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Improving Lake Rotoiti Water Quality

12 July 2023

Improving Lake Rotoiti Water Quality

We’re all concerned about water quality.

Weed spraying is a regular thing but it sometimes doesn’t seem to keep the lake weed under control and it’s not a good long term solution for better water quality.

Here’s some good advice from Mark Thomson of the LRCA Committee on what you can do personally to help improve Lake Rotoiti’s water quality.

We know that water quality, algae and weed growth are all directly affected by excessive nutrient supply and these suggestions are all about reducing the nutrient supply into the lake.

Nutrients in our lakes are things like:

Fertiliser runoff

Grass clippings, leaves and plant debris blown or thrown in

Floating clumps of weed dislodged by boating activity and storms

House gutters flowing into the lake

Silt runoff

Sewerage seepage

Water runoff from the road

Contaminated domestic stormwater - leaves, chemicals, paints etc

Rubbish and food waste.

Here’s some ideas of things you can do to help keep our lake as clean as possible:

Stormwater - if possible, direct your stormwater away from the lake. Consider installing a detention tank to settle out contaminants before sending stormwater into the lake.

Lawns - Don't allow grass clippings to get into the lake. DON'T fertilise your lawn.

Create a barrier zone - If your property is lakefront, plant native filter plants like Harakeke (flax), native grasses, small shrubs etc to form a 1 metre deep barrier across the lakefront. This will also help stop erosion.

Garden - Remove exotic/deciduous trees & bushes that drop leaves and flowers and replace with evergreen natives.

General maintenance - Keep your gutters clean and free of leaves and twigs.

Earthworks - Ensure no runoff gets into the stormwater and the lake.

Floating weed clumps – bring these on to dry land and dispose of them in your garden compost. If left in the lake, they provide the perfect nutrients for new weed growth and murky water. Don’t drive through them as your propellor will just cut them up, increasing nutrient supply.

Boating - Propellers stirring up the mud on the bottom of the lake release nutrients so lift your propellor in shallow waters. Sterilise your boat and trailer before launching if it has been used in any other lake or river to rid it of unwanted organisms. Propellers and wake also introduce large amounts of air/oxygen into the lake which directly affects weed and algae growth so go slow in shallower water.