Lake Hayes water quality monitoring buoy providing valuable information

The water quality monitoring buoy installed last year in Lake Hayes by the Otago Regional Council has provided valuable information about the dire water quality conditions that recently resulted in the death of a number of brown trout in the lake.

Dead Trout found at the south west end of Lake Hayes, just off the raupo beds on March 13, 2020.

Cyanobacteria bloomed in February 2020 causing the lake to be closed to swimming again.

Water quality over recent years has deteriorated, resulting in a major reduction in trout numbers. The few trout that survive struggle with poor water quality in summer and the recent observation of numerous dead trout in the lake highlights the stresses that trout in the lake must now endure.

A flood in Mill Creek due to heavy rains in early February 2020 carried high loads of sediment and nutrients into the lake.  

Subsequently, calm, warm weather provided the perfect conditions for cyanobacteria (also known as blue-green algae) to bloom in the lake – visitors to the lake will have noticed a thick green scum on the lake surface. The lake was then officially closed to recreation for a period of time due to the risk of toxin production by the cyanobacteria. A consequence of these conditions in the lake resulted in very high pH, and low dissolved oxygen concentrations, at a time when the water was very warm. These conditions put great stress on the trout population, and unfortunately dead trout began to be observed on the lake shore.  

For over 10 years, the Friends of Lake Hayes have been lobbying the Otago Regional and Queenstown Lakes District Councils to come up with a plan to restore the water quality of Lake Hayes to an acceptable level. We think four tasks are required to accomplish this:

1. Reinstating the 1995 Lake Hayes Management Strategy. 

2. Completing a science-driven integrated lake and catchment management plan, which should sit within the Otago Regional Council’s Water Plan.

3. Updating the rules in the Queenstown Lakes District Plan requiring best management practice in relation to land use in the catchment.

4. Encouraging improvement in lake water quality by improving the sediment and nutrient retention of the catchment by, for example, restoring previously drained wetlands.  

The Friends of Lake Hayes have started this process by identifying land for replanting and restoring wetlands around Mill Creek. It is the intention that this plan is community driven and is supported by all stakeholders.