- 2076 Asoj · 8 marks
Rural area 22000 L/day river supply (question text cut)
Short answer
Daily demand 22 m3, river yield 21.6 m3/day (slight deficit). Assuming inflow = yield, peak rates exceed inflow. Balancing capacity by mass curve = 9.4 m3 (adopt 10 m3).
A rural area has designed year demand of water 22000 liters per day. The demand is met by a continuous system of supply from a river source with measured safe yield of 0.25 lps. The consumption pattern is as follows:
| Time (Hour) | 5-7 | 7-12 | 12-17 | 17-19 | 19-5 |
|---|---|---|---|---|---|
| Consumption (%) | 25 | 35 | 20 | 20 | 0 |
[The printed paper states no explicit question after the data; the capacity of the balancing tank is to be determined.]
Given data
- Daily demand = 22,000 L = 22 m³/day
- River safe yield = 0.25 lps = 21.6 m³/day = 0.9 m³/h
- Demand: 5–7 h 25%, 7–12 h 35%, 12–17 h 20%, 17–19 h 20%, 19–5 h 0%
Check of source and need of storage
The printed paper gives no explicit question, so the capacity of the balancing tank is found. The safe yield (21.6 m³/day) is slightly less than the demand (22 m³/day), a deficit of 0.4 m³/day (1.8%), which a tank cannot remove (it needs a small extra supply or demand control). The demand rates in 5–7 h and 7–12 h (2.75 and 1.54 m³/h) exceed the inflow of 0.9 m³/h, so the tank is necessary.
Mass-curve table (analytical method)
Inflow: 0.9 m³/h (safe yield). 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 | 5.50 | 1.80 | -3.70 | -3.70 |
| 07:00–12:00 | 7.70 | 4.50 | -3.20 | -6.90 |
| 12:00–17:00 | 4.40 | 4.50 | +0.10 | -6.80 |
| 17:00–19:00 | 4.40 | 1.80 | -2.60 | -9.40 |
| 19:00–05:00 | 0.00 | 9.00 | +9.00 | -0.40 |
Total demand = 22.00 m³; total inflow = 21.60 m³.
Capacity
- Maximum cumulative surplus = 0.00 m³
- Maximum cumulative deficit = 9.40 m³
- Balancing capacity = max. surplus + max. deficit = 0.00 + 9.40 = 9.40 m³
- Here the daily inflow (21.60 m³) is 0.40 m³ less than the demand, so nothing overflows; the cumulative ends at −0.40 m³, and without the extra 0.40 m³/day the tank would slowly run down day after day.
Answer: Balancing tank capacity ≈ 9.4 m³ (adopt 10 m³). If the inflow were 22/24 = 0.917 m³/h (shortage made up), the capacity would be 9.17 m³, nearly the same.
✓ Answer checked by Claude Opus 5.5 (high effort)
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