Water Shortage Direction for Opihi River and tributaries
A Water Shortage Direction for the Opihi River and its tributaries – which includes the Opuha River and Lake Opuha – is in effect from Saturday 1 September for 14 days.
The Direction requires Opuha Water Limited to maintain a minimum flow of 5.2 cubic metres per second in the Opihi River (at the Saleyards Bridge) when the lake is above 375 metres.
The lake level is currently around 390 metres. The Opuha Environmental Flow Release Advisory Group (OEFRAG), comprising representatives from district councils, farmers, Opuha Water Limited (OWL), river users and tangata whenua, agreed to the release level of 5.2 cubic metres for a 14-day period to enable minimum water release from the Opuha Dam in order to build up water storage.
There are no irrigation restrictions in this Direction. However, OEFRAG has requested that OWL ensure water permit holders affiliated to the Opuha Dam reduce their water takes to 75% of their consented volume.
Lake capacity, lake inflows and snow pack are all important to the amount of water available for river flows and irrigation over a season. All three are causing OEFRAG concern at present.
OEFRAG chairperson Judy Blakemore said: “While we acknowledge that it is early in the irrigation season for this action, we believe a precautionary response is warranted given the low lake levels, lake inflows and snow pack currently seen in the catchment.
“The winter months have seen a lack of rainfall,” she said. “The gauge at Opuha Dam has only recorded 42.5mm of rain since 1 June. Unfortunately, the rain we experienced earlier this week was not meaningful for the catchment and therefore failed to ease our water shortage concerns.”
OWL CEO Andrew Mockford said: “Looking ahead to short and mid-term forecasts, we are not seeing any significant rain on the horizon that will change the conditions significantly.
“Longer term (seasonal) forecasts are still debating whether an El Nino pattern is coming (although looking more likely than not), but point towards lower than normal rainfall in the next 2-3 months.”
“These early months of the irrigation season are the ones where river restrictions are more amenable due to higher minimum flows,” said Judy Blakemore. “The peak summer months have lower minimum flows and therefore there is much less ability to make any meaningful impact, as the 2014/15 season demonstrated.
“The drought that year clearly illustrated the need for early intervention,” she said. “We acted too late in 2014, not putting restriction on until 1December. We want to do everything in our power to ensure that the 2018/19 season is not a repeat of 2014/15 which saw an empty lake, very low river flows and a stop to all irrigation.
“We are confident that the 5.2-cumec flow will be sufficient to maintain fish passage, especially with the Opihi River mouth having been opened by Environment Canterbury earlier this week.”
Environment Canterbury has authority under section 329 of the Resource Management Act 1991 to notify the Water Shortage Direction.