In drylands it is better not to store water in dams due to evaporation, which causes salts to build up in the water, damaging the soil. It is better to store the water in the soil and in perennial plants. Building swales on contour and check dams in gullies are a couple effective ways to stop water from running across the land and to get it to sink into the soil. In drylands water can safely be stored in large enclosed tanks, but these can be expensive to buy or build.
Yes I understand. I plan on building contour swales and possibly Gabions to store water under the soil. But I also need surface water to use for shallow rooted trees in their first few years. This is my dilemma.
I think if you make a dam relatively deep compared to the surface area, you can avoid some of the evaporation problem. If you can construct a dam in a gully (which takes proper engineering) you can store many more gallons of water than if you simply dig a hole in a low flat space.
That hillside looks like it gets extra water, the grass seems thick there. Is that from water off the roof? If so it could certainly be directed down toward the dam. It's definitely worth a try making a dam. I think in Bill Mollison's "Designers Manual" he shows open water dams in deserts shaded by trees. Obviously you won't have trees right away, but you might be able to plant some to eventually shade the pond to slow evaporation. Also to act as a windbreak.
Yes I'm thinking trees also posibly grape vines if I can find a way to suspend them over the dam.
Actually the hills are the border of the property. But you are right I am thinking of building contour swales at the bottom of these hills and have them flow into the dam.
The dam will be located just in front of the concrete structure. That is the path of a major waterway coming from the mountains. Not sure how much water flows from there. I'm guessing quite a bit when it rains. I'm hoping to capture most of that water.
Does any one know if you have to seal the dam or will it just seal itself in time?
If not what's the best way to naturally seal it?
Our upstream neighbor built a dam in the seasonal creek without compacting it properly and it completely washed out during the flood this Spring, sending all the dam material, including their old asphalt driveway chunks, onto our land. It isn't really something an amateur should attempt. Our neighbor across the road had a proper pond built and it took a guy with a bulldozer a few days to dig and compact it, and it holds water nicely. It is not on the creek channel, either.
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