Updating and reinstating the1995 Lake Hayes Management Strategy

FOLH would like to acknowledge the support of the Otago Regional Council who have ratified 2 key actions requested by FOLH in their submission on the ORC 2020-2021 Operating Plan.

The issues addressed in the comprehensive Lake Hayes Management Strategy (1995) remain largely unchanged today. However, to bring it up to date, data from the current ORC catchment nutrient study needs to replace the old nutrient load information. Similarly, the catchment land use information needs to be updated to reflect the move away from agriculture to tourism-based activities, resorts, golf courses and residential development. Most of the work needed to update this document has already been completed - it just needs to be professionally compiled. The 1995 Strategy was widely supported by stakeholders and, therefore, could easily be readopted once updated.

The Lake Hayes Management Strategy is not an operational plan but a contextual framework for all the initiatives which together will lead to the recovery of Lake Hayes. In hindsight, had we carried on with it in 2003 the lake would already be well down the track to recovery by now. The sad thing is that while so much discussion and debate has been going on about the state of the lake, no positive actions have been undertaken lake or catchment since then.

To get things moving, FOLH identified 2 initiatives in the 1995 Strategy, which, if implemented, could begin some positive actions to improve the lake health.

2. Managing lake water inflows and outflows

ORC, FOLH and their respective science advisors agreed that targeted augmentation of Mill Creek with cool, low nutrient water from the Arrow River irrigation scheme would benefit lake health at relatively low cost and with little risk. Further to this, the Lake Buoy would be able to measure the effect of this intervention and provide feedback on how and when to augment the water.   ORC agreed that this would be a useful management action and built 80% of required infrastructure at Millbrook Resort to allow this to happen.

ORC identified the Lake Hayes outlet culvert as a limiting factor in this project and FOLH supports ORC’s initiative to review the specs of the culvert with a view to upgrading the culvert to avoid the recent lake flooding issues that have been identified by FOLH. This single culvert replaced 2 smaller culverts which when installed replaced a bridge that had been at the Lake Hayes outlet, allowing stream to flow unconstrained.  In the 1960s, lake levels were controlled by the natural lake outlet profile. 

Lake level does affect lake health, as shoreline flooding releases large amounts of soil phosphorus and erodes lake shores. All this was researched and described in the 1995 Lake Hayes Management Strategy, which described optimal lake height, lake level variation and culvert design. Considering the substantial time elapsed since the ORC built the infrastructure for flow augmentation from the Arrow River, it is heartening to know that ORC’s proposal to review the outlet culvert should be relative simple to carry out because most of the relevant data will be collated as part of the 1995 Strategy update.