One in ten river catchment areas could have problems from too much water being drawn out.

This was the first to address the problem of farm fertilisers leaching into the soil in vulnerable river catchment areas.

The river catchment has sandy soils and steep topography, as with other rivers that supply the city.

During the floods of 2007, more than a full month's rainfall fell in 24 hours on the river catchment.

The river catchment lies in a temperate climatic zone.