Grahamstown Dam spilled more than 10 billion litres of water last week @newcastleheraldpic.twitter杭州龙凤论坛m/QhhnN2UlPw
— Tim Connell (@TimConnell) January 11, 2016
THEN: Hunter Water’s Jeremy Bath and Greg Mason, left, at the Grahamstown Dam Spillway last January when the water reached its lowest summer ebb in 10 years.
A YEAR after the Hunter’s dams reached their lowest summer ebb in a decade,rain has overfilled them by billions of litres.
Last weekthe gates of Grahamstown Dam were opened as rain rushed throughthe Hunter’s four major reservoirs –Grahamstown, Chichester, Tomago and Anna Bay –more dramatically than during last April’s storm.
NOW: A year on, record rain has overfilled the Hunter’s four major dams by billions of litres and prompted an unprecedented operational opening of the dam gates.
Grahamstown, a year after languishing at 76.4 per cent full,spilled more than 10 billion litres of water last week.
“It was already at about 96 per cent when the rain started,” Hunter Water interim chief executiveJeremyBath said.
“It’s the first time we’ve opened the gates for any reason other than maintenance.”
The burgeoning supply represents the most water Hunter Water has overseenforthis period in January in the utility’s 120-year history.
Last Wednesday was Newcastle’s wettest January day on record, and delivered 200 millimetres of rain to someof the Hunter.
Chichester Dam, the region’s oldest water store, spilled more than six billion litres and was still spilling, Mr Bath said on Monday,after dwindling last Augusttoa twenty-three-year low of45 per cent.
Thepresent wealth of water is a far cry fromthe 1960s and late 1970s to early 1980s, when Chichester was little more than aduck pond withcracks openingalong the dam floor.
Members of the public can view the ongoing spill at Chichesterfree of chargefrom an observational deck.
Temperatures ofup to40 degrees are forecast in parts oftheHunter forthe next three days, and Hunter Waterexpectsthe heat and high demandto noticeablydepleteshallow, evaporation-prone Grahamstown Dam.
“Whenever the temperature hits close to 40 degrees, the general rule is that whatever we use that day we’ll lose again to evaporation,” Mr Bath said.
“I expect we’ll go from 100 per cent to about 97 per cent.”
Last week’s rain also threatened to overwhelm workers at the Burwood Waste Water Treatment Plant, who dealt with a record 435.8 million litres of sewage on Wednesday.
Nine-tenths of that was storm water. Atypicalday brings about 45 million litres of “flow”through the plant.
Thenext highest volume of flowon record is from a storm inMarch 2013thatproduced388 million and 396 million litres onconsecutivedays.
The Pasha Bulka storm in June 2007 produced around361 million litres of flowper day.
Plant operators responded toless flow during lastApril’sstorm, butsome of that was because several hundredHunter Watersewer pump stations were without power.