Technical Reports

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Assessing nitrate discharge into Canterbury groundwater

Nitrate discharge to groundwater from agricultural land use: An initial assessment for the Canterbury Plains May 2009 [PDF 4.5MB]

A report has been released assessing nitrate discharge into groundwater on the Canterbury Plains from rural land uses. The report, commissioned by the Canterbury Water Management Strategy Steering Group, arose from public concern about the effects of agricultural land use on groundwater quality.

The report looks at nitrate discharge from rural land use and its implications for water quality in two situations: shallow groundwater quality on the Canterbury Plains and deeper groundwater quality for Central Canterbury.

Continued access to clean drinking water always comes through in public consultation as one of the key issues for water management and the report provides the Steering Group with some predictions about the impact of nitrate discharge on groundwater quality.

The report, compiled over six years, provides evidence that nitrate discharge from agricultural land use on the Canterbury Plains has a negative impact on the quality of water at shallow groundwater levels, and in some situations, exceeds drinking water nitrate standards.

The report also shows groundwater quality generally improves with depths below the groundwater surface because of mixing with high quality groundwater from river recharge.

Most large drinking water supplies, including Christchurch, take water from deep groundwater. In Christchurch there are two other factors that help protect water quality from land use effects. The first is the confining layers above the aquifers where Christchurch city takes its water. The second is that we are in the process of implementing land use controls over the area of land where nitrate could get into the aquifer.

The report shows contamination in shallow ground water is directly related to land use and there are areas of compromised groundwater drinking supplies in rural Canterbury. Careful land use management is therefore a reality and further land use intensification in the Canterbury Plains will be dependent on reducing current levels of nitrate leaching.

The report compares the effects of improving practices on existing agricultural land to the effects of changing land use. Improving practices on existing agricultural land will have the greatest effect on the availability of quality drinking water from shallow groundwater.

The report will be used by the Canterbury Water Management Strategy, run by the Mayoral Forum, to help guide them and others when looking at the best way to sustainably manage Canterbury's future water resources.

Effects of Rural Land Use on Water Quality

Effects of Rural Land Use on Water Quality - May 2003 [PDF 7.29MB]

This report is a comprehensive review of the effects of agriculture on water quality in New Zealand. Published in 2003, it was commissioned by the Ministry for the Environment to assist the work of local and regional government policy staff.

The report was coordinated by NIWA and written by scientists from several crown research institutes and Lincoln University. It includes discussion on groundwater contamination, the effects of nutrients from pastoral land use, water quality impacts of arable and horticultural land use and the effects of nutrients and sediments on surface waters.

Permission from the Ministry of the Environment to reproduce this report is acknowledged.

Context report

CSWS context report - December 2007 [PDF 65KB]

This report, prepared in December 2007, provides a comprehensive background to the Canterbury Strategic Water Study and a summary of the next steps in the Canterbury Water Management Strategy process including the public engagement programme taking place in Milestone 4.

The Canterbury Strategic Water Study involves a number of stages, with several now completed.

Stage 1

Canterbury Strategic Water Study Stage 1 report - August 2002 [PDF 7.83MB]

The first stage of the study, published in 2002, involved an evaluation of the current and likely future water supply and demand throughout the region. Stage 1 was undertaken by Lincoln Environmental.

Stage 1 concluded that, on an annual basis, there is enough water in Canterbury to meet likely future demand - but some catchments are ‘water short’ and peak demands could not be met on a weekly basis. It also concluded that water storage should be considered as part of meeting future demands for water - primarily for irrigation - to supplement supply in times of low natural flows.

Stage 2

Canterbury Strategic Water Study Stage 2 - Main Report - Dec 2008 [PDF 9.45MB]

Canterbury Strategic Water Study Stage 2 - Appendices [PDF 2.66MB]

The second stage of the programme under the Canterbury Mayoral Forum began in 2004 and identifies potential water storages in Canterbury and their hydrological feasibility, including the area they could irrigate and their impacts on river flows.

Stage 3

Canterbury Strategic Water Study Stage 3 report [PDF 716KB]

The third stage of the study, also undertaken for the Canterbury Mayoral Forum, began in early 2006. It involved a preliminary evaluation by multi-stakeholder groups of the environmental, social, cultural and economic impacts of the water storage options identified in Stage 2.

Stage 3 identified two over-arching critical issues - land use intensification and its effects on water quality; and maintaining or improving, flow variability in rivers and streams. Both issues need to be explored and subjected to comprehensive public debate before Canterbury is in a position to make sustainable, long-term decisions about water storage or water management more broadly.

Stage 4

The fourth stage of the study includes the programme of public consultation that is the subject of this website and is to be undertaken during 2008. It has benefited from the work of the three previous studies. The objective is to create a water management strategy for Canterbury. Stage 4 is being led by the Steering Group which reports to the Canterbury Mayoral Forum.

Other Scientific Studies »

Stage 5 to 6

Information for stakeholders
The papers below were considered by the Canterbury Water Management Strategy Steering Group at its meetings in 2008/2009.

Summaries from 2008 stakeholder workshops