Canterbury water this season
Our seasonal outlook indicates how much water is in Canterbury's soils, aquifers, rivers and streams, compared against the long-term median for that time of year.
Winter 2021 saw a return to normal or above normal rainfall levels for most of the region, a marked change from significantly dry winters in recent years.
That, combined with heavy rainfall events earlier in the year, means that most of Canterbury enters spring with healthy soil moisture levels and river flows.
Groundwater levels vary according to location and depth, but some parts of the Canterbury plains continue to see record low groundwater levels, a particular concern going into irrigation season.
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Groundwater levels are typically the highest in spring, because of recharge over winter and recovery from the pumping of the previous irrigation season.
In early 2021, groundwater levels in most wells, especially on the plains, were very low until heavy rainfall in late May.
Levels have fallen slightly from the highs of June, but in most shallow wells, particularly those close to the foothills or near rivers, levels remain within the normal range for the time of year.
In some areas, groundwater levels did not benefit from extra winter recharge.
In the coastal Ashburton-Rakaia area, the Leeston-Southbridge and Tai Tapu areas, Coastal South Canterbury and in Waipara, groundwater levels in deeper wells have been very low since early 2020, and some wells are entering the irrigation season with levels at record lows.
Significant rainfall in July and August in northern and western Canterbury has helped to keep flows high throughout the alpine catchments and in some of the northern foothill catchments.
There was even some out-of-river flooding in the Waiau catchment in mid-July, after the significant rain event that thrashed Westland and Marlborough also reached into Canterbury.
River flows in the central and southern foothill catchments and in most of the spring fed streams from the Ashley River south were generally average-to-high in August, while flows in Banks Peninsula streams were near average.
Soil moisture levels over most of Canterbury plains were near normal at the beginning of September, with some slightly wetter areas along the coast in northern and southern Canterbury.
Soil moisture data and imagery is provided by NIWA.
Winter was wetter than normal in the west, particularly in the mountains north of Aoraki/Mt Cook. The rest of the region generally had normal rainfall.
Here you can find a summary of previous seasonal outlooks. Click on accordion to read more about a particular season.
Heavy rainfall and high river flows in late May significantly changed the groundwater picture across much of Canterbury.
Groundwater levels were at record lows in many places, but recharge from the wet weather has benefited most areas.
In most shallower wells, groundwater levels have returned to near median for the time of year. Levels in many deeper wells are still below median.
Water levels are below median in around 58% of the wells we monitor, an improvement from 93% in May.
River and stream flows
River and stream flows were very low throughout most of the region through Autumn, but significant rainfall at the end of May changed the picture completely, and floods resulted in central and southern foothill catchments.
A number of foothill sites have recorded higher than the long-term median flow for the month of June, while a number of springfed and lowland streams are still recording below median flows.
Banks Peninsula streams are flowing at about normal for June.
Soil moisture over much of the Canterbury plains was exceptionally low until the heavy rainfall event in late May.
That rainfall and subsequent precipitation in June mean that soil moisture as of 1 July was slightly above or well above normal levels for this time of year across most of Canterbury, with only South Canterbury and the eastern Banks Peninsula drier than normal.
The extreme rainfall event of late May resulted in rainfall well above the three-month normal for a large section of the mid-Canterbury foothills and a section of the plains.
However, when balanced with the proceeding dry months, the rest of Canterbury saw average rainfall levels for the period.