Identifying leakage to groundwater from Lake Rerewhakaaitu using isotopic and water quality data

• Published in: Journal of hydrology, New Zealand Vol. 47; no. 2; pp. 85 - 106
• Main Authors: Reeves, Robert R., Morgenstern, Uwe, Daughney, Christopher J., Stewart, Michael K., Gordon, Dougall
• Format: Journal Article
• Language: English
• Published: New Zealand Hydrological Society 01-01-2008
• Subjects: Analysis; Aquifers; Cluster analysis; Freshwater; Groundwater; Groundwater recharge; Igneous rocks; Lake water; Lakes; Stable isotopes; Streams; Surface water; Water chemistry; Water quality; Watersheds; New Zealand
• ISSN: 0022-1708; 2463-3933

Stable isotopes (¹⁸O, ²H), water dating, and major anion and cation water chemistry of springs, groundwater bores, a stream and a lake have been used to identify areas of discharge from Lake Rerewhakaaitu. Groundwater aquifers and spring discharges to the north and west of Lake Rerewhakaaitu are found to contain up to 79% lake water. Hierarchical cluster analysis is used to group sites into three clusters based on the major anion/cation water chemistry. Defining meaningful hierarchical clusters was difficult due to the similarity of the chemical compositions between sites. The three clusters defined in this study do not clearly identify the sites containing lake water. However, the hierarchical cluster analyses can be used to infer sites that are likely to contain proportions of lake water in the groundwater, and therefore provides a method to identify sites that may contain lake water. The groundwater and spring discharges to the north and west of Lake Rerewhakaaitu flow into a different surface water catchment, thus providing a hydrological link between two different surface water catchments. This has implications for catchment management in the greater Rerewhakaaitu area.