Popular with water skiers, this small lake has hosted algal blooms every summer for many years. The small catchment hosts dairy, sheep & beef and deer farms. Landowners have worked closely with the landowners in this catchment to develop the Action Plan.
The Lake Okaro Action Plan has been approved by the Rotorua Lakes Strategy Joint Committee and is available on request.
Action Plan Status: Operative
Quality Now: 5.6 TLI
Quality Goal: 5.0 TLI
- Major wetland completed February 2006 to filter nutrients from farmland
- Detention ponds to slow stormwater flows for better wetland treatment
Ongoing improved fencing and plantings around lake margin and streams.
- Lake mineral dosing with modified Zeolite to absorb phosphorus releases from the lakebed sediment (see below).
- On-farm nutrient management.
- Construction of a HerdHome for the catchment’s dairy farm, to capture dairy effluent and reduce nutrient loss from urine/dung patches.
- New nutrient discharge rules have been tailored for Lake Okaro. They are currently “proposed” and will not take effect until fully operative – mid-2008 at the earliest. The rules are similar to the existing ‘Rule 11’, but simpler, to reflect the small number of landowners in the catchment.
Environment Bay of Plenty will apply a modified zeolite layer to the Lake Okaro lakebed in late August 2007. The application will be carried out while the lake is fully mixed and before the lake water stratifies into separate layers. The zeolite won’t initially absorb phosphorus in the water column. This is because we want to see if the zeolite will ‘cap’ phosphorus releases from the lakebed sediments.
Environment Bay of Plenty may also be applying zeolite in March or April 2008 – this time to remove phosphorus from the water column itself. At this time phosphorus levels in the bottom layer of Lake Okaro are close to their annual maximum. For this application, fine zeolite designed to settle only very slowly would be used and applied at a depth of 5m.
A comprehensive monitoring programme will look at:
- The physics, chemistry and phytoplankton ecology of Lake Okaro before, during and after the trial (until March 2009).
- Physiological and toxicological effects on indicator species, including indigenous food sources(until April 2008).
- How well the zeolite application has worked.
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