Book review: urban geology

Web of Scienc

Book review: estimating groundwater recharge

Web of Scienc

Snow impact on groundwater recharge in Table Mountain Group aquifer systems with a case study of the Kommissiekraal River catchment South Africa

Snowmelt in the mountainous areas of the Table Mountain Group (TMG) in South Africa is believed to be one of sources of groundwater recharge in some winter seasons. This paper provides a scientific assessment of snow impact on groundwater recharge in Table Mountain Group Aquifer Systems for the first time. Snowfall periodically occurs on the highest mountain ranges of about 1 000 to 1 200 m above mean sea level (a.m.s.l) in the TMG area. Snow over the mountainous catchments is often observed on the gentle side of the slope, which is substantially affected by wind and vegetation. Based on climatic analysis, recharge processes and Landsat 7 Enhanced Thematic Mapper (ETM) images, the recharge areas influenced by snowmelt in the TMG are identified as those catchments that are located above 1 000 m a.m.s.l. Physical processes within the snowpack are very complex involving mass and energy balances as well as heat and mass transport. Snowmelt rate was calculated using a variable degree-day melt factor determined as a function of snowpack density and vegetation cover. The hourly snowmelt rates estimated with different new snow density models. Groundwater recharge from snowmelt is affected by snowmelt mechanisms and local recharge conditions. The recharge rate is constrained by characteristics of the fractures rather than snowmelt rate. Recharge is also discounted due to prevailing interflow occurring in favourite geomorphological locations. This hypothesis is confirmed by an infiltration experiment in which up to 13.6% of the infiltrating water can recharge the aquifer.Web of Scienc

A tensor approach to the estimation of hydraulic conductivities in Table Mountain Group aquifers of South Africa

Based on the field measurements of the physical properties of fractured rocks, the anisotropic properties of hydraulic conductivity (HC) of the fractured rock aquifer can be assessed and presented using a tensor approach called hydraulic conductivity tensor. Three types of HC values, namely point value, axial value and flow direction one, are derived for their possible applications. The HC values computed from the data measured on the weathered or disturbed zones of rock outcrops tend to give the upper limit values. To simulate realistic variations of the hydraulic property in a fractured rock aquifer, two correction coefficients, i.e. the fracture roughness and combined stress conditions, are adapted to calibrate the tensor model application. The application results in the Table Mountain Group (TMG) aquifers show that the relationship between the HC value and fracture burial depths follows an exponential form with the power hyperbola.Web of Scienc

A water balance approach to the sustainable management of groundwater in South Africa

The water balance approach, based on the principles of conservation of mass, is applied to the issue of sustainable groundwater management in South Africa, incorporating the ethos of the National Water Act of 1998, prioritising basic human needs and the needs of aquatic ecosystems over inessential uses. The principle of water balance is described and the benefits (such as prevention of resource misallocation), of applying such an approach to groundwater management, are outlined, with additional practical considerations briefly reviewed. It is hoped that the approach will be tested and refined through application to groundwater case studies.Web of Scienc

Groundwater management issues in Southern Africa – An IWRM perspective

In contrast to its strategic role as essential resource to help achieve community development and poverty alleviation in the Southern African Development Community (SADC), groundwater has remained a poorly understood and managed resource. This was the finding of a scoping study regarding the status of groundwater resources management in SADC. The key premise for the assessment was that groundwater resource management must take place within an IWRM framework and the IWRM Toolbox developed by the Global Water Partnership was used as the scope and content for the assessment. The SADC region has well- developed policies for regional development and IWRM, as well as a relatively strong focus on groundwater resources. This article questions whether problems relating to Africa’s sustainable utilisation and management of groundwater is a unique groundwater problem or must also be related to the challenges experienced in general with the implementation of an IWRM approach in Africa. A key finding was that groundwater management links to groundwater-dependent sectors like agriculture, rural development, health and environment are not well- established in policy or in practice. Internationally, there is a recognition, that such a, quite common, situation can only be addressed through a long-term process through which viable national, regional and local systems can evolve, within a strategic framework in which these intended relationships between diverse sets of interventions or management approaches and the development goals are brought out. However, such a strategic, multi-stakeholder-driven approach also still remains the major challenge in Africa for IWRM implementation as a whole. Recent continent-wide initiatives, like the development of IWRM and water efficiency plans for each country and multi-stakeholder water dialogue processes, have been taken to address this challenge. It is therefore crucial that groundwater becomes an integral part of these and related initiatives. New AMCOW and SADC initiatives for groundwater provide a major opportunity to achieve this.Keywords: groundwater, community development, sustainable utilisation and management, IWR

Review: groundwater management and groundwater/surface-water interaction in the context of South African water policy

Groundwater/surface-water interaction is receiv¬ing increasing focus in Africa due to its importance to ecologic systems and sustainability. In South Africa's 1998 National Water Act (NWA), water-use licenses, including groundwater, are granted only after defining the Reserve, the amount of water needed to supply basic human needs and preserve some ecological integrity. Accurate quantification of groundwater con¬tributions to ecosystems for successful implementation of the NWA proves challenging; many of South Africa's aquifers are in heterogeneous and anisotropic fractured-rock settings. This paper reviews the current conceptualizations and investigative approaches regard¬ing groundwater/surface-water interactions in the con¬text of South African policies. Some selected pitfall experiences are emphasized. The most common approach in South Africa is estimation of average annual fluxes at the scale of fourth-order catchments (~500 km2) with base flow separation techniques and then subtracting the groundwater discharge rate from the recharge rate. This approach might be a good start, but it ignores spatial and temporal variability, potentially missing local impacts associated with production-well placement. As South Africa's NWA has already been emulated in many countries including Zambia, Zimbabwe and Kenya, the successes and failures of the South African experience dealing with the groundwater/surface-water interaction will be analyzed to guide future policy directions.Web of Scienc

Groundwater management issues in Southern Africa – An IWRM perspective

In contrast to its strategic role as essential resource to help achieve community development and poverty alleviation in the Southern African Development Community (SADC), groundwater has remained a poorly understood and managed resource. This was the finding of a scoping study regarding the status of groundwater resources management in SADC. The key premise for the assessment was that groundwater resource management must take place within an IWRM framework and the IWRM Toolbox developed by the Global Water Partnership was used as the scope and content for the assessment. The SADC region has well- developed policies for regional development and IWRM, as well as a relatively strong focus on groundwater resources. This article questions whether problems relating to Africa’s sustainable utilisation and management of groundwater is a unique groundwater problem or must also be related to the challenges experienced in general with the implementation of an IWRM approach in Africa. A key finding was that groundwater management links to groundwater-dependent sectors like agriculture, rural development, health and environment are not well- established in policy or in practice. Internationally, there is a recognition, that such a, quite common, situation can only be addressed through a long-term process through which viable national, regional and local systems can evolve, within a strategic framework in which these intended relationships between diverse sets of interventions or management approaches and the development goals are brought out. However, such a strategic, multi-stakeholder-driven approach also still remains the major challenge in Africa for IWRM implementation as a whole. Recent continent-wide initiatives, like the development of IWRM and water efficiency plans for each country and multi-stakeholder water dialogue processes, have been taken to address this challenge. It is therefore crucial that groundwater becomes an integral part of these and related initiatives. New AMCOW and SADC initiatives for groundwater provide a major opportunity to achieve this.Web of Scienc