My city has a catchment area for water but due to drought conditions it's getting lower and lower in current capacity, and water restrictions have been placed into effect for residents and businesses to conserve the water we have left.

I know of tarps or pool covers are used to combat evaporation of small water sources like pools and ponds. Is there a scaled up version of this for large dams? Or are there different/better technologies available to do this at a large scale?

4 Answers 4


Two technologies I know of are plastic balls and solar panels. Both are very visible, and may not be aesthetically acceptable.

Shade balls are used to reduce the exposed surface area and reflect sunlight. They're used in LA for example.

Floating solar panels are expensive but of course produce power, and more efficiently than on neighbouring land because the water cools them . They're a fairly new technology, again used in California and Australia among other places. Like shade balls, they stop much of the evaporation.

  • 1
    From your description of the conditions where you live I suspected that you're in Australia, your profile tells me specifically NSW. There are apparently proposals at the state level to encourage floating solar
    – Chris H
    Dec 18, 2019 at 9:12
  • correct, and that is good to know, thanks!
    – Robotnik
    Dec 18, 2019 at 10:31
  • Municipal water supplies tend to be unable to provide what is really needed, unless you just happen to be a bit thirsty at the moment. Please consider the alternatives. Dec 28, 2019 at 14:12

Each location on the globe has a wide variety of factors that will influence your answer (temperature, humidity, hours of sunlight, etc.) but there are several age-old solutions that come to mind. Please allow me to share my insights.

In most places where you capture a huge volume of runoff there is a very common problem: You get sediment. In my personal water catchment experience I get many tons of sand deposited with every rainfall in the uphill areas, and all areas that retain surface water for more than a few days will gather layers of clay and silt. This is only a problem if your system is unable to regulate it properly.

Provide massive sand capture uphill, and massive sediment capture downhill. Your water needs will take care of themselves if you do so.

Fortunately, I require massive quantities of sand and silt for my endeavors. The challenge is to force Mother Nature to work for me instead of against me, but Mother Nature provides more than I can use, so I need to give Her room to play with what She has in mind. I can easily dam up areas, and she can easily fill them in. Consider what happens when we dance this way.

She insists on providing more than I can ever need. She has Her ways that we would do well to recognize. When She fills my dams with sand and sediment, what do I observe? All downhill creek beds are restored to running water. This is water that seeps out of the layers of sediment that She has provided and continues to provide perpetually. There is no evaporation from underground stores of water.

What I do is that I catch the sand in uphill areas where it naturally accumulates. Sand holds a very high percentage of its volume in water, especially if the lower layers are clay or bedrock that seeps slowly if at all. The aim is to provide a huge underground cistern that holds water like an aquifer. All it takes is a shovel and a wheelbarrow, or a bulldozer if you are motivated by matters of scale.

My uphill areas hold the water in sandy beds that seep water slowly. Downhill areas promote fine particle sediment that drains slowly. This is where my crops flourish. All that which requires nutrients thrives there. This is where I put all organic waste products. My downhill neighbors love me because they see what has become of my insanity. I have inadvertently improved their property value and increased their standard of living because their livestock and gardens now enjoy the benefits of my attempts to be sustainable.

Okay, so I had to spend a few days with a shovel to make sure this all works out to my satisfaction. The workout did me well. I'm old enough to enjoy the exercise and frugal enough to avoid paying for an LA fitness monthly sign up. Observations and outcomes are incontrovertible. It works.

You can do this yourself and no longer be dependent on municipal water supplies. I would advise everyone to do so, but not many are so inclined. The motivation for me has been to avoid a water bill I'm not willing to pay. This kind of simple ancient knowledge is not normally available, so we can be forgiven for our ignorance. In the context of sustainability we are remiss in not understanding it and implementing it properly.

I've tried everything. The only thing that works for me is to store it underground where moth and mold do not corrupt. It's Nature's way. It's working for Her and with Her. It's what they do in the desert when they want to restore Her to her former glory. Please believe me, it's legit.

If you are concerned about visibility, then please consider how that is not a problem in this approach. It scales up well. It might not work well if your area is completely flat, but small degrees of inclination actually make it more feasible. Consult with an expert in hydrology and you will see that I'm not a fool.

Our modern systems do not normally welcome solutions that render you sustainable. Overcome this if you can. If you cannot provide for your own water and power, then you have much to do.

All this newfangled gadgetry is fine. I'm not knocking it, but people with very little intelligence for thousands of years were able to see what we fail to see now. You don't have to be all that bright to see how we can live in harmony with Mother Earth. Remove yourself from any equation that doesn't seem right.

  • This sounds like a pretty great solution - any chance you could share some pictures?
    – Robotnik
    Jan 2, 2020 at 0:40

You can get some mitigation by using oleic acid. This is a simple hydrocarbon with a hydrophilic end. Under still conditions it creates a one molecule thick layer on the surface of the water. Commonly used on swimming pools to reduce heating costs. it's non-poisonous.

The downside is it doesn't shade the water, so the water heats up. Eventually it gets warm enough to evaporate anyway.

  • That can also be an effective and natural way to control mosquitoes because it alters the surface tension of the water which prevents the maturing larva from escaping the water as adults. A few drops of vegetable oil will do the trick on a small pond. Jan 2, 2020 at 12:33
  • I'm not sure that it will work that way. Oleic acid makes for a very thin layer. My experience with veg oil and water (salad dressing) is that it doesn't spread over the entire surface. But it will also reduce air exchange between water and air, which means that the lake is fully dependent on photosynthesis in the water column to not go aerobic. Jan 8, 2020 at 20:07

Floating solar panels, is one, namely beside providing power, they also keep the water shaded. Another is classic tarp like swimming pool covers but a reservoir would need given size, Many thousands/millions of square feet.

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