Lake levels are at their full point of 391m from a river stage height.
The man-made 700ha lake, near Fairlie, is managed for farm irrigation, hydro-power generation, drinking water and recreational purposes, but there has been little demand for irrigation water.
Furthermore, the low energy spot price as a result of full hydro lakes elsewhere has made it often unviable to generate electricity.
Almost exactly two years ago, old trees submerged when the lake was first made were touching the surface at the southern end, and water levels were approaching a 10-year low.
At that stage the lake was at 46% of its operating capacity, before recharging, and it is now at 90.2%.
Opuha Water chief executive Bjorn Triplow said the wet summer had kept the lake in good condition, and historical data showed it would be a lot less normally.
"We are at our [full] operating level at the moment still and at this time of the year with the irrigation and environmental flow season, we would normally be a lot lower by now, but we are in a good place."
He said Opuha Water allowed for dry seasons to make sure there was enough for the lake’s environmental role, but this had been made easier by two wet summers in a row.
"This January has been a lot wetter. We normally forecast for a certain amount of rain through these periods and historically that’s what we’ve seen. However, we are probably seeing a lot more of those extremes from dry years to a lot more water like we’ve seen this year."
He said there was no demand from irrigation schemes at this stage, and little irrigating by farmers since Christmas.
"Certainly having the water around has allowed us to put a lot of volume through the generator. However, the energy spot price has been pretty terrible as there is plenty of water in every other hydro lake around the country."
He said the return on investment and wear and tear of equipment was considered for hydro generation and weighed up with the energy spot price.
At times the generator was turned off and the lake water was put through downstream valves and discharged, he said.
"The environmental driver of Opuha is our top priority and water demand and use is second and all gathered into that is our hydro generation, so the environment is always top of mind."
The dam is in the Opuha River, which joins the Opihi River.
Opuha Water was working out how much lake water was being discharged compared with other uses to demonstrate its environmental value.
The dam generates electricity for the national grid for about 4000 households and supplies water to 16,000ha of farmland.
Mr Triplow said another role of the lake was to help manage floods further downstream during extreme weather events.
He said Opuha Water was displaying information boards during the Pleasant Point community’s 40th anniversary of the 1986 floods from March 13 to 14.
"If the lake’s in a position to do so, we hold a lot of the high flows behind the dam to help mitigate downstream flows in those rivers — to a point in 2021 during a large event [when] we held back about 43 million cubic metres of water behind the dam. Even at that point the stopbanks were at their limits and at one point had broken out to the Arawhenua area of the township of Temuka, so we do our bit for the community."
