Groundwater resource quality objectives for the crocodile west catchment

Abstract

Setting groundwater Resource Quality Objectives (RQOs) are difficult as groundwater is not bound to surface water drainage regions. The primary purpose of this study was to determine generic groundwater RQOs for the Crocodile-West catchment on a regional scale. Secondly, a case study was done to test the methodologies as set out in this thesis and to set numerical RQO limits on a local scale, as this is required for RQOs to be gazetted. To achieve this purpose groundwater resource units (GRUs), units with similar geohydrological features, were delineated based on available geohydrological parameters and a prioritisation strategy was developed. A groundwater profile was delineated for use in the prioritisation tool. The Reserve determination and management class classifications, projects preceded by the Department of Water Affairs (DWA), for Integrate Units of Analysis (IUAs) in the Crocodile-West catchment were consulted in conjunction with a prioritisation strategy as described in this thesis to determine groundwater RQOs for the study area. The groundwater RQOs must promote the Reserve determination and the management classes for each IUA as set out by the DWA. Highly prioritised RUs were identified with use of the developed prioritisation tool. The reason behind prioritisation is to identify areas which need further, more in depth investigation on both groundwater quality and quantity. Adhering to all the RUs at once is impossible as it would be too expensive and time consuming. Regional scale groundwater RQOs and groundwater RQOs for a local scale case study were successfully drafted based on available geohydrological data. GRUs were also successfully delineated and a prioritisation tool developed. The groundwater RQOs for the Crocodile-West catchment can easily be adjusted as more up-to-date data becomes available. The prioritisation tool proved useful in the setting of groundwater RQOs and identifying areas of concern. The quaternary drainage regions were chosen as the reporting RUs for RQOs to encourage Integrated Water Resource Management (IWRM). Also after frequency analysis of the geohydrological data it was found that groundwater in the catchment strongly correlates with the topography. There were no convincing reasons to report groundwater RQOs to any specific geological units. Challenges included - setting RQOs without a public participation process; - Data which isn’t up-to-date; - Groundwater characteristics varying a lot over the entire catchment. It is important that the methodologies for setting groundwater RQOs be updated regularly and with care as they are corner stone guidelines for preventing degradation of our precious resource- groundwater.