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Despite the relatively low rainfall and the arid appearance of the
Maltese Islands, local catchment characteristics are very favourable for the storage of
rainwater and the hydrological cycle provides a generous supply of freshwater which
undoubtedly contributed to the early settlement of the inhabitants.
Surface water resources
Total surface water resources are estimated at 0.5 million m³/year.
Structurally, Malta tilts gently to the east giving rise to a topography that is high
along the western shores and gently slopes down to sea level along the eastern shores.
This implies that the surface drainage lines cross the entire width of the island from
their source close to the western shore before reaching the sea on the east. This
favourable topography, combined with the good water storage capacity of the soil,
excellent infiltration characteristics and effective runoff interception by numerous dams
and cisterns, gives the surface water maximum time to seep into the ground and thus
minimizes runoff losses to the sea. A greater amount of surface runoff, however, is lost
from urban areas via sewers or directly to the sea especially in coastal towns and
villages. Attempts are in hand to tackle the storm water wastage problem for a more
effective use of surface runoff.
Morphologically, the Maltese Islands are divided into two main units by
the Victoria Lines fault, that crosses the northern part of the island of Malta from west
to east. North of this fault, Malta is broken up into a number of horsts and grabens by
less pronounced faults. Drainage is parallel to the general strike of the horst-graben
system and the few intermittent streams flow into the bays to the north-east. The second
morphologic unit lies south of the Victoria Lines fault, where two main drainage systems
are found. The main one converges into the Valletta basin by a system of east- or
north-east-trending streams, while the second one converges into Marsaxlokk bay to the
The renewable groundwater potential on the Maltese Islands is estimated
as being approximately 40 million m³/year. In order not to deplete the storage capacity
of the main aquifer without causing salt water intrusion, only 15 million m³/year of
groundwater would be potentially extractable. Based on the 1995 figures of the Water
Services Corporation, however, 19.75 million m³/year were extracted from 13 pumping
stations, approximately 160 boreholes in Malta and Gozo, and about 2800 registered private
wells (the latter extracting an estimated total of 2.44 million m³/year). This means that
groundwater depletion does in fact take place. Moreover, there is significant extraction
from illegal and unregistered wells (probably up to 2.97 million m³/year), leading to a
total groundwater extraction of 22.72 million m³/year.
Most runoff occurs after heavy torrential rain. This is the only time
when surface water flows, for a few days at most, along the beds of the major valleys. To
retain this storm discharge, a large number of small dams have been constructed across the
drainage lines. They also serve the purpose of reducing the rate of soil erosion. Open
reservoirs have been constructed along recently made roads to minimize runoff. Total dam
capacity is estimated at 154 000 m³.
Desalinated water and treated wastewater
At present 31.4 million m³/year of desalinated water are being produced
from four sea water Reverse Osmosis Plants and one brackish water Reverse Osmosis Plant,
but this is a rather expensive procedure. In 1993, of the total produced wastewater
estimated at 23.7 million m³, about 1.82 million m³ was treated and 1.56 million m³ of
this was reused.