Experimental Analysis of the Effects of Selected Water Quality Parameters' on Soil Infiltration Dynamics under Controlled Temperatures

Abstract

The movement of water into soil is a critical process influencing irrigation efficiency, infiltration processes, groundwater recharge, soil moisture availability, and sustainable agricultural production. While soil characteristics have traditionally been regarded as the principal factors controlling infiltration, the influence of the physical quality of infiltrating water has received comparatively less attention. This study experimentally analyzed the effects of viscosity, density, and turbidity, on soil infiltration dynamics under controlled temperature conditions of 20°C, 25°C, 30°C, and 35°C. The study was conducted on an agricultural soil. The land slope/topography was determined as 1.7%, showing the land area to be relatively flat with a climatic condition of high rainfall and atmospheric moisture. Soil samples were collected from three locations within the experimental plot and subjected to laboratory analysis with the following results obtained: particle size distribution as 81% sand and 18% silt, proving the area to be loam-sand dominated, average moisture contents of 4.50%, 5.21%, and 4.90% for Locations A, B, and C, respectively, showing that the area has low moisture content. Hydraulic conductivity values of 6.505 × 10⁻³ cm/s, 6.513 × 10⁻³ cm/s, and 6.505 × 10⁻³ cm/s respectively were obtained, indicating relatively high permeability. Infiltration rates gradually decreased with time from 15.6 cm/h to 7.8 cm/h, 25.2 cm/h to 6.6 cm/h, and 20.4 cm/h to 7.8 cm/h at Locations A, B, and C, respectively, which shows that the area has good infiltration characteristics. Water samples were subjected to water test. The results showed that viscosity decreased with increasing temperature. The mean viscosity decreased from 5.072 mPa·s at 20°C to 4.298SmPa·s at 35°C, representing an overall reduction of approximately 15.3%. Two-way ANOVA showed that temperature significantly affected viscosity (F(3,33) = 36.24, p < 0.001), while water source had no significant effect (F(11,33) = 1.31, p = 0.261). Density also decreased progressively with increasing temperature, while both temperature (F(3,33) = 47.47, p < 0.001) and water source (F(11,33) = 24.48, p < 0.001) significantly affected density, with the statistics explaining 92.6% of the observed variation (R² = 0.926). Turbidity showed considerable variation among water sources, with borehole and rainfall water recording relatively low values, while surface water, ponds, rivers, and floodwater recorded considerably higher values, with some exceeding 1400 NTU. Water source was the dominant factor influencing turbidity (F(11,33) = 4356.1, p < 0.001), while temperature had a statistically significant but relatively small effect (F(3,33) = 17.27, p < 0.001). Mean turbidity increased from 270.3 NTU at 20°C to 297.9 NTU at 35°C. Among the parameters investigated, viscosity was the most temperature-sensitive, followed by density; however, there was an exception in the turbidity parameter where the turbidity value was observed to be increasing with an increase in temperature, thereby influencing infiltration primarily through suspended sediment deposition and pore blockage. The study therefore establishes that cleaner water sources with low turbidity are more suitable for maintaining soil infiltration, while temperature should be treated as an essential interacting variable in the assessment of water quality effects on soil infiltration dynamics.