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Assessment of Groundwater Availability from Recession Flows and Instream Flow Requirements of Rivers in South Africa
Expanded Title:Groundwater is an important resource for multiple uses in South Africa. However, setting limits to its sustainable abstraction while assuring basic human needs is a must. Due to prevalent data scarcity related to groundwater replenishment, which is the traditional basis for estimating groundwater availability, the present report presents a novel method for determining allocatable groundwater in quaternary catchment through information on stream-flows. Using established methodologies for assessing base-flows, recession flows, and in-stream ecological flow requirements, the methodology develops a combined stepwise methodology to determine annual groundwater storage volumes in the catchments using linear reservoir theory, essentially linking low flows proportionally to upstream groundwater storages. The approach was trialled for twenty-one perennial and relatively undisturbed quaternary catchments with long-term and good stream-flow records. Using the Desktop Reserve Model to estimate in-stream ecological flow requirements of the streams and equating these with ecological groundwater reserve, excess base-flows were converted into groundwater storages on an annual basis. Results show that groundwater development potential exists in nineteen of the catchments, with upper limits to allocatable groundwater volumes ranging from 0.01 to 1.58 MCM/yr over the catchments. With a secured availability of these volumes 75% of the years, variability between years is assumed to be manageable. A significant (R2 = 0.86) correlation between base-flow index and the drainage time scale for the catchments underscored the physical basis of the methodology and also enables the reduction of the procedure by one step, omitting recession flow analysis. The method serves as an important complementary tool for the assessment of the groundwater part of the Reserve and the groundwater directed measures.
Date Published:01/05/2015
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:Consultant
WRC Report No:KV 339/15
ISBN No:978-1-4312-0677-3
Authors:Ebrahim GY; Villholth KG
Project No:K8/1049
Document Size:4 074 KB
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