Groundwater is a finite recource.
I find it really annoying when people talk about continuing to use bores and add more bores to Perth's shallow groundwater aquifers for watering gardens as though the water is going to magically keep replenishing itself.
The Perth Basin is an unconfined aquifer, meaning it is open to the air, showing up above ground as wetlands and lakes. Decreasing rainfall over many years and land use change as bushland is cleared and surfaces across the suburbs have been paved reduces the infiltration of rain water back into the recharge areas of the Perth Basin metropolitan aquifers. Water is being taken form these area much much faster that it can be replaced by natural rainfall.
|Guage pool in the hills near Perth. The rate of flow into Perth dams has reduced dramatically in the last 30 years.|
Yet more and more people have installed bores over the years and they are allowed to water more often each week than scheme water users. I believe this allows bore users to continue to ignore the efforts of the Water Corp and Dept of Water to wean us off our European strength water use even more than the general population. Sadly the Water Crop and Dept of Water seems to waste just as much as anybody.
A huge amount of water gets lost through leaks in the system, from dripping taps and leaking toilets to large scale leaks along water supply lines so we all need to do our bit to preserve the precious resource.
|One of Perth's dams, showing the low water level.|
Problems of using too much bore water.
Saltwater intrusion can occur where too much fresh water is removed by bores, allowing the salty water below to replace the fresh.
High nutrient levels in some aquifers due to fertiliser over use on the soil above them has enriched the groundwater to the point that bore water is feeding plants as well as watering (and no, this isn't really a great thing). I've had two quite trustworthy sources tell me this but haven't read a report on it.
Watertanks are brilliant, however with useful Perth rainfall generally only falling during the winter months, to get the maximum use out of a reasonable sized water tank it should be plumbed into the house for laundry and toilet use so it can be used instead of scheme water throughout the rainy months.
Collecting rainwater to water your garden in winter is not going to make a lot of difference, as the water can end up being stored for a while until the rain stops, unlike if the tank is plumbed to the house, where it gets to empty and refill regularly, making better use of the available ongoing rainfall throughout the season.
The waterwise message in garden is slowly getting through and other water saving technologies are being used, such as greywater systems and low pressure sprinklers that make large droplets and therefore avoid misting which wastes a lot of water to evaporation.
We live in a dry city on a dry continent and must look for better ways to reduce our water use. Itn's not vey energy efficient to turn salt water into fresh, so we'd be better not to pollute or waste what little we have. Turning off taps properly and fixing leaks makes a huge difference over time.
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