State of Canterbury Region Water Resource 2004 (Report U04/101)

This report reviews the state of Canterbury’s water resources going into the 2004/05 summer.

 Download the entire report  3.83MB

or download and read sections of the report, including:

 Preconditions  959kb

 Current conditions  2MB

 Prognosis  164kb

 Appendices  1.1MB

Executive Summary

Winter (June/July/August) 2004 rainfall in Canterbury was above average in alpine and foothills regions and somewhat below average in eastern areas. Values as low as 60 to 75 percent of average occurred around Waipara in North Canterbury and in South Canterbury. Cumulative totals over the last 12 months for all lowland gauges were in the normal range, although values for gauges in the lower Waitaki Valley (Duntroon) and near Kaikoura (Hapuku) were consistently below normal.

Winter streamflows reflect the seasonal rainfalls: alpine-sourced rivers had flows near their long-term winter medians, but most other winter streamflows were well below the winter medians. Above average September rainfalls in the northern parts of the region brought many September streamflows close to the long-term September medians, but lower than normal flows continued in the Selwyn/Waikirikiri, Doyleston Drain, and South Canterbury Rivers (Opihi, Waihao, Hakataramea).

Flows have been sufficient in rivers to maintain generally average levels in shallow aquifers, although levels are lower than in Spring 2003. Rainfall recharged shallow aquifers are typically lower than average due to a lack of winter recharge, with the exception of the coastal Christchurch area where recharge at Lincoln and Christchurch lysimeter sites was normal. Deeper aquifer levels have also been affected by a series of low recharge winters, with many wells displaying a sluggish recovery from record lows in January 2004.

Projections for November 2004 to January 2005 prepared by NIWA on 2 November 2004 for the South Island east coast are for normal or below normal rainfall and soil moisture levels, near average temperatures and below normal streamflows. For alpine regions and alpinesourced rivers, normal or above normal rainfalls, average or below average temperatures and normal streamflows are predicted.

Shallow groundwater levels are generally average although lower than in Spring 2003. With average rainfall and average to below average river flows predicted throughout the rest of 2004, groundwater levels can be expected to remain average. Lows may be experienced in river recharged systems, especially in the South Canterbury region. For deep aquifers, a series of winters with low rainfall recharge has meant that most wells approached the 2004/05 season with lower levels than in 2003. Following the pattern of previous summers, groundwater levels can be expected to again reach record lows in response to increased abstraction.