No quick fix coming for record low water levels
Water levels across the Canterbury region remain at record low levels, according to Environment Canterbury’s monitoring, with the region facing more dry days ahead.
Agriculture Minister Todd McClay declared a medium-scale adverse event for the Canterbury and Otago regions in March because of drought conditions.
ECan’s surface water science manager Elaine Moriarty said the council’s monitoring showed record low water levels across the region.
“Our monitoring is clear – Canterbury is extremely dry, following months of increased temperatures and average to below-average rainfall across the region,” she said.
“Many of our water level monitoring sites are at the lowest they have ever been.”
Moriarty said all metrics the council used to monitor the region’s water, including rainfall, river flows and groundwater, painted the same picture – “one of a very dry region”.
“Back-to-back dry seasons, with little recharge from rain over winter, can lead to very low groundwater levels and spring-fed stream flows – a phenomenon that occurred in 2016 and 2017, when consecutive dry seasons led to very low flows in the Selwyn River.”
El Niño, a weather pattern that lasts for nine to 12 months and occurs when the ocean surface temperatures in the Pacific Ocean rise above normal levels, arrived in September 2023, bringing with it more frequent dry westerly winds.
“Although El Niño conditions were felt throughout summer, rainfall early in the season helped prepare the region for the dry conditions that were to come in mid to late summer,” Moriarty said.
“In March, nearly half of the sites where we monitor groundwater levels were low or very low, even more so in Mid and South Canterbury.
“Likewise, the average water flow at many sites has also been low or very low compared to previous years.
“Several foothill rivers, mostly in South Canterbury, have experienced some of their lowest river flows on record in February and March.”
Moriarty said brief rain in mid-April provided temporary relief for the alpine catchments and across Mid and South Canterbury.
“However, the foothill and coastal areas of North Canterbury experienced little reprieve.
“There is currently a water shortage direction in place for Lake Opuha.”
Niwa’s latest seasonal outlook for June to August, released on Friday, shows that temperatures are expected to be near or above average.
“Westerly quarter winds will likely cause spells of milder temperatures,” the report says.
Rainfall is expected to be near normal or below normal, with June having “an elevated chance” of being drier than normal.
Soil moisture levels and river flows are most likely to be below normal.
Moriarty said that as the climate continued to warm over the next century, there was expected to be a gradual increase in dry days, along with an increased chance of drought.
“Some catchments will be affected more than others.
“For areas that are already dry, such as the Mackenzie Country, the future is looking even drier.
“Rural areas that sit at the foot of the Southern Alps, from Twizel through to Hanmer Springs, are likely to become some of the country's drought hotspots.”