How good is our groundwater?
The West Coast Region has substantial groundwater resources that serve as an important source of water for drinking and other purposes by communities and individuals, agriculture, and other industries and users. Most currently identified groundwater resources in the West Coast Region are located in alluvial materials adjacent to the Region’s major rivers such as the Grey and Hokitika and, similarly, most resource consents to take groundwater have been issued for users within the Grey District. Groundwater quality in the West Coast Region is monitored in samples from seven National Groundwater Monitoring Programme wells. The Council obtains water level data for these and 22 other wells.
It was concluded in both relevant GNS work and Baker (2004) that groundwater quality in the West Coast Region is generally good in comparison to guidelines such as New Zealand Drinking Water Standards. There are two exceptions to this general case: (1) numerous exceedances for health-based bacterial indicators; and (2) exceedances of the aesthetic-based guidelines for iron and/or manganese in samples from some wells. Although nitrate-nitrogen concentrations did not exceed guideline values in sampled wells, levels in some cases were sufficiently high as to indicate anthropogenic sources (including agricultural). These guidelines are used as a reference point and would not necessarily apply if the well involved is not used to supply water for human consumption or water used in farm dairies for milking and cleaning equipment that contact milk. Additionally, there are statistically significant increasing trends for chloride, nitrate-nitrogen, and sulphate in most of the NGMP wells in the West Coast Region. This is consistent with and may reflect intensified dairying operations in the West Coast Region over the last 10 to 15 years. However, nitrogen isotope data indicates that the source of nitrogen is more likely fertilizer or soil organic nitrogen than animal wastes. An additional factor is that age dating data for groundwater samples indicate ages on the order of 12 years in the Grey River drainage and eight years in the Hokitika River drainage. In that event, the full impact of intensifying dairying operations may not yet be evident.
Groundwater Quality SOE Reports:
Click here to download the 2009 West Coast Groundwater Quality Report (PDF, 1.7MB)
Click here to download the 2005 West Coast Groundwater Quality Report (PDF, 3.4MB)