Water quality for irrigated-rice-based cropping system in the Oda river valley bottom at Besease, Ghana

The Valley Bottom Rice Development Project was started in Ghana in 1990 under the Agricultural Sector Rehabilitation Programme of the Ministry of Food and Agriculture. To assess the quality of river and shallow groundwater for irrigation at the Besease project site, physico-chemical analysis were carried out from 1994 to 1997 and the results were evaluated. The total dissolved solids (TDS) of river water ranged from 60.00 to 260.00 mg 1''-1,with a mean of 117.99 mg 1''-1,and that of groundwater ranged from 95.00 to 482.00 mg 1''-1with a mean of 297.8 mg mg 1'-1. The adjusted sodium absorption ratio (ASAR) of river water ranged from 0.08 to 0.28 with a mean of 0.12, and that of groundwater ranged from 0.24 to 2.62 with a mean of 1.72. Based on these and other measurements, both river and shallow groundwater are suitable for irrigated rice farming in the Oda river valley bottom at Besease. However, the study indicated excess bicarbonate (HCO3'-)content of groundwater (mean: 16.24 meg 1''-''1), capable of reducing the yield and quality of rice. (au)