River Continuum Water Quality Dynamics in the Dry Rangeland Landscape of Lake Elementaita Watershed, Nakuru County, Kenya

The aim of the study was to compare the spatial variability of water quality in rivers within the Lake Elementaita watershed in the Great Rift Valley (GRV) and determine the: a) variation across the three rivers, b) magnitude of change along the river continuums and c) influence of river continuum length (distance), altitudinal gradient and catchment area. Water sampling and testing of sixteen parameters was undertaken in 55 sites in River Mbaruk (19 sites), River Chamuka (16 sites), Mbaruk-Chamuka confluence section (2 sites), River Kariandusi (10 sites) and Lake Elementaita (8 sites). This was undertaken through in-situ testing with a portable multi-parameter analyser (Hanna Model HI-98194) and laboratory analysis using a wide range of techniques, including titrimetric analysis, flame photometry and spectrophotometry. Thereafter, the values of pH, TDS, turbidity, alkalinity, chloride, sulphate, calcium, and magnesium were used for computing the water quality index (WQI) along the three rivers. The findings showed significant water quality variation across the three catchments in relation to water pH, TDS, EC, alkalinity, Cl. and SO4, with a 60-100 fold increase in pH, TDS, EC, Cl. and SO4 from the headwaters to the downstream. The results of the Pearson’s correlation analysis indicated significant positive relationships for:- a) riverine continuum length with TDS, Cl, F- and Na, b) catchment area with pH, TDS, EC, alkalinity, Cl, F, PO4, SO4, Mg, Na and K, and c) inverse relationship for continuum altitudinal gradient with pH, EC, Cl, F- and PO4.