Water requirement of crops and reservoir planing

THIRD YEAR DIPLOMA IN CIVIL ENGINEERING
SUB- W.R.E

1. CROP WATER REQUIREMENT Prof.M.B Chougule , DKTE’S YCP Ichalkaranji Crop water requirement is the water required by the plants for its survival, growth, development and to produce economic parts. This requirement is applied either naturally by precipitation or artificially by irrigation.

2. Functions of Irrigation Water Soil furnishes the following for the plant life: 1 . To supply water partially or totally for crop need 2. To cool both the soil and the plant 3 . Provides water for its transpiration. 4 . Dissolves minerals for its nutrition . 5. Provides Oxygen for its metabolism. 6 . Serves as anchor for its roots . 7. To enhance fertilizer application- fertigation 8. To Leach Excess Salts 9 . To improve Groundwater storage 10 . To Facilitate continuous cropping

3. CROPING SEASONS AND CROPS IN MAHARASHTRA

4. IMPORTANT DEFINATIONS 1) Crop period : It is the period in number of days that crop takes from the instant of its sowing to that of its harvesting . 2) Base period : It is the period in days from first watering at the time of sowing to the last watering before harvesting . 3) Duty (D) : Duty is the area in hectares (ha) irrigated by one cubic per meter per second of water flowing continuously for the base period for a particular crop (Ha/ cumec ) 4) Delta ( Δ ) : Delta is total depth of water required by a crop during the entire period of the crop from first to last watering for complete maturity of the crop.

5. Average duty/tank duty It is flow duty calculated at the head (beginning) of distribution (a type of canal ) or main canal for small irrigation It is always less than duty as it takes all types of losses in account. GROSS DUTY/TANK DUTY: Gross duty is the area under different crops irrigated by one million cubic meters of stored in tank in one year CROP ROTATION:- it has been observed that if same crop is sowing again and again the yield gets decreased.

6. . The main advantage of crop rotation is it helps in proper use of land resources and it also increases fertility of soil. THE USUAL CROP ROTATION IS Jawar -gram-fallow Wheat- jawar - gram Cotton- jawar -groundnut Cotton-wheat-gram Rice-gram

7. Paleo irrigation: Some times it is observed that in the initial stages before the crop is sown the land is very dry. In such case the soil is moistened with water so as to help in sowing. This is known as paleo irrigation. CASH CROPS: a cash crop which can not Be consumed directly by cultivators but has to encashed in market for processing. Eg -Tea, cotton, tobacco, sugercane Intensity of Irrigation (I.I ): Percentage of CCA that is cultivated in a particular season . Area irrigated per season/total irrigable area

8. Kor depth and kor period The distribution of water during the base period is not uniform, since crops require maximum water during first watering after the crops have grown a few centimeters . During the subsequent watering the quantity of water needed by crops gradually decreases and is least when crop gains maturity. The first watering is known as kor watering, and the depth applied is known as kor depth. The portion of the base period in which kor watering is needed is known as kor period. While designing the capacity of a channel, kor water must be taken into account since discharge in the canal has to be maximum during this time.

9. SEASONAL DUTY: It is the average duty for all crops usually sown during crop season. In this type of duty all the losses are taken into consideration and are mainly used for water planning Crop ratio: The ratio of area irrigated in Rabi season to that irrigated in Kharif season is known as crop ratio. The crop ratio is so selected that the discharge in the canal during both the seasons may be uniform .

10. Time factor The time factor of a canal is the ratio of the number of days the canal has actually run to the number of days of irrigation period. For example, if the number of days of irrigation period = 12, and the canal has actually run for 5 days, the time factor will be 5/12. ( Note: A day has a period of 24 hours (i.e. it includes the night also ). Capacity factor: This is the ratio of the mean supply discharge to the full supply discharge of a canal.

11. COMMAND AREA: It is the area on the downstream side of a project to which water can reach by gravity Gross Commanded Area (GCA ): The total area lying between drainage boundaries which can be commanded or irrigated by a canal system or water course is known as gross commanded area. Culturable Commanded Area (CCA ): Gross commanded area contains some unfertile barren land, local ponds, villages, graveyards etc which are actually unculturable areas. The gross commanded area minus these unculturable area on which crops can be grown satisfactorily is known as Culturable Commanded Area . CCA = GCA – Unculturable Area

12. Culturable Cultivated Area: The area on which crop is grown at a particular time or crop season . Culturable Uncultivated Area: The area on which no crop is grown at a particular time or crop season Irrigable command area (ICA): It is that area of culturable command area which can be actually irrigated.

13. . 1acre=0.404T hectares 1hectare=10⁴ sq. meters 1 cusec=0.0283 cumec 1 cumec /day=8.64 hectare- meeter

14. Following are the different factors affecting on duty :- 1 ) Method & system of irrigation 2) Mode of applying water 3) Method of cultivation 4) Time & frequency of tilling 5) Type of crop 6) Base period of crop 7) Climatic condition of area 8) Quality of water 9) Method of assessment 10) Canal condition 11) Character of soil & sub-soil of the canal 12) Character of soil & sub-soil of the irrigation field

15. METHODS OF IMPROVING DUTY 1 . Suitable method of applying water to the crops should be used. 2 . The land should be properly ploughed and leveled before sowing the crop. It should be given good tilth . 3 . The land should be cultivated frequently, since frequent cultivation reduces loss of moisture specially when the ground water is within capillary reach of ground surface. 4 . The canals should be lined. This reduces seepage and percolation losses. Also, water can be conveyed quickly, thus reducing, evaporation losses . 5. Parallel canals should be constructed. If there are two canals running side by side, the F.S.L. will be lowered, and the losses will thus be reduced . 6. The idle length of the canal should be reduced. 7 . The alignment of the canal either in sandy soil or in fissured rock should be avoided. 8 . The canal should be so aligned that the areas to be cultivated are concentrated along it. W

16. . 9. The source of supply should be such that it gives good quality of water. 10 . The rotation of crops must be practiced. 11 . Volumetric method of assessment should be used. 12 . The farmers must be trained in the proper use of water, so that they apply correct quantity of water at correct timing. 13. The land should be redistributed to the farmers so that they get only as much land as they are capable of managing it. 14 . Research stations should be established in various localities to study the soil, the seed and conservation of moisture. The problems concerning the economical use of water should be studied at research stations. 15 . The canal administrative staff should be efficient, responsible and honest. The operation of the canal system should be such that the farmers both at the head of the canal as well as at the tail end get water as and when they need it.

17. Consumptive Use of Water (CU) Water requirement of crop is the total quantity of water from the time the crop is sown to the time it is harvested. This water requirement may vary from crop to crop, from soil to soil and period to period. Water required to meet the demand of evapotranspiration and metabolic activities of the crop togeather is known as consumptive use (CU) of water

18. Factors Affecting Consumptive Use (CU) Evaporation which is dependent on humidity Mean monthly temperature Monthly precipitation Wind velocity in the locality which affects evaporation Soil type and its topography Cropping pattern, growth stage and type of crop Growing season of the crop Method of applying irrigation Irrigation water depth Day light hours

19. assessment of irrigation water Methods of assessment: 1) Volumetric assessment 2) Assessment on area basis 3) Assessment on seasonal basis 4) Composite rate 5) Permanent assessment

20. 1. Volumetric assessment: In this method charges are levied on actual volume of water supplied to the cultivators. This is ideal system under which cultivators has incentive for using water economically. However this method has no practical value induce up till now. This method is necessary to install numerous water meter on irrigation outlets, scattered all over the canal system. It is very costly process and difficult to maintain also.

21. 2. Assessment on area basis: In India this type of assessment is generally adopted, the charges are levied on the actual area which is under irrigation. The charges are fixed crop wise. This method has a few disadvantages as the charges are levied on area basis and not on the actual quantity of water used. It leads to wasteful use of water. This type of irrigation encourages intensive irrigation rather than extensive irrigation.

22. 3. Assessment on seasonal basis: In this type of assessment the assessment is based on the kind of crop grown in that area in crop season. 4 . Composite rate basis: In this type of assessment the combined land revenue and tax are levied on cultivators. It is not normally in practice.

23. 5. Permanent Assessment or Betterment Levy. In area where canals are provided as insurance against drought, the farmers are levied at a fixed rate every year irrespective of the fact whether or not they use the canal water. In drought year, the farmers are allowed to draw canal supplies without paying charges extra to normal betterment levy.

24. SR.NO AREA BASIS VOLUMETRIC BASIS 01 The charges are laid on the area actually irrigated The charges are laid on the measurement of discharge entering to field. 02 Discharge measuring devices are not required Discharge measuring devices are required. 03 It may lead to excess use and wastage of water. As former know the charges are on actual volume of water use no such wastage is made. 04 Skilled staff is not required. Qualified skilled staff is required. 05 Initial cost is very less . Cost is high due to installation of water measuring instruments. 06 Maintenance is not required. Frequent maintenance is required.

25. . Duty varies at varies points of measurement from head of water course to head of canal. Explain. 1.In canal irrigation system, the water flows from head of water course to head of canal. 2. During the passage of water from these irrigation channels, water is lost due to evaporation and percolation . 3. Duty of water for crop , is the number of hectares of land which the water can irrigate. Therefore, If the water requirement of crop is more , less number of hectares of land it will irrigate 4. If water consumed is more , duty will be less. It becomes clear that duty of water at the head of the water course wiil be less than the duty of water on the field . because when water flows from the head of water course and reaches the field , some water is lost as transit losses.