Abstract
This study evaluated the possibility of conjunctive use (CU) of shallow ground water (SGW) and surface water for irrigation use at Wonji Shoa Sugar Estate (WSSE)(Ethiopia). Irrigation suitability was investigated by taking 46 SGW samples from piezometers and hand-dug wells. Many physicochemical parameters (Mg2+, Na+, Ca2+, K+, CO3-, SO42-, HCO3-, Cl-, TH, EC, TDS and pH) and other indices (MAR (magnesium adsorption ratio), SSP (soluble sodium percentage), SAR (sodium absorption ratio), RSC (residual sodium carbonate), KR (Kelly’s ratio) and permeability index (PI)) were analyzed following standard procedures. The salinity and infiltration problems of SGW were found to be none to moderate with none chloride and boron ion toxicity. The sodium ion toxicity problems are slight to moderate. The SGW is generally categorized under C3S1 (high salinity and low sodium hazard). However, a high value of SSP and RSC indicate a high possibility of occurrence of infiltration problem when using the SGW. Hence, the CU of SGW and surface water must be practiced to minimize the potential problems of infiltration, salinization and their associated problems on soil and sugarcane productivity. Therefore, during CU planning, the optimum irrigation scheduling that considers the in situ use of groundwater table must be practiced.