1) Gorge :-

    A narrow passage between mountains which is a possible site for construction of a dam.

    2) Dam :-

    A dam is a barrier, usually of large size, built across a river or stream for impounding water or creating a reservoir. 

    3) Coffer dam :- 

    A temporary dam to exclude water from a work site.

    4) Retention dams :-

    Small earth dams constructed to retain water for short periods of time to control excessive run-off and soil erosion.

    5) Reservoir :- 

    An artificially impounded body of water constructed for the purpose of storage, regulation and control of water. 

    6) Freeboard :- 

    The vertical distance between the maximum water level and the top of a dam. 

    7) Diversion weir :-

    A low dam across a river or stream for the purpose of diverting all or part of the flow into canals or channels taking off from either or both its banks. 

    8) Barrage :-

    Barrage is a barrier across a river provided with a series of gates to regulate water surface level upstream and to divert flow into the canal on one or both its banks. 

    It is distinguished from a weir that it is gated over its entire length and may not have a raised sill. 

    9) Aqueduct :-

    It is a cross-drainage work in which the canal is carried over a drainage canal or natural stream.

    10) Canal supply regulation :-

    The process of manipulating and distributing water supplies at the source of supply as per the demands of irrigation. 

    This includes regulation at different off-taking canals or among branches and distributories on the same canal. 

    The purpose is to provide equitable distribution of water and deliver the required quantity at various canal outlets. 

    It is also designed to prevent or reduce the silt entering the different reaches in a canal system.

    11) Command area :-

    The area that can be irrigated from an irrigation canal or canal system by gravity flow due to its location higher than the surrounding land.

    12) Field command :-

    It is the difference in elevation between the water level in the water course and the level of the highest point in the area to be irrigated. 

    13) Gross command area (GCA) :-

    It is the total area which can be irrigated by a certain channel or a project. 

    It includes the area covered by roads, culverts, unculturable areas, villages, and other areas which are not available for cultivation within a command area. 

    14) Water right :-

    A quantity of water per year to which each farm or user within an irrigated area is legally entitled. 

    A permit to claim the use of water for beneficial purposes is limited by its economical use and subjected to other rights of older rate of use, called ‘priority’ or prior appropriation.

    15) Irrigation project :-

    A project meant either solely or primarily for irrigation purposes, including development and improvement of land, although it may incidently serve other purposes.

    16) Spate irrigation :-

    A method of random irrigation using flood waters of a normally dry river system. 

    It includes the construction of earthern diversion embankments across the river bed and canals leading to embanked (bunded) fields, where water is ponded till it is infiltrated.

    17) Kharif :- 

    The summer south-west monsoon crop in the Indian subcontinent, with the onset of rains in May/ June and withdrawal of rains mainly during September/October.

    18) Rabi :-

    Winter cropping season (usually October/ November to March/April).

    19) Irrigation scheduling :-

    Planning the distribution of irrigation water, including specifying allocations and preparing timetables for the amounts of water and locations and making proper adjustments in them.

    20) On-farm development :-

    Land development below the canal outlet, including land leveling/grading, construction of field channels and drains, preventing soil degradation by erosion and providing for soil fertility development through appropriate crop rotations with leguminous crops intervening with cereals/oilseeds and other crops.

    21) Performance improvement :-

    Enhancing the well-being of an irrigation system, including productivity, financial costs and preventing adverse social, health, environmental and other effects.

    22) Communal irrigation system :-

    An irrigation system managed by a community of irrigators.

    23) Farmer joint management :-

    Irrigation system manage ment on a segment of the canal system, involving both farmers and irrigation staff.

    24) Water basin :-

    A hydrologically delineated area that is drained by a river system.

    25) Gross irrigated area :-

    Area of land irrigated in a year (2 irrigation seasons counting as two).

    26) Net irrigated area :-

    The area of land that receives irrigation water in a year, irrespective of the number of crop seasons (e.g., 2 or 3 irrigation seasons in a year are counted as one).

    27) Culturable command area (CCA) :-

    It is the portion of the GCA which is culturable or cultivable. 

    CCA = GCA –  unculturable area in the GCA

    28) Intensity of irrigation :-

    It is the ratio of irrigated to irrigable area.

    29) Irrigation potential :-

    The irrigation potential of a project is the gross area that can be irrigated with the amount of water available under the envisaged cropping pattern. 

    30) Cultivable area :- 

    Area of land potentially fit for cultivation. This term may or may not include part or all of the forests and permanent pastures.

    31) Cultivated area :-

    Area under annual and permanent crops. It refers to the area actually cultivated and does not include land which is fallow.

    32) Permanent crops :-

    Crops which occupy the land for long periods that do not need to be replanted after each harvest. 

    This does not include woodland and forests which are classified separately.

    33) Annual crops :-

    Temporary (annual) crops which are grown during a crop season.

    34) Harvested crops under irrigation :-

    Total harvested irrigated area for the crop for a given year. Areas under double cropping is counted twice.

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