The problem with leaves
Leaves are organic. They just break down and disappear, right?
Wrong. Leaf litter is one of the biggest contaminants when it comes to stormwater.
Each autumn, millions of deciduous trees all over the ACT and region put on an amazing show of autumn colour and then drop all their leaves. Street sweepers collect some and keen gardeners turn them into mulch and compost, but most are washed or blown into the stormwater system and into our creeks, rivers and lakes.
It’s not just autumn leaves that cause problems. Native trees drop leaves as well, particularly during summer. Then there’s grass clippings, prunings, tree bark and animal droppings. Yes, that’s right - your pooch’s poo is toxic to our waterways too .
When nutrients go bad
All these organics add up to what’s called a high nutrient load. Sounds like good news. Again, no.
Nutrients are good for our waterways but excessive nutrients cause all sorts of problems, including blue-green algal blooms which often result in lake closures.
Like algae, aquatic plants thrive on nutrients but when the load is too high, explosive growth can occur, followed by rapid decay and depleted oxygen levels. And we all know that without oxygen, aquatic animals die.