Evaluation of domestic rainwater catchment systems in Ng'arua Division, Laikipia District, Kenya
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The purpose of the study was to evaluate the technical and socioeconomic performance of existing domestic rainwater harvesting system projects in Sipili and 01 Moran Locations of Ng'arua Division, Laikipia District in Rift Valley Province. This was accomplished by determining the technical adequacy of the rainwater catchment systems, assessing the efficiency of implementation procedures, determining the cost-benefit ratios and the effects and impacts of the projects on the community. A design rainfall reliability of 70% was used. Simulation or water balance analysis of existing RWCS was used to determine the various parameters necessary for this research work. A mean water supply of 17,145 litres per year, a performance index of 67% and a mean probability of failure of36% were obtained. About 64% of the total number of household rainwater catchment systems had a reliability ofless than 50% and a mean cost-benefit ratio 0[0.36. Roof catchment surfaces in combination with stone block or ferrocement tanks were found to provide good quality rainwater. Most people in this area boil their water before drinking regardless of the source. About 50% of the tanks experienced water leakage through cracks. The quality of the construction work and the method of curing are seen as the major shortcomings, causing serious cracking of the tanks. Adequate training of the members in self-help groups on the methods of tank construction and improved curing of the tanks using, say, wet sisal bags, are recommended. Rainwater catchment systems design charts were constructed to serve as useful guidelines in the design of new rainwater catchment systems and in the evaluation of the adequacy of existing ones. The use of rainwater as a portable water supply in Ng' arua has been demonstrated through the field assessment to be a practical alternative to unsuitable or saline groundwater or polluted surface water sources. Despite serious financial constraints which have limited the speed of implementation of rainwater harvesting projects, residents have been able to come together in self-help groups and this has greatly helped in the mobilisation oflabour for rainwater catchment systems construction and also facilitated the acquisition of external assistance from donors and church organisations.