SUITABILITY OF SHALLOW GROUNDWATER FOR IRRIGATION: THE CASE OF THE WONJI SHOA SUGAR ESTATE (ETHIOPIA)

This study evaluated the possibility of conjunctive use (CU) of shallow groundwater (SGW) and surface water for irrigation at the 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 analysed following standard procedures. The salinity and infiltration problems of SGW were found to be none to moderate with no 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 indicates a high possibility of occurrence of infiltration problems when using SGW. Hence, CU of SGW and surface water must be practised to minimize the potential problems of infiltration and salinization and their associated difficulties in soil and sugar cane productivity. Therefore, during CU planning, optimum irrigation scheduling that considers the in situ use of groundwater table must be practised.