Aquifer Project Background and Methods

Aquifers in New Zealand

Aquifers are underground layers of water-bearing rock or unconsolidated materials such as sand, gravel, silt, through which groundwater flows. They are relied upon as a source of recharge for rivers, estuaries, lakes and wetlands.

New Zealand’s aquifers held an estimated 711 billion cubic metres of groundwater in 2014 (source) and provide 35% of the nation’s consumptive water use (source). Unconfined aquifers hold approximately 96 percent of that total (source). By 2015 about 200 aquifers had been identified in New Zealand by White (2001), Moreau and Bekele (2015) and Lovett and Cameron (2015). These aquifers are an important source of water for drinking, agriculture and industry, and are therefore highly valuable for the economy. This nationwide groundwater resource has been valued at approximately $8 billion NZD (source).

Issue

We have little understanding about the total biological content and functioning of these subsurface ecosystems. How groundwater biology and more especially microorganisms respond to and mitigate nationally and globally problematic agricultural pollutants, such as nitrate. High nitrate concentrations have been shown to have an impact on human health, but can also alter groundwater ecosystems (for example, by leading to eutrophication in connected surface water) (MA, 2005).

The main objective of this project is to improve our knowledge of poorly understood aquifer biology, and its impact on groundwater quality.

We hypothesis that:

  • Aquifer microbial metabolism will strongly reflect non-agricultural and agricultural influences on groundwater chemistry
  • Groundwater microorganisms play an important role in mitigating nutrient pollution

Our field sites

Below is a map showing sampling sites for both Canterbury aquifer genomics and a genome informed aquifer survey. The sites for Canterbury aquifer genomics are located in the Canterbury plains spanning across two aquifers, the Central Plains and Waimakariri- Ashley plains. These are shallow and unconfined sandy gravel aquifers which are globally common. Unconfined aquifers are strongly influenced by surface water percolating down. The wells sampled are situated on farm land and reserves, forming a nitrate gradient.

The sites sampled for a genome informed survey are located in regions across New Zealand such as Wellington, Auckland, Waikato and Canterbury. The aquifers are mainly alluvial sand/gravel but we did include other lithologies, such as volcanic and shell bed aquifers. The wells are situated on different types of land use such as industrial, agricultural, dairy, urban and reserves. Wells were chosen to span a range of different nitrate, sulfate, dissolved organic carbon and dissolved oxygen concentrations.

Map of New Zealand highlighting the regions where groundwater samples were collected.