New guidelines for managing groundwater
To help protect the quality of groundwater flowing from wells, springs, small lakes and wetlands, guidelines are being developed to estimate where these features gather their water.
Managing aquifers effectively requires sound understanding of capture zones – the area of land that feeds into the aquifer – as well as of the way land use can affect water quality.
Capture zones that surround a water body do not necessarily follow a simple rule. They vary greatly in size and shape depending on hydrogeology and terrain.
There has been no standardised and robust approach to delineate capture zones in New Zealand. So this year, GNS Science, in collaboration with ERS, produced a set of guidelines for councils on protecting water features, such as wells, streams, and wetlands that receive inflow from groundwater. Currently in draft form, the guidelines are designed to support the national environmental standard for human drinking water, implemented in 2008. The national guideline requires councils to know whether a proposed land activity will lie within the capture zone of a drinking water supply source.
Our guidelines provide a uniform and defensible approach for determining the size and geometry of the groundwater contributing area for a water feature. They are an essential management tool for long-term protection of the quality and quantity of New Zealand’s freshwater resources.
To develop the guidelines, we reviewed techniques for measuring capture zones from several countries, and identified seven methods suited to New Zealand conditions. We then trialled these methods in different geological settings to ensure they are appropriate for New Zealand. Our guidelines lead the users through a stepwise process of deciding which of the seven methods are appropriate for their needs. A draft version of our guidelines has been circulated to several councils for comment and the feedback from users has helped refine the product substantially.
Some Regional Councils are already applying the methodology to wells and are looking to extend it to springs. They report that it helps significantly in understanding groundwater flow paths. More particularly, the methods described in the guidelines clearly identify where contamination might be coming from.
John Callen – GNS Science
P: 04 570 4732 E: j.callan@gns.cri.nz