摘要
Freshwater availability in sufficient quantity and quality is necessary for both people and nature.Environmental flow data is useful in the management and allocation of water resources.This study aimed at quantifying stream flows and their trends in the Malewa Basin rivers in central rift valley,Kenya.Daily stream flow data(1960-2013)in four gauges(2GB01,2GB05,2GB0708 and 2GC04)were subjected to exploratory data analysis,fixed interval method of baseflow separation and Mann Kendall trend test.The results shows that on average,the Malewa river at Gauge 2GB01 discharge(excluding abstractions)about 191.2 million cubic metres of water annually,equivalent to a discharge of 6.06 m3/s.While discharges had not experienced a step change,huge annual fluctuations were noted suggesting periodicity with changes in climatic conditions.No trend was noted in annual stream data for the four gauges assessed.However,extreme low and high flows,median flows and baseflows for daily data showed either positive or negative trends.The baseflow index for daily flows showed trends:2GB01(Z=4.519),2GB05(Z=-6.861),2GB0708(Z=-16.326)and 2GC04(Z=5.593).The findings suggest that Malewa rivers are likely experiencing effects of extreme climatic conditions and land cover changes.Land cover degradation seems to create conditions of increased flow,although the intensity varies from sub-catchment to another.The data also seems to suggest that stream discharge is much dependent on baseflows.There is need to regulate water use,improve soil cover and manage or adapt to the adverse effects of climate change.Key words:Streamflow,baseflow,trend,discharge.1.Introduction?Freshwater availability in sufficient quantity and quality is necessary for both people and nature.The concept of environmental flows has been the subject of study and consideration[1-5].Environmental flow information guides on how water is managed and allocated to different competing uses.The need for improved water efficiency in the allocation has led to increasing focus on environmental flows or environmental water allocations[6],although national and international policies have not yet accounted for them[7].Streamflow volumes and trends are important for decision making on water allocation.As reported by Kundzewicz,W.Z.,et al.[8],changes in?
