Marginal water resources management

Agriculture and sustainable water management play vital role in promoting rural growth, sustaining the environment, and reducing poverty. After a century of expansion of large-scale surface irrigation and decades of rapid groundwater development, opportunities to harness new resources are fewer and more expensive. Improving the productivity of existing water use and reusing secondhand water are therefore becoming common objectives.

Conjunctive use of saline groundwater and surface water should also be undertaken to aid in lowering water table elevations, hence to reduce the need for drainage and its disposal, and to conserve water. Various means should be used to reclaim or to dispose of the ultimate unusable final drainage effluent.

To achieve these goals, new technologies and management practices must be developed and implemented. Efficiency of irrigation must be increased by the adoption of appropriate management strategies, systems and practices and through education and training. Such measures must be chosen with recognition of the natural processes operative in irrigated, geohydrologic systems, not just those on-farm, and with an understanding of how they affect the quality of soil and water resources, not just crop production. Some practices can be used to control salinity within the crop rootzone, while other practices can be used to control salinity within larger units of management, such as irrigation projects and river basins.

Dealing with salinity in irrigation water:

•  irrigate only well-drained soils
•  irrigate more frequently and determine
•  leaching requirement
•  minimize contact with plant leaves
•  plant salt-tolerant crops
•  avoid irrigation to seedlings and young plants

Improved water resource management will be vital to sustaining crop productivity levels in the face of both climate variability and longer-term change. In areas that are currently dependent primarily on rain-fed agriculture, the conjunctive use of surface and ground water resources will play an increasingly important role in enabling farmers to adapt to fast changing climatic conditions. However, it is also clear that in the face of rising domestic and industrial demand, additional efforts are necessary to ensure efficient management of water resources. With climate change and variability increasing pressure on available water resources (and especially, net irrigation requirements), improved water management is one of the most important long-term adaptation options that countries must pursue. (read more…and more...)

What Is Agricultural Water Management? Agricultural water management includes irrigation on large and small schemes and farms, drainage of irrigated and rain fed areas, watershed restoration, recycled water use, rainwater harvesting, and all in-field water management practices. The agenda for improved water resources management: to ensure that agricultural water is managed within an integrated basin approach, to allocate water to environmental uses, to prepare for the likely increase in recycled water use in irrigation, and to devise long-term approaches to issues of waterlogging and salinization.

There is “more technology available than we know what to do with” (box 1). Technology to improve water service on major schemes is well known and available; on-farm technologies such as piped distribution, drip, and bubbler are widely available and becoming more affordable; many water management and crop husbandry improvements are known; drainage, drought management, and flood control technologies are all well developed; and technology exists for watershed management and for even the most unpromising of marginal rainfed systems. Much technology already exists and only needs to be put to work. Adoption of water-saving technologies has been slow and performance below potential. Adoption requires knowledge, reliable water service, and an economic environment that provides undistorted incentives, manageable risk, and access to product and credit markets.

Ultimately, farmers will adopt new technology when it is shown to increase incomes and reduce risk, and when there is market access. However, the intensification needed to feed the world and to raise rural incomes in coming decades cannot rely only on existing technologies; the size of the increase needed creates a future research agenda on water and land productivity, both for irrigated and rainfed production.

Box 1 . Some Technologies and Management Practices • Large scheme irrigation improvement • On-farm improvement • Conjunctive use • Drainage technology • Reuse of treated waste and drainage water • Supplemental irrigation • Groundwater recharge (read more…)

The adoption of new crop/water management strategies will further enhance the agricultural use of saline waters. Irrigated agriculture could be expanded considerably through the implementation of certain strategies which allow greater use of more saline waters for irrigation. Considerable saline water, including drainage waters from irrigation projects and frequently associated shallow ground waters, is available in many parts of the world, including the US, Egypt, Israel, Pakistan, India, Australia, Russia and Central Asian countries.

Today unprocessed brackish water is used for watering agricultural produce in many countires , albeit in limited amounts. Numerous studies showed that some types of agricultural produce, for example cotton, tomato and melon, respond positively to brackish water (with specific electrical conductivity up to 7-8 dS/m, which is equivalent to 0.41-0.47 percent salinity (NaCl) ). However, in order to minimize the accumulation of salt around the rootstock of plants and also ensure discharge of accumulated salts, it is important to: a) use drip irrigation to supply saline water and b) grow plants in soilless substrate or in light-textured soils (sandy or argillaceous-sandy soils). All this can save significant amounts of drinking water while watering plants that can grow on brackish water .

Watering methods have various specific features which define their suitability for drainage and saline water with the purpose of minimizing/preventing risks connected with the use of such water.

The below chart shows relevant restrictions on management or convenience of application of the most suitable methods of minimizing these risks, as well as the main aspects that determine sutability of watering methods used with saline water.

 

 Chart. Suitability of watering methods for saline water irrigation

(Source : Luis Santos Pereira, Theib Oweis, Abdelaziz Zairi. Overview . Watering management in conditions of water shortage)

Irrgation method	Salt accumulation in the root zone	Foliar contact avoiding toxicity	Ability to infiltrate water and refill the root zone	Control of crop stress and yield reduction
Basin irrigation	Not likely to occure except for the under-irrigated parts of the field when uniformity of water application is very poor; leaching fraction difficult to control in traditional systems	It is possible only for bootom leaves in low crops and fodder crops, and druing the first stage of growth of annual crops	Adequate because large volumes of water are generally applied at each irrigation and water remains in the basin until infiltration is complete	Adequate because toxicity is mostly avoided, salst are moved down through the root zone , infiltration is completed and irrigation can be scheduled for
Corrugated basin irrigation	Salts tend to accumulate on the top of the ridge ; leaching prior to seeding or planting is required for germination and crop establishment	Exceptionally because crops are grown on ridges	As for flat basins	As for flat basins but depending on avoiding salt stress at plant emergence and crop establishment
Border irrigation	As for basin irrigation but infiltration control is more difficult as well as the control of the leaching fraction	As for flat basins	Because water infiltrates while flowing on the soil surface , run - off lossess increase when infiltration decreases	Crop stress is likely to occur due to reduced infiltration so inducing relatively high yield losses
Furrow irrigation	Salts tend to accumulate on the top of the ridge ; leaching is required prior to seeding / planting	Exeptionally because crops are grown on ridges	Salinity induced infiltration problems cause very high run-off losses	Crop stress is very likely to occur due to reduced infiltration so inducing significant yield losses
Sprinkler irrigation	Not likely to occur with set systems except for the under - irrigated parts of the field ; leaching difficult or impossible with equipment designed for light and frequent irrigation	Severe leaf damage can occur definitely affecting yields, mainly if frequent irrigation would be used	Salinity induced infiltration problems including soil crusting may cause very high run-off losses	Crop stress is very likely to occur due to toxicity by contat with the leaves and fruits, and reduced infiltration, thus significant yiueld losses may occur
Mivro irrigation: drip and subsurface irrigation	Not likely to occur except for the under-irrigated parts of the field due to low uniformity, including due to clogging when water filtration is poor	Not likely to occur	Problems generally do not occur except when there are not enough emitters and under - irrigation is practiced	These systems are able to provide for crop stress and toxicity control, so yield losses are minimized
Micro irrigation: micro-sprinkling and microspray	Not likely to occur except for the under-irrigated parts of the field due to low uniformity and clogging: leaching easy to control	Leaf damage can occur, definitely affecting yields of annual crops but less for tree crops	Problems are similar to those for set sprinklers, so run-off losses may be important	Toxicity due to direct contact with the leaves and crop stress when non uniformity and run-off occur may cause high yield losses

 

Best practices examples

A selected review of some representative examples of the commercial use that has been made of saline waters for irrigation under different circumstances around the world follows. The examples were chosen to be representative of the worldwide experience of such use and because relevant information, including water quality, climate, soil type, crops, irrigation systems and methods, other management practices, yields and period of use, was available.

UZBEKISTAN

 

Cultivating of salt-tolerant food and forage crops in the Kyzylkum desert using mineralized irrigation water from a flowing artesian well for pasture-based livestock production were demonstrated.

Total forage shortage in the Kyzylkum desert is about 540 thousand tons (15% of total demand). Considering this, production of reserve stock of forage is a relevant task. The Kyzylkum desert has artesian wells, which each produce 13-15 l/sec. Water in the wells had neutral acidity (pH- 7,4) & medium salinity (EC=5.6-8.3 dS/m). The cultivation technology of salinity tolerant crops (halophytes) for livestock forage was introduced on the basis of irrigation using water from these wells. The suitability of these feeds to various groups of livestock animals was determined and a system of pre-feeding preparation was developed, taking into account the mineralization of irrigation water and quality of the halophytes. The purpose of this technology is land improvement through retention of topsoil, rehabilitation of vegetation cover, prevention of overgrazing through reducing livestock pressure by organizing irrigated forage production. The agricultural processes for establishing irrigated land are traditional and include plot leveling, plowing, chiseling, harrowing, sowing, cutting irrigation furrows and caring for the plantation.

The following forage crops were successfully tested: winter cereal crops (Movlono barley, Kyrgyzskaya-1 rye, Prag Serebristy triticale, Kroshka millet), forage crops (Belozubaya maize, Aip-13150 pearl millet, Oq Zhuhori and Venichnoe sorghum, Sudan grass, Tashkentskaya and Eureca alfalfa, D-1 and D-2, common licorice) & forage halophytes (К. scoparia (L.) Schrad, Bassia hyssopifolia (Pallas) O. Kuntze, S. altissima & Climacoptera lanata).

Using mineralized waters for irrigation is only possible in soils with a light texture. The introduction of crop rotation with halophytes, which remove up to 40% of salts from the soil, is also mandatory for the ecologically sustainable application of saline water… There are 63 artesian wells in the Kanimekh district, which can be used for irrigated crop farming on an area of 350-400 ha. In the Kyzylkum desert, this technology may be introduced on an area of 25,000 ha.

( read more … Use of mineralized artezian water to organize irrigated crop farming in the Kyzylkum).

 

Using saline water in cotton plant cultivating

A number of scientists conducted researches to study saline water’s influence on a number of agricultural crops. In our case, studies connected with saline water ’ s influence on cotton plant are of particular interests. Specifically, we can note the work of Baraon Argeta and Carlos Roman entitled “Cotton plant’s response to saline water irrigation under conditions of Kazakhstan’s Mirzachol Steppe” … (read more…).

Under shortage of river water and in conditions of old-irrigated and prairie gray soil, it is preferable to use saline drainage water with the salt concentration of up to 2.5 grams per liter (dissolved solids), as this helps to produce good cotton harvest (up to 58 hundredweights per hectare). Using saline water with a high concentration of salts (dissolved solids up to 5.5 grams per liter) is allowed only in the second growing season (in the first season – river water irrigation) …

It was established that cotton plant ’ s resistance to soil salinity is low in the first half of vegetation period and high in the second half. If saline water is used in the first half of vegetation and river water – in the second half, cotton harvest goes down by 15.6 percent (5.2 hundredweights per hectare). In this case, it is preferable to use river water in the first half of vegetation and saline water in the second half (cotton harvest reduces only by 7.2 percent – 3 hundredweights per hectare)…

Also, under the salt concentration of up to 2.5 grams per liter, saline water has minimum influence on the physiological processes in cotton plants. Saline waters with salt concentration of over 2.5 grams per liter exert maximum influence on the level of carbohydrates in leaves (reduction of glucose and fructose with a simultaneous rise in the levels of sucrose and reductive carbonhydrates), which may serve as a feasibility parameter for using such waters for irrigation. At the same time, saline water irrigation does not have negative effect on ripeness index, maximum strength and thickness of fiber. Metric count decreases but fiber strength increases. (read more…).

 

ISRAEL

To ensure sustainable development and water security, Israel has made enormous efforts to improve water resources management. The rigorous enforcement of policy, strategic approach and financial measures has enabled effective management of the nation’s scarce water resources and high water productivity, and made the country a world leader in many aspects of water resource management.  

Irrigation water conservation

In recognizing the much higher efficiency of drip irrigation and micro-sprinkling irrigation than furrow irrigation (in Israel it is about 90%), Israel has overtime made a major technological shift in irrigation practices. Users have widely adopted water saving measures such as water metering, pipe replacement, electronic monitoring and retrofitting for the urban use sector and have also vigorously promoted water saving devices such as water-efficient toilet flushing, basins and upgrading of taps and showers.

Reclaimed wastewater effluents as alternative water source. Treated domestic effluents, estimated at 400 MCM, form the largest potential water source. Currently, about 250 MCM of such effluents, treated to varying degrees, are utilized for irrigation. The rest is discharged into waterways and the sea due to lack of treatment and reuse facilities… (read more… )

Israel’s success with water management demonstrates high water use efficiency and productivity, especially in the agricultural sector, and sustainable socio-economic growth in spite of the physical water scarcity:

■ The Israeli government has been highly successful in addressing the water scarcity problem, while maintaining a steady rate of economic growth and accommodating the demand of an increasing population. It established well defined water allocation and rights system to enable efficient distribution of water via the national distribution system to the three main user sectors—municipal, agriculture and industry;

■ Over the years, the agricultural water use has decreased and diversified substantially. In 1990 freshwater accounted for about 95% of water used by agriculture. This percentage dropped to 55% by 2001 and to 45% by 2008. Around one-third of water used by agriculture now is from reclaimed wastewater effluents,with a further one-fifth from brackish (saline) water. Brackish water is used for irrigation of salinity-tolerant crops;

■ They have achieved high agricultural water productivity through preferential policies, technological transformation and cropping pattern change moving to higher value crops, reducing average requirement for water per unit of land from 8,700 m 3 per hectare in 1975 to some 5,500 m 3 today. In the meantime, the country saw a 2.2% annual average growth rate of agricultural production over the period of 1990–2008 which is higher than most OECD countries… (read more… )

 

RUSSIA

The method of saline water irrigation was worked out and patented ( Russian Federation patent No 2284687). The proposed invention is intended for using in the field of agriculture and may be used during the irrigation of agricultural crops. The purpose of this invention – is to ensure longer and effective saline water irrigation at land plots by preventing accumulation of salts in top soil.

This method involves loosening soil at a depth that exceeds the depth of tillage ahead of the seeding season or in autumn. Then water distributing elements in the shape of ditches are made, which are separated by rollers. Furrows are made on top of these rollers which are then filled with absorbing material, such as compost. After the irrigation and harvesting season, ploughing is carried out by overturning soil using plough with plough point. Moreover, at areas where cereals are harvested, remains plants are mulched and evenly applied to the surface. This method makes it possible to significantly limit the accumulation of salts in the arable layer and ensure longer and effective irrigation of the area with saline water … (read more…)

 

UNITED STATES OF AMERICA

In the USA, saline waters have been successfully used for irrigation for periods of from 75 to 100 years in several areas of the Southwest, including the Arkansas River Valley of Colorado, the Salt River Valley of Arizona, and the Rio Grande and Pecos River Valleys of New Mexico and West Texas (Erickson 1980). The principal crops grown in these areas are cotton, sugar beet, alfalfa,grain sorghum and small grains. (read more… and more...and more...)

In the Pecos Valley of West Texas, groundwater averaging about 2500 mg/l TDS, but ranging far higher (at least to 6000 mg/l), has been successfully used to irrigate about 81 000 hectares of land for three decades (Moore and Hefner 1977; Miyamoto et al. 1984). In this Valley, the rainfall is less than 300 mm, most of which occurs in showers of less than 25 mm. The major crops include cotton, small grains, grain sorghum and alfalfa. The soils are calcareous (pH 7.5 to 8.3) with a calcium carbonate equivalent of between 20 and 30 percent; they are also low in organic matter and show little structural development. Soil textures range from silt loams to silty clay loams. Infiltration rates average about 0.5 cm per hour. Internal drainage is good; water tables are usually below 3 m. The soils display slaked-aggregate conditions immediately following rainfall; the resulting crusting often necessitates replanting of crops, if it occurs during the seedling establishment period.

…Cotton is grown successfully with a gypsiferous water of up to 8 dS/m EC using alternate-row, furrow irrigation and double-row plantings on wide beds or by using single- row plantings on narrow beds and then "decapping" the peaks of the beds to remove resulting salt crusts prior to seedling emergence. Sprinkler irrigation of cotton is carried out during night or twilight hours using water of up to about 5 dS/m in EC.

…Alfalfa and several other forages are produced with minimal yield losses using waters of up to 3 to 5 dS/m, as have been tomatoes. Alfalfa yields in saline areas near Dell City have been 12.3 to 13.4 t/ha.

.In summary, the experience in Far West Texas shows that good crop production of suitable crops can be achieved with use of saline waters (up to about 8 dS/m in EC) for irrigation if care is taken to obtain stand.

It was shown that various halophytes (such as Atriplex nummalatia) have potential for use as crop plants and can be grown with seawater. Yields of forage have been achieved which exceed the average yield of conventional crops, like alfalfa, irrigated with freshwater. The most productive halophytes yielded the equivalent of 8 to 17 metric tons of dry matter per hectare.

… Some halophytes, such as Salicornia, appear to have even better potential as oil seed crops. The use of secondary drainage waters for the growth of such crops after their first use for more conventional crops would facilitate the disposal of drainage waters by reducing the ultimate volume needing such disposal. (read more… )

Drainage water is used for crop production on many farms in California, USA . For example, saline subsurface drainage water is blended with Delta-Mendota Canal water in the Broadview Water District of California to form blended water of a salinity equivalent to 3.2 dS/m and since 1956 is used to grow a variety of crops. Over time, the cropping pattern in this district has changed as the water quality has decreased. Crops now grown are mostly cotton, barley and alfalfa. Representative salinities and potentials for use as irrigation waters and drainage waters from the major irrigated areas of the USA are described by Rhoades (1977).

Brackish drainage water has been successfully reused for irrigation . In U.S. Salinity Lab experiments, wheat irrigated with saline Alamo River water after seedling establishment with less saline Colorado River water showed no loss of yield. The control field received Colorado River water only. Similar results were achieved with other crops.

The strategy is to irrigate salt sensitive crops (lettuce, alfalfa, etc.) in the rotation with low-salinity water and salt-tolerant crops (cotton, sugarbeets, wheat, etc.) with saline water. Fortolerant crops, the switch to saline water usually occurs after seedling - establishment; preplant irrigations and initial irrigations being done with low salinity water. The feasibility of this strategy is supported by data obtained in field experiments…

Two cropping patterns are being tested at the Imperial Valley location: a successive-crop and a block rotation. The two-year successive-crop rotation consists of wheat, sugarbeets, and melons.

Colorado River water (900 mg/L total dissolved salts) is being used in the preplant and early irrigations of wheat and sugar beets and for all irrigations of melons. The remaining irrigations are from the Alamo River (drainage water of 3,500 mg/L total dissolved salts)… (read more… )

 

The use of brackish groundwater is reported from Tunisia, India and Israel .

ISRAEL

Considerable use has been made of saline waters for irrigation in Israel. The majority of the saline groundwaters range between 2 and 8 dS/m in EC (about 1200 to 5600 mg/l in TDS). The average annual evapotranspiration is about 20 000 m 3 per hectare. Average annual rainfall exceeds 200 mm in over half of the country and is about 500 mm in the main agricultural area (600 mm in the coastal plain); most of rain falls in the winter season. The climate is Mediterranean with a moderately hot, dry summer (April to March). Heavy dews occur in many parts of the country, especially near the coast. Mostly sprinkler or drip irrigation is used. The soils are generally permeable and drainage is good. Much of the saline water is introduced into the national carrier system; thus it is diluted before use. Because most of the crops are irrigated by sprinkler methods, some crops suffer poor emergence related to crusting. Thus they are sometimes started by furrow irrigation.

Extra water (equivalent to about 25 to 30 percent in excess of evapotranspiration) is typically given for leaching. According to Israeli general recommendations, light- and medium-textured soils can be irrigated with any saline water in the range of the salinity tolerance of the crop, and heavy soils can be irrigated with waters having EC values of up to 3.5-5.5 dS/m where artificial drainage is provided (gypsum applications are advised for such waters).

Cotton is successfully grown commercially in the Nahal Oz area of Israel with saline groundwater of 5 dS/m in EC and 26 of SAR provided the silty clay soil is treated annually with gypsum and national carrier water is used (usually during the winter) to bring the soil to field capacity through a depth of 150 to 180 cm prior to planting (Frenkel and Shainberg 1975; Keren and Shainberg 1978).

De-Malach et al. (1978) state that in the central Negev of Israel, sugar beet is grown with saline groundwater of EC = 4.4 dS/m under sprinkler irrigation. (read more… )

TUNISIA

The saline Medjerda River water of Tunisia (average annual EC of 3.0 dS/m) is successfully used to irrigate date palm, sorghum, barley, alfalfa, rye grass and artichokes. The soils are calcareous (up to 35 percent CaCO 3) heavy clays with low infiltration rates, especially after winter rainfall. During the growing season large cracks form (fissures of up to 5 cm in width) as the soil dries, subsequently permitting water to enter rapidly when first irrigated. Winter rainfall produces leaching of salts only to depths in the soil of about 15 cm.

In 1962, the Tunisian Government created a Research Centre for the Utilization of Saline Waters for Irrigation (CRUESI), with the assistance of the Special Fund of the United Nations and UNESCO. A technical report describes their findings through 1969 (UNESCO/UNDP 1970). This work was carried out at the scale of commercial farming operations to ascertain how various crops would yield when irrigated in various ways (all surface methods) with saline waters.

Experiment stations were chosen to be representative of the various combinations of soils, climates arid irrigation water compositions prevalent in Tunisia. The soils varied in texture from light to heavy, the irrigation waters varied in salinity from 2000 to 6500 mg/1 TDS and the rainfall varied from 90 to 420 mm.

Good yields of appropriate crops can be obtained with use of typical well waters for irrigation (though with some reduction relative to the use of freshwater) provided certain precautions are taken. Salinity in the irrigation waters is concluded not to be an insurmountable barrier.

These Tunisian studies point out the need to pay close attention to other factors besides salinity per se (some of which, however, are influenced by salinity) which must also be controlled if successful irrigation with saline waters is to be achieved. (read more…)

INDIA

Crops are successfully grown in some parts of India under conditions quite different from those existing in typical, semi-arid regions. Much of the research and experience in India through 1980 has been summarized by Gupta and Pahwa (1981). Of particular benefit to the continued use of saline waters for irrigation in parts of India are the monsoon rains. It has been observed that very saline waters can be used for irrigation in these areas without excessive long-term build-up of soil salinity because of the extensive seasonal leaching that occurs there (Pal et al. 1984; Jai 1981; Manchanda and Chawla 1981; Tripathi and Pal 1979). These findings illustrate the high potential to gain benefit from the use of quite saline waters for irrigation in regions which receive sufficient rainfall to prevent the build-up of excessive soil salinity over time.

A field survey made during the period 1983-1985 showed that extensive use (104,000 shallow tube wells pumping 106,000 hectare-metres of water per year) is being made (since about 1975) of shallow-saline groundwater of EC up to 8 dS/m for irrigation in nine districts of Haryana State India (Boumans et al. 1988). In four of the districts, the saline water is solely used for irrigation, while in the remaining five it is used either after it is blended with fresh canal water or in alternation with the canal water.

… Wells had EC values exceeding 7 dS/m, hence it appears that this level is about the maximum that the farmers have found to be acceptable for long-term use. Yield depressions of 30-40 percent are apparently acceptable to these farmers. Still it is obvious that saline waters have been used successfully, even as the sole supply, for irrigation in these districts of India.

Presently about 235 MCM/year is being used successfully to irrigate olive and date-palm orchards, alfalfa, cereals and wood trees (of which 60 MCM from continuing flowing springs).

Due to over-irrigation without appropriate drainage facilities, seepage as well as run off to low lying land, salinity and waterlogging have developed in some lands of the oasis. To reduce drainage water volumes, minimize water pollution and safely dispose of the ultimate unusable final drainage water, new strategies are being developed and experimented by the Government authorities in Siwa Oasis (similar problems exist in Dakhla oasis). These include:

• use of natural flowing springs to irrigate winter crops such as cereals and forage; use of saline water over 5 dS/m to irrigate salt tolerant crops like barley, vetches, Rhodes grass, sugar beet, etc.;
• use of biologically-active drainage water for the production of windbreak and growing wood trees;
• reuse of drainage water (average salinity is EC 6.0 dS/m with SAR values of 10 to 15) after blending with good quality water (recently drilled deep well of salinity EC 0.4dS/m with SAR of 5) or by alternating the drainage water with good water. (read more…)

EGYPT

Egypt is a predominantly arid country and the scattered rain showers in the north can hardly support any agricultural crops. Agriculture thus depends mainly on irrigation from the River Nile (55.5 BCM per year). The needed increase in food production to support the acceleration of population growth (2.7%), compels the country to use all sources of water (i.e. drainage water, groundwater and treated sewage water) for the expansion of irrigated agriculture.

The policy of the Egyptian Government is to use drainage water (up to salinity of 4.5 dS/m) after it is blended with fresh Nile water (if its salinity exceeds 1.0 dS/m) to form blended water of a salinity equivalent to 1.0 dS/m. The drainage water presently used for irrigation amounts to 4.7 BCM per annum and it is likely to increase to 7 BCM per annum.

In fact, direct use of drainage water for irrigation with salinity varying from 2 to 3 dS/m, is common in the districts of Northern Delta where there are no other alternatives or in areas of limited better water quality supply. Farmers in Beheira, Kafr-El-Sheikh, Damietta and Dakhlia Governorates have successfully used drainage water directly for periods of 25 years to irrigate over 10 000 ha of land, using traditional farming practices.

The soil texture ranges from sand, silt loam to clay with calcium carbonate content of 2 to 20 percent and very low in organic matter. The major crops include clover "Berseem", rice, wheat, barley, sugarbeet and cotton. Yield reductions of 25 to 30 percent are apparently acceptable to local farmers. Yield reductions observed are attributed to waterlogging and salinization resulting from over-irrigation and other forms of poor agricultural, soil and water management. Pilot studies carried out in Kafr el Sheik and Beheira Governorates showed that by applying appropriate management practices (i.e. crop selection, use of soil amendments, deep ploughing, tillage for seedbed preparation, land levelling, fertilization, minimum leaching requirements, mulching and organic manuring), drainage water of salinity 2 to 2.5 dS/m can be safely used for irrigation without long term hazardous consequences to crops or soils.

The use of saline drainage water in Egypt was reported by Abu-Zeid (1988). About 2.3 thousand million m 3 of drainage wastewater are discharged annually to the Mediterranean Sea via return to the Nile River in Upper Egypt; 12 thousand million m 3 are discharged directly into the sea and northern lakes; 2 to 3 thousand million m 3 are used for irrigating about 405,000 ha of land. About 75 percent of the drainage water discharged into the sea has a salinity of less than 3000 mg/l. The policy of the Government of Egypt is to use drainage water directly for irrigation if its salinity is less than 700 mg/I; to mix it 1:1 with Nile water (180 to 250 mg/l) if the concentration is 700 to 1500; or 1:2 or 1:3 with Nile water if its concentration is 1500 to 3000 mg/I; and to avoid reuse if the salinity of the drainage water exceeds 3000 mg/l. (read more…)