Lake Mul­wala to be emp­tied this win­ter

Yarrawonga Chronicle - - Front Page - BY JARED LOUGHNAN

Lake Mul­wala will be low­ered by about 3.5 me­tres this win­ter to fa­cil­i­tate works around the lake fore­shore and to con­trol weed.

Af­ter much spec­u­la­tion in re­cent months Mur­ray–Dar­ling Basin Au­thor­ity (MDBA) and Goul­burn-Mur­ray Water (GMW) con­firmed last Fri­day the lake would start to be emp­tied at the end of April and be full again by early Au­gust.

Au­thor­i­ties have com­mit­ted to low­er­ing the lake ev­ery few years to mainly con­trol the in­va­sive aquatic weed, Ege­ria densa.

In the last 10 years Lake Mul­wala has been low­ered four times in 2008, 2009, 2011 and again in 2015.

Vic­to­rian De­part­ment of Pri­mary In­dus­tries ex­pert Dr Tony Dug­dale told the Chron­i­cle in 2011 it was “un­likely Lake Mul­wala will ever be rid of Ege­ria densa”.

“Not un­less some­thing com­pletely out of the or­di­nary or unexpected hap­pened. Draw­ing down the water in the lake to ex­pose the Ege­ria to air is the most ef­fec­tive and read­ily avail­able method of con­trol,” Dr Dug­daale said.

In an eco­nomic boon for Yar­ra­wonga Mul­wala the ad­vanced no­tice of the draw­down in 2015 al­lowed time to plan more than an es­ti­mated $1 mil­lion in pub­lic and pri­vate works in and around the lake.

Works in­cluded the con­struc­tion and re­pair of ma­jor re­tain­ing walls, build­ing of around 30 jet­ties, ero­sion con­trol works and the main­te­nance of boat ramps.

GMW Gen­eral Man­ager Cus­tomer Op­er­a­tions, Scott Bar­ber, said that win­ter draw­down was im­por­tant be­cause it en­ables struc­tural works to be un­der­taken around the lake.

“We’ll use this op­por­tu­nity to up­grade the re­tain­ing wall along the Yar­ra­wonga fore­shore and look to as­sess and im­prove boat ramps if needed,” Mr Bar­ber said.

“The main rea­son for the win­ter draw­down is to con­trol the ex­ten­sive build-up of the highly in­va­sive aquatic weed Ege­ria densa which can dis­place na­tive sub­mersed veg­e­ta­tion and im­pacts on the lake’s us­age, mak­ing it harder to swim, fish, launch boats and water ski.

“We have lis­tened and taken on-board com­mu­nity feed­back about the build-up of the aquatic weed in the lake and sug­ges­tions of a draw­down this year to re­duce the weeds im­pact on recre­ational ac­tiv­i­ties.

“Pre­vi­ous win­ter draw-downs have proved ef­fec­tive in con­trol­ling the wa­ter­weed which dies off as it dries out and when ex­posed to frost.”

MDBA’s head of River Man­age­ment, An­drew Reynolds said the lake will be back to its usual level in early Au­gust.

“Lake lev­els will start to fall slowly from 30 April by about 70cm un­til mid-May when the ir­ri­ga­tion sea­son ends,” Mr Reynolds said

“Once we are sure that ir­ri­ga­tion water de­liv­ery to customers is fin­ished for the year, we’ll ac­cel­er­ate the draw­down un­til Lake Mul­wala is 3.5 me­tres lower than nor­mal—a level we ex­pect to hold un­til mid-July when re­fill­ing will start.

“The draw­down will be man­aged in a way that poses min­i­mal risk of im­pact­ing on avail­able water re­sources in the com­ing sea­son.

“I recog­nise that Lake Mul­wala is im­por­tant to the lo­cal com­mu­nity and that any sig­nif­i­cant change in the lake level may have so­cial and eco­nomic ef­fects,” Mr Reynolds said.

“The low­er­ing will ex­pose the lake flats, which will be muddy, re­duc­ing amenity, ac­cess and the abil­ity to launch boats from the boat ramps. Peo­ple will still be able to boat and fish in the main river chan­nel that runs through the lake but will need to launch their boats up­stream.

“Along with GMW we have been talk­ing with com­mu­nity mem­bers, coun­cil and tour- ism op­er­a­tors to try to min­imise and limit dis­rup­tions.”

Last year GMW and the MDBA re­leased the Wa­ter­weed Wipe­out app. The tool is de­signed to help the com­mu­nity bet­ter un­der­stand the man­age­ment tech­niques used to con­trol the in­va­sive weed. Wa­ter­weed Wipe­out is free and avail­able from the App Store and Google Play for Ap­ple and An­droid phones and tablet de­vices.

In ac­cor­dance with the long­stand­ing Mur­ray–Dar­ling Basin Agree­ment, River Mur­ray op­er­a­tions as­sets are owned by a ‘Joint Ven­ture’ com­pris­ing of basin state and fed­eral gov­ern­ments. The MDBA is tasked to op­er­ate the River Mur­ray system on be­half of the Joint Ven­ture. GMW is the state con­struct­ing au­thor­ity re­spon­si­ble for man­ag­ing and main­tain­ing Lake Mul­wala un­der the di­rec­tion of the MDBA.

A low­ered Lake Mul­wala this win­ter will again pro­vide a unique spec­ta­cle.

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