Geospatial analysis of soil hydraulic properties in the ETI Mpanga irrigation scheme of Rwanda

Abstract However the effectiveness of irrigation practices is heavily influenced by the underlying soil hydraulic properties, which govern water retention, Efficient water management is essential for sustainable agricultural productivity, especially in irrigation-dependent areas like the ETI Mpanga Irrigation Scheme. The research focused on soil properties such as moisture content, bulk density, field capacity, wilting point, hydraulic conductivity, and available water content. Specifically, to analyze the dynamics of soil hydraulic properties by soil depth and LULC change, to assess the statistical relationships among soil hydraulic properties and to map and interpret the spatial distribution of key soil hydraulic properties across the ETI Mpanga Irrigation. Statistical and spatial analyses were conducted using Pearson correlation, Principal Component Analysis (PCA) with Varimax rotation, Mean Absolute Error (MAE), Root Mean Square Error (RMSE), and the coefficient of determination (R²).The Inverse Distance Weight (IDW) was used to spatially represent the variability of hydraulic properties. Field data revealed significant spatial variability in soil characteristics. Soil water content ranged from 2.28% to 13.67%, and bulk density varied from 0.13 to 2.2 g/cm³. Low bulk density (0.13–0.55 g/cm³) in the eastern and southwestern zones indicated loose, organic-rich soils, while high bulk density (1.4–1.8 g/cm³) and severe compaction (> 1.8 g/cm³) in central areas suggested clay-rich soils and heavy machinery use, limiting infiltration and root growth. Field capacity ranged from 40.16 to 197.37 cm³/cm³, and wilting point from 6.03 to 27.82 cm³/cm³, with higher values in clayey soils. Hydraulic conductivity varied between 11.1 and 37.6 cm/day, with sandy soils showing higher rates. Available water content ranged from 5.29 to 21.49 cm³/cm³, highest in loamy soils. The findings highlight the importance of understanding soil hydraulic properties for optimizing irrigation. LULC changes significantly influenced soil compaction and water availability. The study recommends applying gypsum in areas where bulk density exceeds 1.6 g/cm³ to reduce compaction and improve soil hydraulic performance.