Effect of Irrigation Water Type on Infiltration Rates of Sandy Soils PDF

Keywords

Infiltration, water quality, sewage water, soil texture

Abstract

A laboratory experiment was conducted to test the effect of three water types (tap water, well water and sewage water) on the infiltration rate of three soils varying in texture (sand, loamy sand and sandy clay loam). A stationary rainfall simulator dispensing water at a rate of 45mm h-1, connected to the different sources of water, was used to measure the infiltration rates. A total of 5 runs were carried out using each water quality. The volume of runoff against the time was recorded at each 5 minute interval. The infiltration rate was calculated as the difference between the water applied and the excesses water measured as surface runoff. Infiltration rates at the first run were rapid in all the three soils and then progressively declined as the number of runs increased. The same trend was observed for each water quality tested. The reduction in infiltration rate with increasing number of runs for pre wetted surface than for the initial dry surface was attributed to the break down and settling of fine particles that took place earlier during prewetting. The infiltration curves for all the three soils when irrigated with different qualities of water was not distinguishable. The relationship between infiltration rate as a function of time for the treatments applied were tested using Kostiakov equation 1 = Bt-n. The infiltration data gave a coefficient of determination R2 > 0.90 for all the treatments. The infiltration parameters B, and n varied strongly with respect to soil texture Values of B decreased with changing soil textures, being highest for the sandy soil and lowest for the sandy clay loam soil, whereas n values showed the opposite trend. It was concluded that the effect of soil texture on infiltration rate was very pronounced while water qualities showed a little effect.