Evaluation of water supply system Case study in Naka ... - ENGEES

Evaluation of water supply system – Case study in Naka, Nigeria5.2 Infrastructure and level of services5.2.1 Physical infrastructure stateThe current assets were different to the one planned in 1998: from a design supplying15 public taps (from which only 12 taps are found today) to a system with at least 90added individual connections or yard taps. The system had many leakages: one third(32%) of the taps were broken assets (either turning head broken or tap totallymissing) and there were breakages on the pipe-lines, 8 being noticed during thesurvey. Some of the breakages were caused voluntarily by motorcyclists who fetchedwater through broken pipes to wash their machine; others were due to workers whobroke the pipe when digging to implant cable pillars. The pipes were often veryshallow buried and easily damaged. Many taps lacked maintained cement platforms,sometimes leading to the occurrence of stagnant water.The sedimentation tank, the clear-water tank (and the over-head tank in a lessimportant level) were in an advanced state of corrosion, which was a source of seriousleakages in the clear water tank, reduction of storage capacity as well as un-sealedstrength support of the clear-water tank structure, endangering the stability.5.2.2 Water quantityThe water quantity available was difficult to estimate considering the high irregularityof the water supply. Values were determined by taking the effective rate of pumpingin the ideal case of 6 hours pumping (far from reality) during the day so that it waspossible to estimate if the irregular supply was the only cause of insufficient waterquantity.The first surprising result concerns the very low intake pumping rate of 7m 3 /h,observed since the beginning of the functioning of the WTP in 1998, whereas thedesign planned a rate of 20m 3 /h. However, even if it was working at the designed rateof 20m 3 /h during 6 hours per day, it would not achieve the suggested 20 litres per dayper capita for all Naka population. The high population growth rate of Naka is a bigchallenge: a design report for water written in 1981 estimated the current populationat 4,100 and forecasted the population to reach 6,000 in 2000 (current estimation in2006 around 20 000). The irregular and low rate of pumping, coupled with the highCranfield University at Silsoe 20 Florianne Bourrigault (2006)