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  1. #81
    Twister_Ken's Avatar
    Twister_Ken is offline Registered User
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    Quote Originally Posted by dancrane View Post
    Here's a crazy thought, then...

    ...feel free to point out the flaws that I haven't thought of yet, it being less than a minute since it came to me...

    If a very tidal river like the Arun, was dammed at its mouth, down in Littlehampton...surely the substantial lower course of the river, which currently floods with brine every high tide, could be permanently filled with fresh water, without inundating any new land?

    Quite an engineering job, doubtless, but no more than has been achieved before, surely? The fact that the Arun's mouth is no more than 50m wide, might make it a good deal easier (faster, anyway) to build.

    The flat land around Chichester/Bognor is largely agricultural...and must need a good deal of watering in drought periods. The river-water wouldn't need a lot of lifting, from the present high-water mark, to reach crop-spots.

    Isn't current policy, to make excuses, while every hour, thousand of tonnes of usable fresh river water pours into the sea?

    Umm...I just remembered this is a boating forum. Well, couldn't the dam incorporate a lock, for access? Like many marinas?
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  2. #82
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    Not much water flows down the Arun in drought periods.
    Yes you could dam it, and draw off the water, but it's not a big area, being a narrow river with a short tidal section. I would also not be surprised if the water turned brackish due to salt water permeating the land at sea level?
    You also have to deal with the considerable amount of silt that it carries.
    Also the way the tidal section is used to drain the surrounding area.

    I think some water is already drawn off the Arun a little higher up?
    It is probably a case of cost/benefit. Land around that area is very expensive, so any impact on property costs a lot. Water is still cheap but we cannot predict how reliable the rain is in future years.
    In greece, many houses have a 'cistern' holding perhaps a hundred cubic metres under the house. That is worth doing, because water costs a lot there if you are not on the mains, I think around 10 or 20 euro a cubic metre is what our friends pay. If our water gets ten times as expensive as it is now, it may be worthwhile to store our own rainwater here, but it does add a lot to the cost of a house.

  3. #83
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    Quote Originally Posted by dancrane View Post
    If a very tidal river like the Arun, was dammed at its mouth, down in Littlehampton...surely the substantial lower course of the river, which currently floods with brine every high tide, could be permanently filled with fresh water, without inundating any new land?
    They have done this in Holland as part of flood defences.

    It caused a lot of damage to the ecology of the region and now most of the sea dams are open to allow some exchange of fresh / sea water.
    Vince
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  4. #84
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    Quote Originally Posted by WilliamUK View Post
    Tidal rivers expose the shallows twice a day. Permanent flooding is permanent.

    That should be the absolute last resort to be considered only when everything else has been tried... including population relocation.
    I agree it'd likely be a terrible loss to wildlife, but possibly a boon to human existence thereabouts. I think it might be optimistic to expect humans to up-sticks and head for where there's water, rather than quickly and relatively easily, storing river water.

    Quote Originally Posted by maby View Post
    I think it would also take a very long time before the water contained in such areas would be drinkable - it will be sitting on mud and sand that is well loaded with salt.
    This would be an osmosis question, wouldn't it? I mean, if salt in the riverbed rapidly leaches into the dammed fresh water, it can be all let out at a low water spring, then allowed to refill...a few flushes like that (or a few dozen?) and there'll be less salt each time, no?

    If on the other hand, the salt only slowly pollutes the accumulated river water, a good deal might be extracted (particularly upstream) before the majority needs to be let go, seawards.

    Either way, longterm, it must offer the enormous resource of the river basin's outpourings, lots of which are currently lost.

  5. #85
    WilliamUK is offline Registered User
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    Quote Originally Posted by dancrane View Post
    I agree it'd likely be a terrible loss to wildlife, but possibly a boon to human existence thereabouts. I think it might be optimistic to expect humans to up-sticks and head for where there's water, rather than quickly and relatively easily, storing river water.
    I'm not an "overpopulation", human-hating nut so please don't mistake what I'm going to say here.

    Human existence thereabouts is the main part of the problem. It is our overuse of water, our insistence on using drinking water for almost everything, our lack of motivation to be conservative with or re-use water and our lack of will to actually fix the problems we cause that waste good water.

    I'm not saying I expect people to up sticks. I'm saying we should not wipe out masses of habitat because we can't be bothered doing things the right way.

    If we (rightly) eliminate the option of permanently flooding tidal estuaries and instead focus on ourselves we have basically three options.

    1> Do it the hard, right way and change the way we use water while stemming the systemic waste.
    2> Do nothing and put up with shortages.
    3> Move.

    Throughout human history people have moved for resources. I'm not really sure why we think we should be all that different now. Sure, technology has allowed us to largely ignore our natural way, and politics (all the way from serfdom to now) have prevented us from following it (now, as then, you effectively need permission to move)... but that is the entire cause of our current problem - and probably future ones.

    We have come to choose where to live based entirely on where we grew up and/or where we want to live... with little or no attention paid to where we should live based on available resources.

    Sure, building a dam across the mouth of an estuary and permanently flooding the area with fresh water would be easier and probably cheaper than fixing the problem, but do you seriously think that's looking forwards?
    With wasteful water-use, leaky systems and the almost complete disregard for resources when considering where or how to live... we could dam every estuary in the dry parts of the British Isles, have 40 days and nights of biblical-grade rain to give them a head start and they'd still end up short of water.

    All that lost habitat in exchange for being able to continue on our wasteful little way.

    Seems like a poor trade to me.
    William
    Blithe Spirit - Lark 1804.

  6. #86
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    Default I was thinking as you do, William, but speaking as devil's advocate...

    Please, don’t make me look like the bad guy, here. I’m much inclined to encourage seawater loo-cisterns, sensible restraint in fresh-water usage, and fixing those insanely wasteful leaks. But…

    …as a species, surely we are already vastly over-populous for the area we occupy, and unless, on improbably scrupulous moral bases, we resolve to emigrate, we must pillage whatever opportunities nature unwittingly supplies.

    However ugly that sounds, it’s far more likely than ‘doing the right thing’, as I’d personally prefer...

    ...if we're in for a long period of droughts, as well as having ever-more population to wash and water, we'll need every answer.

    PS, Ken, I've got nothing against birds! Some of my best friends...

  7. #87
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    Quote Originally Posted by dancrane View Post
    Iím much inclined to encourage seawater loo-cisterns,
    So you're going to lay sea water distirbution mains to every house in parallel with the existing potable water mains.
    That would make a National water transfer system look cheap! Oh and the sea water would probably kill off the bugs in the biological sewage treatment plants.

    One of many, many non-starters on this thread.
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  8. #88
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    Quote Originally Posted by DJE View Post
    ...the sea water would probably kill off the bugs in the biological sewage treatment plants.
    That, I didn't know. Good point, if it's true. Pity you dressed it up as snarling criticism.

    I expect you're right. Much better to do nothing. Why worry?

  9. #89
    WilliamUK is offline Registered User
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    Quote Originally Posted by dancrane View Post
    Please, don’t make me look like the bad guy, here.
    Certainly not trying to do that.
    I'm addressing the ideas, not the person having them...
    When I'm talking about suggestions and the things we do wrong, I'm talking about possible solutions to the problem we all have, not shooting messengers.

    I’m much inclined to encourage seawater loo-cisterns, sensible restraint in fresh-water usage, and fixing those insanely wasteful leaks. But…
    Seawater where appropriate, but probably not generally.
    There's no need whatsoever to use seawater to flush toilets when every house with running water has a plentiful supply of grey water they could use for the job.

    …as a species, surely we are already vastly over-populous for the area we occupy, and unless, on improbably scrupulous moral bases, we resolve to emigrate, we must pillage whatever opportunities nature unwittingly supplies.

    However ugly that sounds, it’s far more likely than ‘doing the right thing’, as I’d personally prefer...

    ...if we're in for a long period of droughts, as well as having ever-more population to wash and water, we'll need every answer.

    PS, Ken, I've got nothing against birds! Some of my best friends...
    Perfectly clean rainwater falls on our roofs, into gutters and down into the sewers. Why does it not flow into our gutters, into a cistern below the house and only when that's watered the whole garden and is still overflowing on into the sewer?

    Such a system (edit - I mean estuary damming here) would almost certainly be paid for through taxation. A costly and phenomenally wasteful means of funding. I wouldn't even want to hazard a guess at how much such a dam would cost (on just one river) but I suspect it might actually be CHEAPER (and if not, not much more expensive) to embark on a program of moving to parallel domestic systems (rainwater collection, grey-water reuse for gardens and flushing... possibly even micro-production of potable water on the domestic or local level in the very long term) and without any of the environmental disaster that damming invites.

    I don't believe we DO need every answer to meet the water needs... I believe we need the right answers.

    Continuing with the status quo as far as water systems and use are concerned precludes any possibility of having enough to go around long term.

    Leaks must be stopped rapidly when found. Proactive methods to FIND leaks must be begun. Potable water should be used primarily for drinking. Rainwater should be collected domestically. Grey water should be used in all appropriate ways (toilets, gardens and so on).

    Until we've done all of the above and started requiring all new housing estates to be built with parallel water systems (potable and non-potable), cisterns and so on... we shouldn't even be considering large scale habitat destruction to take up the slack.
    William
    Blithe Spirit - Lark 1804.

  10. #90
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    Agreed. That's all very sound good sense. I just don't see it being the government position, any time soon.

    I just heard the south is in for heavy rain. That should defer their need to worry, for a week or so...

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