Other Water Source Options
The Water Corporation is exploring catchment management and cloud seeding to determine if they are options for Perth’s water future. They are both rainfall dependent.
Catchment management
Forest or catchment management includes various techniques to improve the state of the forest and conserve the environment. Catchment thinning is one such technique that has been used in the past to improve the environment and increase streamflows.
In 2002, the need for a better understanding of the interaction between water, land and biodiversity in our forested catchments was identified to provide informed decisions on their future management. To address this need the Water Corporation prepared a proposal to undertake extensive research in the Wungong Drinking Water Catchment.
The Wungong Catchment is a drinking water catchment 60 kilometres South East of Perth. The catchment has been previously logged and mined for bauxite. It lies within a high rainfall zone and is considered a degraded regrowth forest consisting of mainly jarrah and marri trees.
A 12-year trial is currently underway in the Wungong Catchment to observe how removing certain types of trees affect streamflows and biodiversity in the forest. This tree removal process is known as forest or catchment thinning.
The Water Corporation has partnered with environmental agencies, universities and research institutions to implement an extensive research and monitoring program. The trial will be assessed regularly to incorporate adaptive management responses.
An extension to include other forested catchments would be considered only if the community and Government are comfortable with the findings.
If similar forest management is applied to other metropolitan catchments in the high rainfall zone there is a potential to yield an additional 25 gigalitres of water per year, based on current rainfall. Catchment management is dependent on rainfall.
Cloud seeding
Cloud seeding attempts to artificially generate rain by implanting clouds with particles such as silver iodide crystals. This is usually carried out by sprinkling the particles from above by plane, which is fitted with silver iodide burners mounted under each wing. Using weather forecasting techniques, suitable clouds are identified based on the location of the target area and the prevailing winds.
A seeded cloud will take 30 minutes to precipitate and seeding areas are chosen upwind of the target. Clouds moving over Perth could be seeded which would cause them to release rain over the catchment areas thereby increasing streamflow to the dams.
In 2007, the Water Corporation commissioned the Bureau of Meteorology to undertake a study into the effectiveness of cloud seeding in Perth. The study concluded that cloud seeding should not be seen as a short-term response to drought but rather as a longer-term water management tool. It recommended further field-testing and evaluation.
Further trials over a number of years would need to be undertaken by the State Government to consider impacts on other sectors including agriculture and the environment.
The Water Corporation is not currently considering cloud seeding as a future source option.
