State of the Water Resource Report 2011 released | infonews.co.nz New Zealand News

Environment Canterbury has released its annual State of the Water Resource Report for 2011.

The report provides a summary of groundwater and surface water resources leading into the irrigation season and looks at the water resource between May and September 2011 for each of the ten Canterbury Water zones.

It provides a summary of rainfall, mean daily river flows, as well as groundwater levels for each of the ten zones, based on representative sites within each zone.

Ken Taylor, Environment Canterbury Director – Investigations and Monitoring, said rainfall in the region was generally below average during the analysis period due to the La Nina weather cycle.

“Rainfall across the region was average to well below average and as a result the majority of rivers levels were below average too. The reduction in rainfall also saw soil moisture levels drop across the region.

“Ground water levels, however, were higher than average at the end of the analysis period in most areas.

“The lower rainfall and soil moisture levels are in part due to the La Nina phase of the El Nino Southern Oscillation (ENSO) phenomenon, which has a modest effect on New Zealand’s climate.

“In 2011 we saw a La Nina phase of the ENSO set in and we expect this to continue to the end of 2011, resulting in decreased westerly flows and more stable anti-cyclonic air flows across the region.

“As a result we expect rainfall, moisture levels, and river flows will be in the normal range in the coming months,” he said.

The full State of the Water Report 2011 can be downloaded from here: State of Canterbury Region Water Resource reports.

A summary of the findings can be found below.

Summary by zone – May to September 2010

Zone	Rainfall	River flows	Groundwater
Kaikōura	Below average. The May event was the highest on record.	Average at the start of May. Decreased to below average by the end of September.	Levels were average to below average and showed a normal seasonal recovery from summer lows
Hurunui-Waiau	Below average.	Alpine rivers above average in first two months and below average in last two months Eastern river flows below average.	Generally at average levels, with fluctuations above and below average. Some central wells above average and some southern wells are below average. Some deeper wells are indicating a gradual decline in winter peaks from season to season
Waimakariri	Below average at most sites.	Ashley/Rakahuri well below average. Waimakariri average.	Levels were average and showed a normal seasonal recovery from summer lows.
Christchurch / West Melton	Average to below average.	Flows in the Waimakariri ranged from below to above average. Flows in the Avon/Otakaro were above average.	Generally lower than average. Some confined aquifers in eastern ChCh show anomalously low pressures.
Banks Peninsula	Below average.	Levels were below, to well below average
Selwyn-Waihora	Alpine rainfall average. Foothills and plains well below average.	Alpine fed rivers had above average flows for the first to months, and below average for the last two. Lowland streams were at average flows. Foothill streams were below average	Generally in good shape – most wells average to high levels. Well near Hororata is at record high levels.
Ashburton	Alpine rainfall average overall Foothills average overall but record low in August for some sites	Overall average flows (with fluctuations) in alpine-fed rivers. Foothill streams above average to below average. Lowland streams well below average.	Generally average to above average. Some shallow wells below average to lack of recent rain.
Orari-Opihi-Pareora	Alpine rainfall generally average with some months above, and some below. Above average rainfall in foothills in May, but below average to well below since then.	Alpine rivers average overall with fluctuations above and below average.	Levels above average. Peaked in July and August
Lower Waitaki-South Coastal Canterbury	Above average in May. Below average for the rest of the winter.	High levels in May but below average to well below average for the rest of the period.	Average levels and showed a normal seasonal recovery from summer lows.
Upper Waitaki	Below average. Near record low at some sites in Augsut.	Average flows.