Suitability of Athi River water for irrigation within Athi River town and its environs

Abstract

The main aim of this study was to assess the suitability of the Athi River water for irrigation in Athi River area and its environs. The study area was within Athi River and Muthwani ward within Mavoko Constituency and in Machakos County, Kenya. Seven sampling points were selected along the study transect (about 8 km) and sampling was done once every week from 21 st January to 6 th March 2015 (dry season). The water samples collected were analyzed for selected physico-chemical and bacteriological parameters. Field observations and administration of questionnaires was used to identify major sources of pollution into the river. The data collected was analyzed using SPSS version 16 and Microsoft Office Excel 2007. The level of E.coli was above the NEMA and FAO standards at all sampling points (1,073 ± 355-2,203 ± 433 MPN/100ml). The range of concentration and values of physico-chemical parameters were pH 7.74 - 8.71;, TDS, 497.57-1731 mg/L;, Electrical conductivity (EC), 0.72-2.47 dS/m; Ca, 0.03-0.54 me/L; Mg, 0.20-0.64 me/L; Na, 0.28-0.85 me/L;, Magnesium Hazard, 47.6-86.8; Cr, 0.02-0.11 mg/L; Pb, 0.08 - 0.25 mg/L; and Sodium Adsorption Ratio (SAR), 0.44-1.31. Municipal effluent was identified as the major source of water pollution. Most of the parameters in the water samples were within the recommended limits though there was an increasing trend in their concentration from sampling point 1 to sampling point 7. Moderate sodicity hazard was reported at three sampling points. Based on the results of physico-chemical parameters Athi River water within the study area can be classified as suitable for irrigation. However it imperative that periodic monitoring of river water quality and effluent discharges into the river is done and the public is made aware of the dangers paused by the high concentration of E.coli. Future studies/ research need to consider the analysis of pollutants in the plant and animal tissues to ascertain the potential impact of biomagnification and bioaccumulation the pollutants.