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.

Summer 2021/2022

With several precipitation events and a few nor-westers over spring, we enter summer with soil moisture at healthy levels across Canterbury, while groundwater levels across most of the region are near or slightly below median levels for the time of year.

Weak La Niña conditions are expected to lead to normal or below normal rainfall over the summer irrigation season, while river and stream flows are expected to be below normal over the next few months.  

View quarterly reports on:

  Groundwater levels

  River and stream flows

  Soil moisture levels

  Rainfall

  View previous seasons’ reports

 

Groundwater

Groundwater levels in early summer have begun to decline from spring highs, as temperatures increase and irrigators pump more groundwater.

As of the end of November, about 60% of the wells we monitor had groundwater levels in the Average range signified by the yellow dots on the maps below. Some 30% of the wells had levels in the Low or Very Low ranges (orange and red dots), while 10% had levels in the High or Very high ranges (green and blue dots).

In some areas, groundwater levels did not benefit from the extra recharge we had over the past winter. In the Ashburton and Leeston-Southbridge areas, groundwater levels have been low since early 2020. We also see low levels currently in the upper Orari catchment, the lower Waitaki catchment, around Rangiora, and around McLeans Island west of Christchurch.

North

Groundwater level map north

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Central

Groundwater level map central

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South

Groundwater level map south

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River and stream flows

Spring rainfall throughout the region was similar to expectations and this is reflected in many of the median flow values for November. The majority of sites in North Canterbury are showing Average median flows in both the large alpine and small coastal catchments.

Central Canterbury is more variable, with values mainly ranging from Average to Low, including some foothill sites and some spring-fed streams. A couple of Christchurch city sites show Very High median flows for November.

South Canterbury is also a mixed picture, with several sites showing High November flows compared to normal, while a significant number of sites flowing at Average or Low rates.

View live river flow data.

North

Riverflow map north

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Central

Riverflow map central

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South

Riverflow map south

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Soil moisture levels in Canterbury. Data provided by NIWA

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Soil moisture

Early summer soil moisture levels are average to slightly below the long-term median for the season in most of North Canterbury, with coastal Kaikoura and Banks Peninsula the driest areas.

For most of mid- and South Canterbury, soil moisture is higher than expected for early summer, especially in the upper Waitaki and Mackenzie country.

Soil moisture data and imagery is provided by NIWA.

 

 

 

 

 

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Rainfall

Spring rainfall was close to the long-term median level for the season across Canterbury, with some of the alps receiving slightly more rain than expected, and some coastal areas slightly less.

View live rainfall data.

 

 

 

 

 

Previous reports 

Here you can find a summary of previous seasonal outlooks. Click on accordion to read more about a particular season.

Spring 2021

Groundwater

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.

River and stream flows

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

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.

Rainfall

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.

Winter 2021

Groundwater

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

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.  

Rainfall 

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. 

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