Predicting the Effects of Changing Water‐Table Levels and Associated Soil Moisture Regimes for Soil Survey Interpretations

Abstract

AbstractA one‐dimensional computer model for simulating the soil moisture regime was used to calculate evapotranspiration and equivalent productions of grass for six different soils. Input data consisted of rooting depths, moisture retention curves and hydraulic conductivity curves. Physical boundary conditions were derived from climatic data and depths to water table. Average relative production was calculated for actual water table fluctuations and for lowered levels, thus simulating the effects of ground water extraction. Productions for the six soils reacted quite differently to lowering of the water table. A classification was developed to characterize the different reactions. A SYMAP computer program was used to produce maps (which were based on soil maps) showing the effects in different soils to lowering of the water table. Storage of basic data on tape allows the production of many maps on demand for natural conditions and for conditions changed by man. Soil survey interpretation thus becomes a matter of offering many choices rather than a qualitative judgement based on actual conditions. The model can be used to express variability of mapping units on a soil map by simulating moisture regimes for the range of soil properties observed within the mapping unit.