- Asked 2/30
- 2069 Chaitra · 4 marks
Impounded reservoir, 6202 million L per month
Short answer
Monthly inflows are converted to volumes. The analytical mass curve method finds the largest cumulative deficit of 20.40×10^6 m³ at the end of July. Required reservoir capacity ≈ 20.40 million m³ (20,405 ML).
The city has an average water demand of 6202 million liters per month. Calculate the capacity of the impounded reservoir. The flow in the river is shown below.
| Month | Inflow (m/s) |
|---|---|
| January | 2.97 |
| February | 1.99 |
| March | 1.00 |
| April | 0.00 |
| May | 0.51 |
| June | 1.00 |
| July | 2.00 |
| August | 3.00 |
| September | 4.00 |
| October | 5.00 |
| November | 4.00 |
| December | 2.80 |
Convert the monthly flows to volumes () and apply the mass curve (analytical) method. Demand per month (1 ML = 1000 m).
Monthly inflow volumes
| Month | Days | Inflow (m3/s) | Volume (Mm3) |
|---|---|---|---|
| Jan | 31 | 2.97 | 7.955 |
| Feb | 28 | 1.99 | 4.814 |
| Mar | 31 | 1.00 | 2.678 |
| Apr | 30 | 0.00 | 0.000 |
| May | 31 | 0.51 | 1.366 |
| Jun | 30 | 1.00 | 2.592 |
| Jul | 31 | 2.00 | 5.357 |
| Aug | 31 | 3.00 | 8.035 |
| Sep | 30 | 4.00 | 10.368 |
| Oct | 31 | 5.00 | 13.392 |
| Nov | 30 | 4.00 | 10.368 |
| Dec | 31 | 2.80 | 7.500 |
Total inflow Mm; total demand Mm. The two are equal, so the reservoir must carry the whole yearly regulation.
Cumulative deficit (reservoir full at the start of the deficit period)
| Month | Inflow (Mm3) | Demand (Mm3) | Surplus/deficit | Cumulative deficit |
|---|---|---|---|---|
| Feb | 4.814 | 6.202 | -1.388 | -1.388 |
| Mar | 2.678 | 6.202 | -3.524 | -4.911 |
| Apr | 0.000 | 6.202 | -6.202 | -11.113 |
| May | 1.366 | 6.202 | -4.836 | -15.949 |
| Jun | 2.592 | 6.202 | -3.610 | -19.559 |
| Jul | 5.357 | 6.202 | -0.845 | -20.405 |
The inflow is below the demand from Feb to Jul; the cumulative deficit is largest at the end of Jul.
Answer: Capacity of the impounded reservoir = 20.40 million m ( ML).
✓ Answer checked by Claude Opus 5.5 (high effort)
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