2 Renmark to border LAP area assessment - EPA - Sa.gov.au

River Murray and Lower Lakes catchment risk assessment for water quality: Results and management options
saline and connected to the river) and creek (Big and Little Toolunka creeks) discharges. Run of the river
and other salinity modelling studies have noted significant saline groundwater inputs in the RW LAP
region between Waikerie and Morgan supporting this general level of risk. Horticultural land use in these
areas is predominantly citrus and grapes that employ drip and/or canopy irrigation (Croucher 2005).
Large irrigated areas have increased saline groundwater flows to the river and floodplain by creating an
‘irrigation mound’ (elevated water head under irrigation areas). Irrigation displaces approximately 950
tonnes of salt per day within the RW LAP area: 210 tonnes enters the river and the rest is stored on the
floodplain (RW LAP 1999). There is some uncertainty about the ecological impact of salinity from saline
discharges to the river, as salinity levels have historically been variable (MDBC 1988).
Several management schemes are in place or planned to manage salt in the region, including from the
high risks identified above. SA Water operates two large salt interception schemes located at Waikerie
and Woolpunda which work by capturing saline groundwater using deep bores near the river and pumping
it away to a specially created disposal basin at Stockyard Plain (15 km south-west of Waikerie). Before
these schemes were implemented, the River Murray was carrying up to 250 tonnes per day of salt past
Woolpunda and 100 tonnes a day past Waikerie. Recent surveys show these salinity levels have decreased
to less than 10 tonnes a day in each area7 . Irrigation drainage that used to enter Ramco lagoon is also
now being diverted to the Waikerie scheme and a management plan is in place for this lagoon. A Hart
lagoon wetland management plan has been developed to manage the wetting and drying cycles of the
lagoon to maintain and enhance native flora and fauna communities, and reduce the impact of salinity
on the wetland. Irrigation practices have generally improved in the Riverland area and flood irrigation is
now rare. An on-ground water efficiency project is currently providing irrigators with information and
increasing awareness of best-practice land management. While irrigation technology has been well
adopted throughout the region, this project aims to provide high-level understanding of current bestpractice
techniques. The Riverland revegetation incentive scheme has also been in operation, in which
groups or individual landholders are encouraged to rehabilitate wetlands and other native vegetation
sites within their property.
The non-permanently connected wetlands were rated as a moderate risk during large rainfall events or
floods when salt, previously trapped in the floodplain and non-flowing creeks, is mobilised and flushed
into the river proper. The risk may be higher during the initial ‘first flush’ of such an event; further
research is needed to refine the risk assessment. The RW LAP area is part of the combined Riverland
network, where several small-scale projects are in place to monitor discharges from lagoons and
wetlands within the region.
Nutrients
Several large horticulture areas noted above as high risks for salinity also received a high risk ranking for
leakage of nutrients (in particular nitrate) through groundwater to the river, based on their large-scale
saline groundwater inputs. Elevated levels have been reported under irrigation areas in other areas of
South Australia (eg Northern Adelaide Plains, EPA 2003a). Some lagoons (Hart and Ramco) that receive
irrigation drainage and are permanently connected to the river also received a high-risk ranking.
7 See
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