- Asked 2/30
- 2068 Baisakh (old course) · 8 marks
Balancing reservoir: town 1.2 million, 45 L/head
Short answer
Balancing capacity is 18,360 m³ (surplus 8,910 m³ plus deficit 9,450 m³ from two-shift pumping at 6,750 m³/h). Adding 1% fire storage (540 m³) gives total reservoir capacity of 18,900 m³.
A newly established town with a population of 1.2 million is to be supplied with water daily at 45 liters per capita. Water have to be stored also for fire demand keeping at least 1% of total demand. The variation in demand is as follows:
| Time | Consumption % |
|---|---|
| 05.00 - 07.00 | 25 |
| 07.00 - 12.00 | 35 |
| 12.00 - 17.00 | 20 |
| 17.00 - 19.00 | 20 |
| 19.00 - 05.00 | 0 |
Determine analytically the balancing reservoir capacity assuming pumping to be done at an uniform rate and the period of pumping is 5.00 A.M. to 10.00 A.M. and 5.00 P.M. to 8.00 P.M. in two shifts.
Given data
- Population 1,200,000 × 45 lpcd = 54,000 m³/day
- Pumping in two shifts, 5–10 h and 17–20 h (8 h in all), at a rate 54,000/8 = 6,750 m³/h
- Fire storage = 1% of the total daily demand
Mass-curve table (analytical method)
Inflow: 6,750 m³/h during 5–10 h and 17–20 h. Time is counted from the start of the first demand period; a positive cumulative value means surplus in the tank.
| Time | Demand (m³) | Inflow (m³) | Inflow − demand | Cumulative |
|---|---|---|---|---|
| 05:00–07:00 | 13500.00 | 13500.00 | +0.00 | +0.00 |
| 07:00–10:00 | 11340.00 | 20250.00 | +8910.00 | +8910.00 |
| 10:00–12:00 | 7560.00 | 0.00 | -7560.00 | +1350.00 |
| 12:00–17:00 | 10800.00 | 0.00 | -10800.00 | -9450.00 |
| 17:00–19:00 | 10800.00 | 13500.00 | +2700.00 | -6750.00 |
| 19:00–20:00 | 0.00 | 6750.00 | +6750.00 | +0.00 |
| 20:00–05:00 | 0.00 | 0.00 | +0.00 | +0.00 |
Total demand = 54000.00 m³; total inflow = 54000.00 m³.
Capacity
- Maximum cumulative surplus = 8910.00 m³
- Maximum cumulative deficit = 9450.00 m³
- Balancing capacity = max. surplus + max. deficit = 8910.00 + 9450.00 = 18360.00 m³
- Fire storage = 1% of daily demand = 0.01 × 54000 = 540.00 m³
- Total capacity = 18360.00 + 540.00 = 18900.00 m³
Answer: Balancing capacity 18,360 m³ + fire storage 540 m³ = 18,900 m³ total.
✓ Answer checked by Claude Opus 5.5 (high effort)
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