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Potential Climate Change Impacts on Karoo Aquifers
Expanded Title:The potential impacts of climate change on water resources and hydrology for Africa and Southern Africa have received considerable attention from hydrologists during the last decade. However, very little research has been conducted on the future impact of climate change on groundwater resources in South Africa. Climate change can affect groundwater levels, recharge and groundwater contribution to baseflow. This document serves as a first step in assessing the impact of climate change on South African Karoo aquifers. Typical impacts include: The sensitivity of groundwater to drought depends on the amount of recharge. The western part of South Africa is semi-arid and has a lower recharge rate. This makes rural areas to be more susceptible to drought as a result making access to rural water supplies even more vulnerable. The first step in our approach involves the creation of a climate change vulnerability profile. In analogy with the DRASTIC methodology the DART methodology was developed. The parameters considered in the DART methodology are as follows: D – Depth to water level change; A – Aquifer type (storativity); R – Recharge and T – Transmissivity. The DRASTIC methodology was developed to express aquifer vulnerability with reference to the threat of pollution. The DART methodology focus more on typical parameters used in sustainability studies, but also indirectly accommodate the issue of quality due to the fact that the water quality is likely to deteriorate with a drop in water level over time as the salt load will concentrate. Two scenarios are considered; current and future. The current scenario is representative of the current precipitation patterns and the future scenario is representative of the predicted scenario based on the selected GCM. The results presented in this document demonstrate a method for mapping vulnerability that can be used to assess climate impacts in the context of regional to national scale. The major limitation of this approach is that the total water balance is not considered as a whole. Coupled surface-groundwater models are required for local scale assessment of possible climate change impacts based on GCM scenarios. These coupled models require extensive data sets to accurately describe the study area. The advantage of this approach is that the water balance is considered as a whole. Despite current levels of uncertainty concerning the impacts of climate change on groundwater in South Africa, much can be achieved by preparing for the worst and ensuring that adequate data and a plan of action are available for appropriate resource management decision-making. From the analysis presented, the following recommendations can be made for future work: Drought impact studies, in which impacts on groundwater withdrawal and quality are assessed; Among the urgent research needs are those that may lead to reducing uncertainty, both to better understand how climate change might affect groundwater and to assist water managers who need to adapt to climate change. Research should be focused on reducing uncertainties in understanding, observations, and projections of climate change, its impacts and vulnerabilities. Climate change modelling and impact modelling have to be better integrated and this requires solving a range of difficult problems related to scale mismatch and uncertainty.
Date Published:01/03/2013
Document Type:Research Report
Document Keywords:Ground Water, Hydrology
Document Format:Report
Document File Type:pdf
Research Report Type:Consultant
WRC Report No:KV 308/12
ISBN No:978-1-4312-0379-6
Authors:Dennis I; Dennis R; Rantlhomela P; Hogan C
Project No:K8/864
Originator:WRC
Document Size:6 094 KB
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