Pond Boss Forums POND CONSTRUCTION Soil questions Ponds to hold Acequia (aquaduct) water

hey:) I'm new here, recently working as land manager on a site in Andalucia, southern Spain. We have aquaducts (acequias) running through the top of the property, with constant water flow year round (from snowy mountains). Our farm has a gate in the aquaduct opening to a channel leading the water down into the valley, and straight out the other end (erosion galore). To make better use of this abundance, and to prevent further erosion of the channel, we are planning to build 3 retention ponds. Two are a few meters outside the main water movement channel - we can control how much water goes in - and one is basically in the pathway of the main channel slightly to one side so it doesnt get the full momentum force. Each pond is about 3m in diameter and 2m deep. We dug test slices, and the majority of the soil is loamy sand, but there is some clay in the lower layers.

Because there is quite a lot of water and movement going on, I am wondering about how to make strong, leak proof ponds. We have at our disposal lots of big heavy stones and about 400kg of bentonite clay. Wondering about materials but also structure for the pond sides and banks, and what vegetation to use to hold them in steady. Any suggestions?

The big stones won’t hold back water. You need a mix of clay and soil. 100% clay tends to dry and crack. So, you mix an aggregate of clay and soil.

Welcome to Pond Boss.

It is difficult to give you proper advice without fully understanding your plans and design requirements.

Do you have complete control of the aqueduct gate at the top of the channel? Meaning you can regulate the exact flow rate of water by manipulating the gate. Also, you are never forced to open the gate all of the way due to local regulations or to mitigate a flood during a heavy rain event.

Knowing those factors will significantly change your engineering requirements compared to "full open" flow.

Are you just trying to stop erosion down your slope? If so, then limiting the water is the best option.

When you say you want to use your available water resource, is that for a small household, or are you going to irrigate crops over an area of 100 hectares?

If we get some more info, you can probably get some more useful advice.


Welcome to Pond Boss!

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Thanks for the warm welcome to Pond Boss, what an amazing platform.

We have complete control over the gate, but once it is open the flow it quite strong, and it is hard to regulate it in between closed and open. We are allowed to have the gate open three days a week, and this water mostly runs through the main channel into the river.

The purpose of these retention ponds is to spread this running water more effectively through the land to irrigate trees (wild and cultivated), as the landscape here is extremely dry and the microclimate near the water allows for more vegetation and life. Maybe for this reason, the pond adjacent to the main channel makes less sense, so we are not totally sure about that one.

There is also a fear that in the coming years the water access will decrease, and so we want to have more sites on the land where water can spread, sink and be utilized for vegetation.

We are also a bit concerned about mosquitos, wondering if there are some methods for keeping mozzies out of the pond area.

Thank you for now!!

Excellent news in your update.

Having water during the dry summer months in a Mediterranean climate is a very valuable resource. Does your acequia run water all year?

Modern piping materials are the easiest way to control water flows, and one big advantage we have over "ancient" engineers.

Are you allowed to set up a siphon hose over your gate to take water? (Is that legal now, and would it NOT jeopardize your water usage amounts in future years?)

With a siphon, you could take easily controlled amounts of water, and have zero erosion risks down your slope.

Your large slope is also a benefit to you. Instead of pumping water to any of your usage sites, you can "gravity feed" water to any location on your property.

I think one option would be to build a single, large retention pond at a good location near the TOP of your slope. Fill it from the gate (or siphon pipe) as needed.

You can then run a large pipe (5 cm?) down the hill from your pond and to a large number of tees with control valves. You can then open any section of your irrigation pipes to water as you desire through smaller distribution pipes. You should probably do a search on "drip irrigation" methods and equipment. That is how I water the tree plantings on my very dry farm. It is VERY efficient for water usage, and can be installed easily by non-professionals.

Piping is much easier and cheaper to install and maintain compared to the construction work of building a series of ponds down the hill. However, ponds are certainly more beautiful!

For your main retention pond at the top of the slope, I would consider using a pond liner. They are not that expensive for the pond size you are considering, and it would guarantee that your pond did not leak (if installed correctly). The liner does need to be tucked into a little trench outside of the borders of the pond. If you have nice boulders available on site, that might be an attractive way to cover the edges of the pond liner and make a beautiful, hillside pond.

Every pond will eventually start supporting multiple living organisms, including mosquitos. In the U.S., we have a minnow called gambusia that love to eat mosquito larva so much, that their common name is "mosquito fish". However, many types of minnows and smaller fish will eat up your mosquito larva. Just make sure you use an approved indigenous fish species.

Just throwing out more ideas for you to consider for your big project. As you start to consider more detailed planning of your project, you can always keep coming back for more specific answers. There is usually an expert on the forum for almost every topic.

I am loving the pond love and the knowledge, thank you so much.

We do have pipes that we use to take acequia water for irrigation our syntropic agroforestry system (where we grow most of our food) using drip lines, but the problem with the pipes is that these ancient aquaducts are filled with sediment and then we are dealing with clogs on a weekly basis (if not daily..). The idea of gravity feeding a complex system of ponds as canals is that we wont need to maintain it as much, and can leave gravity to do more of the work in spreading the water out throughout the land.

We built a nice check dam at the top below the gate, where the water is now slightly stalled and can potentially be diverted in a few other directions (working on digging some safe channels), and we also dug out 2 new channels diverting additional water along some terraces. Our landscape is very steep (1:1 most of the areas) so we can only build serious structures on the bottom forth of the property.

Out of the pond sites, we are going to go with two of them, both with the purpose of bringing more vegetation and life to dry parts of the land. I wonder if we can irrigate some trees around the pond just by having some seepage into the ground (which trees can access this slowly leaking water and from how far away?

Also, what kind of vegetation will hold in the banks of the pond?

We bought 400kg of bentonite clay, but the ponds are too small for a roller, and we do want some seepage, not completely sealed up. How would you recommend using the clay to seal without a big machine?

Not sure how to post pics here, but I'd add a few of what we have done so far.

Thanks to all you amazing pond experts out there:)

One solution to sediment-laden water is a settling pond.

If you fill it from your gate, then MOST of the sediment should be settled out within a day. (Charged clay particles can stay in suspense for a long time, but some are small enough to go through irrigation drip emitters without clogging.)

The best practice is to then place your water inlet pipe a few feet below the surface of the water. That way you do not draw sediment off of the bottom, or draw in leaves, twigs, or pine needles that are floating on the surface.

Most of us try to avoid having trees immediately adjacent to the pond. Their roots will try to poke through your "bentonite seal" and the leaves will slowly accumulate in your pond and leave it a little shallower every year. Further, having a "sealed pond" that allows for seepage to water trees is going to be a very delicate balancing act. I don't even know how to make suggestions for that?

If you are not going to use gravity to feed your water system, there are lots of little 12V pumps available. You just need a deep-cycle battery and a small solar panel to charge it. Put the pump on a timer, and then pump for one hour a day (for example) into the adjacent irrigation system. That way you could plant your trees in a line away from the pond, in a circle, or in any pattern that looks nice for your farm. Your sunlight to run the pump will be at a minimum in November-December-January. However, I think that is your rainy season?

Your bentonite MIGHT work without a roller. After you spread and mix it with the soil in your pond bottom and sides, I would bring up a load of water and then mist your mixture so it is inclined to stay in place. You will then need to SLOWLY fill the pond. A big rush of water all at once will tend to move your bentonite mixture out of the way and perhaps leave a path for a water leak.

Most people in the U.S. probably use a grass type matched to their region to serve as their erosion control on the banks of the newly constructed pond. Some people even use a blend of grasses. (Typically with something that comes up fast like rye to jump start the process.) I would select something functional AND attractive, since the area around a pond on the hillside will probably be visible from many places on your property. I suppose you could even do a mix of native wild flowers if you have something that has a dense root system and likes to spread.

I would try to arrange to water your planted vegetation at the very start, so you can get it well established before it has to survive through the next dry season.


There is a very specific process for doing that correctly. I am no kind of expert on that topic.

You should probably write that up as a new post in the "Soil Questions" sub-forum. Add any information you can about your existing soil, and the area and the depth of the ponds you are planning on sealing. Hopefully, you can get some specific expert advice on that topic.