Micro-Capture to increase food production in dryland areas
This article discusses a low cost way to increase the food production on desert and degraded lands while reducing the impact of droughts. This is accomplished without increasing demand for ground water and can even help recharge the local aquifer. This is accomplished by maximizing water retention on the land where rain water falls so the soil has time to absorb it. By creating small pockets of deeply moistened soil we can grow new fodder producing trees. The process can can work in dry regions with very little rainfall.
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The approach can help ranches in Texas and other dryland grazing areas by providing a drought resistant source of fodder to augment the food naturally available on their land. It creates a series of micro-reservoirs where water can be concentrated to create a deep pockets of moist soil where fodder producing grasses and trees like willows can be grown even if those trees would normally be unable to survive.
Micro catchment, micro-weirs and check dams are similar concepts. Check dams are generally built across dry drainage using rock dams to catch soil and soil and water. They provide an excellent way to fertilize soil, stabilize drainage and were used throughout Colorado, Utah and New Mexico. Our approach expands the traditional check dam concept by finding a larger number of ideally suited locations where they can be easily located to capture between 250 and 3500 gallons per dam. They are normally constructed as a rubble rock dam packed with dirt rather than the carefully built rock walls commonly shown.
Building check dams dams is relatively simple. We simply identify where water will run off surrounding land during a moderate rainstorm then we create reservoirs using rocks, sand, mud and optional plastic to impound some of that water. If we choose the right places to install the reservoirs using the natural terrain we can minimize cost and impact. Most of these check dams are less than 2 to 3 foot tall and and are built on normally dry land using locally available materials.
A rainstorm that drops ½” of rain would require 0.123 acres of land to deliver 1,000 gallons of water needed to fill a medium-small reservoir assuming the first 20% soaks into the surface soil. A 32,000 acre ranch such as Circle Ranch in west texas could potentially have 260 thousand of these micro reservoirs impounding 260 million gallons of water per storm. If each of these micro reservoirs ends up producing a conservative 150 pounds of drought resilient fodder then you could end up with 39 million pounds of additional drought resistant fodder for the ranch. You normally size the weirs for the average storm runoff but a 1,000 gallon reservoir will occupy a space 7’ X 7’ X 3’ deep or 9.4’ X 9.4’ X 1.5’ deep.
According to rainfall records Sierra Diablo mountains received several storms that delivered more than 1/2 inch of rain even during the 2015-2016 drought. A check dam in this area would have been filled at least 8 times even during a significant drought.
Assuming each cow eats 1,200 pounds per year and the gross value between the animal and calf drops is $5,000. over a 6 year period that makes the value per cow about $833 per year. 39 Million pounds of new food could support 32,000 additional animals or reduce the amount of purchased feed. If the value remains $833 per head per year then it could represent a gross profit increase of 26 million per year. If the cost of installing the check dams averages $150 per dam the total cost would be 39 million providing a sub 5 year payback. Perhaps a more practical approach would be for the rancher to retain their existing herd while dramatically reducing purchased feed and be ready to survive the next drought with minimal impact.
The concept started as a way to retain and buffer water from storms in deforested tropical areas where they experience soil erosion, flooding and dry rivers due to reduced water buffering ability. The same solution can be applied to provide an increased food supply in many if not most dryland ecosystems.
Until now one challenge with deploying large scale micro-catchment has been identifying all the locations where rain falling on the land would collect in sufficient volume to make a weir useful. It is desirable to create many small collection points 250 to 3500 gallons so each point can grow additional fodder or food. By capturing the water as high as possible working down it allows even small ranches to create hundreds of new fodder production oasis each one providing more food than the land can normally provide without consuming any additional ground water.
By analyzing the natural profile of the land it becomes possible to determine how water will naturally drain off the land. We can identify places where small and inexpensive weirs could be built using rocks and sand to capture between 250 and 3500 gallons of water per storm. This analysis is normally a labor intensive process that requires special skills and surveying tools. Our software does the hard work using NASA elevation data so we can make the process accessible to people around the world.
NASA recently made available a data set tells us the elevation of every small square piece of land. Using this we can determine where water falling on that land is likely to drain using software algorithms. We can show each recommended check-dam on a web map and print out data points so you can find them with an inexpensive GPS.
We want to provide freely accessible web based software that can show users every point on their land where water draining during rainfall would collect more than 250 gallons or the amount they specify. Local users can then select from those locations to construct check dams to capture or slow the water down before it can drain off the land.
We need a grant to finish the software. It will be easier to obtain that grant when we find a rancher or farmer who promises to use the output to construct some weirs on their land to test and demonstrate the rest of the plan. Please Introduce us or support the work directly
The key with the software is it starts at the high land point and following the terrain to lower areas of land under the assumption that water will always flow downhill. The software eventually locates a natural depression that could capture sufficient water to make installing a Weir worthwhile.
- By keeping the reservoirs small, the micro-weirs can be constructed by hand using rocks, sand and optional plastic liners.
- By constructing them on normally dry ground we avoid damaging riparian zones and make them easier to construct.
- By constructing them high and working down we increase the number of fodder growth points that can be constructed.
- By concentrating new fodder at points away from creek and river bottoms we minimize grazing and animal traffic damage in those those sensitive zones.
The software will eventually try to optimize the check dam locations to find the locations where you can impound the maximum water with the smallest weir since that should represent less work.
Note: It is easy to see the water collection point in larger ravines or creeks but these points are more difficult to dam with hand constructed check dams and they are often considered riparian zones that are more sensitive and may be subjected to increased regulatory overhead. In any case a single larger body of water simply doesn’t provide as much opportunity to grow increased amounts of food.
If you can help then please contact us.
Thanks Joe Ellsworth
CTO of Air Solar Water
Disclaimer: The food production and financial returns described above are meant to be illustrative of how one would go about creating such a ROI model for the technlogy. Each farm and ranch will yield different numbers because the food costs, probability of drought, animal values all vary by region and even by weather patterns. These systems take time to take effect. You need time to plan new trees during the wet season and several years for the trees to grow to where they can produce significant amounts of additional fodder.
- Micro capture to mitigate soil erosion due to deforestation
- Grow Dryland a complete process for growing desert trees
- Simple Water Harvesting in the Desert
- Rainwater Harvesting by Desert Permaculture
- Water Harvesting Traditions in the desert southwest.
- Water Harvesting for Desert Urbanites by John Patterson Permaculture.org Catch all the water than falls on your lot and store it in the soil. The Trick is to slow the waters movement, direct it, and hold it on the surface where absorption into the soil can occur and plants can make use of it. Perennials have an advantage because they can survive long droughts with deep root systems.
- Village Homes Solar Develemnt in Davis CA caputres 100% of it precipitation using clever check dams combined with swales.
- Wildfell ferrocement tank An interesting way to capture large volumes of liquid water that can be used for wildlife and stock watering. Nice addition to micro-capture dams.
- Runoff Homestead a working example in west central new mexico
- Land Restoration a watershed perspective
- Harvest waters with microcatchments by dan howellCalculating the size of catchment to support a tree
- Is Rainwater harvesting in the desert worth it? An interesting articles that explains the true cost of water versus the perceived cost of water.
- Rainwater harvesting for drylands and beyond by Brad Lancaster
- Desert Water Harvesting Initiative