UNDERSTANDING REAL LEAKAGE RATES FROM WATER RETICULATION: IMPLICATIONS FOR THE PLANNING AND DESIGN OF RURAL WATER SUPPLY SYSTEMS

Rural water systems in South Africa are typically planned and designed to provide a supply of 25 litres per capita per day, with a 10 % allowance for losses. This paper contrasts the typical allowance for losses with actual data from a number of examples of operating schemes, as well as with the predicted figures derived from the standard formula used internationally for the benchmarking of leakage from water reticulation. The observed leakage rates are then compared with national and international experience using the Infrastructure Leakage Index (the ILI), and are found to be within the normal range. It is shown that if typical South African ILI values are applied to rural water design in South Africa, many of our schemes are seriously underdesigned in terms of the adequacy of the bulk supply. The implication is that the provision made for losses in the planning and design of rural water schemes in South Africa is quite inadequate. The failure to plan for realistic losses means that many schemes will only be able to provide a very limited supply of water, substantially less than the intended 25 litres per capita per day