Collingham, E.B. and Newman, R.J. 1984. A Permanent Wellpoint Scheme for the Control of Saline Groundwater. Fourth Australian - New Zealand Conference on Geomechanics, Perth, 14 - 18 May, 1984.

Saline groundwater stored beneath Lake Victoria in south-west NSW is discharging to Rufus River and thereby effecting the salinity of the water in the Murray River. A case study is presented which details the investigation, design, construction and commissioning stages of a permanent wellpoint scheme for the extraction of the highly saline groundwater beneath the Lake.
The interception scheme, known as the Rufus River Groundwater Interception Scheme, was commissioned in late 1983 and funded by the River Murray Commission at a cost of $3.3 million.

Lake Victoria is the source of the salinity problem in the area. The lake was a natural lake which has since been converted into a massive off-stream storage for the River Murray by raising its top water level. Freshwater stored in the lake forces salty groundwater in the sands beneath the lake to migrate towards the Rufus River.
Rufus River is used as the discharge channel which returns water stored in the lake back to the River Murray. Although Rufus River is only 3 km in length, the natural groundwater salinity adjacent to it is so high and the groundwater inflow rate is so large that the channel collects salt in the order of 200 tonnes per day.
A typical soil profile beneath the lake consisted of clays to 4 metres, followed by medium grained sand to 12 meters. From 12 metres to 28 metres a coarse sand with clay floc is present, which is underlain by clayey sand.

• 178 wellpoints were installed with PVC pipe and 4 km of 150mm suction manifold;
• 4 pumping stations were installed and the main centrifugal pump had a capacity of up to 20 L/s;
• all joints were glued carefully to avoid potential air leakages;
• flexible PVS helicoil suction hose was used for the cross connections from the wellpoint to the manifold;
• each wellpoint contains an inspection cover at the surface;
• following installation, each of the wellpoints were individually developed and yield tested (at a vacuum of 95 kPa the typical yield was 2 L/s); and
• the vacuum relief valve was set to correspond to the required groundwater drawdown level.

Prior to construction, the design and performance of the wellpoint system was modelled to enable for maximum economic efficiency.

At the time the report was written, the performance of the scheme had not been monitored.

The technical and economic feasibility of the trial interception scheme undertaken at Rufus River are yet to be determined. If successful, the primary benefit derived from the interception scheme is the protection of the River Murray from highly saline groundwater inflows, and as a result significant economic returns are generated.
The economic viability and technical practicalities of such an interception scheme in a dryland context would require the value and degree of protection provided to a receiving water body to be determined on a site by site basis.

The following are key determining factors for the successful implementation of groundwater interception schemes in dryland areas:

• adequate discharge from the groundwater bores to achieve a drawdown below the water level of the receiving water body;
• a suitable disposal strategy; and
• a perceived or actual benefit from the protection of the surface water body.