GOVERNMENT OF ODISHADEPARTMENT OF WATER RESOURCES INDUCTION TRAINING PROGRAMME MODULE-IV (INVESTIGATION) COURSE CODE: INV-IV Command Area Survey. Finalization of L.S & D.S CHIEF ENGINEER, PPF & INV. 1 2 .ODISHA. BHUBANESWAR. Culturable Uncultivated Area: 3 . there may be some high level culturable areas.A): The total area including roads.C. where the irrigation water cannot flow under gravitational force from the canal. barren land. from the G. which can be economically irrigated from the project is called gross- command area.C.A. 5.. is known as culturable commanded area. Command Area Survey Some technical terms as regards to water application are as follows: 1. only a part of the area can be irrigated. forest. it is the total area over which water of irrigation canals can flow under gravity.A. Gross-Command Area (G. Such areas may be irrigated by tube-wells or other methods of irrigation. Un-command Area: In the culturable command area. villages etc. As a matter of fact.. Culturable Command Area(C. 4. It is obtained by deducting uncultured area like ponds.C. depending upon the available source.C. Such field areas are declared un-command areas and no water is allotted to them. Culturable Cultivated Area: The area which is used for growing crops in the particular season. In other words.A): That area over which cultivation is possible within project G. village etc. 2. 3. but crops are not grown in a particular season. Spot levels are taken on the corner points of the square grid without referring to the plots of the village. How Command Area Survey is conducted Command area survey can be carried out on the village maps. roads. forest. Spot levels are taken on each plot of the village and smooth curves(contour) of 1. are deleted and the net area is termed as culturable command area(CCA). After drawing the contour lines the obligatory areas like hills. Alignment Of Main Canal/Ridge Line/Valley Line/Chak Boundary/Distribution System Main Canal: This is the canal which is directly taken off from a river or reservoir. schools.00mtr interval are drawn along the points of equal levels. which known as grid plan method of contouring. A contour map is attached for reference. human settlement. The area left for the crops of next season is known as culturable uncultivated area. Branch Canals: 4 . The area where irrigation is possible. Contour survey can be carried out from spot level basis or grid plan method. ponds. It functions as a carrier of feed canal to branch and other canals. It is usually of large size and no direct irrigation is done from it to the fields except under special circumstances. Approximate command area (ayacut area) can be calculated from the topo sheet and number of villages to be involved in the command area. 25 to 0. Most of the irrigation is done by distributaries. it is not possible to supply water from one canal. but serve as a feeder of the distributaries. As most area along the distributaries and branches is high and cannot be irrigated. About 10-15 outlets are provided in each minor.As the command area of big canals is very large. Minors carry discharge from 0. Water Course: These are also known as field channels and are constructed and maintained by the farmers. therefore at such places a minor is run more or less parallel along the branch canal to irrigate these fields. Distributaries: These are channels which carry small discharge of 0. Minors: Sometimes these are also known as minor distributaries. which are known as branch canals. Each branch canal is responsible to irrigate a particular area. Outlets are provided in the minors at various points for irrigation purpose. They draw their quantity of water from the branch canals.50 Cumec. But in special circumstances outlets for irrigation purposes can be provided on high spots. as they carry water to various places of the command area.5 to 7.0 Cumecs. They draw their water from the distributaries. For supplying the water to the total area the main canal is bifurcated into two or more canals. which cannot be irrigated from the distributaries. These are small channels which draw 5 . The branch canals also do not supply water direct to the fields. Usually main canals are constructed along the contour lines for some length near the diversion head work. Now-a-days farmers are being stressed to make the water courses lined to save the precious water from percolation loss. These canals also do not meet with any cross drainage works. They may be lined or unlined. As this canal can irrigate fields on its both the sides.water from the minors through their outlets and carry it direct to the fields for irrigation purposes. Branch canals and distributaries are also constructed as far as possible on the contour lines. Most of the irrigation canals are ridge canal. 6 . therefore their construction cost is also low. While doing the construction of these canals if the ridge takes sharp turn. In special cases they can also draw water from branches and distributaries. because it reduces the length of the canal and thereby construction cost. These canals are usually taken off from the contour canal. If irrigation facilities are to be provided for the higher areas. Ridge Canal: The canals constructed on the ridge or water shed line are known as ridge canals. its command area is more. The contour canal irrigates the areas whose elevation is lower than the elevation of the canal. the alignment of the canal should be made straight as far as possible. because water flows under gravity from it to the fields. The contours chosen for the alignment should include all the contours of the area to be irrigated. lift irrigation canals are provided. Canal Alignment: These canals are constructed nearly parallel to the contour lines of the area. The distributory. therefore. If the command area are located on both sides of the dam/barrage two main canals are planed on both sides on the barrage /dam at suitable location. A number of main canal alignment are decided upon the area of the command and the location.50mtr below the MWL in case of barrage. therefore. The main canal fixes the boundary of the command area. establishing layouts of the chaks in the command of a given channel is the first step of the planning 7 .00km distance till the canal reaches a bigger Nalla or water body.00mtr in 5. Chak Boundary Introduction The chak or outlet command is a basic unit for irrigation management in the command of Minor. Generally the off-taking point of the main canal is fixed at 1. A main canal alignment runs a contour line which decreases 1. Usually these are parallel to the natural drainage of the area. otherwise heavy velocity will erode them. distributory or any other parent channel. no cross drainage works are required in them. Distribution system of the canal (distributary. Therefore. These canals have steep bed slope. minor. minor and sub-minor generally follows ridge line of the area in order to distribute water on both sides of the canal through its outlets. lining is done in them. sub-minor) are decided to distribute the water to the entire command area through its canal Network.Side Slope Canal: These canals are aligned approximately at right angles to the contour canals along the slope between the ridges and the valleys. process.3 m should be adopted.875lps / ha. The corresponding to the CCA discharge required in Cumecs @0. A map is attached showing the contour lines. Depth of flow.) o Maximum permissible area which can be irrigated in peak rotation by prescribed discharge in a given flow period.2 or 0. o Other factor like village boundary. local depressions. For this purpose. mean velocity in mtr/sec after calculating the critical velocity and CVR the Bed level of the canal is fixed with full supply level. Preparation of LS & DS. Layout of chaks: Following factors are considered for finalizing chak boundaries and total layout of chaks. high patches. canal alignment with distribution system and chak boundary. o Topography (Ridges. o The number of farmers to be served. vallies. Continuing in the same process the other minors 8 . is calculated with 10% excess for fixing the canal parameter like Bed width . of Canals The command area (CCA) of a minor or sub-minor is decided on the contour map drawn in suitable scale. Longitudinal slope of the canal. o Maximum length of field channel. the contour map of the command of minor or distributory to the scale of 1:2000(1:4000 if command is very big) with contour interval of 0. road/railway lines. etc. etc. S Birdie & Ramchandra Das. Designed Bed level. The LS of the canals are drawn from the head regulator of the canal to the tail end with fixation of FSD. velocity in mtr/sec. NSL and RD in mtr.are /sub-minors are designed from the tail end of the canal towards head of the canal and the final discharge is fixed at the head regulator of the canal. WS slope. 9 .0 AND DESIGN STATEMENT OF PAUNSIA DISTRIBUTORY OFFTAKING FROM RD 26260. 2. L.0M OF BETNOTI BRANCH CANAL ARE ATTACHED FOR REFERENCE Book Reference: 1. FS discharge.S OF KRUSHNA CHANDRAPUR SUB-MINOR-1 FROM CH: 00 TO 624. Irrigation Engineering by G. bed width. Designed FSL. Irrigation Engineering and Hydraulic Structures by Santosh Kumar Garg. Free Board. Bank width. 10 . 11 . 12 . 13 . 14 . 15 . 16 .