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Irrigation and drainage
In 1990, the total water managed area, all equipped for full or partial
control irrigation, was estimated at 763 ha, which is about 7% of the agricultural land.
Of this area, 280 ha are equipped for irrigation by treated sewage water from a sewage
treatment plant, which was completed in 1983 to provide 7 000 m³ water per
day, but at present 240 ha are actually irrigated per year using 1.22 million m³ of
treated wastewater. Tenders have been issued to upgrade this sewage treatment plant to
produce 17 000 m³ per day for irrigation and industrial purposes. Work is expected to be
completed by early 1997.
Plans are also under way to construct three other sewage treatment
plants, two in Malta and one in Gozo, with a total capacity of 73 000 m³ per day to treat
all the sewage produced in the country by the year 2000. Hence the total available treated
wastewater would be about 90 000 m³ per day. Since the maximum daily irrigation water
requirements are estimated at 60 m /ha per day (July/August), the potential area for
irrigation from treated wastewater would be 1 500 ha if all the wastewater was reused for
irrigation. The potential area to be irrigated from treated wastewater could even be
increased up to 2 500 ha if wastewater could be stored in winter (when irrigation water
requirements are lower) for use during the summer. However, this solution is financially
prohibitive. Thus, the total irrigation potential is estimated at 2 000 ha, of which 500
ha irrigated by groundwater and 1 500 ha irrigated by treated wastewater. Nevertheless,
there are several limitations to reaching this potential including fund availability,
problems of access to the fields, the size and fragmentation of farm holdings, farm labour
demand, marketing, water charges and the Groundwater Protection Zones. From preliminary
cost estimates of water distribution networks to supply treated wastewater to farmers from
the new sewage treatment plants, the capital investment required would amount to $US 11
According to the Agricultural Census, 483 ha is the area actually
irrigated by groundwater, while the Water Services Corporation (WSC) recorded an area of
only about 269 ha irrigated by groundwater. The difference can be explained by looking at
the history of groundwater extraction in Malta. Groundwater abstraction is administered
and regulated by WSC and the law states that nobody is allowed to sink shafts to exploit
the groundwater since this is used as potable water. However, before this legislation,
which was enacted in 1943, several farmers had sunk shafts to abstract water. The
thousands of sunk shafts are the property of the farmers themselves and though, under the
law, the abstraction of water is controlled by WSC, the shafts are administered
individually by farmers. Each shaft may irrigate only a hectare or two, depending on the
area cultivated by the farmer when the shaft was sunk some 60 or 70 years ago. But
individual records of present water abstraction are not kept and these shafts are
scattered over all rural areas, but predominantly in the north of the country. The number
of private wells officially registered by WSC is about 2800, to which an important number
of unregistered wells should be added. Total groundwater withdrawal from the wells is
estimated at 5.41 million m³/year, of which 2.44 million m³ extracted by registered
wells and an estimated 2.97 million m /year by unregistered wells.
Apart from the treated wastewater and groundwater used for irrigation,
water harvesting practices are also widely spread all over the islands. Throughout the
centuries, several farmers have built or dug small reservoirs in the rock to collect
rainwater to be used mainly as supplementary irrigation. Recently, several reservoirs with
capacities of 100 - 2 000 m³ were constructed for irrigation in spring or early summer,
some with financial assistance from the government. Though this water collection may seem
insignificant, it is in fact very important to provide a supplementary source of water for
Maltese agriculture and it covers an area estimated at 1 953 ha. For example, probably
over 1 000 ha of the 1 400 hectares spring potato crop which is planted in the rainy
season in December and January, and harvested in May and June, is irrigated with this
source of water in the absence of rainfall. Similarly, unquantified large areas of
vegetable production may also receive additional irrigation from this surface runoff water
from September to early June.
On the areas irrigated by treated wastewater, the distribution network
for surface irrigation was originally constructed of concrete channels which created
problems and brought complaints from farmers wanting their share of irrigation water.
Though a report was drawn up by a consultancy firm to improve this system, funds were
never made available to execute the works. Fortunately, the farmers have themselves
invested heavily in installing micro-irrigation equipment to irrigate cash crops. Part of
the area is also equipped with sprinklers to irrigate potatoes in spring since the potato
crop is more responsive to sprinkler irrigation. Out of a total managed area of 763 ha, it
is estimated that 500 ha are equipped with micro-irrigation systems, 150 ha with sprinkler
irrigation systems, while on the remaining 113 ha surface irrigation is practiced. The cost of irrigation development is in the range of $US 1 600/ha for micro-irrigation, while the operation and maintenance costs are about $US 800/ha per year.
There are three categories of farming in the irrigation subsector and an
estimated 3 000 farmers, both full-time and part-time, are involved:
- Most of the irrigated farms are normally leased to farmers and operated
by individuals. The source of water is often shared with others, since both the land and
water rights are inherited with the lease resulting in land fragmentation. Very often the
irrigated farm is scattered over various localities giving rise to problems of access to
the fields, conveyance of water and laying of irrigation networks and schemes. Some
farmers frequently have shares of water rights from various groundwater sources which may
further complicate the irrigation scheduling. There are no water charges for abstraction
of groundwater from these private boreholes.
- The irrigation scheme which is supplied with treated wastewater from the
sewage treatment plant is run by a government agency. Treated water is supplied to five
government reservoirs and by means of a channel system is distributed to farmers for a
nominal fee of $US 100/ha. This was considered as a social project to increase revenue in
the farming community. The running of the individual farms is however entirely the
responsibility of the farmer.
- Water from government-owned boreholes producing 0.09 million m³/year
second class water (high nitrate or high salinity) is offered to farmers in the vicinity
at $US 0. 11/m³, in preference to using it for domestic supply.
The major crops under full or partial control irrigation are melons,
tomatoes, potatoes, pumpkins, marrow and cauliflower, with a total cropped area
of 1 807 ha (average cropping intensity is 2.5). In addition, the areas benefiting from
water harvesting techniques (1953 ha) are generally cropped once a year. With the
introduction of micro-irrigation and improved farming practices, the yields of some
products significantly increased during the period 1990-95. Yields of melons increased
from 6 tons/ha in 1990 to an estimated 20 tons/ha in 1995.
Revenue from one hectare of fully irrigated land is calculated to be $US
24 750, which is at least ten times the revenue from dry farming. The main reason is that
vegetable production during the totally dry period, from May to the end of August, may
only be carried out under constant irrigation. Moreover, owing to favourable temperatures,
with full irrigation a cropping intensity of 3 may be achieved. In the case of treated
wastewater irrigation scheme, cropping intensity averages about 2.
Drainage is not practiced in Malta since infiltration rates are high,
averaging 74 mm/hr. The few small wetland areas adjacent to the sea have been declared
conservation areas, two of which are bird sanctuaries.
There are no salinization problems since any salt accumulation in the
top layer of the soil is washed down through the shallow soils with regular frequent
irrigation and torrential rains in the winter. Moreover both groundwater aquifers are deep
and do not rise to the top soil.