State of the environment monitoring Waikato lake water quality

Report: TR 2021/26

Authors: Mat Allan and Mafalda Baptista

This report describes the current and past state of water quality, and its inherent trends, within the Waikato Regional Council State of the Environment (SOE) lakes monitoring network.

The Waikato region's shallow lakes are under pressure from a combination of factors, including nutrient loads well above critical loading, impacts of pest fish, lake level fluctuations, climate change and, in many lakes, hysteresis and negative feedback loops derived from alternative turbid stable states.

Lake water quality was assessed using National Policy Statement for Freshwater (NPS-FM 2020) bands, and results show that most shallow Waikato lakes are below the national bottom line for at least one attribute.

Since monitoring began, there has been more degradation in total suspended solids (TSS), total nitrogen (TN) and water clarity, and improving trend in chlorophyll a (CHLA) and total phosphorus (TP).