ABSTRACT
Groundwater practitioners are often challenged with questions like: how sure are you of the sustainable yield? What will be the impact of future changing rainfall patterns? How sure are you that my borehole will not be impacted? Numerical modelling is a powerful tool to address these questions and deal with uncertainties both in the data, and in the conceptual understanding of the data. This is shown with several models from the Western Cape of South Africa.
Numerical modelling for the Water Availability Assessment Study of the Berg Water Management Area provided information to support pre-feasibility planning decisions, such as groundwater availability, and the potential impact of large-scale abstraction on surface-water systems and on ecologically sensitive environments.
A regional model in the Hermanus area, for the municipal supply well field, shows that the magnitude of recharge has a significant effect on the groundwater system, supporting the notion that gaining accuracy in recharge numbers is an important activity. Conversely, the testing of various conceptual possibilities for the recharge pathway shows that this has minimal impact on the water levels at the well field.
Relying on a combination of good conceptual analysis with sound modelling techniques, models can go a long way to provide quantitative answers to key management questions.
