Some discharge characteristics of rivers Rwamuthambi and Ragati subcatchments of the upper Tana catchment in Kenya

Abstract

The purpose of this study was an evaluation of hydrological aspects within the rivers Rwamuthambi and Ragati sub-catchments, relating to certain discharge and suspended sediment load characteristics. This was with respect to annual variability of discharge; existence or absence of persistence in the discharge series; peak and low flow frequencies; and the magnitudes and variability of suspended sediment loads. The Ragati and Rwamuthambi sub-catchments of the Upper Tana cover an area approximately 448.2 Km2. The sub-catchments are drained by rivers Ragati and Rwamuthambi originating from the Mt. Kenya forest. They cover a region that fall within parts of Kirinyaga and Nyeri districts of Central Province, Kenya. The methodology adopted in this study involved a preliminary data collection exercise followed by qualitative and quantitative analysis. Data on sediment load was collected through water sampling followed by laboratory analysis while river discharge data was got through flow gauging and supplemented with secondary data. The statistical methods of data analysis employed included Analysis of variance (ANOVA), Time Series Analysis,Frequency Analysis and the Student's ttest. Fro~disCharge data analysis, it was observed that the reliabiliti of established discharge-rating curves in defining the discharge-gauge height relationships diminished with time