Waterbalance of a bare soil in an arid environment

TitleWaterbalance of a bare soil in an arid environment
Publication TypeThesis
Year of Publication1992
AuthorsHollanders P
Number of Pages74
Date Published1992
UniversityNew Mexico Tech, Socorro and Agricultural University, The Netherlands
Thesis TypeM.S. Thesis (DRAFT)pp
Accession NumberJRN00164
Call Number00657
Keywordsdissertation, dissertations, model, groundwater recharge, model, Swacrop, model, waterbalance, soil, groundwater recharge, theses, thesis, transect, groundwater recharge, water, ground recharge
Abstract

Groundwater recharge is the process whereby the surplus or infiltration over evapotranspiration drains from the root zone and continues to flow downward through the unsaturated or so called 'vadose' zone toward the watertable where it replenishes the groundwater reservoir (Freeze and Cherry, 1979). Arid regions are commonly defined as areas where the potential evapotranspiration exceeds the precipitation most of the time. Because in general there is no excess of infiltration water in these areas and the groundwater table is very deep, the assumption is often made that recharge in desert areas is negligible or non-existing. This assumption has led to the deliberate placement of facilities for land disposals of toxic and radioactive wastes in desert regions, in the expectation that such wastes will remain immobile in the soil (Gee and Hillel, 1988). This might be true for certain areas at certain times, but even in deserts occasional short term periods with heavy rain, as well as the nature of the soil and its vegetative cover can particularly contribute to recharge. These days the need for quantitative determination of groundwater recharge in arid regions is increasing and the ability to efficiently model water flow through unsaturated soils is becoming more important. The objectives of this study are (1) the calibration of the computer program Swacrop for a bare soil and (2) a quantification of the precipitation-recharge process. Swacrop is a transient one-dimensional finite-difference model which simulates the water for the unsaturated zone, with possible root water uptake by vegetation. The water flow is calculated using the Richard's equation. Recharge is calculated as the potential recharge and is equal to the sum of the downward flux of water at the bottom of the simulated profile and the change of water storage in the profile.... For the calibration of the model a bare soil lysimeter experiment was used. To prevent the problems of infiltration into very dry soils, the simulation for the first 2 years of the long-term lysimeter experiment are skipped.