ARAM, 13-14 (2001-2002), 403-421 U. AVNER 403 ANCIENT WATER MANAGEMENT IN THE SOUTHERN NEGEV UZI AVNER INTRODUCTION The southern Negev is an extremely arid area, with summer temperatures above 400C, an average annual precipitation of 28 mm, and an annual potential evaporation rate of 4000 mm. This negative water balance causes the area to be poor in water sources and limits the Saharo-Arabian vegetation almost to- tally to wadi beds. Certainly, the desert presents several obstacles to the devel- opment of human communities, the foremost of which is the scarcity of water, for drinking, for everyday uses, for animals and for agriculture. Considering the environmental conditions, one would expect the Southern Negev to be al- most devoid of ancient remains of human presence and activity. However, the harshest part of this area, from ‘Uvda Valley and southward (see Map 1), is surprisingly rich in archaeological sites. A complete sequence of settlement is found during the last 10,000 years, with a wide range of activi- ties such as hunting, grazing, agriculture, trade, copper production, some gold production and others (Avner et al 1994). In this article I will describe several methods of water exploitation in the region. The first will concern the early agricultural settlement in ‘Uvda Valley, 6th to 3rd millennia B.C., the others relate to the Nabatean and the Early Islamic period. AGRICULTURAL SETTLEMENT IN ‘UVDA VALLEY ‘Uvda Valley (Wadi ‘Uqfi in Arabic), 40 km north of the Gulf of Aqaba (Fig. 1), was first briefly described by A. Musil (1907:180-182, 1926:85). He described the Îaiwat Beduin cultivating the eastern side of the valley and rent- ing plots to the residents of ‘Aqaba. Musil also recognized ancient remains on this side of the valley. The first archaeological survey was made by Rothenberg (1967b:303-307) who documented 15 sites, while citing others distinguishable from the air. During 1978-1982 I led a survey team which was part of the Negev Emergency Survey, under the auspices of the Israel Depart- ment of Antiquities (today the Israel Antiquities Authority). The survey was intended to precede the redeployment of the Israeli army from Sinai, while ‘Uvda Valley itself was selected for a new air base. The survey was never completed. The western side of the valley was only briefly surveyed and re- vealed a small number of sites. However, one third of the area on the eastern 404 ANCIENT WATER MANAGEMENT IN THE SOUTHERN NEGEV side was meticulously surveyed, resulting in the documentation of approxi- mately 400 sites in an area of 50 sq km (Fig. 2). This site density was unex- pectedly high considering the present environment. The remains in the valley present a complete sequence of settlement, from the Pre-Pottery Neolithic B (PPNB) to the present. A major excavation operation took place in February 1980, when 22 sites were excavated by 20 archaeologists and 180 volunteers. These were later followed by smaller scale excavations, and conservation works (Avner 1998 with references).1 Most surveyed sites were dated to the 6th-3rd millennia B.C., i.e. the Pot- tery Neolithic, Chalcolithic and the Early Bronze Age. They included 154 habitation sites, 32 corrals, 40 tent camps, 30 threshing floors, water installa- tions of various types, and many cult sites (Fig. 2). Ample agricultural tools were collected during the survey and excavations, among them flint adzes, hundreds of sickle blades and grinding stones, and two stone plough tips, the earliest found in the Near East. Botanical remains included a few olive pits and grains of domesticated cereal, while indications of other crops were also found. Quite surprisingly, grazing was only of secondary importance to the ag- riculture in this area. A demographic study demonstrated that ca. 3000 people lived in the area at the settlements’ climax, in the 3rd millennium B.C. (Avner 1998). THE CULTIVATED FIELDS AND FLOOD IRRIGATION A unique combination of environmental conditions, fertile soil and hydrol- ogy situation, made this vast agricultural settlement possible. The soil along the eastern side of the valley contains lime-sand, which is rarely found in the world. It makes the soil light, well-ventilated, easily tilled, and highly water absorbent. At a depth of 0.5 m it consists of 50-70% lime-sand, 20-40% silt and 10-14% clay. The soil is slightly alkaline (Ph 7.8-8.35), with a low level of salinity, only 0.9-2.3 milimo (units of electrical conductivity). The water ab- sorption capacity is very high, up to 39% of its volume.2 The clay percentage increases with depth, reaching 18-23% at a depth of 1.2 m, a situation which minimizes water loss through seepage. This fact, along with the high water content capacity, enabled excellent watering of the soil at the “efficient root- depth”, for cereal, bushes, and even trees. These qualities are well demon- 1 Initial plans for the air base required destruction of 104 sites. However, after long negotia- tions, the plans were re-adjusted so that all but one site remained outside the base perimeter. The U.S. Army Corps. of Engineers constructing the base also displayed a high sensitivity to the an- cient sites and avoided damage. Today, the sites are accessible and an archaeological park is in an advanced stage of planning. 2 I thank Igor Mindel, of the Jewish Agency in Beer Sheva‘, who provided this information. Mindel tested the soil during 1983-1986. U. AVNER 405 strated by fairly dense plant growth on the eastern side of the valley, outside the wadi channels, in contrast to the rest of the southern Negev. Sand Worm- wood (Artemisia monosperma) a Mediterranean plant, remains large and green even through the summer, and White Saxaul (Haloxilon persicum) reaches 5 m in height, the tallest known in the Negev and Sinai. In a situation of low precipitation, as in ‘Uvda Valley, only floods can sup- ply the amount of water necessary for cereals. The drainage area of ‘Uvda Val- ley is ca. 400 sq km, mainly to the south, 550-892 m above sea level. Most of the surface is barren rock which absorbs a comparatively small amount of the rain water. In addition, most desert rains fall in a concentrated way (Shanan et al 1967; Finkel & Finkel 1979; Sharon 1979), so that even a small amount is often enough to create floods (Fig. 3). Here, another element becomes impor- tant. The gradient of the valley is moderate, from 500 m above sea level in the south to 415 m in the north. The gradient is 1% in the south and only 0.3% in the northern part. The flood water flow is slow, does not wash the soil away, and is well absorbed.3 Since the eastern side is lower than the western by 20 m, all wadis merge on this side, which is better irrigated (Fig. 4). Following a flood, a thick growth of wild cereal appears (Fig. 5). These natural conditions were successfully exploited by the inhabitants of the valley. Observation of surface and aerial photographs reveals a system of low earth embankments perpendicular to the water channels, sometimes with one layer of rocks on top (Fig. 6). These embankments may have contributed greatly to the quality of the cultivated land. They retarded the flow of water, further increased the amount of water absorbed by the soil, prevented soil and seed erosion, increased the sedimentation of new soil enriched with organic material with each flood, and widened the irrigated strip. Another long em- bankment running south-north is discernible, west of the water channels (Fig. 6), most probably constructed to limit the irrigated strip to approximately 500 m. This actually turned the east-west embankments into a series of “limans”. This produced an important result, that the inhabitants were able to plough and sow the land before the first flood, not 2-3 weeks later as practiced by the Beduins. In addition, the enrichment of the soil with organic material brought by the flood, as well as dung from animals grazing on the stubble, al- lowed cultivation year after year, with no need to lay the fields fallow.4 The embankments in ‘Uvda Valley were not well dated. However, several arguments favor early dates: 1. The Neger Beduin did not attempt to control 3 The total drainage area of N. Hayun, including ‘Uvda Valley, is 1116 sq km, and the annual average flood water volume in the northern end reaches 1,000,150 cu m. This is the second larg- est amount of flood water in the Negev, after N. Paran, with 2,005,000 cu m (Finkel & Finkel 1979:134). 4 Repeated cultivation of fields without fallowing or overuse of the soil is described by Marx (1988:90) in connection with Beduin agriculture in the Beer Sheva area, even though in this case it was not flood agriculture, and the only source of fertilization was the animal dung. 406 ANCIENT WATER MANAGEMENT IN THE SOUTHERN NEGEV flood water in any way (see Avner 1998:175-177). 2. Flint and pottery of the 5th-3rd millennia B.C. predominated in every surface collection of finds near the embankments (on their eastern end), and this is the period of most of the agricultural remains. 3. In N. Paran, 40 km north of ‘Uvda Valley, I discovered the remains of an agricultural field based on rectangular limans and water con- duits (Figs. 7, 8). The limans are surrounded by embankments identical in technique to those of ‘Uvda Valley. The present remains cover seven hectares, and on the surface many flint adzes were collected (Fig.