Question

A city of 87,000 people has an average daily per capita water demand of 100 gal/person-day. The projected total peak water demand for the entire population is most nearly:

(A) 4 MGD

(B) 9 MGD

(C) 16 MGD

(D) 18 MGD

Answer 1

As we know peak factor is inversely related to population.

If population is less than 50,000 then peak factor is 3.

If population is between 50,000 and 200,000 then peak factor is 2.5

If population is greater than 200,000 then peak factor is 2.

In our case population is 87000 which lies between 50,000 and 200,000 so peak factor should be 2.5

Now annual average daily water demand = 87000×100

= 8.7 MGD

PEAK WATER DEMAND = 2.5×8.7 = 21.75 MGD

Also from Goodrich equation, peak demand or ma imum hourly demand = 2.7×annual average daily demand = 2.7×8.7 = 23.49 MLD.

Since no option matches as all options are lower than the calculated values so option having maximum value should be chosen.

So, peak demand will be 18 MGD. OPTION ( D).