Glossary/water dictionary

Alphabetical     Full list     References

impermeable layer

A layer of solid material, such as rock or clay, through which water is not allowed to pass.^


An operationally measurable term used in logical framework analyses, such as objectively verifiable indicator (OVI) for the verification of project objectives and results with regard to quantity, quality, time, place and beneficiaries.^

individual irrigation system

Systems located downstream of the outlets served by the collective irrigation system and meant to deliver water to the farms or fields of an individual area.^

industrial water use

Water used for industrial purposes in such industries as steel, chemical, paper, and petroleum refining. Inthe US, water for industrial uses comes mainly (80%) from self-supplied sources, such as a local wells or withdrawal points in a river, but some water comes from public-supplied sources, such as the county/city water department.^


Flow of water from the land surface into the subsurface.^

infiltration rate

The rate at which water penetrates the surface of a soil. The term usually refers to water occurring as precipitation, but it is also applied to water flowing or standing upon soil^

injection well

Refers to a well constructed for the purpose of injecting treated wastewater directly into the ground. Wastewater is generally forced (pumped) into the well for dispersal or storage into a designated aquifer. Injection wells are generally drilled into aquifers that do not deliver drinking water, unused aquifers, or below freshwater levels.^

institutional arrangements

An interrelated set of entities and rules that serves to organise societies’ activities for achieving social goals. The institutional arrangements should ensure that the integrated approach is included in decisions and policies regarding river basin management and irrigation development.^


A structure placed in a surface water source to permit water withdrawal.^

integrated river basin management

The process of formulating and implementing a course of action to achieve specific objectives involving the natural, agricultural and human resources of a river basin, and taking into account the social, economic and institutional factors operating in a river basin and their impact on the environment. It signifies the interactions of components and the dominance of components in the particular area.^


The controlled application of water for agricultural purposes through man-made systems to supply water requirements not satisfied by rainfall. ^

irrigation cycle

Successive deliveries of water on all the units of a network in such a way as to achieve a given irrigation on the entire field concerned.^

irrigation efficiency

The ratio or percentage of the irrigation water consumed by crops of an irrigated farm, field or project to the water diverted from the source of supply. It is called 'farm irrigation efficiency' or 'farm delivery efficiency' when measured at the farm head-gate; 'field irrigation efficiency' when measured at the field or plot; and 'water conveyance and delivery efficiency' or 'overall efficiency' when measured at the source of supply.^

irrigation potential

Total possible area brought under irrigation, plus that which can be planned for irrigation in a river basin, region or country, from available water resources, with designs based on good technical practice at the time of assessing the potential.^

irrigation requirements

The quantity of water exclusive of precipitation, i.e. quantity of irrigation water, required for normal crop production. It includes soil evaporation and some unavoidable losses under the given conditions. It is usually expressed in water-depth units (millimetres) and may be stated in monthly, seasonal or annual terms, or for a crop period.^

irrigation water quality table

This indicates guidelines for the interpretation of water quality for crop production. The table was adapted from the University of California Committee of Consultants, the United States, in 1974 and revised in 1979. It emphasises the longterm influence of water quality on crop production and farm management.^

irrigation water use

Water application on lands to assist in the growing of crops and pastures or to maintain vegetative growth in recreational lands, such as parks and golf courses.^