Dams Filling |
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Morrocco Dams Data of Mud Filling |
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Area of catchment |
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Started in 60 - 80' dams checked 1991 |
< 1000km2 |
1000 - 2000 km2 |
2500 - 5000 km2 |
5000 - 15000 km2 |
>25000 km2 |
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Average year of start of operation |
1973 |
1976 |
1972 |
1966 |
1973 |
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Average area of catchment (km2) |
355 |
1567 |
4051 |
10400 |
39210 |
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Average original capacity (millions of m3) |
33 |
330 |
545 |
862 |
1725 |
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Average year input (millions of m3) |
78 |
355 |
316 |
799 |
1960 |
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Average regularized capacity (millions of m3) |
24 |
189 |
348 |
490 |
1085 |
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year average mud filling (millions tons/year) |
0.77 |
1.49 |
2.7 |
4.3 |
10.5 |
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year average degradation (ton/km2.year) |
2900 |
878 |
695 |
450 |
280 |
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average concentration (g/l) |
9 |
4 |
13 |
7 |
8 |
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Average mud filling end of june 1991 |
6 |
21 |
33 |
62 |
170 |
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Average period of mud filling |
15 |
23 |
25 |
17 |
17 |
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Average proportion of lost capacity |
0.25 |
0.10 |
0.08 |
0.07 |
0.19 |
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Average area dominated |
3210 |
23343 |
35065 |
63385 |
95700 |
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Average height on foundations type (m) |
39 |
83 |
78 |
101 |
73 |
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produced energy (GW/ year) |
|
41 |
50 |
260 |
163 |
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Correction to mud filling of dam |
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Multiple factor Model of Land mudfilling Degradation North Africa |
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over elevation |
affluent regulation |
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Any lithologic type (n=38) |
Degradation = 10 |
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forestation |
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|
|
High erosion (n=15) |
Degradation = 10 |
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Some major historic dams in Africa |
(n=17) |
Degradation = 10 |
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lake/ river |
km2 |
year |
years for filling |
deep (m) |
(m) |
year rate of renewal |
North Africa: all |
Degradation = 10 |
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Kariba (Zambeze) |
5300 |
1959 |
4.5 |
125 |
14 |
1/9 |
North Africa: marns, schistes, silts, shales, flysch |
Degradation = 10 |
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Volta (Volta) |
8300 |
1964 |
5 |
74 |
3 |
1/4 |
North Africa: chalk, limestone, shales-limestones |
Degradation = 10 |
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Nasser (Nil) |
6216 |
1964 |
10 |
130 |
20 |
1/2 |
North Africa: quartz, granit, sandstone |
Degradation = 10 |
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Kainji 5Niger) |
1270 |
1968 |
0.25 |
60 |
10 |
4/1 |
Degradation (ton/km2.year); Area (km2); year water Layer run off (mm/year) |
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Cahora Bassa |
2739 |
1974 |
0.33 |
151 |
38 |
1/1 |
|
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Proposal of cure for semi desertic river dam 350 mm rainfall / year (780km2 catchment area) |
Dam classification |
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|
cost/year (US$2009) |
life period |
regularized volume (m3) |
cost of regularized volume |
category |
high (m) |
volume (hm3) |
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minimum maintaining |
80200 |
15 |
30 |
0.31 |
small |
< 15 |
0.05 - 1.0 |
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protection+ trails for plantation + 13% forestation of catchment area |
98500 |
30 |
35 |
0.27 |
intermediate |
|
1.01 - 50 |
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+ 26% forestation of catchment area |
105250 |
35 |
40 |
0.25 |
Big |
> 30 |
> 50 |
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+ 39% forestation of catchment area |
113750 |
40 |
45 |
0.24 |
|
|
|
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basic + 39% forestation of catchment area + steps / afluents |
134015 |
50 |
55 |
0.22 |
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Sector threats to freshwater environments. |
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Sector |
Measure of threat |
Impacts (Add to each, biodiversity loss) |
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Agriculture |
11% of land in crops, 26% in pasture. 3/4 of human water withdrawals, 250 million hectares under irrigation. |
Runoff of toxic pesticides (fish kills); fertilisers and manure (eutrophication); soil (turbidity and siltation). Overgrazing (loss plant cover, bank stability). |
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Deforestation
|
50% of world’s forests lost; widespread clearcut instead of selective harvesting. |
Soil erosion (turbidity and sedimentation. Rapid runoff. Loss stream food/habitat (leaves, wood, insects). Changed hydrological cycles. |
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Dams |
60% world’s river flow regulated. 15% world’s precipitation held in 500,000 km2 of reservoirs. Blocking of movement of localand long-distance migrations in neighbour-hood of dam. |
Fish migrations blocked; stocks lost. Seasonal flows changed; flows reduced. 25 million km river habitat modified. Flood plains & deltas lost. Lowered fish production. Sediment/turbidity/nutrient changes. Running to still water. |
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Industry and urban areas |
Release toxic substances, hormone blockers, untreated sewage. 1/4 of human water withdrawals. |
Fish kills and advisories. Impaired reproduction. Eutrophication. Reduced flows. |
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Aquaculture and introductions |
Escape of alien species. Pollution. |
Competition with and loss of native biota. Spread alien pests and diseases. Loss of native habitats. Genetic pollution. Eutrophication. |
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Channelisation and levee construction |
Simplification of river structure. 500,000 km of river altered for shipping. |
Loss of habitats, flood plains and wetlands. |
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Fishing |
Over-harvesting. Gear damage. |
Reduced populations, loss of stocks, changed food webs, and habitat loss. |
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Acid rain |
Reduction of pH (increase in acidity) of lakes and streams down to 4.5 or lower in thousands of water bodies in North America and Europe. |
Reduction of populations or extirpation of species of molluscs, amphibians, fishes, |
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Human popu-lation and |
Doubled to 6 billion since 1975. |
Population/consumption rate increases magnify each sector impact above. Humans use 54% of geographically & temporally accessible water. |
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