Sustainable groundwater use, the capture principle, and adaptive management

Abstract

The purpose of this paper is to review the case for using 'capture' rather than recharge as the conceptual basis for sustainable groundwater use in South Africa. Capture refers to the sum of the increase in recharge and decrease in discharge brought about by pumping. Definitions of sustainability are reviewed, and the capture process is outlined. Implications for using the capture principle in the implementation of the NWA are discussed, and adaptive management is proposed as an appropriate management approach. Implications for groundwater monitoring are also discussed. Case studies are described that support the need for adaptive management and the application of the capture principle.

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

“…The approaches advocated by Parsons and Wentzel (2007) and that presented by Seward et al (2006) are actually not necessarily in conflict. Seward et al (2006) challenge DWAF's approach by arguing that the water-balancing process does not account for where the water is coming from.…”

“…There is, therefore, no single "safe" or "sustainable" groundwater yield, but only a range of permissible yields that depend not only on physical aquifer properties, but also on balancing social, economic and ecological concerns. Seward et al (2006) therefore advocate adaptive management in recognition that our knowledge of groundwater systems will always be inadequate. Groundwater licensing and extraction should be a well-planned iterative process based on good modeling of the groundwater system (conceptual or mathematical), monitoring the effects of the abstractions and adjusting the licensing as necessary.…”

“…Pumped groundwater must come from one of three sources: (1) a change in storage and a resulting decline in the potentiometric surface, a source that by definition is not sustainable; (2) an increase in recharge such as capture of water from adjacent aquifers or surface-water bodies; or (3) a decrease in discharge including reduction in baseflow, spring flow, reduced yields from other borehole or reduced water extraction by phreatophytes. Seward et al (2006) recognize that any groundwater extraction is likely to eventually affect groundwater discharge rates. There is, therefore, no single "safe" or "sustainable" groundwater yield, but only a range of permissible yields that depend not only on physical aquifer properties, but also on balancing social, economic and ecological concerns.…”

“…In the case of rivers, this is an important component of the in-stream flow requirements. Seward (2010) and Seward et al (2006) regard the approach represented by Eq. 1 as conceptually flawed.…”

“…The RQOs are ideally defined with broad stakeholder participation, and they define the limits of acceptable development (i.e., acceptable risk) using parameters that can be numeric or descriptive, but need to be simple and measurable (Parsons and Wentzel 2007). For groundwater resources, RQOs may be set to avoid damaging ecosystems, drying up springs and other boreholes, saltwater intrusion, land subsidence or formation of sinkholes (Seward et al 2006). Groundwater RQOs typically apply to groundwater quality, levels, gradients, pumping rates and land use including prohibition of certain activities within delineated protection zones (Parsons and Wentzel 2007).…”