Assessing urban nonpoint source water pollution in Christchurch

Abstract

A need has been identified for more information on the origins and impacts of contaminants to encourage moves towards preventative solutions to the problems of nonpoint source degradation of the aquatic environment. This study addresses information requirements by investigating the key nonpoint source contaminants of concern to water quality in Christchurch urban waterways, developing a ranking scheme to establish priority contaminants, and quantifying the sources of one priority contaminant. Using the Christchurch study as a template, the study also focuses on how the complex information generated on nonpoint source pollution may be effectively utilised in waterway management.

A review of historical, biological and physico-chemical data in urban Christchurch indicates that there are several degraded waterways and reveals that nutrients, heavy metal and sediments are the nonpoint source contaminants of most concern in Christchurch urban waterways. A contaminant ranking scheme is developed which incorporates the potential effects of nonpoint source contaminants on community values. A ranking scheme may provide water managers with a mechanism to prioritise monitoring or abatement.

One of the highest ranked contaminants was zinc and this metal was chosen for source analysis. Likely contributors of zinc to the aquatic environment were identified through a screening process. A quantitative assessment of the loads generated from various sources of zinc revealed that zinc is predominantly derived from tyres and zinc-clad roofing materials.

An integrated approach to analysis and management of nonpoint source water pollution is developed. Greater integration of the complex information needed to define nonpoint source water quality problems is the initial approach to qualifying the issues of nonpoint source pollution for planning and policy development. Management is facilitated by information gathering and utilisation processes that provide the justifications for pollution abatement.