Groundwater: our source of security in an uncertain future

PREFACE Groundwater: Our source of security in an uncertain future S Adams, J Cobbing, I Dennis and K Riemann This special edition of Water SA comprises an assemblage of scientific papers and technical notes presented at the International Conference on Groundwater: Our Source of Security in an Uncertain Future, held from 19 to 21 September 2011 in Pretoria, South Africa. A fifth of the world’s population already lives in areas that are characterised by water scarcity. It is estimated that groundwater is already a primary source of drinking water for as many as 2 billion people and supports a significant part of the world’s irrigated agriculture. Groundwater is an important resource for maintaining socioeconomic and environmental systems. Groundwater makes up the bulk of the freshwater resources on Earth and is generally underutilised in many parts of the world. MacDonald et al. (2012) estimated that there could be 100 times more groundwater in Africa than the available surface water resources. Groundwater availability is also less sensitive to annual and interannual rainfall fluctuations and is considered to be an excellent buffer during dry periods. Droughts and increased demands have triggered the search for alternative water supply options. Environmental stresses driven by the growth in population and urbanisation and the resulting energy, transport and development trends at country and global levels have further increased water shortages (World Bank, 2010), which in turn have led to more emphasis being placed on groundwater. Despite this raised profile, there are still numerous challenges. Some of the high-level challenges, not necessarily unique to groundwater, include (Adams et al., 2012): • Global change (e.g. climate change and variability) • (Ground)water pollution and depletion • Rapid urbanisation with increasing supply demands and higher pollutant loads • Coupling of the various reservoir fluxes in time and space • Governance of (ground)water and related resources • Data collection (monitoring) and data availability (management) • Uncertainty quantification (e.g. model and parameter uncertainties) • Poor land-use planning • Scale and heterogeneity • Capacity development • Complete description of complex systems • Groundwater valuation and financing Over-utilisation and the poor management of the groundwater resource are often due to poor or non-existent management plans and governance provisions. Often described as the ‘silent revolution’, groundwater use, mainly by agriculture (and to a lesser extent de-watering of mines, and municipal water supply), has led to declining water levels of several aquifer systems around the world and the perception that groundwater is an unreliable resource. The proper management of the resource is thus crucial and includes an understanding of numerous factors. These factors vary from infrastructure-related issues, data collection and interpretation, to the tools (including models and frameworks) used to guide groundwater managers within the legal constraints as dictated by authorities. This special edition of Water SA provides useful insights on groundwater resource management and provides sound answers to many challenges facing the industry, as discussed in more detail in the papers included in this issue: Foster et al. maintain that Sub-Saharan Africa is mainly experiencing ‘economic water scarcity’ due to the lack of investment in infrastructure. Information on aquifer characteristics, groundwater recharge rates, flow regimes, quality controls and use is still ‘patchy’ in most cases. However, considerable efforts have gone into mapping the world’s aquifers at local, regional and global scales. Improved estimates of groundwater recharge are essential for the sustainable management of groundwater resources. However, sustainable groundwater development depends on increased abstraction being compensated for by increased recharge and/or reduced discharge; referred to as the ‘capture principle’ (Seward et al., 2006). Stone and Edmunds estimated the rate of groundwater recharge through the dune-sands of the Kalahari overlying the Stampriet Basin in Namibia. They used the chloride mass balance method for a first estimate of the direct recharge rate through the dune-sands. This is an example of the application of proven techniques in the search for better groundwater management. Holland provides an assessment for the factors responsible for improved groundwater yields within geologically-complex hard-rock terrains. Du Toit et al. show the value of re-interpreting existing datasets to show that groundwater resources in the Limpopo Province of South Africa can be utilised as a bulk water supply option. Pavelic et al. present a simple analytical framework that can be used to assist with decision making for irrigation from groundwater, and to determine the potential areal extent under different cropping patterns. However, limited data availability and uncertainties associated with certain parameters hamper the expansion of the approach to other areas. Whilst in some instances excellent data gathering and management is taking place, in most other places limited data gathering and management occurs. Groundwater resource Available on website http://www.wrc.org.za ISSN 0378-4738 (Print) = Water SA Vol. 38 No. 3 International Conference on Groundwater Special Edition 2012 ISSN 1816-7950 (On-line) = Water SA Vol. 38 No. 3 International Conference on Groundwater Special Edition 2012 357 planning should be brought into the realm of surface-water resource planning by applying the concepts of assured yields. Murray et al. developed these concepts into 2 models; the Aquifer Assured Yield and the Aquifer Firm Yield Models, and demonstrated the successful application of these within the Karoo aquifer system of South Africa. Murray et al. also show that with proper planning tools favourable groundwater potential areas can be identified for bulk use. However, groundwater systems are more complex, and thus inherently more difficult to manage, than surface water. Also, groundwater availability is less sensitive to annual and inter-annual rainfall fluctuations than surface water (Giordano, 2009); though over time the overall impact of these fluctuations will be negative. The role that groundwater can play in minimising the impact of climate change threats is significant but would require careful management. Dennis and Dennis have developed the DART (Depth to water-level change, Aquifer type (storativity), Recharge and Transmissivity) index, which can be used to identify areas that could potentially experience changes in their groundwater resources as a result of climate change. Groundwater sustainability is considered to be a value-driven process, based on intra- and inter-generational equity, which balances the needs of the environment, society and economy (Gleeson et al., 2011). However, the social aspects of groundwater development projects are (...truncated)