Sharing Water
by Prof. Ueli Brunner
(University of Zurich, Switzerland)
Water is a precious good; it is basic for all life. Thereforesharing water means first of all sharing the water between differentstakeholders, Man being just one among them. Human needs may absorbup to 40% of an ecosystem without stressing it (Cosgrove &Rijsberman 2000, p. 25).
| | animals |
| plants | |
| | irrigation 70% |
| household 10% | |
| industry 20% | |
| religion 1% |
It is essential that Man leaves enough water to nature in order topreserve the local climate, keep a high biodiversity and perpetuate awell-functioning ecosystem. Among the human needs by far the largestportion is used by irrigation agriculture, especially in aridregions. For industrial and household purposes only about a third isused.
Sharing water also has to be seen in space. Where may the runoffwater be used? Shall the rainwater be caught at the place where itfalls? In this respect Yemen has a great advantage in comparison withe.g., Iraq or Egypt, which must share the water with neighbouringcountries. Sharing water in space is in Yemen solely a nationalproblem.
A permanent discussion about sharing water in time is going on.Shall the water be used at once or shall it be stored for laterneeds? May fossil water be consumed by one generation? Closely linkedwith this discussion is the subject of sharing water by origin.Nature presents different sources of water e.g., rainwater,episodical and periodical surface water, perennial rivers or lakes,groundwater or spring water. Water use should be based on a vastvariety of sources.
A comparison of the ancient situation with the Islamic period andthe modern situation leads to helpful information about how theproblems of today may be solved.
The centers of the South Arabian kingdoms lay on the border of theRamlat as-Sab'atayn. Their agricultural economy was based on theYemeni sayl irrigation. The method consisted in catching thefloods by an earthen deflector dam, conducting the water by a channelinto a large walled field, which was flooded knee-deep. Surplus waterflowed to the next field by an overflow or, if it was the last in arow, back to the wadi. The huge amount of water in the field was toomuch to be totally retained in the soil. So some of it recharged thegroundwater leaching the salt of the former irrigation period on itsway to the aquifer. The safety of the system was given by a weakdeflector dam which - in case of an uncommonly large flood - waswashed away, leaving intact the channel and fields (Brunner &Kohler 97, p. 175). The fertility was guaranteed by the silt whichsedimented on the fields with every irrigation. Therefore the Yemenisayl irrigation was, and still is, sustainable in its propermanner. The only severe problem it faced was the rising level of thefields.
In the South Arabian period almost every wadi had its extensivesayl irrigated area (Brunner 1997a, p. 192). Flat wadi floorsconsisting solely of silt and gullied now by erosion tell us aboutit. Even the famous two gardens of the Sabeans were irrigated in thismanner because the function of the Great Dam consisted in raising thewater to the level of the oases and by no means to store water(Brunner 00, p. 76). So two thousand years ago farmers for centuriescreated fertile wadi floors which are the most prosperous landreserve of today (Brunner 97b, p. 84).
At the same time the mountainous region of Yemen was quite denselypopulated. Due to higher rainfall people there were based on rainfedagriculture. In order to profit from rain people had to level theirfields so that the precious water drops were retained in the soil anddid not wash it away in the rugged landscape. Where the amount ofprecipitation required was unsure, collector fields were prepared toharvest water for the prepared arable land (Brunner & Kohler 97,p. 174). In this way, especially in the Himyaritic period, a secondman-made landscape was shaped. As every farmer in the lowlands knows,the terraces in the highland are the best insurance againstdisastrous flash floods in their region.
From the point of view of sharing water the South Arabian periodmay best be summed up in the following table:
• in space:- highland: rainfed agriculture & rainwater harvesting
- lowland: sayl irrigation
• in time:- at once (surface water)
- slowly (groundwater)
- storage in cisterns for household
• by stakeholders:- agriculture
- nature
- household
- religion
• by source:- periodical surface water for Yemeni sayl irrigation
- rainwater for rainfed agriculture
- groundwater in small quantities
Three conclusions may be drawn. First, the highland terracesprotect the irrigated fields in the lowland. Second, surface waterrecharges the aquifer which is used in small portions all yeararound. Third, the human part in utilizing water is perfect andleaves enough for nature.
The beginning of Islam brought a shift of the population in twodirections. Many tribes migrated to the north to take part in theconquest to spread the new religion. Other groups moved from thelowland to the highland of Yemen (Brunner 99, p. 78). The main reasonfor doing so is part of the well known story of the final collapse ofthe Great Dam in Ma'rib. The former fertile fields fell barren. Thefarmers in the large wadis around the Ramlat as-Sab'atayn would havebeen forced to construct bigger diversion dams in order to lift thesayl onto the level of the fields. With the diminishing power of thelocal leaders the necessary organization was missing. So the fertilearable land on the ancient oases could not been reached anymore. Thelarge-scale sayl irrigation gave way to a small-scale sayl irrigationalong the eroded parts of the wadi (Brunner 97b, p. 84).
The situation in the highland did not change fundamentally. Theemigration decreased the hardship on the rainfed agriculture at thebeginning. But with the increase of the population in the lastcenturies land use reached its limit. Every possible spot on themountain slopes served the agriculture either by being terraced or bybeing cleaned and used as water collecting field. Like this theterraced landscape of Yemen was still intensified. Today it rangesamong the most beautiful man-made mountain sceneries on earth.
Altogether only little changed in sharing water. Maybe a littlemore water was retained in the highland than in ancient times. Theportion of sayl water used for irrigation in the lowland diminishedslightly so there was enough water for the rich savannah -ikevegetation with its fauna along the wadis and the groundwater wasrecharged regularly. The distribution in space was dominated by theIslamic law that farmers upstream are favored rather than the onesdownstream (Caponera 73, p. 12). Cisterns and wells both with limitedcapacities provided the little water needed for household andreligious purposes.
The present situation is characterized by a rapid increase ofdiesel-pumps all over the country and an exploding demand for waterby the fast growing cities. Furthermore one plant, qat,dominates agriculture in the highland because of its high return ofinvestment; qat and a slowly establishing industrial sector appear asnew consumers of water. All these four characteristics are based onthe idea that water is evident and may be used all year round.Sharing water in time has disappeared. Permanent, unlimited water useis in the head of every farmer and every housewife.
Beside this major shift an outline from the point of view ofsharing water may also show the minor changes.
Sharing water
• in space:- In the highland rainfed agriculture has diminished because it is labour intensive and produces mainly food crops.
- First attempts to bring water to another region by pipes or cistern lorries are established. Urban areas are preferred to rural ones.
- The prosperous irrigated agriculture in the lowland has multiplied the demand for water in this region.
• in time:- Permanent use is common.
- The new Ma'rib dam stores periodical surface water for later use.
• by stakeholders:- The so far unchallenged claim of the agriculture is competed with by domestic and industrial users.
- The rich qat farmers define the market of water in the highland.
- Nature is losing its part of water and faces the new problem of polluted water.
• by source:- Rainwater is less used than before.
- Groundwater is widely overused.
- Periodical surface water is still diverted for irrigation.
The method above applied of monitoring the water use from fourdifferent viewpoints leads to the following conclusions:
• More stakeholders are looking for water than in ancient times. Therefore the so far competitive stakeholders should complement each other. Domestic and industrial users may first use the water but then give it back to nature properly cleaned, so it can be reused by agriculture.• The water problem has to be seen as a national issue. Highland and lowland are a combined water system. The rainfed agriculture on the terraced fields is the best protection for the sayl irrigated oases down in the wadis. If less water is used in the highland it does not mean that there will be more water for the lowland.
• The water management lies in one hand because the water problem can not be divided. A single institution has to handle all aspects of water use including ecological targets.
• Surface water storage may change natural conditions. The evaporation of the new lake deteriorates the local climate in Ma'rib. Sweet water aquifers along the sea coast become salty if they are not recharged regularly.
• In recent years the demand for water in Yemen has been satisfied mainly by groundwater. Depending on only one water source is against Yemeni tradition. Rainfed agriculture must be strengthened by the government and traditional methods of rainwater harvesting for agricultural and domestic use must be forced.
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Brunner U.: Jemen - Vom Weihrauch zum Erdöl.Böhlau-Verlag Wien, 1999.
Brunner U.: Geography and Human Settlements in Ancient SouthernArabia. Arabian archaeology and epigraphy 8, p. 190-202,1997a.
Brunner U.: The history of irrigation in the WâdîMarhah. Seminar for Arabian Studies 27, p. 75-85, 1997b.
Brunner U. & Kohler St.: Bewässerung im Jemen. MareErythræum 1, p. 171-195. Staatliches Museum fürVölkerkunde München, 1997.
Caponera D. A.: Water laws in moslem countries. Irrigationand drainage paper 20/1, FAO Rome 1973.
Cherchi S.: Auswirkungen des Staudammes von Ma'rib, Jemen, aufUmwelt und Gesellschaft. Master thesis, Dept. of Geography, Univ.of Zurich, 1998.
Cosgrove W. J. & Rijsberman F. R.: World Water Vision -Making Water Everybody's Business. World Water Council. EarthscanPublications Ltd., London 2000.
Uil H. & Dufour F. C.: Water Resources - Wadi Adhanah andMarib Area. Main report. Report WRAY 15, Ministry of Oil andMineral Resources & TNO Institute of Applied Geoscience, Sana'a& Delft 1990.