Estimating Reservoir Capacity Loss From Sedimentation David C. - - PowerPoint PPT Presentation

Estimating Reservoir Capacity Loss From Sedimentation

David C. Froehlich, Pramod Narayan, and M anoj Kumar

Dam Rehabilitation and Improvement Project (DRIP)

Estimating Sedimentation – Three Approaches

• From sediment discharge rating curves

combined with flow-duration relations.

• From calculations of the total amount of

land surface erosion, the ability of the sediment to be transported to the reservoir, and the reservoir trapping efficiency.

• From predictions based on sedimentation in

existing reservoirs in which the accumulated deposits have been surveyed

• ver a sufficiently long period.

General Form of Capacity Loss M odel

1 2 3 4 5 3 2 2 3

ˆ ln ln ln ln ln where ˆ expected reservoir capacity loss (Mm ) reservoir catchment area (km ) reservoir surface area (km ) initial reservoir storage capacity (Mm ) time s

c r

• c

r

• Y

A A C T Y A A C T                ince initial filling of reservoir (years) model parameters

i

 

0.10 0.05 0.8 0.9 0.15 0.30 0.50 0.65

0.0064 ; eastward flowing rivers ˆ 0.030 ; westward flowing rivers

c r

• c

r

• A

A C T Y A A C T      

2 ln ln

0.930 0.601

east east

Y Y

r s  

2 ln ln

0.881 0.492

west west

Y Y

r s  

Reservoir Half-life T50% (years)

 

 

5 4 3 2

1 1 50% 1

0.5 exp

c r

• T

A A C

   



  

        

   

1.11 0.15 0.1 0.3 50% 1.54 0.15 0.3 0.5

78.0 ; eastward flowing rivers (years) 16.6 ; westward flowing rivers

c r

• c

r

• A

A C T A A C

   

     

100 x (1-α)% Prediction Interval

     

1 2 2 , ln ln 1 2 3 4 5

two-tailed Student's t-distributio ˆ ln 1 130 (eastward), 90 (westward) 5 , , , , 1,ln ,ln , n ,ln n l

n p Y Y c r

• Y

t s t n p A A C T



    

 

               f F F f f

 

1 ln

0.53544 0.01893 0.02723 0.01289 0.11471 0.01893 0.00406 0.00194 0.00135 0.00102 0.02723 0.00194 0.01194 0.00777 0.00253 0.01289 0.00135 0.00777 0.00832 0.00080 0.11471 0.00102 0.00253 0.00080 0.030

east

Y 

                F F 75                

 

1 ln

0.71542 0.04684 0.05769 0.02803 0.13602 0.04684 0.01149 0.01089 0.00054 0.00148 0.05769 0.01089 0.05549 0.03532 0.00830 0.02803 0.00054 0.03532 0.03160 0.00854 0.13602 0.00148 0.00830 0.00854 0.043

west

Y 

                F F 25                

Eastward flowing rivers Westward flowing rivers

Upper 95% prediction limit Lower 95% prediction limit

Upper 95% prediction limit Lower 95% prediction limit

Summary and Conclusions

0.10 0.05 0.8 0.9 0.15 0.30 0.50 0.65

0.0064 ; eastward ˆ 0.030 ; westward

c r

• c

r

• A

A C T Y A A C T      

   

1.11 0.15 0.1 0.3 50% 1.54 0.15 0.3 0.5

78.0 ; eastward 16.6 ; westward

c r

• c

r

• A

A C T A A C

   

     

 

1 2 2 , ln ln

ˆ ln 1

n p Y Y

Y t s

  

          f F F f