin is over 50 million tons/ year, yet only 2.5 million tons/ year are discharged into the Potomac River estuary (68H1). Comments: Fournier (60F1) measured sediment-accumulation in numerous small catchments about the globe. A global soil-erosion rate value of 58 Gt./ year was obtained (68H1). Other workers used data from larger catchments and obtained smaller estimates of erosion, e.g. Schumm (63S1) estimated 41 Gt./ year based on data from 30-mi2 US catchments, and 20.5 Gt./ year based on data from 1500-mi2 US catchments. Extrapolating these data back to small (1 sq. mile) basins would give a gross soil loss of about 61 Gt./ year. Both Fournier and Schumm neglected topsoil losses to urbanization, salinization, and wind erosion, none of which are insignificant relative to water-erosion.

    More recent estimates by Brown and Wolf (85B3), (84B2) divided an estimate (reviewed in (68H1) and (87W1) of the rate of sediment delivery to oceans by an estimated global-average sediment-delivery ratio (0.25). They also claimed to account for sediment storage in dam backwaters. They estimated the gross global rate of soil erosion to be 37.3 Gt./ year. The method has some inadequacies:

  15. Values for rates of sediment delivery to oceans suffer from errors (83M2) which produce significant under-estimation: (1) sampling of sediment concentrations well below the water surface is inadequate; (2) rivers are rarely studied during flood-stage when sediment yields are much greater; (3) rivers in less-developed countries (where erosion rates are larger) are less well studied; (4) bed loads (typically 5-10% of total sediment load for large rivers and more for smaller rivers) are often neglected, (5) sediment loads in small rivers are often estimated from measurements on larger rivers which typically have much smaller sediment loads per unit area of drainage basin.
  16. Their estimate (unpublished) of sediment-entrapment rate in backwaters of the world's dams appears much too low;
  17. A large body of information on the dependence of sediment-delivery ratio on watershed area is not used;
  18. Losses to urbanization, salinization and wind erosion are neglected,
  19. Topsoil erosion is not distinguished from sub-soil erosion.
  20. (End of Comments)

    Sediment transport to oceans is often under-estimated because of:

  21. Inadequate sediment sampling with depth;
  22. Rivers are poorly studied in flood-stage when sediment yields are far larger
  23. Rivers in less-developed countries are less-well studied;
  24. Sediment loads in small rivers are under-estimated because sediment yields decrease about 7-fold for each 10-fold increase in drainage basin area;
  25. Bed load is often not considered (83M2).

More than 40% of the world's particulate load is carried by highly turbid waters (Cs>1.5 g/l) (2.3% of the water discharge). These rivers are found in arid and semi-arid zones (Indus, Orange, Rio Grande, Colorado, Huang Ho) (p. 421 of (82M1)). Comments: Arid and semi-arid zones contain mainly grazing land, not cropland.

Sediment-Transport Data for Rivers with Largest Sediment Loads (Drainage area (Col. 2) is in units of 1000 km2.)
River - - - - - - - - - | - |Transport|
- - - - - - - - - - - - |Area|Gt./year| References
Huang He (Yellow)(China)| 668| ~1.200 | 89B2
Huang He (Yellow)(China)| 668| >1.000 | 89P2
Huang He (Yellow)(China)| 668| ~1.600 | 84B2, 84B3
Huang Ho (China)~ ~ ~ ~ |? ? | ~1.900 | 70P1, p.27
Ganges- -(India)~ ~ ~ ~ |1100| ~1.455 | 84B2, 84B3
Amazon- -(Brazil) ~ ~ ~ |? ? | ~0.363 | 84B2, 84B3
Mississippi (US)~ ~ ~ ~ |? ? | ~0.300 | 84B2, 84B3
Irrawaddy (Burma) ~ ~ ~ |? ? | ~0.299 | 84B2, 84B3
Kosi (India)~ ~ ~ ~ ~ ~ |? ? | ~0.172 | 84B2, 84B3
Mekong (Thailand) ~ ~ ~ |? ? | ~0.170 | 84B2, 84B3
Nile (Egypt)~ ~ ~ ~ ~ ~ |? ? | ~0.111 | 84B2, 84B3

Sediment Load Transported to the Sea by Major Rivers, early 1980s (87W1), (89P2)
(Drainage Area (Col. 2) is in units of 1000 km2.)
(Suspended Load (Col. 3) is in units of million tons/ year.)
River System (Region) - - - |Area|Load
Ganges-Brahmaputra (S.Asia) |1480|3000
Huang He (Yellow) ~ ~ ~ ~ ~ | 770|1080
Amazon- -(South America)~ ~ |6150| 900
Chang Jiang (Yangtze)(China)|1940| 478
Irrawaddy- -(Burma) ~ ~ ~ ~ | 430| 265
Magdalena -(Colombia) ~ ~ ~ | 240| 220
Mississippi -(US) ~ ~ ~ ~ ~ |3270| 210
Orinoco ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ | 990| 210

Sediment Yields of Selected Rivers of the World (Ref. 3 of (81R1))
Col.3 = Total drainage area (1000 km2)
Col.4 = Ave. Annual Suspended Sediment load (million tonnes)
Col.5 = Ave. Annual Suspended Sediment load (tonnes/ km2)
Col.6 = Ave. Discharge at the River's Mouth (m3/ sec.)
River - - -|Country |Col.3|Col.4 |Col.5 |Col.6*
Yellow ~ ~ |China ~ | ~680|1890~ | 2800 |* 1500
Yangtze~ ~ |China ~ | 1950| 449~ | ~256 | 21900
Amazon ~ ~ |Brazil~ | 5800| 363~ | ~ 63 |182000
Mississippi|USA ~ ~ | 3230| 312~ | ~ 97 | 17900
Missouri ~ |USA ~ ~ | 1380| 218~ | ~160 | ~1960
MeKong ~ ~ |Thailand| ~800| 170~ | ~210 | 11100
Nile ~ ~ ~ |Egypt ~ | 2990| 111~ | ~ 37 | ~2840
Danube ~ ~ |USSR~ ~ | ~820| ~19.4| ~ 24 | ~6190
Po ~ ~ ~ ~ |Italy ~ | ~ 55| ~15.2| ~280 | ~1450
* (m3/ sec.) x 0.03156 = km3/ year

Rivers between Korea and Pakistan carry over 6.4 Gt./ year of sediment to oceans, vs. under 0.3 Gt./ year for rest of Asia (83M2).

Sub-Part [Ge9] ~ Sediment Transport to Oceans ~ Yellow River (China) ~
Sediment load = 37 kg/ m3 at its delta (81H1). Sediment yields of the Huanghe (Yellow River) average 1395 tonnes/km2/ year over the whole drainage area, but may reach 50,000 tonnes/ km2/ year in the Loes Plateau (Zhang et al in (92H1)). The Huanghe transports 1.1 Gt./ year of suspended sediment, corresponding to a mean water discharge of 41 km3/ year to the sea. The river is 5500 km. long, with a total drainage basin area of 0.75 million km2 (92H1). Loess is the main sediment source of the Huanghe (92H1). The Huanghe is characterized by relatively low trace metal concentrations, relative to rivers draining industrialized regions (92H1). Only 50% of the loess-covered area suffers severe erosion (over 5000 tonnes/km2/ year) (92H1). More than 90% of Huanghe sediments is deposited in the lower part of the river course and modern delta. Suspended sediments entering the Huanghai (Yellow Sea) via Bohai Strait are 5 million tonnes/ year (Zhang, 1988, in 92H1). Observations over 40 years indicate sediment load from 0.24-2.1 Gt./ year (92H1).

Sub-Part [Ge10] ~ Sediment Transport to Oceans ~ Peruvian Rivers ~
Peru's rivers on a narrow coastal strip carry off 0.623 km3 (1.22 Gt./ year) of sediment (85T1). Comments: Hard to believe: all the world's rivers carry only 18 Gt./ year (see table above).

Sub-Part [Ge11] ~ Sediment Transport to Oceans ~ Great Lakes ~
Some 25-30 million tonnes/ year of sediment have been deposited in the Great Lakes since 1850 (Kemp et al, 1976, 1977, 1978). 10-15 million of this is derived from rivers. Most of the remainder is derived from erosion of shore-line bluffs. St. Lawrence River sediment discharge: 1.3 million tonnes/ year (90M1).

Sub-Part [Ge12] ~ Sediment Transport to Oceans ~ Southeastern US ~
Five rivers in GA, SC and NC draining into the Atlantic Ocean carry 3 million tonnes/ year of sediment (Trimble, 1974, in (90M1)).

Sub-Part [Ge13] ~ Sediment Transport to Oceans ~ Sediments Deposited at River Mouths ~
Baltimore's harbor has moved downstream over 6 miles in 200 years ((74C1), p. 22). Comments: See the Antiquities portion of this document for a lot more data of this type.

Part [Gf] ~ Dissolved-solids transport to Oceans ~

The average of six estimates of total dissolved load transport from rivers to oceans from a review by Walling (87W1) is 3.6 Gt./ year. According to Meybeck (1979 in (87W1)), 65% of the dissolved load represents products of chemical denudation of land. The remaining 35% represents atmospheric inputs in precipitation and uptake of atmospheric CO2 in weathering reactions (87W1). This indicates that the rate of dissolved-solids transfer from land to oceans of 2.3 Gt./ year. Comments: An implicit assumption here is that none of the organic-chemical denudation of land is mineralized (converted to CO2) on its way to the oceans.

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SECTION (4-H) ~ Grazing Land Erosion ~

Data presented in (55F1) and in a non-referenced source cited in (55F1) indicates that soil loss (tonnes/ km2/ year) from rangeland is about 0.1 times that from cropland, other conditions being equal. Comments: Since this data is clearly in conflict with river sediments data, this data should probably be taken as an estimate of sheet- and rill erosion on rangeland. (The bulk of rangeland erosion occurs by gully erosion and, in particular, stream-bank erosion.)

In a study of soil erosion from pasture and range, percent bare ground explained 82% of the soil loss (91H2). (Another effect: height of vegetation). Comments: Overgrazing pressure is clearly the dominant influence of soil erosion from pastures and rangeland.

More than 40% of the world's particulate load is carried by highly turbid waters (sediment concentrations in excess of 1.5 grams/ liter) (2.3% of the water discharged to oceans). These rivers are found in arid and semi-arid zones (Indus, Orange, Rio Grande, Colorado, Huang Ho) (p. 421 of (82M1)).

Status of Global Dry-land# Degradation as of 1983-84 (89P2)
(Col.2 = Area at least moderately degraded (million km2))
(Col.3 = Total global area of that land category (million km2))
(Col.4 = Area deteriorating to zero net economic return (million km2/ year))
Land Category - - |Col.2|Col.3| Col.4
Rangeland ~ ~ ~ ~ |31.0 |36.90| 0.177(0.48%/year)
Rainfed Cropland~ | 3.35| 5.68| 0.020(0.35%/year)
Irrigated Cropland| 0.40| 1.29| 0.006(0.47%/year)
Totals~ ~ ~ ~ ~ ~ |34.75|43.87| 0.203(0.46%/year)

#arid, semi-arid, sub-humid climatic zones
Comments:
Arid lands tend to be more fragile than moister lands. Over-grazing is more widespread than soil erosion. (Most rangeland is arid land and is overgrazed; flat cropland usually shows negligible erosion.). Rangeland economics may be inherently more marginal than cropland economics. So conclusions comparing rangeland erosion to cropland erosion are hard to draw.

Runoff characteristics of sagebrush rangeland are described and related to runoff predictions by SWRRB (Simulator for Water Resources in Rural Basins) in (91W1). A study of the relative role of factors influencing soil erosion loss from pastures and rangeland is given in (91H2).

Severe water erosion has permanently damaged much grazing land along the Kenya-Uganda border where the Karamojong, Turkana and Samburu people live (Refs 1 and 33 of (90D1)).

Nearly 50% of Zimbabwean "communal" grazing areas were rated as "bare" to "very overgrazed" (Ref. 2 of (92T1)). Already-degraded rangeland in Zimbabwe loses up to 9100 tonnes/ km2/ year (FAO study) (90C1). The same pattern prevails throughout sub-Saharan Africa (90C1).

Grazing land in Baluchistan (in Pakistan) suffered almost universal soil erosion in the early 1940s, and worsened thereafter. It also seems certain that erosion has reduced permanent soil productivity nearly everywhere on the sloping grazing lands of the Northwest Frontier and Punjab provinces (Ref. 25 of (92D1)). Overgrazing has led to extensive runoff and subsequent erosion over a large part of arid S.W. Asia, (Pakistan in the east to Syria and Israel in the west) (92D1).

Evidence that grazing land Erosion is greater than Cropland Erosion (Table 3 of (64J1)). Suspended load data are in units of tons/ mi2/ year
Colorado R. ~ | 1082| Missouri R. ~ ~ ~ ~ | 454
Yellowstone R.| ~455| San Juan R. ~ ~ ~ ~ | 445
Brazos R. ~ ~ | 1000| Rio Grande R. ~ ~ ~ | 352
Pecos R.~ ~ ~ | ~685| (Table 2,Ref. 68H1.)|
(Compare these numbers to US average: 245 tons/ mi2/ year.)

SECTION (4-I) ~ Deforestation-Caused Erosion ~ [I1]~General, [I2]~Italy, [I3]~US, [I4]~Southeast Asia, [I5]~Africa, [I6]~Asian Sub-Continent, [I7]~USSR,

Part [I1] ~ Deforestation-Caused Erosion ~ General ~

Two main environmental concerns for the future:

Clear-cutting on steep, but stable, slopes may cause a 10-fold increase in annual sediment yield, but yields return to pre-logging conditions within a few years (Ref. 25 of (78C2)). Comments: Erosion yields on forested lands are so low (when not being logged) that a 10-fold increase is still an insignificant erosion rate.

Deforestation was the major and direct cause of accelerated erosion in the eastern Mediterranean area thousands of years ago (Ref. 33 of (92D1)) and in hills and mountains of China, India, Nepal, Soviet Union and other countries of Asia more recently (Ref. 59 of (92D1)).

Part [I2] ~ Deforestation-Caused Erosion ~ Europe ~
Lombardi, studying the silting of lagoons near Venice in 1840, deduced that the Po River sediment transport was 2.5 times higher since 1600 than in the previous 200 years. He attributed the increased sedimentation to deforestation in the mountain headwaters of the Po River (78C2).

Part [I3] ~ Deforestation-Caused Erosion ~ United States ~

Sub-Part [I3a] ~ Deforestation-Caused Erosion ~ United States ~ California 
In California's North Coastal Region (where logging is the predominant activity), sheet/gully erosion accounts for 19% of total erosion; landslides account for 24%; stream-bank erosion accounts for 57% (Ref. 12 of (78C2)).

Suspended Sediment Yields in North Coastal Basins of California (78C2) (Yields are in tons/ sq. mile/ year and (tonnes/ km2/ year)) (Drainage Areas are in units of mi2 and km2.)
Area - - - - - - - - - - - - - - - -|Drainage~ |Yield
Eel River at Scotia (1958-1964) ~ ~ |3113(8059)| 4330(1520)
Eel River at Scotia (1958-1967) ~ ~ |3113(8059)|10080(3540)
Eel River at Scotia (1971-1973) ~ ~ |3113(8059)| 4400(1540)
Vanduzen R. near Bridgeville(1958-67| 216( 559)| 7208(2530)
Mad River near Arcata (1958-1970) ~ | 485(1256)| 4600(1615)
Redwood Creek at Orich (1971-1973)~ | 278( 720)| 8100(2840)
(These yields are attributed to conversion of forest to grassland, over-grazing, road building on unstable (volcanic) terrain, and poor logging practices.)

[I4] ~ Deforestation-Caused Erosion ~ Southeast Asia ~

Sub-Part [I4a] ~ Deforestation-Caused Erosion ~ Southeast Asia ~ Indonesia ~
In Java and Bali, 400,000 km2 are badly eroded as a result of deforestation (84G1).

In Sarawak, soil loss from logged areas was over 10,000 tons/ km2/ year, vs. about 10 ton/ km2/ year from primary forest (96G3).

Sub-Part [I4b] ~ Deforestation-Caused Erosion ~ Southeast Asia ~ Philippines ~
Deforestation is blamed for landslides that killed 7000 people in Ormoc Province (Philippines) and clogged 2 of 3 turbines with silt in a dam 30 miles from Valencia (93B2).

Sub-Part [I4c] ~ Deforestation-Caused Erosion ~ Southeast Asia ~ Thailand ~
Estimated (USLE) erosion rates run as high as 100,000 tonnes/ km2/ year on steep deforested land where intensive subsistence agriculture is practiced in Thailand. Deforestation and erosion both appear to be even worse in the Karat Plateau of Northeastern Thailand (Ref. 17 of (92D1)).

Part [I5] ~ Deforestation-Caused Erosion ~ Africa ~
On deforested eastern rain forests of Madagascar, soil erosion rates as high as 25,000 tonnes/ km2/ year have been reported (Ref. 33 of (90G1)).

Part [I6] ~ Deforestation-Caused Erosion ~ Asian Sub-Continent ~
Nepal may have the most acute erosion, caused mainly by deforestation (92D1).

Part [I7] ~ Deforestation-Caused Erosion ~ USSR (former) ~
In the Caucasus (USSR), gullying and mudflows are common where tree cutting has occurred on slopes greater than 30% (92D1).

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