Study Area (Central Arava Valley)

Figure 3.3: Schematic plan of RSDSC potable water transmission to Israel

Research Results

3.1 Study Area (Central Arava Valley)

The Arava Valley is a unique area with many extreme features. With the most extreme desert climate in Israel, the area is a rift valley developed along a tectonic suture, the Dead Sea Transform. This tectonic feature extends longitudinally some 1000 km from the Red Sea to the zone of plate convergence in southern Turkey and is part of the 6500-km-long Syrian–African Rift Valley. The area is also part of the 30˚ latitude global belt of deserts. The Arava Valley extends over a 165-Km long section of this system, between the southern tip of the Dead Sea and the Gulf of Eilat/Aqaba. The elevation of the valley varies from ~400 m below sea level at the Dead Sea shore to 210 m above sea level in the Arvat Yafruq region in the center of the valley, and then descends southward to sea level at the Gulf of Aqaba/Eilat (Goldreich and Karni, 2001). The valley ranges in width and has three distinct parts: the Northern Arava, an almost rectangular area, approximately 14 km in length; the Central Arava, 74 km long and up to 32 km wide; and the Southern Arava, 77 km long and five to 15 km wide (Efrat, 1993). It is

Source: Adapted from (Coyne et Bellier, 2009)

Central Arava

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edged by mountain ranges made up of Precambrian to Tertiary rock formations. The eastern side reaches the Edom Mountains, exposing crystalline rocks and sandstones, reaching elevations of 1000m and to the west are the hills of the Negev highlands, mostly composed of limestones, dolomites, and marls reaching elevations of 500m (Avni et al., 2001; Ginat et al., 1998; Rosenthal and Bein, 2001; Shirav-Schwartz et al., 2006).

This geology forms a regional drainage basin into which both surface and groundwaters flow, covered and underlain by a thick layer of alluvial clastic sediments deposited since Neogene times. Wherever wadis flow into the valley, alluvial fans have accumulated. As a result of the greater volume of water flowing from the east, alluvial fans are larger and thicker on this side of the valley. Surface water is exclusively in the form of flash floods which develop sporadically and may reach high flow volumes over short time. Some 5mm of rainfall may cause floods due to the relatively impermeable soil cover. The water drains to the final drainage basins:

the Dead Sea in the north and Gulf of Aqaba/Eilat in the south (Rosenthal et al., 1990).

Groundwater in the Arava Valley includes regional aquifers that drain across the Rift margins into the local alluvial aquifers. The morphotectonic setting of the region dictates a hydrogeological regime through which deep confined aquifers leak upwards, merge and mix with shallow aquifers and local brines. Due to this mixing, groundwater of varying quality is exploited throughout the valley. Four aquifers are exploited along the margins of the Arava valley, shown in figure 3.4. Two aquifers are in Cretaceous rocks and the other two are in Neogene and the alluvial fill Quaternary strata. The Lower Cretaceous Kurnub Group (upper part of the Nubian Sandstone sequence) is composed of sandstones and clays and contains water that is mostly

―fossil‖ with low rate of natural replenishment, and nonrenewable under the current hydrological regime. Leakage from this aquifer into the overlying permeable Neogene and Quaternary alluvial strata and Judea Group beds is present due to high artesian pressures. The Judea Group aquifer is also recharged through floods running over its exposures in the wadis draining to the valley. The Alluvial Fill aquifer, made up of the Neogene Hazeva Formation and the Quarternary Arava Formation consists of alternating alluvial clay, sand and some conglomerate beds. Due to this geology, the Fill aquifer forms an aquiferial system made up of sub-aquifers hydraulically connected and of limited areal extension. Along with leakage from the

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―fossil‖ aquifer, water in the Fill aquifer is derived from direct recharge from flooding and seasonal rainwater over the bordering mountains though developed alluvial fans (Rosenthal and Bein, 2001; Rosenthal et al., 1990; Shirav-Schwartz et al., 2006).

Figure 0.1: Spatial extension of aquifers along the Arava Valley

The water of the Arava is of variable quality and chemical composition. In the Kurnub Group, the water is somewhat brackish and characterized by high sulfate content. Brackish to saline groundwater with higher mineral content is found in various sections of the valley, mostly at the southernmost and northernmost segments. Groundwater recharged by floods, such as the water in the alluvial aquifer system, is of low salinity and is therefore of prime importance both

Source: (Shirav-Schwartz et al., 2006)

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for agriculture and the tourism industry (Rosenthal and Bein, 2001). In the Central Arava region (the focus area of this research) 80% of the exploited groundwater is derived from this alluvial fill aquifer system. The remaining 20% is drawn from the deeper Kurnub Group aquifers (Naor and Granit, 2000; Oren et al., 2004; Yechieli et al., 1992). Figure 3.5 shows a cross section of the alluvial aquifer.

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Figure 0.2: Geological cross section depicting aquifers in the Zofar region, Central Arava Valley

However, differences in water quality vary greatly. The Hazeva Formation exhibits salinity ranges between 250 and 450mg of Cl per liter and the Arava Formation can have up to 650mg Cl per liter. Despite this variance, the central region exhibits much lower TDS (total

Source: (Shirav-Schwartz et al., 2006)

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dissolved solids) levels than the southern region of the valley (where values range from 1100mgCl/liter to greater than 3700mgCl/liter). Minor differences can result in major effects on agriculture, and the slightly lower salinity experienced in the Central Arava‘s aquifer makes intensive agriculture in this region of the Arava more feasible than farther south in the valley, where less than 50% as much agricultural land is cultivated, visible in figures 3.5 and 3.6 (Shirav-Schwartz et al., 2006; Strom, 2003).

Figure 0.3: Total cultivated land comparison, Central Arava (Arava Tichona) & Southern Arava (Hevel Eilot) Source: (Strom, 2003)

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Figure 0.4: Water quality as measured by EC (ppm TDS), comparision Central and Southern Arava

The Arava Valley has some of the highest solar radiation and temperatures in Israel. The mean annual temperature in the valley is 25˚C, however temperatures fluctuate greatly throughout the year and during the winter season, frosts can occur in various parts of the region.

Common winter temperatures are usually around 14-16˚C with extreme minimums falling below 10˚C. Conversely, summer temperatures are some of the highest in the country, averaging between 34 and 40 ºC with peaks as high as 45 ºC (Goldreich and Karni, 2001; Rosenthal and Bein, 2001; IMF, 2010).

Distance from the Mediterranean Sea, high temperatures, and northerly dry winds turn the Arava into the most arid part of the country. This extreme aridity increases southward in the Arava and is characterized by small seasonal rainfall amounts. Historically, annual rainfall averages of 50mm or less have been recorded (Adar et al., 1992). In the past decade, compiled annual rainfall averages in the Central Arava have been between 25mm and 38mm, with noticeably steep declining trends in average rainfall in the past three years (Central and Northern Arava R&D, 2009).

Source: (Mekorot, Central & Southern Arava Water Commissioners, Strom, 2003)

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Table 1.1 : Compiled rain data for winters 1991-2009 in the Central Arava

Hatzeva

At the same time, evaporation rates in the Arava Valley are the highest in Israel, with the yearly rate of evaporation between 60 and 100 times greater than the seasonal rain amount. The mean annual rate of evaporation exceeds 3,000 mm, with maximum values between 13.8 and 14.7mm/day measured during June and July, and minimums during December and January between 3.5 and 4.5mm/day, shown in figure 3.8. This is in stark contrast compared to only 1,600–1,800 mm annually experienced on the coastal plain of Israel. Northern and southern

Source: Central and Northern Arava R & D, 2009

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sections of the Valley experience higher evaporation rates than those in the central region, due to its situation at a higher elevation. With slightly lower average temperatures, the evaporation rate is on average 6% lower (Goldreich and Karni, 2001).

Figure 0.5: Mean annual evaporation rates in Arava Valley

The economic basis of the settlements in the Arava Valley is mainly agricultural, in spite of the aforementioned unique climate. With relatively high temperatures even in winter months, the Arava benefits from seasonal differences with other regions. Agriculture in the valley thrives on growing crops that are generally ‗out of season‘ products in Europe and supplying them to these markets at a competitive price. Before 1951, no permanent settlements existed in the Arava, and the region remained unsettled on both the current Israeli and Jordanian sides.

Settlements on the Israeli side of the Arava began three years after the establishment of the State of Israel in 1948 with the aim of dispersing population in the Negev and along the Arava. The immediate goal of the Israeli government was to populate the Arava in a linear pattern, from north to south, in order to protect the long border between Israel and Jordan.

Motivated by both ideology and circumstances, the early pioneers set up two unique forms of agricultural settlements: the kibbutz, a collective community in which the means of

Source: (Goldreich and Karni, 2001)

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production are communally owned and income is equally distributed; and the moshav, a co-operative village where each family maintains its own household and works its own land, while purchasing and marketing are conducted cooperatively (Markou and Stavri, 2005). In 1951 the first kibbutz Yotvata was established in the Southern Arava. Following the initial success in developing agriculture at Kibbutz Yotvata (particularly the production of winter vegetables in the salty soil) settlements continued to be developed rapidly throughout the 1970‘s and 1980‘s.

By the end of the 1980‘s the number of settlements in the valley numbered twenty.

In the Central Arava, the regional centre of Sappir was set up with packing houses, community services and a school as the center of the area. Including Sappir, the region is made up of seven settlements. Five of the settlements are agricultural villages, including the settlements Ein Yahav, Hatzeva, Idan Paran and Tzofar. The most recently constructed settlement of Tzukim is not agriculturally based, but rather centers around the expanding tourism industry in the region. A map of the region is depicted in figure 3.9.

Figure 0.6: Map of Central Arava region

Source: (Central and Northern Arava R&D, 2009)

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