Management of a karoo fractured-rock aquifer system - Kalkveld water user association (WUA)

Due to large-scale development of groundwater resources for irrigation purposes the Kalkveld area has been identified by DWAF as an area where a water user association ( WUA) should be established in order to achieve better management of the resource. The area represents typical Karoo type fractured-rock aquifers, which consist mainly of sandstone, mudstone, shale and siltstone. The majority of boreholes drilled in Karoo formations have very low immediate yields (< 1 l/s). However, large volumes of groundwater are pumped from boreholes in the Kalkveld area for irrigation of commercial crops. Thus, these aquifers have a more complex and unpredictable behaviour than normally described in the literature. Groundwater management units have been delineated based on: similar hydraulic properties; recharge characteristics; land use; geology (including the distribution of surface calcrete deposits); rainfall; and hydrochemistry. A numerical flow model was constructed for the area to evaluate the impact of increased abstraction on the groundwater resources as well as to evaluate the response of the delineated water management units/areas. To facilitate long- term management of the groundwater resources a user-friendly prediction and management tool was developed. The tool together with the recommended monitoring and management measures should enable DWAF and the WUA to manage the groundwater resource in a sustainable manner.