Design demand 2025, geometric method, rural village

The last census is 2001, so for 2025, $n = 2.4$ decades.

Population by geometrical increase method

Geometrical increase method

Average growth rate per decade (geometric mean): $r = \left(\dfrac{22{,}800}{8{,}500}\right)^{1/4}-1 = 27.976\%$

$$P_{2025} = P_n(1+r)^n = 22{,}800\times(1+0.27976)^{2.4} = 41{,}214$$

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. The number of animals is not given, so I assume one big animal per 10 persons and one small animal per 5 persons of the design population. Fire demand is neglected.

Losses and wastage $= 15\%$ of net demand $= 312{,}961$ l/day

$$Q_{avg} = 2{,}086{,}405 + 312{,}961 = 2{,}399{,}366\ \text{l/day} = 2{,}399.37\ \mathrm{m^3/day} = 27.77\ \text{l/s}$$

Answer: Population in 2025 = 41,214; design water demand = 2,399 m$^3$/day (27.8 l/s).