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Glossary of technical terms

Anadromous fish: Fish which at certain seasons ascend rivers from the sea or ocean to spawn, e.g., salmon.

Aquifer: A water bearing stratum of permeable rock, sand or gravel.

Cavernous geology: Underground stratum or zones with rock or soil conditions having caverns or cavities.

Constructed evaporation pond (basin): Area for impoundment of saline drainage water for evapoconcentration (desiccation). Typically constructed by excavating soils from the interior of basins to build up their embankments. Such ponds may contain more than one cell.

Constructed wetland: Conversion of an area into a wetland by building dikes, small dams and/or shaping land to provide an appropriate water regime for hydrophytic vegetation.

Controlled drainage: The operation of a water table management system with water table control structures adjusted to limit drainage system discharge, and to maintain a free water surface (water table) within the soil profile.

Conventional drainage: Subsurface drainage without water table control structures.

Designated salt sinks: A depository for saline waters and salt deposits such as oceans, saline lakes, wetlands or evaporation ponds.

Flow-through wetlands: Constructed wetlands or natural depressional areas prepared to facilitate the controlled movement of surface waters through specially selected vegetation to enhance removal of pollutants and improve water quality.

Free outlet drainage: See conventional drainage.

Geohydraulic characteristics: Physical properties of the soil and subsoil that have an impact on the internal movement of water, nutrients and pollutants.

Helminths: Parasitic worms of the phylum platyhelminthes including digenetic flukes (class Trematoda, e.g., Schistosoma spp.) and tapeworms (class Cestoidea, e.g., Taenia solium, pork tapeworm).

Hydrophytic vegetation: Plants which must be in water, either completely submerged or emersed, for part of their life cycle.

Hypersaline water: Water with excessive or supersaturated salt content.

Imhoff tank: Two-stage wastewater treatment tank combining sedimentation of settleable solids in an upper compartment and anaerobic digestion of the settled solids in a lower compartment.

Improved drainage: Any technique aimed at improving the natural drainage capacity of land; it can be either surface drainage or subsurface drainage, or a combination of both.

Interactive management programme: Real time monitoring and evaluations to operate an agricultural water supply system efficiently and effectively.

Pond mineralogy: Classification of evaporite minerals precipitated out of impounded water. These include calcite, gypsum, halite and thenardite.

Preferential flow: Movement of water and solutes through large cracks or worm holes in the soil profile.

Schistosomiasis: Also known as bilharziasis, this a disease caused by blood flukes (see helminths). The flukes live in the venules of the large intestine (Schistosoma mansoni), small intestine (S. japonicum) and urinary bladder (S. haematobium), and have limited pathogenic effects. Symptoms appear upon the release of eggs which cause ulceration and abscesses of the intestinal or urinary walls, leading to bloody diarrhoea or urine and abdominal pain. S. mansoni is the most common causative organism and S. haematobium the rarest and least severe. S. japonicum causes the most severe symptoms and is the most likely to be fatal.

Sub-irrigation: Operation of a water table management system by adding water to a subsurface drainage system to maintain a free water surface in the soil profile at a desired elevation (see controlled drainage).

Subsurface drainage: Any drainage system (either drainage wells, open ditches or buried drain pipes) that controls the water table.

Surface drainage: Planned removal of excess water from the land surface by means of natural or constructed channels, including the shaping and grading of land surfaces where necessary.

Vertical drainage: A system of deep wells designed to control the water table.

Waterfowl habitat: Vegetation and water regimes which facilitate the breeding, nesting, feeding and cover required for the production and proliferation of ducks, geese and other waterfowl.

Water table management system: See controlled drainage and sub-irrigation.

Wetlands: Lands that are inundated or saturated by surface water or groundwater at a frequency and duration sufficient to support a prevalence of hydrophytic vegetation typically adapted for plant and animal life in saturated soil conditions.

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