Aquifer

A geological formation that will yield water to a well in sufficient quantities to make its extraction feasible for beneficial use; permeable layers of underground rock or sand that hold or transmit groundwater below the water table.

Artesian

A geological formation, in which the water exists under sufficient hydrostatic pressure (i.e. exceeding atmospheric pressure) so that it can discharge to the surface without pumping.

Ayni

A type of falaj originating from a spring.

Brine

High salt-concentration water: it is heavily mineralised, containing organic and heavy-metal contaminants.

Dawudi

Type of falaj, which originates from a well.

Demand

In the present context, the amount of water required per unit of time.

Distillation

Water-treatment method, whereby the water is boiled and the resulting steam condensed in a separate vessel. Contaminants, with higher boiling points than water, do not vaporise and so remain in the flask in which the boiling occurs.

Effluent

Any substance, particularly a liquid, that enters the environment from a localised source of pollution. This often refers to wastewater (from a sewage-treatment or industrial plant) that contaminates the local ecosystem.

Electrical conductivity

In the present context, this is a measure of the ability of the considered water to conduct electricity. The conductance is related to the type and concentration of ions in the solution and so its value can provide an indication of the concentration of dissolved solids in the water.

Falaj (plural: aflaj)

A surface and/or underground channel, fed by wells or springs, built to provide a community’s water-supply: gravity provides the power to convey the water to where it is used.

Ghail

Type of falaj in which water is taken from a wadi.

Ground-water

Water within the ground that supplies the wells and springs; water in the zone of saturation where all the openings in rocks and soil are filled; the upper surface of the ground water forms the water table.

High-brackish water

This has a total concentration of dissolved solids exceeding 6000 parts per million.

Hydrologic cycle

This consists of evaporation from open stretches of water through to its subsequent condensation and/or precipitation as rain or snow and return under gravity, via streams, wadis and rivers, to lakes and the sea.

Jabal (plural: jibal)

Arabic word ‘mountain’.

Munzifah

Type of well using counter weights attached at one end of a pole and a bucket at the other in order to raise water from a near-the-surface underground water-source.

Orographic effect

Rainfall that occurs as a result of warm, humid air impinging upon topographic features, such as mountains.

Perennial

In the present context, a term applied to water that flows all year round, year after year.

Potable water

Water which is acceptable and also safe for drinking by humans.

Recharge dam

Water may enter an underground aquifer via faults, fractures or direct absorption, through the lower surface of a major reservoir held in place by a recharge dam.

Reverse osmosis

A water-purification process, whereby water is forced through a semi-permeable membrane which inhibits the transmission of impurities.

Saline water

Water containing more than 1000 parts per million of dissolved solids of any type.

Sludge

The slime that settles on the bottom of a sedimentation tank in a sewage-treatment plant and which should be disposed of by digestion or other safe methods or recycled to the land.

Spring

An issue of water from the ground; a natural fountain; a source supplying a reservoir of water.

Surface water

Water that flows in streams, rivers, lakes or wetlands, as well as in reservoirs constructed by humans.

Sustainable management

Method of exploiting a resource that can be continued indefinitely. Removal of water each year from an aquifer in excess of the annual recharge rate is, in the long term, not sustainable.

Total dissolved solids

The sum of all inorganic and organic particulate materials in the considered water sample.

Wadi

Stream or river bed which conveys flash floods eventually to the sea.

Waste-water

Water containing wastes or water contaminated by coming into contact with wastes: includes process-generated and contaminated rainfall run-offs.

Water table

The level, usually below the ground’s surface, where the fissures and pores in the strata are saturated with water. The surface of an unconfined aquifer; its level fluctuates due to seasonal precipitation. Where the water table is above the local land-level, a spring, river or lake is formed.

Water well

Any artificial excavation constructed with the purpose of exploring for or extracting ground water.

Zajarah

A type of well, for which animal muscle-power is harnessed in order to raise the water to above the surface of the ground.

Reliable supplies of freshwater are essential to sustain life, facilitate desirable developments and protect the environment. Unfortunately, in Oman, water supplies are frequently inadequate, exploited in an unsustainable manner or can be excessively expensive. Nevertheless, compared with other arid-zone countries, Oman is fortunate, as it can be self sufficient naturally with respect to potable water, provided the fresh-water resources are used wisely. This requires an understanding of the mechanisms of occurrence of water in the country and careful husbandry. In this context, the most important water problems facing Oman are: (i) prolonged droughts leading to too much water being extracted from the aquifers; (ii) near the coast, the seepage of saline water into the aquifers; and (iii) falaj and well depletion through excessive abstraction for drinking water and agriculture. So a balanced demand-management programme, involving adjusting the rate of consumption to the speed of replenishment of the water resources, is necessary to ensure long-term viability.

Fortunately potable water is a renewable resource; that is, through the hydrologic cycle, additional water becomes available both on the ground’s surface and underground. Obtaining this vital resource at the point-of-use, without the expenditure of further purchased energy, is desirable. Hence harnessing solar energy, the use of gravitational energy of the collected rain or the natural excess-pressures in artesian aquifers can all contribute to achieving this aim, and so their use where economically viable should be encouraged.