Staff from the Department for Environment and Water’s Water Resource Monitoring Unit (WRMU) have seen many changes along the South Australian leg of the River Murray over their time.
With river management and monitoring continuing to evolve and get more sophisticated each year, the team are beginning to notice conditions slowly improving in certain areas of the river.
The WRMU team celebrated a significant milestone this year undertaking their 25th Run of River (RoR) salinity survey which assess salinity accessions along the South Australian leg of the river from the Victorian border to Blanchetown.
Manager Monitoring Operations Tim Branford said managing salinity is one of the biggest challenges in the Murray–Darling Basin.
“If it’s not properly managed, salinity degrades water quality, hinders plant growth and reduces biodiversity and agricultural productivity,” Tim said.
“The RoR survey work estimates the amount of salt being added to the Murray per river kilometre so we’re able to see any salinity increases in the water.
“We can then put intervention measures in place to address the problem before the salinity accessions get too high.”
Tim said over 25 years the WRMU has developed the knowledge, techniques and equipment to allow annual assessment of the salt accession to the River Murray, particularly in those areas operating Salt Interception Schemes (SIS).
“It’s gratifying to celebrate 25 years of the RoR surveys. The program’s longevity is testament to the efforts of past and present staff in providing essential salinity data to inform river management,” Tim said.
“We’ve seen a lot of changes over 25 years with huge improvements in the technology and how we collect the data.
“We can now analyse data spatially and do it over time as well as distance. Previously it’d take weeks to do 600 kilometres of the river whereas now it takes three weeks to do up to 2,500 kilometres.
“We’re the only state to be running salinity surveys over such a long period of time and that’s allowed us to report on the success of the scheme over many years.”
Salinity requires ongoing management and the MDBA and State governments undertake salinity management activities and carefully monitor salinity levels to prevent it from becoming a significant problem.
The amount of salt from groundwater going into the river depends on a lot of drivers, but the main ones are natural flows, irrigation drainage, flood history (including environmental watering), climate, and the salt interceptions schemes (SIS).
Principal Groundwater Modeller Juliette Woods said her team build groundwater models which simulate past and future salt loads from groundwater going to the river.
“We have a suite of overlapping models spanning the South Australian border to Wellington and use them to better understand how much different actions influence the amount of salt entering the river,” Juliette said.
“For example, irrigation expansion can increase salt in the river, improved water use efficiency can decrease the salt, and SISs are designed to reduce the salt.
“We run what-if scenarios that are used for Basin Plan reporting and to inform SIS operations, government policy, environmental watering operations and collaborative research projects.
“The RoR data is absolutely critical for model development and updates.
“We run simulations of past decades and amend the model until its outputs match well with observed water levels and RoR salt loads - a process we call ‘calibration’ or ‘history-matching’. When the models match historical RoR, this gives us confidence in model results.”