Watering Trucking Worked Example

Population 10,000 persons
Minimum water requirement 15 litres/person/day
Daily water requirement 150, 000 litres/day
Allow 20% for wastage and new arrivals
Water to be tankered 180,00 litres/day

Water to be trucked along a rough 10km track from a single borehole.
Rigid 5,000 litre tankers are suitable and can be hired locally.
One way journey time @ 20km/hr is 30 minutes.

Borehole pump discharges at 5 litres/sec.
Time to fill 5,000 litre tanker is 17 minutes.

Offloading by gravity is around 6 minutes.

Calculate turnaround time of tanker.

Time to fill tanker			17 minutes
Journey time from filling point	30
Time for offloading			6
Return journey			30
Net turnaround time		83
Add 30% for contingencies		108 minutes (1.8 hours)

Number of deliveries per tanker per day 	= working hours/turnaround time
					= 12 / 1.8	= 6 journeys

Total deliveries needed per day		= daily tankered water / volume per tanker
					= 180,000 / 5,000	= 36 tanker deliveries

Number of tankers required = 6.

Summary:

A total of 6 tankers of 5,000 litres capacity will be required to make 6 deliveries each per day to supply enough water at 15 litres/person/day for 10,000 people at 10km distance.