The Manafwa subcatchment region, is located in the tropical Mt. Elgon climatic zone, which experiences a bi-model rainfall pattern. The average annual rainfall totals about 1,500 mm with rainy seasons occurring in the months of April till June and August till November. The mean annual maximum temperature is 27 ˚C and annual minimum temperature 15 ˚C.
The Mt. Elgon forest takes an important function of the ground and surface water resources of the Manafwa subcatchment. The infiltration rates vary from 1.2 cm/h to 363 cm/h depending on soil characteristics.
The Manafwa river is served by eight permanent tributaries. From it’s source to the outlet of the subcatchment at the Manafwa Waterworks, the river has a flow length of 43 km.