Rain hope but system secure

Water managers have described winter and spring rain and subsequent inflows into reservoirs this year as critical in maintaining a security buffer for regional supply.

But they remain confident, despite hot, dry and windy conditions depleting reserves, there is enough water in Grampians storages to meet regional ‘consumptive’ needs for the next couple of years.

Gwmwater managing director Mark Williams said the Wimmera-mallee Pipeline was continuing to do its job in consolidating water security for a vast region.

He agreed circumstances were ‘tighter’ than at the same time last year, but the Wimmera-mallee Pipeline was preventing considerable seepage and evaporation and – apart from regional stock and domestic supply – had allowed Gwmwater to continue to supply designated recreation water bodies.

“From a consumptive perspective we have about two years of supply in the Grampians system, which is solid level of security,” Mr Williams said.

“Conditions are a bit tighter in providing supply via the Northern Mallee Pipeline from Murray and Goulburn systems.

“The general message is that we would like to have a wet season to replenish the resource right across the region.”

Gwmwater water resources manager Kym Wilson said more than 200,000 megalitres remained in storage in the Grampians system, representing almost 36 percent of capacity.

“It doesn’t sound a lot but that type of volume, under careful management, provides a high level of security of supply for our towns and farmers well into next year,” he said.

“But rain in the next winter-spring period will be critical in maintaining the same type of levels for this time next year. We’ve had a dry winter and spring, providing about 25 percent of the average inflow for the year to date.

“December had many hot and windy days that led to high evaporation rates.”

Evaporation

Mr Wilson said figures showed more water evaporated from storage reservoirs than Gwmwater had released for supply needs in December.

“About 11,000 megalitres evaporated in December, compared with about 6400 megalitres provided to the region for towns, farms and the environment,” he said.

“More water evaporates than is supplied in most years in December. That’s why it is important to have several reservoirs to manage water efficiently.

“To put it into perspective, Lake Lonsdale represents our most least-efficient storage reservoir. When holding a moderate amount of water it can lose hundreds of megalitres a day straight up into the atmosphere.

“It can be hard to understand because you can’t visualise this water disappearing during hot periods, but it does.

“In comparison, Lake Bellfield is our most efficient reservoir.

“This is a primary consideration when operating and managing the system and can mean moving water to more efficient storages and this can understandably create levels of community anxiety.

“At the end of the day we have to ensure there is water for farms, towns, people, animals and environment and when in below-average rain cycles must be more prudent in operating the system to guarantee supply. We will be watching circumstances closely and plan for the possibility of a dry season ahead.”

Mr Wilson said people keen to know more about regional water-supply planning could find detailed information on Gwmwater’s website, www.gwm water.org.au.