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Irrigating Australia - more food for thought
Jonno wrote:
Re Dams. Of course you cant make it rain more, but you can spread the catchment areas. The spin doctors who tell you "dams don't increase rainfall" are using dams that catch the available rainfall. Using the stupid argument that dams don't increase rain is correct but wrong in reality. We need them where the rain IS falling. That can be anywhere. So you spread your catchment areas...In our case South Gippsland. I'm particularly concerned about Victoria. They have decided to go hand in hand in having a increased population and at the same time not providing dams in catchments that ARE having rainfalls. Instead, they're putting in a desalination plant. Putting up the cost of water.... .... and ... umm... you can predict how damming 'newer' catchments will affect things like stream flow, velocity, the water table, salination levels and availability of potable water for wildlife (oh - and people!), can you? In 200 years of drought and aridity, don't you think there have always been reasons why 'new dams' haven't been employed in the places where you think they should? Just because rain falls in an area doesn't mean it's safe to dam and collect it! What about the Bonanza Dilemma (first saw it on 'Bonanaza' in about 1962): if you dam the headwaters of a stream and enjoy the benefits of its water for your purposes, what about the poor bloke immmediately downstream? What about the even poorer bloke half-way to the sea? The distraught bloke in the tidal zone? Not only that, but the ways in which streams form and runoff contributes to creeks and rivers is not only determined by precipitation. Other factors, such as soil porosity, the existence of bedrock or otherwise, the integrity of the substrates etc etc etc all come into play. Some areas where rain falls plentifully may not be suitable for damming, even though there *appears* to be a plethora of water. Porous soils, for example, often mean that the majority of the rainfall disappears almost immediately into the ground. In the opposite case, the rain may run off (often beneath the soil and vegetation cover, but above a non-porous bedrock such as granite or basalt) to wind up in a completely different catchment area. Damming the existent stream may cause untold damage to an already delicate habitat (which includes you and your water needs!). Hydrology is an incredibly complicated field of study. I've only done a tiny bit of reading and that a long time ago. But I do know a few of the reasons why tampering with streams, damming injudiciously and interfering with naturals systems can cause untold and often irreparable damage. Look at the Snowy River! Who'd have thought such a 'beneficial' scheme would cause such mayhem? My personal soapbox is a dreary little local stream in my area. Forty years ago, powers that be thought to dam it off and prevent the seasonal flooding that interfered with roads, grazing, transport and so on. Now, all these years later, the stream is dead, having been dammed and contained in an artificial concrete bed for so long. When the stream does run, the water is emerald green and serves only to move a massive payload of orphan shopping trolleys a few metres closer to the Big Drain in the middle of town. This stream, in my living memory, was a paradise of wildlife back when it lived! We caught tadpoles and penny turtles from its banks, climbed the sheoaks in its meadows and counted the numerous species of birds that lived off the fish in its waters. AND the commercial concerns the original damming was supposed to have helped are all gone! All of them! When the big Newcastle Flood occurred just recently, the water had nowhere to go because the natural waterways in and around town have been so stuffed up. Instead of following the natural drainage patterns, the excess water backed up in eutrophied, clogged drains and took the line of least resistance. THAT'S what happens when you bugger up waterways without fully understanding what you're doing. My opinion (and you, of course, have a perfect right to your own) is that water is so scarce in this country, we can no longer afford to make disastrous mistakes like those made on the Snowy and the Darling. We need study, conservation of *all* resources and cooperation between all interested parties. Oh, and PS. A desalination plant is a good idea! It makes use of water that has been tainted by the surface salts that wouldn't be there if so many trees hadn't been removed from your catchment! -- Trish {|:-} Newcastle, NSW, Australia |
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