What Happens When a Reservoir Goes Dry?

What Happens When a Reservoir Goes Dry?

Reservoirs are a solution to the tremendous variability in natural water supply, but what happens when they stop filling up?
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People use water at more or less a constant rate and yet, mother nature supplies it in unpredictable sloshes of rain or snow that can change with the seasons and often have considerable dry periods between them. If the sloshes get too far apart, we call it a drought. And at least one study has estimated that the past two decades have been the driest period in more than a thousand years for the southwestern United States, leading to a so-called “mega-drought.” (Source: https://www.npr.org/2022/02/14/1080302434/study-finds-western-megadrought-is-the-worst-in-1-200-years)

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55 Responses

  1. Practical Engineering says:

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  2. Bill Boyles says:

    one point i think maybe this video could have hit a little harder was that reservoirs are sized based on the demand predicted by planners when the reservoir was built. However, the meteoric growth of a lot of areas of the southwest in the last 40-50 years was, to an extent, unforeseen. So not only do you have less water coming in than normal, you have more water going out than expected, exacerbating the problem.

    • grumpybill says:

      Get out of here with your common sense.

    • Chad Neu says:

      @Erulian For what it’s worth, a lot of high tech manufacturing is water neutral or positive. Not all of it, but large companies like Intel actually return more water to their local watersheds in places like Oregon, Arizona, Asia, etc than they remove.

    • Chad Neu says:

      @MyTech what are you even talking about? You posted misinformation, then continued saying irrelevant stuff even after being shown to be incorrect.

    • Blake Harley says:

      ​@MyTech “Externalities are inherently part of the supply and demand evaluation” The definition of a market externality is a side effect which is *not* appropriately captured by costs–i.e. not properly priced by supply and demand. You can argue whether something is an externality and what to do about it which is where values come into play.

    • Fred Flint stone says:

      We have more than enough if we only drink it and don’t polluted it with human waste or add man made chemicals or pollution it with industrial waste du fu fu fun who would have known that

  3. Derek Morgan says:

    A couple of years ago Cape Town faced “Day Zero” when all the water supplying dams would run dry.

    It was a close run thing where emergency measures were enacted to allow citizens to fetch water from designated municipal/government sites.

    An extended period of water saving measures avoided having our taps run dry. It’s easier to survive without electricity (also a problem in SA) than without water! Fortunately rains since then have been good (enough).

    • Fred Taylor says:

      Just the idea of the taps being dry would send people into a panic if they actually saw them dry.

    • Michael Gooden says:

      This is happening right now in Port Elizabeth, South Africa. One dam is empty (too low to extract, even with barge). Communal standpipes have been built. Many suburbs have intermittent water as reservoirs can’t refill enough at night to fill downstream reservoirs. Our country also faces loadshedding of our electricity supply for up to 6 hours a day.

    • MinedMaker says:

      I remember hearing about this in the news, even though I live on the other side of the Earth. Glad things worked out.

    • Toebab says:

      is it weird that I know who you are

  4. Rachel Hornak says:

    This is why the massive exodus to the deserts of the Southwest can’t continue indefinitely. The Sinagua and Hohokam people abandoned many settlements throughout the Southwest long before Europans arrived, and I think unsustainable droughts were a major factor in what happened. They left a lot of canals that we still use today, so it’s clear they were dealing with a water scarcity of their own. It seems we’re still making the same mistakes today.

    • Dirtyharry70585 says:

      @Son Golin … ask bill gates, the largest owner of farm land in the USA growing windmills, not food

    • Dana Coleman says:

      People are dumb and greedy

    • ZeoCyberG says:

      @crazy wheel No, that’s false, California is not the only state that enjoys a warm climate, and even if it wasn’t that still ignores that all the other states combined could grow more than California ever could alone. Besides, you can’t grow anything if you run out of water… There’s ways to grow just about anything in any climate if you really needed to but nothing can grow without water…

    • crazy wheel says:

      @ZeoCyberG again, cause of the hot weather California produces so much food for all of the US, I believe California could save about 30% of water if it only grows food for Californians, true, other states have more water but cause of the weather, they can not grow as much for as California

    • ZeoCyberG says:

      @Christoph Kogler Sorry but it’s not disingenuous because much of that water can be captured and used. Like that 50% includes a lot of rain water and a typical California wet winter can dump an estimated 18 trillion gallons of rain in February alone. But much of it simply going down the drain and in the cities along the coast, it dumps right into the ocean… and that’s just one example!

      Seriously, don’t confuse good intentions with them being competent and actually using resources efficiently. There’s massive waste and they almost never focus on where the majority of the problem actually exists.

  5. Looper says:

    I wonder if this lack of water pressure pushing against the dam will cause structural problems? Just asking…

    • David Scott says:

      @HeRo TuRtle
      I don’t know anything about the use of water for cooling solar panels, but I know a whole lot about using water to cool about everything else and usually water is used with evaporative cooling and thus the water would likely evaporate.

    • Mark Rix says:

      Would have made it kind to hard to initially build if that was the case..

    • HeRo TuRtle says:

      @Areyousure well, after cooling said panels, where does the water go, though? I mean, water that’s used for cooling isn’t necessarily wasted water, since you can either irrigate fields that would use this water anyways, or simply “return” it back to its origin; your statement doesn’t make any sense and sounds more like pulled out of thin air.

    • william meek says:

      @Leo 06 those two things are not related at all.

    • jorge gonzalez-larramendi says:

      @Areyousure areyousure ? minimal water use: only for cleaning.
      any repucarbon winds around your neck of the woods ?

  6. Awnage says:

    A severe drought seems like a good time to do extensive maintenance on exposed sections of the dam.

    • Ginger_NoSoul says:

      @Cyberwar 🤣🤣🤣

    • Jesse Thyrion says:

      Doing extensive maintenance seems like a good way to end a drought. You know it will flood right when they remove something important.

    • beepbop says:

      lol why? The lake is never coming back.

    • Patrick Cooper says:

      @James Pinkerton interesting you say that cuz I honestly think infrastructure is one of the (semi rare) strengths of the US. I don’t think anyone who wanted to criticize the US would start ripping on American dams lmao. Every government is delaying repairs to save money and it turns into a tragedy way to often on a worldwide level. There are a lot of dams in Asia that have the potential to devastating some areas (again sadly already has gone very wrong)

    • Philip M says:

      @James Pinkerton Contractors doing more passes than Ultimate frisbee with those maintenance problems.

  7. M_W_K 1 says:

    Can we just talk about how nice Grady is? Despite nearly every episode being sponsored, he keeps the mention to the minimum and pushes it to the back of the video, focusing on the content before all.

    • John Broussard says:

      Very pleasing communication and delivery. Notice there are no impromptu “you know what I mean” s,” you know what I’m saying”, “at the end of the day”, ” sooner or later” ubiquitous filler trash talk that permeates what passes for informed delivery in these United States today.

    • Murad M says:

      @Benjamin yeap, guilty. I already pay for youtube premium, I don’t want more ads.

    • Eric Gemmell says:

      Dude, Grady is great for sponsors, don’t know what you’re talking about. He got me into brilliant…

    • Jonathan T says:

      I agree.
      I can’t recommend Grady enough to others.
      The content is just superb on all levels and to get this content with only a sponsor mention at the beginning, for free? 🤌👌💪

    • Benjamin says:

      idc i got sponsorblock 😂

  8. Terricon4 says:

    A lack of water is not normally dangerous for a dam. However… a lack of water in your water pipes can be very severe, even if just for a day. If there isn’t constant water and it’s pressure in the pipes you’ll find the built of mineral layers on the walls can crumble and break off. And with so many pipes being lead (especially in the US where instead of doing expensive projects to replace the pipes early we just raised the allowed lead levels up well beyond the safe point and decided we were now hitting our metrics even as things were) you’ll be in serious trouble if this happens in these places. Sudden major changes in the chemical make up of your water can lead to mass poisoning from the water supply. Of lead poisoning and otherwise. If water ever fails in your neighborhood, it’s a very good idea to get some lead tests and have a few people around the neighborhood test their water while running it for a bit once it’s back. Some utilities would do this themselves… others… don’t always….

    • beepbop says:

      Great. So not just water shortages, but poisonous water when it is available.

    • Lands says:

      @Kenny Cheung luckily i live in a place where we rarely get droughts, the well has been there since 1972 and has never once ran dry

    • Kenny Cheung says:

      @Lands You are still not completely off the hook. Your well can dry, if there is not enough rainfall to replenish the underground water reservoir and cause the water table to drop below your well or completely tap out.

    • FSXgta says:

      @Lands If there is extended periods of rain then it can get contaminated, but having ice cold well water is the best thing

    • Barefoot says:

      @Planefan 08 Right? Now I’m thinking back to how aggressive I was in various places I’ve lived, and… scarily, I think it tracks.

  9. Some Old Dude says:

    “A reservoir doesn’t creat water, it just stores what’s already there”
    A concept that still escapes many people in power, leading to bad decisions, and here we are today.

  10. ThePsiclone says:

    Be an interesting (to me at least) topic to know the effects of water level changes on the structure of a large dam like some of those you featured. How does all that concrete drying out affect things? How much does it all move with the relief of pressure against the wall, things like that.

    • Ucmh says:

      @Brandon It’s “would’ve.”

    • Brandon says:

      @Ucmh what? Are you trying to make fun of my second language? I don’t get it

    • Ucmh says:

      @Brandon “would of” Ow, my eyes…!

    • kingduckford says:

      I think a lot of people ask the question because of the fact that museum ships have this problem. Ships are built in dry dock conditions, yet most ships will eventually suffer structural failure if left in dry dock too long, as the ship not only deals with water pressure, but actually relies on it to keep the hull in shape. Thus, permanent dry docking is either unfeasable or requires major engineering (HMS Victory).

      So, it is only natural that people will ask the question about a dam.


      We are kidding ourselves if we truly think draining a reservoir and then refilling it doesn’t come with challenges.

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