Water quality and environmental monitoring of the Avon and Heathcote Rivers

Abstract

The Avon and Heathcote Rivers have been heavily influenced by urban development and intensified land use within Christchurch city. Long term monitoring of these rivers can aid in the generation of temporal environmental trends and act as a baseline for future reference. This can highlight areas of concern and help with prioritisation of restoration projects.

This research compiles monitoring data for the past three decades for the Avon and Heathcote Rivers over and uses this to determine any long term changes in water quality. This information is then compared to known discharge consents to assess their level of contribution to water quality.

Long term monitoring of the Avon and Heathcote Rivers has been inconsistent in frequency and as a result large gaps exist in the water quality data. This makes it challenging to determine temporal trends however the data available does not indicate a decrease in water quality in either river. Given the level of development within both catchments during this time, this may be seen as a positive achievement yet several parameters monitored are above recommended guidelines indicating that improvement to water quality is necessary.

It does not appear that consented discharges to water are having a major impact on the quality of Christchurch rivers. In some instances the commencement or cessation dates of consents coincide with periods where no monitoring has occurred. This may have resulted in the effects of some discharges being missed indicating that a higher consistency in frequency of sampling is necessary in order to determine the impact consented discharges are having on waterways within the city.

Stormwater discharge is a large contributor to the pollution of surface water and ultimately ends up discharging into the Avon and Heathcote Rivers. At present no treatment is required for discharge of the city's stormwater. Given the long term nature of this discharge it may prove beneficial to the quality of the Avon and Heathcote Rivers if some treatment was required prior to stormwater entering the waterways.