What could be in the water? Some things that could be in the water are sewerage, oil, duck manure and rubbish.  Sewerage could run from the houses at the back of the lake.  There is a road going past the lake so oil could run from cars that go by.
click for sound	Accidental or thoughtless? Washing your car in the gutter makes all the soap go down the drain.  If you cook and then pour all the oil down the sink you are polluting the water.  When it rains the fertilizers can be washed away into the waterway.  The water can wash rubbish away and it can end up in the water.
How do we know if water is contaminated? An expert could test the water or an ordinary person could check if waterways are healthy by taking a sample of water.  If there are a lot of water bugs, that means the water is healthy but if you do not have a lot of water bugs that means the water is unhealthy.  You could also test the water by looking for things like dead plants, trees, grass and dead animals.  There could be scum or oil deposits floating on top of the water.
By Ben, Kristy and Arlen