The Development of a New Methodology to Interpret Run oi River Salinity Data to Assess Salt Inflow to The River Murray

Abstract

In addition to the threat posed by high salinity to drinking water, increased salinity in the River Murray also represents a threat to the health of floodplains, wetlands and may increase the costs of infrastructure maintenance. In the Lower Murray Basin most of the salts in the river originate from groundwater. Run of river salinity surveys are used to measure salt inflow. They measure electrical conductivity every kilometre over five consecutive days, at low and steady river flows. For a robust interpretation of salt inflow, the background electrical conductivity has to be removed from the measurements. The existing methodology is robust for analysing cumulative salt inflows over river reaches but assigns salt inflows up to several kilometres downstream from where they actually occur. A new method has therefore been developed to assign the salt inflow more closely to the location where it actually occurs and at the correct rate. The new methodology is based on the assumptions that salt inflow is the function of space only (during the survey) and the background conductivity can be described by the temporal variations observed at a fixed location. These in turn allow better targeting of the high salt inflow zones for salt interception.

Key Words:

• Salinity
• groundwater discharge
• surface water/groundwater interaction
• Australia
• Murray-Darling Basin

Additional information

Notes on contributors

R Burnell

Dr Gabor Bekesi is a Principal Hydrogeologist with Australian Water Environments. Gabor has a BSC(Hons) in Geophysics from the University of Miskolc, Hungary; and MSc in geophysics and a PhD in physical geography from Victoria University of Wellington, New Zealand. Gabor has 28 years’ experience in hydrogeology, including regional groundwater system analysis, and the development and evaluation of both monitoring networks and monitoring data. Gabor has specialist expertise in groundwater sustainability and impact assessments, permitting, negotiating and imposing conditions on water licenses.

G Bekesi

Andrew Telfer is a Director of Australian Water Environments and Senior Principal Hydrogeologist. Andrew holds a Graduate Diploma (First Class) in Applied Science - Applied Geology and a Bachelor of Applied Science in Applied Geology (BAppSc) from the South Australia Institute of Technology. Andrew has specialist expertise in groundwater engineering and groundwater hydraulics, including salt interception scheme borefield investigation, design, implementation, monitoring and reviewing; groundwater-surface water interactions and groundwater-vegetation interactions; aquifer storage and recovery design and implementation; project director of integrated water and catchment management projects; and strategic and applied water resource management. Andrew has used run-of-river and other in-river data to constrain borefield designs to prevent saline groundwater discharge to the River Murray since 1987.

A Telfer

Peter Forward is Principal Engineer Salt Interception with SA Water and is responsible for the management and operations of the salt interception schemes operated by SA Water on behalf of the Murray-Darling Basin Authority. He has worked for SA Water in a wide variety of roles since 1977, and living and working in the Riverland of South Australia from 1981 to 2000 he was involved in many aspects of irrigation and drainage, domestic and country lands water supply, water resources management and River Murray operations prior to assuming his current role.

P Forward

Barry Porter will shortly be retiring after 37 years working on the Murray River in South Australia and interstate. Since 1987 he has been closely involved with the monitoring and evaluation of salinity and salt loads in the Murray River with the South Australian Department for Water Resources and its many incarnations. He has had a major role in developing specific monitoring techniques such as “Runs of River Salinity Surveys” and “Instream 3D salinity mapping” as methodologies for monitoring the success of Salt Interception Schemes and the effects of river management changes on long-term salinity. Barry has managed the River Murray database since 1989, and has had a major involvement in tracking down old data sets and incorporating these into the modern digital archive. He has authored or co-authored many conference papers on salinity and salt load monitoring techniques, and recently has been involved in the development of Nanotem Moving Boat Salinity Mapping as a viable salinity management tool.

B Porter

Rob Burnell is a Principal Engineer and Partner at Australian Water Environments (AWE), with 35 years’ experience in the water industry. He worked for SA Water for 30 years, where he became interested in River Murray salinity issues while undertaking Project/Construction Management of the Waikerie and Woolpunda Salt Interception Schemes. Since joining AWE his focus has been on River Murray salinity through involvement with the design and construction of new salt interception schemes, reviews of established schemes, and analysis of the vast amounts of salinity data with the aim to improve the understanding of groundwater and surface water processes that influence the spatial and temporal distribution of saline inflow to the River Murray.