Hot dry weather and ever-increasing demand for water has seen groundwater levels fall in some parts of Waikato.
High temperatures and lack of rain has prompted Waikato Regional Council to ask farmers and other consent holders to check that they are complying with low-flow restrictions.
The council has also heard from some bore owners who are struggling to access water for stock due to falling groundwater levels.
Senior water scientist Bevan Jenkins said soil moisture levels are drier than the same time last year and much drier than the historical average.
“There are signs of climate change-related water stress in a number of areas and this is being expressed as reduced water availability, which is placing increasing pressure on water users,” Jenkins said.
“There has been a year-on-year increase in groundwater bore drilling permits since 2016-2017 and preliminary analysis shows increased total volumes of surface and groundwater take applications since 2008.”
He said the region has had a number of consecutive dry summers since 2007-2008 and Niwa recently called 2021 the hottest year on record.
“What we are seeing is that the river flows that are low at the moment are the ones that are spring flow dominated,” he said.
Streams in South Waikato that are strongly groundwater-fed are close to or are at record low flows for this time of year. This is due to the lower rate of precipitation recharging groundwater over recent years during winter.
One of these is the Oraka River that runs between Tokoroa and Putāruru.
However, other rivers in the region are running close to normal levels, having benefited from winter rain.
For larger groundwater systems, it was difficult to put a number on how much water was needed to replenish them, because so much is lost through usage and evaporation.
At the end of 2021, groundwater level measurements indicated a range of conditions – bores with close to record high levels, record low levels and average condition had all been recorded.
The low levels of water would have triggered restrictions for some farmers in the region, he said.
Council water allocation team leader Donna Jones said farmers should contact the council to discuss options if the reduced availability of water for stock supply is becoming an urgent issue.
For waterways in parts of the region already starting to experience low-flow conditions, Jones said surface water take consent holders had a responsibility to ensure compliance with their consent conditions.
“As the weather heats up and stream flows drop, there may be a requirement for consent holders to reduce or cease their take. The specific action required will depend on the low flow restriction conditions in the consent,” Jones said.
A consent was needed for any new bore or if an existing bore was deepened.
A separate resource consent may also be required to take water depending on the proposed take location and volume required, she said.
Low-flow conditions of a consent will refer to an appropriate river flow monitoring station and low-flow value. Current river levels should be checked against the consent. Regular water use records are also required, she said.
Waikato Federated Farmers president Jacqui Hahn said low flows matched what other farmers had reported from around the region.
Reduced groundwater levels over summer was not new, but increasing soil moisture deficits have increased over the past 50 years, so the trend is clear.
“Those with takes, regardless of use, need to be thinking of improving efficiency; some systems are much more efficient,” Hahn said.
Providing stock with shade was also important as it reduced water demand, she said.