Development of limited water resources: Historical and technological aspects
"... the moorland will be a pond, very dry a spring" (Isaías 35:7)
The water scarcity has always been the domineering factor in the agriculture of most of the arid Middle East, and his population must have based in small and erratic period rains or in the rivers for his water supply. In Egypt, for example, the Nile is the only source of stable water in what otherwise it would be a desert scenery. In the ancient times the agriculture was limiting itself to narrow ground stripes to both banks of the river. Enclosed today, the agriculture in Egypt concentrates principally along the margins of the Nile.
The climate of the current Israel is hard affected by the proximity of the desert on the south and to the east. Most of the territory of the country qualifies as arid (0 %) or semiarid. The rain precipitation limits itself to the winter and takes place principally between November and March. The annual precipitation average ranges between 400 and 800 mm. in the parts north and west of the country, and it diminishes evidently towards the south and the East. A period dries, in that practically there are no rains, spreads from the beginning of April till the end of October.
Until the beginning of the XXth century, the agriculture in the country was based practically in its entirety on the rain and therefore it was limiting itself to the north of the country and to the coastal zone. In some localities in the north, where there were springs, the fields were irrigated. The water was led by the gravity force from his source to the fields by dirty open channels. Every farmer supposedly had to receive his water portion several hours once every so many days or weeks. Nevertheless, due to the serious loss of water along the route of transport resulted from his rapid filtration in the soil the water was distributed in unequal form and the peasants most removed from the spring were receiving little water. Along the coast, the groundwaters were extracted from wells with the help of treadmills pushed by a donkey or an ox. The water was joining in a pond and hence it was stemming by the gravity force to the nearby plantations (principally orange groves). These wells were excavated to hand and his yield was low.
The notion of which the agriculture needs of a sure water supply begun being comprised at the end of the XIXth century and the beginning of the XXth century. This revolutionary change in the attitude was introduced in the area principally by the placed Jews, who were ready to adopt technologies and advanced methodologies. The above mentioned technologies were introduced by immigrants with a specializing training and professional training between them persons experienced on advanced methods of perforation across hard layers and in the pumping of big quantities of water of deep wells.
The use of the irrigation in the traditional agriculture turns out to be hindered by several limitations:
The water sources, especially under arid and semiarid conditions, are usually very limited and of not easy disposition.
The water is transported to the fields in channels by means of the gravitation, what means that the area must be at level. Steep areas and hillsides, therefore, cannot be irrigated by this method.
The traditional practice of constructing open channels brings like turned out a big loss of water due to his filtration in the soil and while more lengths the channels, major the losses.
The water supply diminishes along the distribution line, what it takes to an unequal distribution of the limited resources.
Another disadvantage of the traditional irrigation is that the supplying of the water is inevitably irregular, what it has like turned out the inability to answer to the needs for the cultivation and therefore the yield is poor.
Considering the circumstances that were prevailing at the beginning of the XXth century in this area, especially the predominance of a dry agriculture that was based almost exclusively on the station rains, the introduction of new concepts involved not merely technical changes but also a deep modification of the strategy and the scale of the progress in the agriculture.
Two basic elements were responsible for the step in the agriculture of a traditional use of water to the modern one: the human factor and the introduction and use of newly well-known technologies.
After the establishment of the British Order, at the end of the First World war, many Jewish immigrants came to Palestine, principally of Europe. This immigration wave was only. Many of the immigrants were highly motivated and anxious for establishing new agricultural establishments. They were ready to examine and to apply new agricultural technologies, were comprising the value of a modern knowledge based on scientific studies, and were eager adopt the councils of scientists and professionals. But perhaps the key factor of his success was his union capacity and of establishing organizations with the intention of collecting funds, of formulating strategic politics and of delineating plans for the physical development. All these efforts culminated in the 20s and of 30 of the XXth century, with the establishment of a big number of agricultural establishments.
As part of the movement for this establishment, geologists were recruited for the groundwaters search, to in whose head the teacher was L. Picard, which came to the country from Germany in 1924. Modern teams of perforation capable of piercing to big depths, across the hard rock layers, new and efficient machines of pumping and materials recently introduced, like metal and cement tubes, they joined to help to the water supply system development. Nevertheless, in addition to the explained more above on the technical efforts, the challenge was consisting in changing radically the concept of what had to be a suitable water supply.
Since it was mentioned previously, the rain precipitation in Israel limits itself to the winter station and diminishes from north on south and of west to this one. Even more, the annual entire precipitation fluctuates greatly, being frequent the dry years. To plan and to construct a system of reliable water supply must take into consideration the above mentioned limitations, that is to say, he must assure a leveling out between the stations (winter and summer), the regions (north and south) and the years (with suitable and inadequate precipitation).
This way, in the first stages, the establishments joined on a local base, invested money in the search of groundwaters and in achieving a more or less permanent water supply.
Later, there was adopted a wider conception of the problem of the water supply. The first effort coordinated for the construction of a project in big scale dates of 1935; the leaders of the above mentioned project were a Levy Eshkol, who was later a Prime minister of Israel, and Simja Blass, an engineer who later stood out in the design and development of all the important water projects of the country. The project was designed and carried out between 1935 and 1938 for Mekorot, the newly founded public company of waters. The water was coming from three wells perforated in the western end of the vale of Jezreel. The principal characteristics of the project were:
Transfer of the water by means of metal pipes to high pressure, allowing an uninterrupted supplying up to distant places. The high pressure was making possible to irrigate the fields with sprinklers, instead of the traditional irrigation for flood.
Incorporation of two tanks of concrete and two open deposits, keys for a constant water supply. The water was pumped to the night deposits, when the cost of the electricity was relatively low; later, the water was supplied to the irrigation system without interruption.
The topic of the disposition of water resources and the potential for an additional development of systems advanced for a suitable supplying was not merely an academic or technical question. It had also political implications. Really, the national rights on the ground are the marrow of the conflict between the Jewish and Arab communities. The politics of the British government was to fix restrictions to the grounds acquisition on the part of the Jews, to the establishment of new establishments and to the immigration to Palestine, being based on the argument that the physical conditions were prohibiting a major growth of the existing population. One of the measurements adopted as the leaders of the Jewish community to resist the British politics was to demonstrate that, with a suitable development, the country could support a much major population. That's why, a considerable effort was invested in the conception and design of water projects.
Water supply projects
At the end of the 30s the figures leaders in the area accepted that the following beginning should guide the future water projects:
Any system developed to provide of water must take into consideration the areas in which there is water and in which the water skimps, as well as between the rainy station and the dry season. Therefore, the water of rivers, floods and springs must be gathered in deposits, underground aquifers and tanks for his possible transfer in supplying tubes in accordance with the needs. Also, the water surplus of the rainy years must be gathered for his use in the dry years.
The water must be moved in pipes under pressure. Although it needs a substantial financial investment, this approach avoids the topographic limitations and minimizes the water losses, promoting this way a saving of long-term water. Also, it guarantees a balanced and just distribution up to the last users.
The planning must be comprehensiva. Namely the water projects must take the water to any place in the country to answer this way to the needs of the increasing population and of a big agricultural development, especially in the Néguev, the south region of the country (the rains scarcity characterizes to the region of the Néguev like arid zone).
From 1939 from now on, several plans were prepared for the water transport towards the Néguev, principally for Simja Blass. A study comprehensivo titled "Water resources in the Earth of Israel: Perspectives of Irrigation and Hydroelectric Development" it was prepared by the water Company Mekorot in 1944, and approximately at the same time, experts of the USA in water and conservation of the ground carried out studies and presented schemes of water projects. W. K. Lowdermilk, a renowned American expert in conservation of soils and hydrology, he published, also in 1944, a book ("Palestine Earth of Promise") on the possibilities of developing water projects in Palestine. In the same year, J. B. Hays, an American expert in dams and water conservation, visited the country to examine the possibilities of planning a water project. His book, "Authority of the Vale of Tennessee of the Jordan", was published a pair of years later. Hays continued his studies after the establishment of the State of Israel (1948) and presented several versions of a main plan for the development of hydroelectric power and of the irrigation. Later there him joined his companion, J. S. Cotton, who presented a main plan in 1955, which was adopted possibly as the government and served like draft for the National Aqueduct.
As part of a movement destined for the establishment of the Néguev, the south arid region of the country, in 1943 three experimental establishments were established there. The principal target was to study the conditions of the soil, the disposition of the water (including information on the annual precipitation) and the type of cultivation that might be obtained in the existing conditions. Eleven additional establishments were established in the Néguev in 1946 and other five in 1947, equipped and financed as earlier for the Jewish national institutions.
From the beginning itself it stayed in clear that in the Néguev the principal factor limitante for the agriculture was the scarcity of the water. The recognition of which a modern and successful agriculture was depending on the irrigation, what in turn was demanding a sure supplying of the water, went to the beginning of a series of studies. These included meteorological, geologic investigations and hidrológicas. One tried to perforate wells and pump the groundwaters close to the establishments; nevertheless, the obtained quantities were enough poor and the salobridad of the water was in general too high for the agricultural use. The attempts of construction of dams and deposits to join the water of the rises of station failed due to the big fluctuations from one year to other in the quantity and intensity of the rises and for technical difficulties. Possibly it went over to the conclusion that the only way of guaranteeing a water supply sure and sufficient for the agriculture in the Néguev was to transport the water from the sources of the north by means of tubes.
The first "Aqueduct of the Néguev", which began to operate in 1947, he made sure a quantity of reliable water, although limited, to most of the establishments of the Néguev (although some of them had still to base on local wells). These modest tubes were transporting wells water in the northwest of the Néguev, an area relatively rich in groundwaters. The first stage, installed and in functioning in 1947, was consisting of 190 km of pipes 6 inches in diameter that were supplying a million cubic meters a year. Later these tubes were changed into diameter of pipes of 20 inches that were providing 30 million cubic meters a year. The importance of these pioneering tubes was that the concept of transporting water of the distant north to water the arid south section of the country remained firmly establish.
This pioneering company it was continued by two projects in big scale for the water supply to the Néguev. The first one was the "Aqueduct Yarkón Néguev", constructed shortly after the establishment of the State of Israel. These tubes 66 inches in diameter were transporting annually 100 millions of cubic meters of water of the river Yarkón al Néguev along a 130 km distance.
A section of the National Aqueduct
Although this was an ambitious project in terms of the available resources in this epoch, very quickly it stayed in clear that a bigger system was needed and comprehensivo, that culminated in the second project in big scale, the ambitious National Aqueduct. The principal function of the National Aqueduct is to transport the water to the south region of the country from the Sea of Galilee (in Hebrew, Yam Kinéret, Lake Kinéret) in the north. Originally, it had to extract the water of the Jordan before his entry to the Sea of Galilee. The first stages of the work in the area began in 1953. Nevertheless, considering the Syrian opposition and a resolution of the United Nations, Israel turned out to be forced to suspend the works and to modify the original plan. The plans finally were approved in 1956 and the National Aqueduct was completed and began to work in 1964. The aqueduct is a combination of underground tubes, open channels, intermediate deposits and tunnels that provide about 400 million cubic meters of water to the year of the Sea of Galilee, which is to approximately 200 meters under the sea level. The water is pumped up to an elevation of about 02 m. on the sea level and it flows for gravity to the coastal region, where from it is pumped to the Néguev.
In addition to Mar de Galilea, two big aquifers, the Aquifer of the Mountain and the Coastal Aquifer, contribute annually to the aqueduct with approximately 350 million cubic meters and 250 million cubic meters respectively.
Does the National Aqueduct work not only like the principal water purveyor, but also like desag? and for the water surpluses of the north in winter and at the beginning of spring, and like source for the spare of the underground aquifers in the coastal region. Most of the regional water systems is incorporated into the National Aqueduct to form a network balanced on that the water could be transported from one line to other one in accordance with the conditions and needs for the moment.
Supplying and demand administration of limited water resources
The resources of fresh water of Israel, which reach an average of 2.000 million cubic meters a year, are being exploited at present up to almost the limit. Nevertheless, the population of the country grows constantly, as the water demand. Urgent measurements must be adopted for the supplying of additional quantities of water. An important potential source there are the marginal waters, a category that understands effluent, brackish water and sea water. The suitable treatment purification in case of the served waters and desalination in that of brackish waters or sea water can provide of the very in need water.
Every time major quantities of served waters have found his way towards the environment, making be in danger the underground aquifers and other fresh water sources. The pressing need to find alternative sources for the water supply, together with the critical condition of the ambience, they led the water Commissioner to establishing the plant Shafdán, produced by Mekorot, a project in big scale for the prosecution of the served waters and the production of purified water. This procedure takes two benefits as results: a) An aquifer in the outskirts serves like underground deposit for the transferred water, preventing his loss for evaporation. The water is pumped when it is needed, in general in summer. b) The water filtration across the layers of the soil provides an additional purification phase.
About 110 million cubic meters of this purified water are transported annually by means of separated tubes called the "Third Aqueduct of the Néguev" to Néguev Occidental for irrigation. Due to the high grade of purity of the treated water, it can be used for all kinds of cultivation without risks for the health.
Additional plants for the prosecution of the served waters are in construction or in planning. It is foreseen that most of the water allocation for the agriculture comes possibly of effluent purified, so that the quality fresh water could be derived from the agricultural uses to the servants.
You plant in minor scale in the Néguev they provide waters treated for the irrigation of the fields located at not very big distance of the source of the effluent one. The treatment is minimal and the use of this water is restricted to cultivation like the cotton. These small projects have demonstrated to be very effective.
There are two categories of water available for the desalination, brackish water and sea water. The desalination of the sea water is costly due to the high salt concentrations. Therefore, the efforts for the cheapest development of a process center at present on the brackish water. In the long term, nevertheless, the sea water also will have to be used like drinking water source.
Several methods of desalination of brackish water have been studied in Israel from beginning of the sixties. Between them, the osmosis reversiva has turned out to be efficient and relatively cheap; nowadays it finds it hard approximately more 25 % to produce drinking water for osmosis reversiva than for purification of served waters.
The principal desalination project finds close to Eilat, a city located on the beach of the Red Sea, in the south end of Israel the driest region of the country, with a quantity of invaluable precipitation. The Eilat population is approximately 40.000 inhabitants, more an annual influence of approximately 500.000 tourists. Until 1997, quite the Eilat drinking water was obtained of the desalination of underground brackish waters. The desalted water takes place by means of osmosis reversiva in two plants with a joint production of about 36.000 cubic meters to the day (approximately 13 million cubic meters a year). As result of the constantly increasing demand of a reliable supplying of drinking water, one added a third unit for the desalination of sea water (the water is pumped of the Red Sea). At present, the production of this unit is of about 3,5 million cubic meters a year.
The brackish water desalination is preferable to the desalination of the sea water, since the necessary energy to produce brackish water drinking water is 0,8 to 1,0 kWh for cubic meter, and 73 % of the water recovers, while to desalt sea water it is needed about 3,85 kWh by cubic meter, and 50 % of the water recovers only. Nevertheless, the brackish water underground is interspersed in relatively big areas and his existence in the Eilat neighborhood is limited. The sea water supply, on the other hand, is infinite. Therefore, the future drinking water production will have to be based principally on the sea water.
In addition to an additional drinking water source assures, the development of an efficient method of desalination will help to revertir the current and dangerous tendency towards the salobridad of the aquifers of fresh water.
In limited form, the brackish water not treated is being put in use for the irrigation of certain cultivation. Many studies have been carried out to investigate if the brackish water can be used for the cultivation irrigation. It was discovered that some of them, like the cotton, the tomato and the melon tolerate the brackish water (up to 7-8 dS/m of electrical conductivity, equivalent to a salinity of 0,41 0,47 % NaCl). Nevertheless, to minimize the salt accumulation about the roots of the plants and to facilitate the elimination of the salt that accumulate, it is essential: a) to use irrigation systems for dripping and b) to cultivate the plants in average or light soil (sandy soil or clayish). In case of this tolerant cultivation, the use of brackish water can achieve a fresh water saving.
Advanced irrigation methods
In Israel, the agricultural sector is the principal water consumer. That's why, in order to reduce the entire water consumption, the quantity of water assigned to the agriculture has been subject to a series of restrictions, especially from beginning of the 90s. Of an entire consumption of 2.008 million cubic meters in 1997, 1.264 millions of m3 (63 %) they were used in the agriculture, in comparison to the situation in 1985, when the water consumption for the agriculture was 1.389 millions of m3 of a whole of 1.920 millions of m3 (72 %). There is not doubt that the efficient use of water for the irrigation is of supreme priority.
One of the most important innovations agrotecnológicas of the modern times is probably the Israeli invention of the irrigation for dripping of Simja Blass and his son (the father conceived the idea, the son developed the drip).
The irrigation as dripping has many advantages for on other irrigation methods:
The water is spilled in uniform form of every drip to the side pipe. This is this way enclosed in areas moderately steep. Even more, the development of compensated drips allows the uniform irrigation of abrupt hillsides up to long distances.
Across the drips, it is possible to give fertilizers to the plant together with the water (fertigación).
The water and the fertilizers are given straight to the system of roots of the plant, instead of to the whole field, economizing this way so much it waters down like fertilizers.
The quantity of proportionate water can come at his ideal level in accordance with the different types of soil, avoiding the water filtration beyond the area of the roots. Even more, the sandy soils, which cannot be irrigated by trenches or by flood, can be watered actively with drips.
The weeds appearance is minimized.
The dry soil between the planted tiers allows to the workpeople and the machinery a comfortable access during the period.
There is made possible the water development of low quality (brackish or effluent waters) because:
The irrigation for dripping, in contrast to the irrigation for sprinklers, allows to use brackish water since the direct contact is eliminated between the water and the sheets, avoiding this way the burns.
The irrigation for dripping does that the salt is washed constantly of the roots, preventing his accumulation in the immediate proximity them. This is important when saline soils take a shower or it takes a shower with brackish water.
The irrigation for dripping allows the use of served waters because the water is given straight to the soil, minimizing the health risks.
It is possible to install drips with a given supply of water (several liters per hour) at any distance adapting itself to the needs for every cultivation.
The irrigation for dripping is the most efficient method, a saving of the water. Since the drips give the water straight to the adjacent place to the roots of the plant, which absorb the water immediately, the evaporation is minimal. This characteristic is especially important under the conditions that prevail in the arid zones. In the irrigation for sprinklers or for methods in the surface, the evaporation turns out to be increased by the wind, while in the irrigation for dripping the influence of the wind is minimal.
The team of irrigation for dripping of good quality can last fifteen to twenty years if it is treated in the appropriate form.
The efficient use of the water is defined as the relation between the quantity of water made use by the plant and the entire quantity of given water. Studies indicate that the irrigation as dripping has an efficient use of the water of about 95 %, opposite to 45 % in the irrigation flush with ground and 75 % in the irrigation for sprinklers. To sum up, then, it is possible to conclude that the irrigation as dripping has many advantages on other methods and is superior to the irrigation flush with ground or for sprinklers as for water saving, especially low conditions of a limited water supply.
The Current Situation
In the last years, the water supply in Israel has reached a stage of critically fragile balance between the supply and the demand like result of several factors:
A sequence of dry years, which provoked an inadequate filling of the water reservations (so much the aquifers in the surface as the tubes) in combination with an excessive pumping of the already scarce reservations of water.
Rapid increase of the population due to the immigration (of 4.8 millions in 1990 to 6,3 millions in 2000 31 % of increase in 10 years), which led to a major water consumption for the domestic use.
Hesitation of the political leaders in the allocation of the financial resources adapted for the very necessary projects in big scale of purification of urban served waters and construction of plants of desalination of sea water.
This critique describes how the limitations of scarce water resources and an arid and semiarid ambience can be overcome by a leadership capable of defining the future needs and of identifying and of implementing the appropriate solutions. The high technologies have demonstrated to be indispensable in this process. Nevertheless, in the last years, the constantly increasing water demand, principally for domestic use, has created a chronic situation in which all the available water of natural sources is used. The only solution to guarantee a water supply so much for the domestic use as for the agricultural use it needs the adoption of several measurements along with the regulations implementation to save water and the immediate construction of big plants of desalination of the sea water and the treatment of effluent urban.
Source: MFA - Foreign Office of Israel