Change in In-Stream Salinity from Interception of Saline Groundwater Discharge into the Lower River Murray, Australia

Abstract

Salt accessions are the major water quality issue of the rivers and streams of the Murray-Darling Basin. The saline Murray Group Aquifer, the salinity of which exceeds 20,000 μS/cm, discharges an estimated 200 t/d of salt into the River Murray in South Australia between Lock 3 and Holder, 40 km downstream. Salinity mitigation works were needed to sustain irrigated agriculture and to maintain the quality of domestic, industrial and urban water supplies. Forty nine wells were drilled to the aquifer between Lock 3 and Holder from late 1989 to August 1990. Pumping of saline groundwater commenced in 1990 to lower the groundwater gradient to the river to zero thus preventing saline water discharging into the river. Telfer and Way estimated that pumping from the aquifer lowered salinity in the river stream by 46.3 μS/cm. Regression analysis of data that restricted it to three years prior to full pumping commenced and to 3 years after zero gradient was achieved, with sites as categorical variables, estimated a reduction of 58.4±9.4μS/cm for flows < 10,000 ML/d resulting in a reduction in salt load of 277 t/d. Regression modelling methodology can be extended to assessments of similar saline groundwater interception schemes.

Key Words:

• Saline accessions
• salinity mitigation
• groundwater pumping
• tube wells
• in-stream salinity
• regression modelling

Additional information

Notes on contributors

A P Meissner

Tony Meissner graduated from the University of Adelaide in 1968 with a BAgSc degree. He undertook potassium fertiliser research in the southeast region of South Australia (SA) from 1969 to 1976 based at Naracoorte. He returned to Adelaide where he completed a BSc in applied mathematics with a major in Applied Statistics. In late 1988, he moved to Loxton in the SA Riverland where he undertook irrigation research, funded by the Murray-Darling Basin Commission (MDBC), contributing to the understanding of irrigation efficiency within horticulture. He was a team leader for Soils & Irrigation in a cooperative interstate research and development program involving the Departments of Agriculture in NSW, Victorial and SA and the CSIRO. In late 1998, he became water licensing manager for the SA Department of Environment, Heritage and Aboriginal Affairs at Berri and later Regional Manager, Department of Water Resources. From January 2005 until January 2006, he worked for the MDBC in Canberra on secondment contributing to salinity policy. On returning to SA he spent a year in implementing the SA Natural Resources Management Plan and later manager of the Berri Hydrology Monitoring and Soil Assessment teams. His responsibilities included overseeing flow and salinity monitoring in the River Murray in SA and ensuring quality control of the SA soil monitoring work. He retired at the end of 2010 after 46 years in SA public service. Since his retirement, he has done part-time consulting on water balance of the irrigation districts of the River Murray in SA and renewed his passion for statistics.