Shallow groundwater has risen across the region due to periods of above average rainfall in 2017, according to Goulburn-Murray Water’s annual watertable study.
The study monitors more than 1000 observation bores and allows G-MW to map shallow groundwater level changes across the Shepparton Irrigation Region, which includes the Murray Valley, Shepparton, Central Goulburn and Rochester irrigation areas.
As part of the study, groundwater has been mapped in depth segments of 0-1m, 1-2m and 2-3m from the ground’s surface.
G-MW drainage systems manager Simon Cowan said the increased area showing shallow groundwater rises could be linked to average to above average annual rainfall, particularly in late autumn and early winter 2017.
‘‘The August 2017 study saw a notable increase in area associated with the 1-2m and 2-3m depth ranges compared to 2016,’’ Mr Cowan said.
‘‘At the same time, the watertable within the shallower 0-1m depth range decreased markedly in 2017.
‘‘The majority of this decrease occurred in an area between Lake Cooper and Waranga Basin. This area tends to show greater annual fluctuations than any other part of the SIR.’’
Mr Cowan said in the 12 months to the end of July 2017, rainfall totalled 549mm, compared to the annual average for this period between 1982 and 2017 of 442mm.
‘‘We tend to see rising watertables when rainfall occurs on a wet catchment. During extended dry periods, there are risks associated with high watertables.’’
While these recent watertable rises are not likely to impact customers, they highlight the value of long-term monitoring and planning.
Goulburn Broken Catchment Management Authority’s sustainable irrigation manager Carl Walters said the mapping project had been undertaken since the early 1980s.
‘‘It’s been a significant and simple tool to help landholders and the community understand what is happening with the rise and fall of the threat of salinity over time,’’ Mr Walters said.
‘‘As rising groundwater is often linked to an increased risk of salinity, the annual watertable study has also helped us with the planning and development of salinity management programs such as surface drainage, watertable management and irrigation efficiency.’’