Question

A reservoir has a capacity of 3 x 106 m3 and a drainage area of 249 km2. The annual inflow is equivalent to 250 mm of runoff from the given drainage area, and annual sediment production is equivalent to a weight of 10.08 x 106 N/km2 of drainage area. The sediment has an average specific weight of 14689 N/m². Assume dead storage as 11% of initial reservoir capacity and an average value of trap efficiency 82%. Determine the number of years it will take for dead storage to be filled with sediment. Answer:

Answer 1

To determine the number of years it will take for dead storage to be filled with sediment, we can follow these steps:

1. Calculate the sediment yield from the drainage area:

Sediment yield (SY) = Sediment production * Drainage area

2. Calculate the annual sediment deposition in the reservoir:

Sediment deposition = Sediment yield * Trap efficiency

3. Calculate the net sediment deposition in the reservoir:

Net sediment deposition = Sediment deposition - Inflow sediment

4. Calculate the volume of sediment needed to fill the dead storage:

Volume of sediment = Dead storage capacity

5. Calculate the number of years it will take for dead storage to be filled:

Number of years = Volume of sediment / Net sediment deposition

Given:

- Dead storage capacity = 11% of initial reservoir capacity

- Trap efficiency = 82%

- Sediment production = 10.08 x 10^6 N/km²

- Drainage area = 249 km²

- Inflow sediment = Annual inflow * Sediment production

First, convert all units to consistent units (e.g., m³, m²) and then perform the calculations using the steps above.

Remember to convert the units consistently throughout the calculations. Once you perform the calculations, you'll have the number of years it will take for the dead storage to be filled with sediment.