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Irrigation and drainage
Evolution of irrigation development
The limited availability of good quality soil and water has resulted in the concentration of agricultural development in a relatively narrow strip of land along the northwestern coast of Bahrain Island with isolated pockets in the north central areas and along the east coast. Most soils have a sandy texture, traces of organic matter (0.05-1.5 percent), a deficiency in major nutrients, low water-holding capacity (available moisture 2-6 percent), and high infiltration rates (> 120 mm/hr). In areas along the coastal strip, calcareous impermeable layers are found at depths of 1-3 metres, causing waterlogging and impeding leaching. Electrical conductivity (EC) in irrigated soils lies within a range of 4-12 mmhos/cm, while in the areas of recently abandoned agriculture (1 065 ha) it could reach 60 mmhos/cm.
In the period from 1956 to 1977, agricultural land decreased from about 6 460 ha (with 3 230 ha cultivated) to about 4 100 ha (with 1 750 ha cultivated). This decrease was attributed mainly to urban expansion, waterlogging and soil salinization due to the deterioration of the quality of the groundwater used in irrigation. In an attempt to reverse the situation, the government initiated a major agricultural development programme in the early 1980s consisting of:
- Replacement of surface irrigation with more water efficient localized irrigation by subsidizing more than 50 percent of the implementation cost;
- Construction of major drainage systems to reduce waterlogging and salt accumulation;
- Provision of agricultural extension services in terms of training and advising farmers on types of crops suitable for agriculture under prevailing conditions;
- Introduction of TSE water in irrigation;
- Reclamation of new agricultural lands.
This resulted in a gradual increase and restoration of agricultural lands to about 4 230 ha, with 4 015 ha cultivated and irrigated at present, all power irrigated. Between 1994 and 2000, there was a 4 percent average increase per year of the area equipped for irrigation. It is difficult to estimate the quantity of groundwater available in the future for agriculture since groundwater quality, and hence its availability for irrigation, changes with time. In 2003, primary groundwater accounted for 90 percent of the total irrigation water (Table 6 and Figure 3).
In 1991, the utilization of 8 million m3/year of tertiary TSE water in reclaimed government lands (280 ha) and on some private farms (150 ha), using sprinkler and localized irrigation techniques, had a palpable effect on the increase of agricultural lands and their productivity. Government subsidy for installation of modern irrigation systems stopped in the 1990s because of lack of funds. Despite efforts to introduce modern irrigation techniques, most farms still use traditional surface irrigation, which causes higher water losses, estimated at between 24 and 40 percent. Sprinkler irrigation is used only in government projects, while localized irrigation is used in government projects and on a limited number of private farms (Figure 4). Most of the land is cultivated either directly by the owner, often with hired labour, or by tenant farmers under a lease agreement lasting one or two years. Such short and insecure periods do not encourage tenants to invest in the installation of modern irrigation systems, which cost 40 percent and even up to 100 percent more than surface irrigation systems since government subsidies for the installation of modern irrigation systems are no longer available. The small size of agricultural landholdings, ranging between 0.5 and 10 ha, with an average of 2.5 ha, and in particular the fragmentation of the agricultural land of farm holdings, further restrict investment in the more expensive modern irrigation techniques.
About half of the cultivated area is covered with high water-consuming perennial date palms under traditional surface irrigation practices. Some basic installations with modern irrigation systems (drip irrigation for vegetables and bubbler irrigation for dates) have been established too, but they are rather poorly operated with no irrigation schedules. Unfortunately, many drip and sprinkler systems have been designed on the basis of incorrect criteria, using the outdated irrigation equipment of the 1970s which is poorly installed and inadequately maintained (FAO, 2002). The overall irrigation efficiency is very low, also demonstrated by the huge amount of water used (almost 160 million m3) on a total irrigated area of just over 4 000 ha.
Role of irrigation in agricultural production, the economy and society
In 1991, of the total equipped area of 3 165 ha, 2 885 ha consisted of small schemes (< 50 ha). Most farms in these small-scale schemes were run under the tenancy system and there were about 250 households on these schemes. The remaining 280 ha of large schemes (> 50 ha) were owned and completely run by the government and irrigated by treated wastewater, with a total of 80 government workers of whom 11 were involved in irrigation (Figure 5).
In 1991, the average cost of irrigation development on small schemes varied between US$6 600/ha for surface irrigation, US$9 300/ha for localized irrigation and US$13 200/ha for sprinkler irrigation. For large schemes the cost was US$16 200/ha for surface irrigation, US$13 600/ha for localized irrigation and US$19 800/ha for sprinkler (central pivot) irrigation. The high costs for large scheme development were attributed to the fact that the major projects were carried out by the government on reclaimed lands. Operation and maintenance costs varied between 10 and 15 percent of the irrigation development costs on small schemes and between 5 and 15 percent on large schemes.
The major crops grown are: dates and fruit trees with a yield of 7.5 tons/ha; vegetables, mainly tomatoes, with a yield of 11.7 tons/ha; and fodder crops, mainly alfalfa, with a relatively high yield of 74.5 tons/ha. There is no cereal production. In the 1980s, there had been an increasing trend in the cultivation of alfalfa for fodder production rather than the cultivation of the traditional date and vegetable crops. Alfalfa tolerates high salinity and is a cash crop grown all year round with high local demand. However, because of the very high irrigation water requirements of alfalfa, it is expected that this trend will have negative implications for the country’s groundwater resources. Horticulture and agriculture flourish in the north, using water from some artesian wells or desalination plants. Gardens grow dates, almonds, pomegranates, figs, citrus fruit, and a wide range of vegetables. In 2000, permanent crops (mainly alfalfa and date palms) covered 75 percent of the irrigated area while vegetables represented the remaining 25 percent (Table 6 and Figure 6). In 2004, Bahrain produced 14 000 tons of fruits and dates and 7 700 tons of vegetables.
Status and evolution of drainage systems
Drainage works have been carried out on 1 850 ha of the irrigated area. The remaining areas still suffer from shallow water tables resulting in waterlogging in the crop root zones and an increasing salinization of the top soil. Drainage requirements are exacerbated by the inefficient surface irrigation systems used. In 1994, drainage works had been completed on about 1 300 ha (Table 6). The existing drainage network consists of open drains, which are very inefficient and difficult to maintain. The average cost of drainage development was estimated at US$6 600/ha.
The only flood protection works carried out in Bahrain are those against rainfall floods and are developed in one residential, modern town located in the west, over an area of 1 300 ha, where there are no agricultural activities.