Effects of Sea Water Intrusion and Surface Water Salinity on Irrigation Water Quality in Ramisi

Abstract

One of the major economic activities in Ramisi is cane growing. However, rain fed farming is not sustainable owing to erratic rainfall patterns and limited agricultural land. River Ramisi is saline, mineralized, unsuitable for domestic and agricultural use, and affected by seawater intrusion during high tides. KISCOL drilled 37 boreholes to bridge the water demand gap but quality is doubtful. This study determined suitability of water sources in Ramisi in terms of salinity and contaminants, risk of salt water intrusion and microorganisms levels. Water samples were collected from boreholes and Rivers Ramisi and Mkurumudzi and analyzed for organic constituents, chemical oxygen demand, dissolved oxygen and electrical conductivity physical and microbiological parameters using Standard Methods. The pH of the water ranged from 6.5-8.5 with exceeding limits for conductivity, chlorides, TDS, turbidity (25 NTU) and TDS (1,238 mg/l). Magnesium, iron, sodium and potassium and nutrients were below permissible levels for irrigation water. Thus River Mkurumudzi and groundwater sources are not at risk of sea water intrusion, but River Ramisi is not. Most surface water sources were contaminated with coliform and E. coli hence not suitable for domestic use. Further research is needed to ascertain quality of the water for both agricultural and domestic uses.