Minor irrigation schemes have probably evolved as a systematic development only after the country’s independence and with the initiation of the Five-Year Plan. These include all ground water and surface water irrigation projects having culturable command area of up to 2000 Ha. Naturally, the groundwater schemes require pumping up of water from tube wells, whereas surface water schemes may include those which involve flow due to gravity as well as lift by pumping from surface water flow irrigation projects include storage and diversion works and are the only means of irrigation in several areas, like the undulating terrains of Central India and the ghats or the hilly tracts of north and north east India. Such projects offer considerable opportunity for rural employment and also help in hard rock areas. When available surface water cannot be used for irrigation through construction of flow irrigation schemes due to topographical limitations, surface water lift irrigation schemes provide the solution.
As such, ground water development is a major activity of the minor irrigation programme. It is mainly a cultivators’ own programme implemented primarily through institutional sources. Adequate energy for pumping ground water is essential for near normal production of crops when there is severe drought. Hence, energy management is also essential.
Under surface flow minor irrigation schemes, water tanks are created by constructing bunds across depressions in undulating terrains. There should be a properly designed spillway for overflowing excess rain water during monsoons and sluice gates for releasing controlled quantities of water to canals. It is obvious that the amount of water expected in the reservoir would be proportional to the catchment area draining into the reservoir and the rainfall in the catchment.
For lift irrigation schemes, pumps have to be installed on the river or canal banks with the suction pipe long enough to be immersed into the flowing water body and should also ensure sufficient draft. At times, floating barges moored to the banks, may have to be installed to accommodate the pumps. Here, the suction pipe would be less but the lift pipe would be longer.
Whenever a problem of design of Minor Irrigation Project is to be dealt, following information should be collected.
- Geological Data: Geological investigation may be done for the suitability of foundation, water tightness of the reservoir and depth of cut off trench.
- Hydrological Data: The hydrology should be prepared for 50 years return period flood and got vetted by the Chief Engineer ID&R Jaipur. The data should be collected as per Annexure 2.
- Miscellaneous Data:
- Probable life of reservoir
- Proposed full tank level and maximum Water Level
- Maximum wind velocity for determination of wave height
- Minimum draw down level/canal sill level
- Calculations for tail water rating curve
- Requirements for roadways
- Capacity and elevations of sluice
- Chemical analysis of river water and ground water
- Length of dam, non overflow and over flow
- Type of dam: earthen, masonry etc. to be provided
- Details of saddle dam, if any
- Soil Test for Borrow Area and Foundation soils
Adequate number of soil samples should be got tested in Material Testing Laboratory of M.T. Dn. Jaipur. Samples from each borrow pit at every 0.30 m depth should be collected. For foundation, the soil samples be collected along proposed dam line for every one-metre depth at least upto 3m depth or till the suitable strata is reached. On each side of nalla / river, samples from foundation soil should be taken at locations maximum, middle and minimum height of dam embankment.
Soil tests to be conducted for soil samples are as below:
- Mechanical analysis
- Liquid limit, plastic limit and shrinkage limit
- Proctor’s Maximum Dry Density and Optimum Moisture Content
- Free swell index
- Specific gravity
- Permeability
- Triaxial shear test (C and f)
- Total soluble salts
- Dispersibility
- Sulphate, Carbonate, Organic matter
- List of Drawings:
- Index map on a scale of 1:50,000 or 1:25,000 showing location of project and location of existing works affecting/ being affected by proposed development
- Submergence area plan at contour interval not more than 0.5 m on a scale preferably 1:4000 and should cover elevation of at least 2 m above the proposed M.W.L. at dam site
- General lay out plan covering works area in the vicinity of dam site with a contour interval of not more than 0.5 m and preferably on a scale 1: 4000
- Capacity and submergence curve
- Block level plan of dam site
- Tail water rating curve (Elevation discharge curve) along with high flood level
- L-section of river 0.5 km upstream and 1.5 km downstream of proposed dam site
- Cross section of river at axis of dam site, one at upstream and three at downstream upto 3 m above H.F.L. on both sides and indicating highest flood levels during floods received so far
- Borrow area plan showing location and description of characteristics of proposed material to be used in the construction of the dam including, soil, sand, gravel etc.
- Borrow area plan indicating
- Depth and size of borrow pits/ are
- Quantity of earth available in each borrow pit/area
- Log of exploration of borrow pit/area indicating type of soils available at different depth
- Soil test results of soil of each borrow area
- Additional Data Required for Remedial Measures for Existing/ Breached Dam
- Design of existing/ breached dam
- Shortcomings of existing/ breached dam
- Technical data of existing/ breached dam
- Details of adjoining structures i.e. canal head regulator, spillway, byewash etc.
- Soil properties of existing dam
Salient Features of…………………………………………….. Minor Irrigation Project
| S. No. | Item |
F.P.S.
|
M.K.S.
|
|
1
|
Gross Catchment Area | ||
|
2
|
Intercepted Catchment Area | ||
|
3
|
Free Catchment Area | ||
|
4
|
Full Tank Level | ||
|
5
|
Maximum Water Level | ||
|
6
|
Top Bank Level | ||
|
7
|
Free Board | ||
|
8
|
Flood Lift | ||
|
9
|
Location
|
||
|
10
|
Average annual rainfall of last 50 years | ||
|
11
|
Expected annual run off | ||
|
12
|
Gross storage capacity | ||
|
13
|
Dead storage capacity | ||
|
14
|
Live storage capacity | ||
|
15
|
Total length of Dam | ||
|
16
|
Top width of Earthen Dam | ||
|
17
|
Design discharge of spillway | ||
|
18
|
Length of waste weir/ spillway | ||
|
19
|
Maximum height of Dam | ||
|
20
|
U/S & D/S slope of Dam | ||
|
21
|
Sill level | ||
|
22
|
Gross Command Area | ||
|
23
|
Culturable Command Area | ||
|
24
|
No. of village benefitted | ||
|
25
|
Submergence area at F.T.L. (ha) | ||
|
26
|
Intensity of Irrigation | ||
|
27
|
Cost of Project | ||
|
28
|
Cost per hectare | ||
|
29
|
Benefit cost ratio | ||
|
30
|
Difference between U/S MWL & D/S Tail Water Level | ||
|
31
|
Duty | ||
|
32
|
Water Allowance at outlet head | ||
|
33
|
Design discharge of canal at head | ||
|
34
|
Length of Main canal |