Spatiotemporal variability of irrigation water quality in the irrigated lands of Mirab Abaya District at Gamo Zone, Southern Ethiopia

Abstract

The quality of irrigation water is a major concern in the Gamo Zone of Ethiopia because of its direct effects on livelihoods and food security. Agricultural productivity in the region has declined due to population pressure, climate variability, and inadequate irrigation water monitoring. This study assessed the spatiotemporal variability of irrigation water quality to evaluate its influence on agricultural productivity in irrigation-based systems. Quantitative irrigation water samples were collected from multiple sites during wet and dry seasons. Key parameters analyzed included electrical conductivity (EC), total dissolved solids (TDS), pH, sodium adsorption ratio (SAR), and biological contaminants. Statistical tools such as analysis of variance (ANOVA) and k-means clustering were used to identify seasonal and spatial variations. The results indicated pronounced spatial and seasonal variability in irrigation water quality. TDS values were about 600 mg/L during the wet season and increased to approximately 1200 mg/L during the dry season in the Fura River and Qola Mulato Lake, posing risks to crop yields. EC ranged from 2.0 to 3.5 mS/cm, reflecting increasing salinity stress. ANOVA showed significant seasonal differences in TDS, EC, and pH, with pH values exceeding 8.5 at all sites, potentially limiting nutrient availability. During the dry season, moderate to severe SAR levels occurred in 66.67% of Fura Lake samples, threatening soil structure. Improving irrigation water quality is therefore essential for sustainable agriculture and food security in the Gamo Zone.