Modeling Lake Naivasha, Kenya and its surroundings is an issue of very high significance because of great socio-cultural, ecological and economic values. The basin comprises a biosphere reserve, a national park with a variety of wildlife, a significant livestock activity, a very fertile land for agriculture and a growing tourism industry. The prevailing system of uncoordinated water resources management in the basin cannot sustain the ever-increasing water needs of the various expanding sectors. Therefore a strategy must be sought to integrate the various sectoral needs against the available water resources in order to attain both economic and ecological sustainability. The study attempts to develop, for the first time in the Lake Naivasha Basin, an integrated water resource management model. In order to understand the situation in the whole catchment and identify where problems exist and the weakness that affect the catchment and their improvement.