Irrigation Suitability Assessment of Effluents From West Kano Rice Irrigation Scheme, Kisumu, Kenya

Abstract

This paper assesses the suitability of West Kano Rice Irrigation Scheme effluents for recycling. Water and wastewater quality variables of ten samples from two sites were determined. The variables were Temperature,
Electrolytic conductivity, Total suspended solids, pH, Calcium, Nitrates, Potassium, Sodium and Total Dissolved Solids (TDS). The results were used to compute the Sodium adsorption ratio (SAR), and further compared with FAO irrigation water standards. The wastewater recorded statistically significant gain in Calcium, Nitrates, and TDS, depicting a heavy loss of these vital soil constituents to Lake Victoria. Nitrate levels indicated a deficit in lake water, and an excess in effluents. The excess nitrates in effluents pollute the lake, but could help as crop nutrients when recycled, while low nitrate levels in the lake water would require an addition of fertilizers to the irrigated soils. Annually, a total of 12.26 million m3 of water and 8.94 million m3 of effluents is pumped into and out of the scheme respectively. The effluent and Lake water has SAR of 35% and 18% respectively, rendering both of poor irrigation quality, though the effluents have a compensatory advantage due to its higher levels of
Calcium (0.91me/l), compared with the Lake water’s 0.48me/l. The wastewater, with an irrigation suitability rating of 45%, was found more suitable for irrigation than the Lake water’s 40%. It was concluded that the
irrigation wastewater was more suitable for use in the scheme than the Lake Victoria waters. It was recommended that the recycling of the irrigation wastewater should be adopted.

Key Words: Irrigation; Recycling; Pollution; Waste; Water Quality; Wastewater.