--- title: "Demand of new municipality 2016, 45,000 pop" subject: "Water Supply Engineering" chapter: 3 key: "semester_5/water_supply_engineering:demand-a76" source: https://www.bctengineer.com/q/semester_5/water_supply_engineering/demand-a76 site: BCT Engineering --- # Demand of new municipality 2016, 45,000 pop Water Supply Engineering · Chapter 3: Quantity of Water - Asked in: 2076 Asoj, 8 marks - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_5/water_supply_engineering/demand-a76 - Whole chapter: https://www.bctengineer.com/md/semester_5/water_supply_engineering/chapter-3 ## Question Data obtained from a baseline survey of a newly formed municipality in year 2016 A.D. are as follows. Population = 45,000, No. of day scholar students in school = 9500, No. of big animals = 8000, No. of small animals = 15000. There are twenty offices, two hospital with total 50 beds. Calculate the water demand of that municipality in design year with base period of 2 years and design period of 20 years. Assume the population growth rate of the community is 1.5% per annum and fire fighting as per National Board of fire under writers. ## Short answer Design population in 2038 is 62,440. Average daily demand is 8,483 m3/day or 98.2 l/s; fire demand is 562 l/s with about 4,050 m3 reserve; distribution design flow is about 739 l/s. ## Answer Survey year 2016; base period 2 years and design period 20 years give the design year 2038, so $n = 22$ years after the survey. #### Design population $$ P_{2038} = 45{,}000\times(1.015)^{22} = 62{,}440 $$ #### Water demand Assumed unit rates for a municipality: domestic 110 lpcd; day scholar 5 l/d; big animal 45 l/d; small animal 5 l/d; office staff 45 l/d (10 staff per office); hospital 340 l/bed/d (IS 1172); losses 15%. | Demand | Quantity | Rate | Demand (l/day) | |---|---|---|---| | Domestic (110 lpcd) | 62,440 | 110 l/c/d | 6,868,440 | | Day scholars | 9,500 | 5 l/c/d | 47,500 | | Big animals | 8,000 | 45 l/d | 360,000 | | Small animals | 15,000 | 5 l/d | 75,000 | | Offices (10 staff each) | 200 | 45 l/staff | 9,000 | | Hospitals (50 beds) | 50 | 340 l/bed/d | 17,000 | | **Net demand** | | | **7,376,940** | Losses and wastage $= 15\%$ of net demand $= 1{,}106{,}541$ l/day $$ Q_{avg} = 7{,}376{,}940 + 1{,}106{,}541 = 8{,}483{,}481\ \text{l/day} = 8{,}483.48\ \mathrm{m^3/day} = 98.19\ \text{l/s} $$ #### Fire demand (National Board of Fire Underwriters formula) $P = 62.44$ thousand. $$ \begin{aligned} Q_f &= 4637\sqrt P\,(1-0.01\sqrt P)\ \text{l/min}\\ &= 4637\times7.902\times(1-0.0790) = 33{,}746\ \text{l/min} = 562.4\ \text{l/s} \end{aligned} $$ For a fire lasting 2 hours, the volume is $Q_f\times120 = 4{,}050\ \mathrm{m^3}$. This volume is kept as fire reserve in the service reservoir; it is not added to the average daily demand, because fire flow is an occasional rate, not a daily consumption. #### Design flow with fire The distribution system is checked for the larger of: - Maximum day demand + fire flow $= 1.8\times98.19 + 562.4 = 176.7 + 562.4 = 739.1$ l/s - Peak hour demand $= 2.7\times98.19 = 265.1$ l/s So the mains are designed for about 739 l/s. **Answer: Design population = 62,440; average daily demand = 8,483 m$^3$/day (98.2 l/s); fire demand = 33,746 l/min (562 l/s), with a 2-hour fire reserve of about 4,050 m$^3$ in storage; design flow for the distribution system (maximum day + fire) $\approx$ 739 l/s.** ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Survey 2016, base period 2 years, design period 20 years. How many years n is the population grown from the survey population? A. 20 years B. 22 years C. 2 years D. 18 years Answer: B. The design year is 2016+2+20 = 2038, so n = 22 years after the survey. (Key point: Design year and n) 2. How is the fire demand handled in this answer? A. It is added directly to the average daily demand as 562 l/s B. It is ignored because it is rare C. It is met from storage and not added to the daily average, but the system is checked for peak flow plus fire flow D. It is taken as 15% of the net demand Answer: C. Fire flow is large but short-lived, so it is supplied from storage and checked for, rather than added to the daily average. (Key point: Fire demand treatment) 3. How are losses and wastage included in Q_avg? A. 15% is subtracted from the net demand B. 15% of only the domestic demand is added C. They are ignored D. 15% of the net demand is added to the net demand Answer: D. Q_avg = 7,376,940 + 15% of 7,376,940 = 8,483,481 l/day. (Key point: Losses and wastage) ## Close variants set in other exams - [Population in survey year from design demand 800 m3](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Apop-s73) — Water Supply Engineering, chapter 3, asked 2× ## Related in Water Supply Engineering - [Demand of rural municipality 2018, 15,000 pop](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Ademand-c74) — Water Supply Engineering, chapter 3 - [Rural village demand, survey 2070 BS, base year 2073](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Ademand-as70) — Water Supply Engineering, chapter 3 - [Demand of rural municipality, base period 3 years](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Ademand-bk79) — Water Supply Engineering, chapter 3 - [Demand of village 2070 BS, base period 5 years](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Ademand-c70) — Water Supply Engineering, chapter 3 - [Average demand, village survey 2013, design 25 years](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Ademand-c73) — Water Supply Engineering, chapter 3, asked 2× - [Population 2088 by three methods, design year demand](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Apop-k72) — Water Supply Engineering, chapter 3