Sensitivity of Infiltration Models in Rural Soils Overlying Unsteady Shallow Groundwater

Abstract

According to the theoretical concept, the infiltration rate gradually decreases as the shallow groundwater rises to the surface of unsaturated soil regardless of the hydraulic conductivity value. It is expected to decrease to the least when the shallow groundwater level reaches the soil surface and the soil is waterlogged. For this, a deep infiltration test was conducted for four types namely as; (soil no.1: sandy clay, soils no.2, 3 and 4: clayey sand) in the laboratory by means of the infiltration box, in which the amount of infiltration is measured with the hypothetical depth of shallow groundwater. In addition, a site test of infiltration was carried out on a sandy clay field soil in the Abu-Gharaq area, west of Babylon Governorate, Iraq, by means of an infiltration square trench with dimensions of 3 m * 3 m * 2.5 m depth. The trench is connected to a drainage ditch by pipes of 3 inches in diameter for removing excess water to maintain constant artificial groundwater. The results showed that the amount of accumulated infiltration depth increases with increasing shallow groundwater depth and k of unsaturated soil zone. The mathematical relationship between them is linear with a correlation coefficient of more than 0.99. Soil texture did not affect the amount of penetration as much as the depth of groundwater.