The main recommendation from this report is that similar studies should be conducted at a regular interval in the future, in order to identify changes in the status of groundwater quality in New Zealand. The following recommendations can be made with respect to the design of future investigations:
- Future investigations should make use of the six key indicators of groundwater quality employed in this report, namely NO3-N, NH4-N, E. coli, Fe, Mn and electrical conductivity, in order to track changes caused by human as well as natural drivers;
- In addition to quarterly to annual monitoring the above-mentioned key indicators of groundwater quality, bi- or triennial surveys should be undertaken to assess the occurrence of emerging contaminants such as pesticides, pharmaceuticals, endocrine disruptors, fertiliser additives (e.g. cadmium), etc.;
- Rates of change in the indicator parameters are generally slow, so a two- or three-yearly interval for repeat investigations of this type is suitable, to allow for detection of significant changes in groundwater quality relative to seasonal variation;
- National and regional commitment is needed to monitoring the indicators of groundwater quality via standardised sampling and analytical methods, at a regular (periodic) interval (ideally quarterly), on an on-going basis, and at a consistent network of monitoring sites, all of which have suitable well-head protection;
- The sites comprising the regional SOE monitoring networks must be selected to provide a representative perspective of groundwater quality for the region, which by necessity will require a certain number of monitoring sites in pristine areas to provide valuable “baseline” (background) data, to determine what threshold should be used to identify groundwater quality issues and trends that are important in a management perspective; and
- The age and origin of the groundwater that is actually being sampled should be determined for each monitoring site, and accurate information pertaining to current and past surrounding land use must be compiled (e.g. from satellite imagery) in order to elucidate the drivers of groundwater quality.