Water Interception
Groundwater discharge can maintain stream flow particularly during dry periods. However, if the quality of the groundwater is poor, this baseflow can degrade surface water quality. Interception schemes are a series of bores along a stretch of river (or lake or wetland) used to extract groundwater before it reaches the stream. Such schemes are a common engineering solution to mitigate stream salinity. By continually pumping from the bores saline groundwater is prevented from entering the river and the river can become a losing stream with fresh river water drawn into the aquifer. The intercepted groundwater is then generally piped to a site distant from the river where it is evaporated. An Australian example is the River Murray where interception schemes have been developed to extract saline groundwater (Telfer and Watkins, 1990).
To highlight the impact of interception schemes on stream-aquifer connectivity, Figure 2 shows the results of a geophysical survey along the River Murray near Waikerie, South Australia (Allen and Merrick, 2004). The colours represent relative electrical conductivity (salinity) in a vertical profile along the river. In the zone of the interception scheme the dark blue (fresh) water has been drawn below the river bed (light blue line). This is in contrast with the regional saline groundwater represented by red in the imagery. These interception schemes are a conjunctive technology that is a critical component of meeting salinity targets for the River Murray.
Figure 1: A schematic cross section of an interception scheme
Figure 2 Electrical conductivity imaging of Murray River at Waikerie SA showing impact of groundwater interception scheme (Allen and Merrick, 2004)
Further Information
Relevant Links
SA Salt Interception Schemes
MDB Joint Works
References
Allen DA, Merrick NP, 2004. Identifying fresh and saline water using hydro-geophysical imagery of strata beneath watercourses. In: Conference Proceedings 9th Murray Darling Basin Groundwater Workshop Bendigo, Victoria 17-19 February 2004.
Hostetler S, Radke B, 1995. An inventory of saline water disposal basins, Murray Basin. Australian Geological Survey Organisation, AGSO Record 1995/4, 2 volumes
Telfer A, Watkins N, 1990 Waikerie salt interception scheme - final design report hydrogeology. South Australia Engineering and Water Supply Department, 90/14, October 1990