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HighPressure

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Posts posted by HighPressure

    Drought - Summer - 2018?

    in Spring Weather Discussion

    Posted

    Rain now will do little if anything to replenish stocks, unless its a sustained wet period. Groundwater levels only recover during the winter and early Spring months, this is because almost all the rain that falls is lost to either evaporation or due to the hard ground will appear in rivers as runoff.  The type of rain you get (I know I sound like British Rail) is also an important factor, sudden downpours, although they will stop immediate demand dead in its tracks in that area, can actually be counter productive.

    The ground has picked up so much particulate matter, that any runoff into rivers causes the (DO) oxygen levels to plummet, the fish die, the water is almost untreatable, and can cause any abstraction taking place to be stopped.

    There is even a special boat known as a bubbler that works the Thames when needed which simply introduces oxygen bubbles into the water to oxygenate the river. 

         

           

    • Thanks 1

    Drought - Summer - 2018?

    in Spring Weather Discussion

    Posted

    10 hours ago, seaside 60 said:

    One question to any knowledgeable people.

    Has the infrastructure changed in the lat say 20 years,
    There are more houses and more people taking loads more water, if we haven't built more reservoirs, storage areas bigger pipes and larger treatment plants.
    Ie the water companies are not building for the future (yes they have repaired many leaking pipes), then this will get worse and worse with even small times of small rainfall totals.
    They are complaining of people taking more water well surely that is obvious when its hot and they should be able to treat enough water when this happens, thats why you invest for the future.

    This is what i think people like Ben and others are referring to, we pay loads for water yet the water companies are not reinvesting enough because of profits for the investers.
    I do understand that if you to build a new reservoir the green people kick up a fuss because wide areas are flooded nature is lost homes and farms are gone etc,

    I can't talk for other areas. and I have been out of the industry for 10 years. As for London, a lot of investment went into modernisation after privatisation, it simply had too, and it was quite lucrative for the companies. Things such as K factors, and leakage targets played a big role in the amount of investment that went in. To give you one example Hampton WTW was still steam powered until 1982 and it took 200 people to run the plant, within 10 yrs or privatisation, it could be run with just 6 people. A huge project on the London Water Ring Main (which I was part of) was undertaken, and treatment works were uprated, however there was very little increase in stored water, which was a political hot potato due to leakage. The argument being you don't need more storage is you are losing 20% of what you already produce.

    There was no real increase in total capacity maybe even a decrease in capacity, although water transfer between internal areas was improved.    

     

     

                  

    • Like 4

    Drought - Summer - 2018?

    in Spring Weather Discussion

    Posted · Edited by HighPressure

    I am not sure we ever used the term drought at Thames with any real meaning. Its pretty much irrelevant, other than it will give companies more leeway to issue restrictions. There are many issues at play which cause problems with supply, yes peak times are more challenging because the longer it stays dry the more water people put on their gardens, this is why you get lower pressures in the evening. A pipe can only take so much water at (x) pressure, water may still not reach the end of the main even if the maximum amount is going in at source.

    As said previously as a storage reservoir drops so does its head pressure and thus flow to a treatment works, once you have a valve 100% open you are totally at the mercy of the level feeding you.

    Another factor which can cause serious problems is algae in the reservoirs, this causes primary filters to clog quicker requiring more frequent back washing. The number of filters online at anytime will have a direct effect on output. Water is drawn off open storage reservoirs at a point below the surface depending on quality, the lower a level goes, and stronger the sun the harder it is to find the quality you need. Shallow reservoirs are a waste of time at this time. 

    All of this is set against daily demand which can be 20% above the average, the shorter nights (the recovery period) mean you have to pump as much as you can to restore levels for the early morning start. This puts the system at risk of burst mains, and that will usually occur just before dawn.

    It is one huge balancing act, that just like the titanic will sink if there is a prolonged period of dry weather. Metropolitan areas will be looking at the clock awaiting the end of school term, as usually means a 10% drop in overall demand as people go on holiday. 

    Groundwater areas often require support from river source supplies to suppliment them as even with a fully working borehole it cannot yield anymore than its maximum, this puts even more strain on the system.  

                  

     

          

    • Like 8

    Drought - Summer - 2018?

    in Spring Weather Discussion

    Posted

    10 minutes ago, Nick L said:

    I find it quite unnerving that something as important as the water supply is in private hands. 

    It was good to start with, a huge amount of good work was done between 89-95, then the greed set in, cuts were made where they should not have been. Profit was gained at the expence of the truth, and risk assessments were fudged. One of the reasons I left the industry, I simply had too many run ins especially regarding leakage which was the big topic of the time..         

    • Like 2

    Drought - Summer - 2018?

    in Spring Weather Discussion

    Posted

    19 minutes ago, Alex said:

    This situation is actually much more common in the SE. Here in Chelmsford in Essex we have not even had 1mm in June, last measurable rain was in May. Normally here we get a very dry spell in the summer, during 2010 we went through a similar spell and then August was wet. I think it’s obviously much more unusual elsewhere and there probably is more panic than is necessary from the water companies.

    You can bet the water companies will be panicking, Profit versus Risk probability is the key calculation. From a technical perspective there is no need for any water shortage in the UK. It has to be remembered that the water companies combined take billions in profits each year, that is calculated against % risk. If there were to be severe water shortages, there a few MD's who will be looking for employment elsewhere.       

    • Like 2

    Drought - Summer - 2018?

    in Spring Weather Discussion

    Posted

    3 minutes ago, Nick L said:

    As much as 75%? Wow. Interesting insight though.

    Hampton the 2nd largest Works has 2 x 100" tunnels supplying it, they will lose head as the storage reservoirs drop in level, the input to the works struggles to keep pace, this causes the output to drop from the works, you then struggle to retrieve potable water reservoirs at night, often bursting mains in an effort to do so. You tend to get a knock on effect..     

    Drought - Summer - 2018?

    in Spring Weather Discussion

    Posted · Edited by HighPressure

    1 hour ago, Nick L said:

    Yep. There's a different between a drought and a water shortage. We're in drought, but far from having a problem with water shortages. It's when you get a dry summer sandwiched between dry winters that you have to worry.

    There sure is lot a difference, its all down to resource management and investment in the system. I have been out of the water industry for 10yrs now but did work through the 1990, 95, and 2003 summers at Thames water. If anyone is actually interested I can tell you what actually happens in these situations and how they are managed. I won't bore you with the many stories, but I was at the sharp end.

    London they say has 100 days of stored supplies in its storage reservoirs to the west and North East London, with around 10% of its daily supply coming from ground water mainly in Kent. The problem with having a theoretical 100 day supply (@200,000 ml) is you have to get it out of the reservoir, treat it and then supply it. Anything less than 75% full starts to give real issues.

    As I say I can only speak for London, but if anyone does want to know anything I am happy to answer.         

             

    • Like 3
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