Glossary/water dictionary

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main drainage system

System which conveys drainage water from the field drainage system to an outlet.^

management of an irrigation development project

Series of actions to design, implement, perpetuate and improve an irrigation development project for the achieving of set objectives.^

maximum contaminant level (MCL)

Yhe designation given by the U.S. Environmental Protection Agency (EPA) to water-quality standards promulgated under the Safe Drinking Water Act. The MCL is the greatest amount of a contaminant that can be present in drinking water without causing a risk to human health.^

method of water delivery

Way of making an irrigation system function to convey water from the source of supply to each field served by the system.^

micro-basin irrigation

A water harvesting method used in small fields on gentle slopes. A moulding of the land surface enables the creation on very small slopes of an artificial micro-relief in each small field. Here the runoff water from the upper portion (runoff area) becomes concentrated in the lower portion (crop area) where the crops are raised, and which are sometimes reduced to a single tree (Negarin method).^

micro-irrigation with mini-diffusers

A micro-irrigation system in which water is emitted in small sprinklings through fixed small diffusers in the form of fine droplets distributed over a certain area, or by individual low pressure jets localising the water on the soil in separate spots. Their discharge is generally limited (20-60 litres/h at 1 bar) and often emitted in the form of circular sectors either to avoid wetting the neck of the trees or to limit the range on the sides of the space between rows, which should remain dry. Their use is limited to orchards^

milligrams per litre (mg/l)

A unit of the concentration of a constituent in water or wastewater. It represents 0.001 gram of a constituent in 1 litre of water. It is approximately equal to one part per million (PPM).^

million gallons per day (Mgd)

A rate of flow of water equal to 133,680.56 cubic feet per day, or 1.5472 cubic feet per second, or 3.0689 acre-feet per day. A flow of one million gallons per day for one year equals 1,120 acre-feet (365 million gallons).^

mining water use

Water use during quarrying rocks and extracting minerals from the land.^


To render or become mild or milder; to modify; to reduce negative impacts of projects, structures or any action on the socio-economy and environment.^

mobile microirrigation

An irrigation machine (generally frontal nozzle-line) in which the mobile nozzle-line functioning at low pressure applies water directly to the space between rows of annual crops. Suspended flexible pipes fitted with mouthpieces at their end feed continuously into small basins dug beforehand or simple partitioned corrugations.^

moisture-holding capacity

The amount of water required to fill all the pore spaces between the soil particles, i.e. the upper limit of the possible moisture content. It is usually expressed as the percentage of the soil volume (1 percent equals 1 mm/dm of soil depth), or sometimes as the percentage of the dry weight of the soil.^

monitoring programme

A programme designed to measure quantitatively or qualitatively the level of a substance over a period of time.^

monitoring well (observation well)

A non-pumping well used for observing the elevation of the water table; or a well used for some anticipated, generally undesirable, conditions, such as encroachment of a saltwater front or a pollutant introduced to groundwater.^

multi-criterion decision making

A multi-criterion decision-making problem means a multi-attribute or a multi-objective decision problem or both. Multicriterion decision making is used to indicate the general field of study which includes decision making in the presence of two or more conflicting objectives and/or decision analysis processes involving two or more attributes.^

municipal water system

A water system that has at least five service connections or which regularly serves 25 individuals for 60 days; also called a 'public water system'.^