Our water sources: Dams, catchments & rainfall

With Fresh Water Thinking we’re looking at
our dams and catchments in new ways. Here’s a question: why is it that when Perth
gets a heavy rainfall, our dam levels don’t
automatically rise at the same time? The answer: it’s all to do with how much
moisture is in the soil in our catchment
areas. A catchment, is an area where water is
collected by the natural landscape, and it’s usually surrounded by high features such as hills or mountains. The soils in our catchments act like a
sponge, soaking up moisture, storing it in
underground aquifers, and gradually releasing it into our rivers and streams, which then flow into our dams. Years of below average rainfall means that Perth’s catchments areas have become drier and drier. So when the rains do come, they are soaked
up by the soil, which leaves us needing a lot more rainfall for the water to eventually find
its way into our dams. What’s more, because Perth’s groundwater
levels are dropping too, it takes even longer for rainfall to seep into the ground, soak the catchments and get the streams flowing. So, there’s the answer. It’s all to do with Perth’s dry catchments. The fact is, even if we do get decent rainfall
in any one year, we’ll still get a lot less inflow to our dams than we would have from the same amount of rainfall, several years ago. With Fresh Water Thinking, we are helping our dams by using them to store water from climate-independent sources such as desalination. It’s all part of our long-term plan to secure our water supply for the future. To find out more, visit our website at

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