The challenges and implications of assessing groundwater recharge: A case study – northern Sandveld, Western Cape,South Africa

Abstract

The Department of Water Affairs and Forestry (DWAF) is currently carrying out detailed hydrogeological studies within the
northern Sandveld area, Western Cape, South Africa. In addition, preliminary studies funded by DWAF, have also been carried
out in the area assessing hydrological, ecological and botanical components. The area is receiving much attention due to its
environmental uniqueness (part of the area is a Ramsar site) and its significant groundwater resources, which are being utilised
for agricultural purposes and municipal water supply. In certain areas this groundwater abstraction is impacting on surface water
flows, groundwater and associated ecosystems.
In order to gain an understanding of the systems and their inter-relationships within the area, it is necessary to carry out water
balance calculations. In carrying out such calculations, the quantification of the “input” component and associated temporal and
spatial variability is important to address. With special emphasis on groundwater recharge, the area may be receiving both direct
groundwater recharge, (as a consequence of precipitation), and distant groundwater inflow, via the large faults that transect the
area, which may be importing groundwater from the inland recharge areas (i.e. the Cederberg Mountains).
Earlier groundwater recharge studies within the area and in geologically similar settings indicate a wide range in recharge
values. With special reference to the primary aquifers, earlier conservative recharge values indicate 8% recharge, with values as high as 15% being obtained. The current study indicates direct recharge values in the region of 0.2 to 3.4%. Assessment
of water balance calculations indicate these recharge values are more realistic. The groundwater recharge quantification has huge significance for the Resource Directed Measures that are also being carried out in the area, in line with the requirements of the South African National Water Act of 1998. The Resource Directed Measures are aimed at ensuring water resource use and development is balanced by protection measures thereby guaranteeing the sustainable use of the resource.

Water SA Vol. 30 (5) 2005: pp.75-81