April was very dry in most areas in Canterbury, with a number of rain gauges recording less than 25% of their April long term means. Rainfall gauges at Arthurs Pass and Mt Cook recorded approximately 60 % of their annual means.

Canterbury foothill rivers and spring fed streams have remained low, with most flowing well below the long term averages for the month of April. Two sites had record low flows for April: the Selwyn River at Coes Ford (near Lincoln) and Omarama Stream (in the Waitaki District). The Selwyn was flowing at only 6 % of the long-term mean for April. Being spring-fed, this river is completely reliant on groundwater levels which are also very low in this area. The Waipara in North Canterbury and the Waihao in South Canterbury have April mean flows of only 12-14% of their long-term figures.

The Alpine Rivers have also recorded relatively low April flows. The Waiau, Hurunui, Waimakariri and Ahuriri rivers all recorded April mean flow less than 60% of the long-term means, while the Rakaia and Rangitata had slightly higher flows (68% of the long term April mean), although these were a sharp decrease from flows in March. The South Ashburton flow recorded was only 44% of the long term mean, which was the lowest April flow on record.

Groundwater levels in the Canterbury region for April 2016 were generally lower than the mean when compared to April records for previous years. Approximately 79% of the wells we monitor for groundwater levels across all of Canterbury had April 2016 readings below the April mean. In general, the spatial distribution of low groundwater levels remains the same as in previous months (September 2015 to March 2016).

The majority of wells with ‘very low’ water levels were located in the coastal Selwyn-Waihora area (near Lincoln & Leeston), the Ashburton plains and the West Melton area (immediately west of Christchurch). Some of these wells are showing record low levels.

The full report is available here

ENDS

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