---
title: "Average demand, village survey 2013, design 25 years"
subject: "Water Supply Engineering"
chapter: 3
key: "semester_5/water_supply_engineering:demand-c73"
source: https://www.bctengineer.com/q/semester_5/water_supply_engineering/demand-c73
site: BCT Engineering
---

# Average demand, village survey 2013, design 25 years

Water Supply Engineering · Chapter 3: Quantity of Water

- Asked in: 2073 Chaitra, 8 marks
- Video: [population forecasting, Arithmetic increase method with example, water supply engineering numericals](https://www.youtube.com/watch?v=K6sSBXtUFY4) — Civil Engineering Exam
- 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-c73
- Whole chapter: https://www.bctengineer.com/md/semester_5/water_supply_engineering/chapter-3

## Question

The survey data collected for a water supply scheme in a village of Nepal is given below:

Survey year = 2013; Base period = 3 years; Design period = 25 years; Population = 1250; Cows = 200; Goats = 500; Chicken = 5000; Annual population growth rate = 1.5%; Day scholar students in a school = 100; Boarder students in a school = 10; No. of Health post = 1; No. of tea shop = 1; No. of VDC office = 1.

Neglect demand for fire fighting. Calculate average water demand for the design year.

## Short answer

Design year 2041, n=28, population 1897. Using Nepal rural rates, net demand is 100744 l/d; adding 15% losses gives 115855 l/d = 115.86 m3/d = 1.34 l/s.

## Answer

Survey year 2013; base period 3 years and design period 25 years: design year 2041, $n = 28$ years after the survey.

#### Design population
$$
P_{2041} = 1250\times(1.015)^{28} = 1{,}897
$$

#### Water demand
**Design values assumed** (Nepal rural water supply practice): domestic 45 lpcd (public taps); day scholar 5 l/d; boarder 45 l/d; office staff 45 l/d with 10 staff per office; big animal (cow, buffalo) 45 l/d; small animal (goat, pig) 5 l/d; poultry 0.2 l/d; health post 1000 l/d; tea shop 500 l/d; losses and wastage 15% of net demand; maximum day factor 1.5 and peak hour factor 3. Fire demand is neglected.

| Demand | Quantity | Rate | Demand (l/day) |
|---|---|---|---|
| Domestic (45 lpcd) | 1,897 | 45 l/c/d | 85,344 |
| Day scholars | 100 | 5 l/c/d | 500 |
| Boarders | 10 | 45 l/c/d | 450 |
| Cows | 200 | 45 l/d | 9,000 |
| Goats | 500 | 5 l/d | 2,500 |
| Chickens | 5,000 | 0.2 l/d | 1,000 |
| Health post | 1 | 1000 l/d | 1,000 |
| Tea shop | 1 | 500 l/d | 500 |
| VDC office (10 staff) | 10 | 45 l/staff | 450 |
| **Net demand** | | | **100,744** |

Losses and wastage $= 15\%$ of net demand $= 15{,}112$ l/day

$$
Q_{avg} = 100{,}744 + 15{,}112 = 115{,}855\ \text{l/day} = 115.86\ \mathrm{m^3/day} = 1.34\ \text{l/s}
$$

**Answer: Design population = 1,897; average water demand = 116 m$^3$/day (1.34 l/s).**

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Survey 2013, base period 3 and design period 25 years. What is n?
   A. 25 years
   B. 30 years
   C. 28 years (design year 2041)
   D. 3 years
   Answer: C. 2013+3+25 = 2041, which is 28 years after the survey. (Key point: Design year)

2. Which set of rates is used for cow, goat and chicken respectively?
   A. 45, 5 and 0.2 l/d
   B. 45, 45 and 5 l/d
   C. 5, 5 and 0.2 l/d
   D. 110, 5 and 1 l/d
   Answer: A. Big animals 45 l/d, small animals 5 l/d, poultry 0.2 l/d. (Key point: Unit rates)

3. Q_avg = 115.86 m^3/day. What is it in l/s?
   A. 13.4 l/s
   B. 1.34 l/s
   C. 0.134 l/s
   D. 4.83 l/s
   Answer: B. 115.86 x 1000/86,400 = 1.34 l/s. (Key point: Unit conversion)

## Close variants set in other exams

- [Total demand, village survey 2013, design 15 years](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Ademand-c69) — Water Supply Engineering, chapter 3, asked 2×

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