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Tampere University of Technology (2014)

Water Network Management Plan for Keetmanshoop, Namibia

Aalto, Matti

Titre : Water Network Management Plan for Keetmanshoop, Namibia

Auteur : Aalto, Matti

Université de soutenance : Tampere University of Technology

Grade : Master of Science (MS) 2014

Résumé
Namibia is one of the driest countries in the world, but water distribution is not technically difficult to implement for population of 2.3 million. Rainy season gives enough water to reservoir lakes for whole year, land is sandy and easy to dig and pipes do not need to be installed deep because air temperature is always on plus degrees. Still weakly organized water distribution causes big losses and extra work in municipality of Keetmanshoop. The municipality buys 1.7 million cubic meters water per year from a bulk water supplier, NamWater. Only 65% of water bought from Namwater is billed from customers. The rest 35% consists mainly of metering errors, leaks and municipality’s own use. Unbilled water causes 4 000 650 N$/y (537 000 m3) losses for municipality. Average annual increase of unpaid bills is 26 % of total sales, which increases economic difficulties. Totally about half of water bought from NamWater is lost through leaks in network or leaks in customers’ water fixtures. Minimum night flow to network is normally 100-110m3/h year round, which is about 50-55% of average daily flow. Tens of valves are leaking, but smaller leaks are seldom fixed as plumbers concentrate on fixing big pipe bursts. In 2012 the main valves were checked with plumbers, water distribution map was updated and the network was planned to be divided in 45 sectors by 104 valves. Already 55 of them are usable, 28 should be added, 13 should be replaced and the condition of 8 should be checked. Because of inactive water meters 818% of business-consumers’ consumption is not measured. Money loss of 300 000 – 700 000 N$/y can be reduced to under 50 000 N$/y by simply replacing inactive meters. Many meters of big users were also inaccurate. Tested meters ran on average 30.3 % less than the real flow. Investments in planning would be profitable. With such big water- and economical losses like in Keetmanshoop, a water engineer could find more savings for municipality than his/her salary costs are. After hiring a water engineer and replacing inactive water meters, next steps are replacing the most important valves and taking the water distribution map in use. After suburb water meters and pressure reducing valves are installed, it is time to start systematically rebuild the network road by road. Simple calculations of money savings are almost always the easiest way to rationalize the importance of investments. Methods of calculating water balance in Keetmanshoop are also suitable for other cases. Even rough calculations show the magnitude of water- and economical losses, which often are sufficient arguments to start developing the water distribution system.

Mots clés : non-revenue water, water distribution network, development, Keetmanshoop, Namibia

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Page publiée le 12 avril 2018, mise à jour le 4 mars 2019