Rainwater Harvesting In Antiquity By Adam Whalley

traces its history way back to biblical times (old testament) Introduction Ancient technology traces its history way back to biblical times (old testament) Despite its long history the technology remains greatly underutilized - If fully developed, rainwater harvesting could, with appropriate storage, provide an important sustainable and environmentally friendly water source for supplementing or even replacing other water supply options in a wide variety of circumstances and locations.

Roman engineering and hydrological experts became masters in rainwater harvesting Used reservoirs and aqueducts to channel and store collected rain from rooftops and courtyards Conveyed water into storage cisterns and with a network of aqueducts this water could then be re-distributed onto fields for irrigation, bath houses, drinking water supplies,etc

Around the Mediterranean most roman cities existed only on the strength of their capacity to gather, move, and store fresh water. “ I decree on behalf of J. Caesar Water for all !”

Roof-water Harvesting With a small amount of conversion and adaptation, ancient water harvesting systems can be adapted to improve effeciency and re-implemented in order to meet modern water requirements. Improved roof WH system, Sri Lanka Old style roof WH System Modernisation and Conversion

Traditionally problems have emerged when it came to storing the collected water stagnant nature of water in gutters and tanks mosquito breeding has been quite common in this type of system. In ancient Ahaspokuna, mosquito breeding was prevented by rearing predatory fish in these tanks!

Thai “Jar Programme” -Existing traditional technology can be adapted and upgraded, in order to meet regional domestic water requirements Simple affordable Ferro-cement jar design (1-2m3) easily constructed by householders 200 litres for rainwater storage became popular, widely adopted Result :Thailand made huge improvements for water supply targets in rural areas using old technologies

Irony A study Indian Centre for Science and the Environment (ICSE), during the 1987 drought indicated that while many of the new supply schemes based on tube well sources dried up, whereas villages that were still depending on the traditional rainwater harvesting technologies for their supplies still had enough water to drink (Agarwal & Narain 1989). A return to the use of traditional rainwater harvesting technologies has therefore been encouraged by the ICSE not only in the arid states of Rajistan and Gujarat where the study took place, but throughout India. - New technology is not always better ?

Field water harvesting systems Khadin walls to divert runoff from hillsides onto crops - Still in use today Tanka clay lined reservoirs Kund covered tank with compacted mud catchment areas The first known construction of a Kund was during 1607 AD in Rajasthan

Local Field water Harvesting technologies: elaborate: tunnel systems of Syria called “Ganats” – Built to carry water from mountain sources several kilometres to fields and towns simple: dikes, ditches, embankments Nabatean civilization in the Negev Desert: In the Negev Desert annual rainfall varies: 200 mm in the north-west 25 mm in the far south is restricted to winter months (November to April). Seasonal rainfall distribution is highly variable and fluctuates widely from year to year.

Major source of water (for use by humans and animals) could only be the collection of surface run-off - obtained from sloping ground during winter rains. sunken cisterns artificially constructed watertight plaster reservoirs recharged by artificially directed surface flows (during each of the infrequent rainstorm events). channels to collect and divert the overland flow towards the cisterns. Remains of a Nabatean Cistern

They aimed to prevent the rain from penetrating the soil on the upper slopes, and so induce maximum run-off rates Then collect this run-off from a large area and direct it to a relatively small cultivated area in the lowlands (run off farming) The hillsides would have been naturally covered by a stone and gravel pavement (inhibits and detains the surface water aiding infiltration. ) Stones were cleared off the slopes and placed into mounds, piles and lines (still observable today). This smoothed the surface and exposed the finer soil -formed a self-sealing crust -boosted surface runoff rates.

Artificial groundwater recharge (by impounding a part of the surface run-off water or adjacent river flow) This water, in due course, finds its way into the subsoil and recharges the ground water,leading to the recharge of well water levels downstream. Recharge ponds (“Nadis”) and tanks have become popular in many places. In Tamil Nadu, where there is now over-exploitation of ground water, farmers are volunteering to spare additional land for percolation tanks. Groundwater Recharge & Conservation - http://www.mercedid.org/recharg.htm

Conclusions The pioneering methods of land and water husbandry employed by ancient civilisations may still be relevant today. In many of the desert fringe lands around the world, where more people than ever are now struggling with aridity and its associated problems, old methods can be adapted and subsequently applied to the great benefit of local communities. Much can now be done to improve water harvesting and storage by means of modern, more efficient technologies. With population demands for water in the future set to increase and the predicted impacts of climate change, it may be that the ancient methods used to harvest water may become more important than they have ever been.

References and reading Agarwal, A. Narain S. 1997. “Dying Wisdom: The Rise, Fall and Potential of India’s Traditional Water Harvesting Systems”, State of India's Environment 4, A Citizens Report, Centre for Science and the Environment, New Delhi. Brooks David B. “WATER: Local-level Management “ In Focus: From Research to Policy. IDRC 2002 ISBN 0-88936-996-8, 80 pp., paperback Evenari, M., Shanan, L Tadmor, N 1971. “The Negev: The Challenge of a Desert”. Harvard University Press, Cambridge, Mass Gould, J. Nissen-Petersen, E. 1999. “Rainwater Catchment Systems for Domestic Supply: Design, Construction and Implementation”, London: I.T. Publications. Rajkumar, et. al. 2000 Lanka Rainwater Harvesting Forum, Report A1: “Current Technology for Storing Domestic Rainwater”, Sri Lanka Rainwater Harvesting Forum 247,Vijaya Kumarnathunga Mawatha Kirulapona, Colombo 5, SRI LANKA. Texas Water Development Board “Texas Guide to Rainwater Harvesting” www.twdb.state.tx.us German Development Group, 2001“RAINWATER HARVESTING - Collecting Water as a Basic Need in the Desert” sourced via web search. http://www.water-2001.de/datenbank/571528843.40079.25/RAINWATER%20HARVESTING-Germany-II.doc