How dams and catchments work video transcript
Previously, rainfall into dams was a major source of water for WA. But with our population increasing and our temperatures getting warmer and a declining rate of rainfall, we've had to adapt to find alternative sources to secure our water futures. Let's look at some numbers.
In the 1960s, dams were our primary source of drinking water supplying 88% of Perth's needs. But now, 60 years later, dams account for about a quarter of our drinking water supply, and in some years, much less. And this will only continue to decrease. You might think that dams are just gigantic bowls used to collect rainfall. However, it's not quite as simple as that.
Dams are fed by something known as streamflow. To understand streamflow, you need to know a little bit about catchments. Catchments are large areas where water is collected within the natural landscape. The outside edge of the catchment area is usually the highest point. Gravity channels the rainfall which lands in these catchments into the lower areas of the landscape. Here, the water makes its way to outlets like creeks, streams, rivers, lakes, oceans or any other body of water. A large amount of water also seeps below ground into our aquifers, or to be held in the soil for plants to enjoy and flourish all year round.
Only when enough rain falls and the ground is fully soaked, will the excess water flow across the surface or discharge from below ground. We call this water ‘streamflow’. And this is what runs into our dams.
With declining rainfall, our catchment areas have become drier and drier and now take longer to become fully soaked. This results in less water captured in our streamflow causing a flow-on. Or should we say no flow-on effect to our dams. So even if we were to create new dams, there just wouldn't be enough water flowing into them to make it worthwhile. But that doesn't mean we're giving up on our dams. Instead, we're giving them a big pump up.
Technology advances allow us to pump drinking water from our network of desalination and groundwater plants into our dams, making them giant reservoirs. This allows us to have multiple reliable stored water sources which are far less reliant on rainfall but still remain ready to collect streamflow, our most cost effective source, when it does occur in our catchment areas. This is one of the ways we're adapting our approach to water planning to shape WA’s water future. Catchment areas and dams will therefore remain a very important part of our water cycle. And we will do everything we can to ensure they remain healthy.
Within Water Corporation, members of our source protection program diligently care for our catchments and dams. Undertaking inspections, by-law enforcement, surveillance, water sampling and giving land use advice. We also rely on our community to do the right thing when visiting catchment areas by respecting the land, following visitor guidelines and reporting anything that may be of concern.
Prevention of contaminants is the safest and most cost effective way to protect our drinking water quality. This is why some activities are not permitted within drinking water catchments, and entry to land near drinking water reservoirs is typically restricted. Unlawful activities can lead to prosecutions. So make sure you observe and follow all signage. More information can be found on our website.
Water plays an intrinsic role in our WA lifestyles. It enables us to enjoy sports ovals, caravan parks, swimming lessons, green gardens and relaxing holidays. We rely on water in almost all aspects of our lives. So it's important not to underestimate its value and protect our water quality at the source.
At Water Corporation, we're working hard and finding innovative ways to secure WA’s water future. Thank you for doing your part too.