Traditional Water Harvesting

 

John Palmbach palmbajp@uwec.edu

 

Part of Water is Life, a class website on water privatization and commodification, produced by students of Geography 378 (International Environmental Problems & Policy) at the University of Wisconsin-Eau Claire, USA, Spring 2004.

 

 

 

WATER IS LIFE homepage

Global supplies

Economic policies

Trade agreements

Industrial use

Agricultural use

Domestic use

How groundwater works

Water stress & human consumption

Effects of shortages on species & crops

Groundwater drawdown

Surface water drawdown

Water companies & water pricing

Water privatization conflicts

Bottled water industry

Bottled water conflicts

Municipal water safety

Water wars & international conflict

Irrigation dams

Bulk water transfers/ river diversions

Water pipelines

Water supertankers

Great Lakes water conflicts

U.S. water policy & conflicts

Technical fixes

Groundwater replenishment

Traditional water harvesting

Alternate directions

 

 

A class project by students in
International
Environmental
Problems & Policy
(Geography 378, Spring 2004, University of Wisconsin-Eau Claire)
 
Assistant Professor
of Geography Zoltan Grossman grossmzc@uwec.edu
(715) 836-4471
P.O. Box 4004,
Eau Claire, WI 54702 USA
 
 

 

 

 

Water harvesting can be traced back through human history almost as far as the origins of agriculture. Water harvesting is defined as the redirection and productive use of rainfall. In some incarnations it resembles a primitive type of irrigation. Unlike conventional irrigation, however, rainwater harvesting does not depend on a constant flow of water; it is totally dependent on rain. Basically, harvesting involves a variety of methods used to get as much water as possible out of each rainfall. Uses were nearly limitless when rain could assumed to be clean. These ancient practices sustained ancient people when conditions would have otherwise totally prevented agriculture. Many peoples in the world have continued to rely on water harvesting practices. Others have returned to it in order to relieve pressure on overburdened undergroundwater tables or municipal water systems. Some Western groups are discovering ways that rainwater harvesting can be used in our society to relieve stress on the environment, save money, and recharge groundwater tables. 

 

Drinking Water: Traditionally rain water has been one of the few water sources known to usually be clean and safe to drink. Today water harvesters must be wary of pesticide contamination, high mineral levels, bacteria and other impurities in their runoff water. Filtering technologies have been used in the past and today to purify it by passing it through a series of rocks, gravels, and sands to scrub out contaminants. These methods have proven to be very effective.

 

Irrigation: Rainwater is the primary source of irrigation for crops around the world. Water harvesting techniques have been employed for thousands of years to get more water to the fields in order to improve crop production. This is the primary traditional use of rainwater harvesting.

 

Sustaining Animals: Because of animals’ higher tolerance for bacteria and other impurities, harvested rainwater is often used as the primary source of water for livestock. Since cattle and sheep are well adapted to drinking rainwater, safer groundwater is often saved for human drinking.
Groundwater Recharge: This is one of the more modern applications for water harvesting. Rain runoff from buildings, parking lots and other man-made structures is funneled into seepage ponds or deep wells in order to directly recharge aquifers. 

 

Case Studies

The people of Jharbeda Mundatola, in the Sundergarh district of India, recently revived their ancient water harvesting tradition in light of a shrinking water supply. Years of dwindling streams and dried up water tables stirred memories of a technology used by their forebearers to control rainwater runoff from the hills above. In 1999 the village restored and reconstructed the local ghaghra, a sort of mountain water reservoir. Older members of the village remembered swimming and playing in the pond created behind the dam of stone and mud which collected rain runoff coming down the slope. The water is collected in behind one or more of these barriers, also known as bunds, and allowed down the hill at a steady rate. This provides the village with drinking, cooking and bathing water in addition to sustaining animals and watering terraced crops and lowland fields. The water gathered is enough to provide for the village even through the worst of dry season droughts. Most of the ghaghra disapeared when British colonial authorities frustrated or dismantled traditional water harvesting techniques by village institutions in order to take full control of their colony. This tribal public works project rescued not only their own village from drying out, but also revived streams and wells in fields and villages in the surrounding valley. More information at humanscapeindia.net

The Zuni Nation of the Colorado Plateau employed a system of water harvesting methods to survive in the dry climate. These people nestled their fields in vast valleys between enormous hills. The Native Americans would build a series of stone and mud walls between the hills to slow the movement of water through the valley. The walls did not hold standing water, but instead prevented soil erosion and slowed runoff long enough for it to permeate the dirt; creating moist rich soil in which to grow crops. This technique is also known as flood water harvesting, and has been used in traditional agriculture all over the world. Many decades of disrepair eventually lead to the total failure of this system and the eventual desertification of many of these valleys. Find out more about the Zuni at Arid Lands

 

“Zuni agriculture represents a long-term successful land conservation strategy with a 100-year hiatus. For over 1,000 years Zuni farmers utilized the exodus of eroded soil and water resources from pinyon-juniper uplands to grow food that sustained their people. As Zunis abandoned traditional farming methods to cope with repression and misguided development strategies of the recent century's dominant culture, the nutrient-laden waters that previously supported them have become an expensive liability.” (Jay B. Norton and Jonathan A. Sandor)

 

Agricultural water harvesting has come in many shapes and sizes. This Table, provided by the FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS gives examples of different agricultural water harvesting systems. They are all dependent on capturing water flowing down hill in what are called catchments. They move the water to the cultivated area and then allow it to permeate the earth.
  Classification Main Uses Description Where Appropriate Limitations

Rough Diagram

negarim microcatchments microcatchment (short slope catchment) technique trees & grass Closed grid of diamond shapes or open-ended "V" s formed by small earth ridges, with infiltration pits For tree planting in situations where land is uneven or only a few tree are planted Not easily mechanised therefore limited to small scale. Not easy to cultivate between tree lines

contour bunds micro catchment (short slope catchment) technique trees & grass Earth bunds on contour spaced at 5-10 metres apart with furrow upslope and cross-ties For tree planting on a large scale especially when mechanised Not suitable for uneven terrain

semi circular bunds micro catchment (short slope catchment) technique rangeland & fodder(also trees) Semi-circular shaped earth bunds with tips on contour. In a series with bunds in staggered formation Useful for grass reseeding, fodder or tree planting in degraded rangeland Cannot be mechanised therefore limited to areas with available hand labour

contour ridges microcatchment (short slope catchment) technique crops Small earth ridges on contour at 1.5m -5m apart with furrow upslope and cross-ties Uncultivated catchment between ridges For crop production in semi-arid areas especially where soil fertile and easy to work Requires new technique of land preparation and planting, therefore may be problem with acceptance

trapezoidal bunds external catchment (long slope catchment) technique crops Trapezoidal shaped earth bunds capturing runoff from external catchment and overflowing around wingtips Widely suitable (in a variety of designs) for crop production in arid and semi-arid areas Labour-intensive and uneven depth of runoff within plot.

contour stone bunds external catchment (long slope catchment) technique crops Small stone bunds constructed on the contour at spacing of 15-35 metres apart slowing and filtering runoff Versatile system for crop production in a wide variety of situations. Easily constructed by resouce-poor farmers Only possible where abundant loose stone available

permeable rock dams floodwater farming technique crops Long low rock dams across valleys slowing and spreading floodwater as well as healing gullies Suitable for situation where gently sloping valleys are becoming gullies and better water spreading is required Very site-specific and needs considerable stone as well as provision of transport

water spreading bunds floodwater farming technique crops & rangeland Earth bunds set at a gradient, with a "dogleg" shape, spreading diverted floodwater For arid areas where water is diverted from watercourse onto crop or fodder block Does not impound much water and maintenance high in early stages after construction

 

Water Harvesting Today

Modernized versions of water harvesting are making a comeback in North America with some environmentally conscious individuals and businesses. Small companies are popping up, especially in the Pacific Northwest, which offers to install water harvesting system in your own home. These rainwater storage systems modify the rain gutters that are already on many homes. The gutters are led to a large storage tank where water is held for future use. Water from the tank is filtered first for large objects such as twigs, leaves, shingle dirt, and insects. Next it passes through two micron filters witch eliminate tiny contaminants down to the size of many bacteria. Finally it passes under an intense ultraviolet light to finish sterilizing it. Then the water is ready for almost any home use. The Ersson family in Portland, Oregon installed the water harvesting system shown above. They use reclaimed water for nearly all of their domestic needs. Showering, laundry, dishes, and cooking all use reclaimed water. They do not yet use it for drinking water, but speculate that they easily could in the near future.

 

A second interesting modern use of water harvesting is known as harvesting for groundwater recharge. This system is similar to the previous system in that it gathers the water that would otherwise simply run off of your roof. It is different, however, in that instead of saving the water in a container it redirects back into the aquifer. This may sound overly simple or useless, but this is not just putting the water back onto the ground. Water that falls to the ground may make it into the undergroundwater reserves, but it will very likely be redirected downstream to a river or pond or (more likely in urban areas) enter the sewer system and be transported far away. Surface water is also much more likely to cause erosion as well as pick up runoff contaminants such as fertilizer and chemicals. The recharge process actually puts the water through a dirt and gravel filter with biological components to clean it and then directs the water down a deep well. This directly recharges the clean cool aquifers without the long delay it otherwise takes water to reach these depths. Water customers in arid and semi-arid climates are already being encouraged to use this technology. The Town of Panchayats Tennessee, for example, has provided the diagram above and encourages its citizens to use this technology.

The Future of Water Harvesting

Many communities in the past and present have effectively employed water harvesting to meet many of their water needs. Ancient technologies have shown themselves to be useful today, and modern water harvesting technologies are improving in leaps and bounds. If we are facing a future of increasing water demand, and possible water conflict, it may prove to be very wise to look to the past for a solution. All the water we need is out there. We simply need to cherish every drop, as our ancestors did.

 

Sources

For more information:

Rainwaterharvest.org

http://www.rainwaterharvesting.org/Rural/whim_tradi.htm

 

Arid Lands News Letter

http://ag.arizona.edu/OALS/ALN/ALNHome.html

 

Food And Agriculture Organization Of The United Nations

http://www.fao.org/docrep/U3160E/U3160E00.htm

 

Ersson family Water Harvesting Website

http://users.easystreet.com/ersson/rainwatr.htm

 

Official State Web Sight Of Tennessee

http://www.tn.gov.in/dtp/rainwater.htm