A Geostatistical-Hydrogeological Approach To Groundwater Monitoring Network Design In South Western Karoo, South Africa

Groundwater in the South Western Karoo is of critical importance in the overall freshwater supply. However groundwater sustainability is vulnerable to natural as well as anthropogenic influence. Groundwater monitoring scheme are employed to provide the necessary information during decision making situations. Groundwater monitoring thus performs in important role in groundwater management and protection. Interest in exploiting potentially vast reserves of shale gas in the deep geological formations in the region, has been met with concerns that can negatively impact the groundwater system. The current monitoring network is not adequately designed to capture the necessary level of information. Hence in this paper a revised monitoring network is designed. A novel geostatistical hydrogeological approach is applied to a case study area in the South Western Karoo. Kriging methods are used to determine required density of the new network using the spatial autocorrelation of water levels in the case study area. Using the spatial autocorrelation range a hexagonal sampling grid is developed. Using key hydrogeological features, such as contaminant pathways and zones of favourable water resources monitoring points are systematically positioned within the sampling grid. Using thus approach the current monitoring network is expanded from 34 points to a total of 95 monitoring points. The new network shows an increase in optimization by lower overall kriging prediction standard error than the current network. This allows more efficient monitoring of baseline conditions and detection monitoring.