Water resources management has traditionally focused on surface water and ground water as if they were separate entities, but nearly all surface-water features (streams, lakes, reservoirs, wetlands, and estuaries) interact with groundwater. Water withdrawal or pollution of one of these water sources can clearly affect the other. Thus, effective land and water management requires a clear understanding of the linkages between groundwater and surface water as it applies to any given hydrologic setting (Colvin et al. 2007).
In the Middle Kunene for instance, groundwater can discharge on to the land surface or surface water can infiltrate into the ground. In the Lower Kunene, the seasonal (ephemeral) streams also function as groundwater aquifers and are thus important elements in the landscape even when there carry no surface water. These ephemeral rivers are “influent” systems, which means that the groundwater tables are fed by the river, rather than a high water table acting as source for the river, as is the case with “effluent” rivers. (See here for further explanation of this phenomenon).
Artesian borehole.
Source: Harald Zauter, 2007
( click to enlarge )
Groundwater/Aquifer Dependent Ecosystems
Aquifer dependent ecosystems occur in areas where aquifer flows and discharge influence ecological patterns and processes. They are ecosystems which require groundwater from aquifers to sustain part of their life-cycle, to maintain a habitat with a water budget, or to maintain a water quality that contrasts with the surrounding ecosystems (Colvin et al. 2007).
The nature of the groundwater-ecosystem interaction has not been reliably established, and the extent to which wetlands such as the Kunene Flats, or pans in the Lower Kunene and other ecosystems are dependent on groundwater is not known and constitutes a fundamental knowledge gap (SADC 2010).
