Infiltration Characteristics of Tropical Soil Based on Water Retention Data

Abstract

Water retention and hydraulic properties of undisturbed tropical soils collected from many regions of Indonesia were analyzed to estimate infiltration characteristics of the soils. Soil texture was classified based on International Society of Soil Science (ISSS) classification. The van-Genuchten model was used to estimate the relationship between water content and matrix potential at pF=1, pF=2, pF=2.54, pF=4.2. The 165 soil water retention data were used to optimize parameters of the model and to find the air entry value. Green-Ampt and Philip's infiltration models were applied to characterize soil infiltrability of each textural type. The Nash and Sutcliffe's efficiency was used to evaluate numerical simulation of cumulative infiltration of Green-Ampt's infiltration model compared to the results of laboratory experiments. The 165 soil samples were classified and were optimized into 10 ISSS textural types: heavy clay, sandy clay, sandy clay loam, sandy loam, sand, light clay, clay loam, loam, silty clay, and silty clay loam. The results of performance evaluation of Green-Ampt's infiltration model showed that Green-Ampt's infiltration model can describe infiltration characteristics by using soil water retention and hydraulic properties data. The tropical soils based on soil texture exhibit contrasting infiltration characteristics as indicated by infiltration rate, length of wetting front and sorptivity. The characteristics of soil infiltrability are mainly influenced by hydraulic conductivity, initial water content, and matrix potential at the wetting front.