Manuherikia Catchment - Minimum Flows

Background

The Manuherikia catchment is located in Central Otago.

Its headwaters are in the Hawkdun Range, St Bathans Range and the Dunstan Mountains.

Falls Dam is located on the main stem, approximately 40 km upstream of Ophir. The Manuherikia River main steam joins the Clutha River/Mata-au at Alexandra. A number of tributaries contribute water to the main stem, including Dunstan Creek, Thompson Creek and Chatto Creek.

There are also four aquifers within the catchment area, this includes Manuherika Basin, Ida Valley Basin, Manuherikia River Alluvium Ribbon Aquifer and Manuherikia Claybound Aquifer.

Minimum Flows

A range of minimum flow limits, have been provided for three flow sites within the Manuherikia catchment:

  • 400 to 600 litres per second at Dunstan Creek
  • 1500 to 1750 litres per second at Ophir
  • 1250 to 1600 litres per second at Campground

These numbers have been informed by hydrology and ecology work that has been completed, with an increase in trout habitat at the sites being identified for these flows.

More work is needed to better understand water reliability

ORC has commissioned NIWA to undertake the build and analysis of a hydrology and water reliability model for the Manuherikia (commonly known as the CHES model).

This work will assist ORC in understanding the catchment and any impacts future restrictions such as minimum flows may have on water reliability.

We had hoped this model would have the first draft completed by the end of October, however there have been delays while we ensure the quality of the data being used to inform the model is accurate.

We now expect the project to be delivered early in 2019. We will continue to keep the community and stakeholders up to date on the progress of this project.

Key community values

A number of key values were identified by the community and have been summarised here:


Preferred management options:


Social, economic and cultural report - coming soon

Social, economic and cultural reports are yet to be completed for the Manuherikia catchment.

As these reports are finalised the minimum flow limit will be narrowed down for each flow site to provide a final figure for notification.



Background

The Manuherikia catchment is located in Central Otago.

Its headwaters are in the Hawkdun Range, St Bathans Range and the Dunstan Mountains.

Falls Dam is located on the main stem, approximately 40 km upstream of Ophir. The Manuherikia River main steam joins the Clutha River/Mata-au at Alexandra. A number of tributaries contribute water to the main stem, including Dunstan Creek, Thompson Creek and Chatto Creek.

There are also four aquifers within the catchment area, this includes Manuherika Basin, Ida Valley Basin, Manuherikia River Alluvium Ribbon Aquifer and Manuherikia Claybound Aquifer.

Minimum Flows

A range of minimum flow limits, have been provided for three flow sites within the Manuherikia catchment:

  • 400 to 600 litres per second at Dunstan Creek
  • 1500 to 1750 litres per second at Ophir
  • 1250 to 1600 litres per second at Campground

These numbers have been informed by hydrology and ecology work that has been completed, with an increase in trout habitat at the sites being identified for these flows.

More work is needed to better understand water reliability

ORC has commissioned NIWA to undertake the build and analysis of a hydrology and water reliability model for the Manuherikia (commonly known as the CHES model).

This work will assist ORC in understanding the catchment and any impacts future restrictions such as minimum flows may have on water reliability.

We had hoped this model would have the first draft completed by the end of October, however there have been delays while we ensure the quality of the data being used to inform the model is accurate.

We now expect the project to be delivered early in 2019. We will continue to keep the community and stakeholders up to date on the progress of this project.

Key community values

A number of key values were identified by the community and have been summarised here:


Preferred management options:


Social, economic and cultural report - coming soon

Social, economic and cultural reports are yet to be completed for the Manuherikia catchment.

As these reports are finalised the minimum flow limit will be narrowed down for each flow site to provide a final figure for notification.