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Reducing uncertainties of evapotranspiration and preferential flow in the estimation of groundwater recharge
Expanded Title:It is widely acknowledged that groundwater recharge estimates can be improved through improved estimation of evapotranspiration (ET) and preferential flow. Uncertainties exist in the estimation of ET that would account for below-potential water use by vegetation as well as preferential flow paths of water and contaminants. Soil water fluxes determining groundwater recharge are also the main drivers of solute and contaminant transport by convection. In that sense, it is inevitable that processes like ET and preferential flow are also relevant to groundwater quality and the protection of groundwater resources. The general objective of this project was to develop improved process-based estimates of groundwater recharge. The approach consisted in establishing field trials at the two study sites. Evapotranspiration measurements were invaluable in gaining understanding of the water use and water balance of two types of fynbos. It was the first time that measurements of ET were done on Atlantis Sand Plain Fynbos and Kogelberg Sandstone Fynbos. Soil hydraulic properties, in particular saturated hydraulic conductivity and preferential flow patterns, play a large role in groundwater recharge. Less variability in the hydraulic properties of Riverlands soils was evident compared to Kogelberg. The uncertainty of the estimates of groundwater recharge depends on the accuracy of measured input data into the model (e.g. scintillometer measurements, weather instrumentation etc.) and variability in environmental factors (rainfall, groundwater levels, vegetation, hydraulic properties etc.). The technique used in the uncertainty analysis showed that the error propagation method can be useful for analysing the influence of input data on the simulated groundwater recharge.
Date Published:03/03/2012
Document Type:Research Report
Document Subjects:Water Resource Management/IWRM - Catchment Management
Document Keywords:Ground Water, Hydrology
Document Format:Report
Document File Type:pdf
Research Report Type:Standard
WRC Report No:1909/1/12
ISBN No:978-4312-0272-0
Authors:Jovanovic N; Bugan RDH; Israel S; Dzikiti S; Kapangaziwiri E; Le Maitre D; Rozanov A; Stander M; Mikes D; May F; Jarmain C; Everson C
Project No:K5/1909
Originator:WRC
Organizations:CSIR Natural Resources and the Environment Stellenbosch; Department of Soil Science, University of Stellenbosch; School of Bioresources Engineering and Environmental Hydrology University of KwaZulu-Natal
Document Size:6 185 KB
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