Irrigation engineering complete (merge).pdf

INTRODUCTION Irrigation Engineering (IDE-222) Dr. S. K. Raul, Assoc. Prof. (SWCE) CAET, OUAT, Bhubaneswar Irrigation is the artificial application of water to soil to assist in the production of crops. Irrigation water is...

INTRODUCTION Irrigation Engineering (IDE-222) Dr. S. K. Raul, Assoc. Prof. (SWCE) CAET, OUAT, Bhubaneswar Irrigation is the artificial application of water to soil to assist in the production of crops. Irrigation water is supplied to supplement the water available from rainfall, soil moisture and the capillary rise of groundwater. (1) Flow irrigation (gravity flow) & (2) Lift irrigation (lifting against gravity). Purpose of irrigation To provide crop insurance against short duration droughts To cool the soil and atmosphere, thereby making more favorable environment for plant growth To add water to soil to supply the moisture essential for plant growth To reduce the hazard of frost To wash out or dilute salts in the soil To reduce the hazard of soil piping To soften tillage pans and clods To delay bund formation by evaporative cooling Merits of Irrigation Crop yields are increased due to irrigation Irrigation increases the amount of land that can be productively farmed Productivity gets stabilized A greater diversity of crops are facilitated Irrigation increases farm income and employment Poverty can be alleviated Irrigation contributes to regional development Mixed cropping is eliminated Irrigation helps generating hydro-electric power Irrigation facilitates communication and navigation Domestic water supply is facilitated by irrigation Irrigation helps in afforestation Irrigation protect plants against frost Irrigation suppress weed growing in rice fields Soil consolidation can be prevented Demerits of Irrigation Irrigation contributes to water pollution resulting in diseases like anemia Diseases like malaria and dengu results due to colder and damper climate Over-irrigation results waterlogging, which in turn reduces crop yield Expensive irrigation water reduces revenue Sources of soil moisture Precipitation Atmospheric water other than precipitation Flood water Groundwater Irrigation Total global water content Global fresh water distribution Water Resources of India India accounts for: About 2.45% of world’s surface area 4% of the world’s water resources and About 16% of world’s population  The total water available from precipitation in India is about 4,000 km3/year  The availability from surface water and replenishable groundwater is 1,869 km3  Out of this only 60% can be put to beneficial uses  Thus, the total utilisable water resource in the country is only 1,122 km3 Sectoral Usage of Surface Water and Groundwater in India River Basins of India  Sl. Average annual No. Name of the River Basin availability (km3/year) 1. Indus (up to Border) 73.31 2. a) Ganga 525.02 b) Brahmaputra ,Barak & Others 585.60 3. Godavari 110.54 BASINWISE WATER AVAILABILITY 4. Krishna 78.12 5. Cauvery 21.36 6. Pennar 6.32 7. East Flowing Rivers Between Mahanadi & Pennar 22.52 8. East Flowing Rivers Between Pennar and Kanyakumari 16.46 9. Mahanadi 66.88 10. Brahmani & Baitarni 28.48 11. Subernarekha 12.37 12. Sabarmati 3.81 13. Mahi 11.02 14. West Flowing Rivers of Kutch, Sabarmati including Luni 15.10 15. Narmada 45.64 16. Tapi 14.88 17. West Flowing Rivers from Tapi to Tadri 87.41 18. West Flowing Rivers from Tadri to Kanyakumari 113.53 19. Area of Inland drainage in Rajasthan desert NEG. 20. Minor River Basins Draining intoBangladesh & Burma 31.00 Total 1869.35 State-Wise Wise Ground Water Resources Availability, Utilization and Stage of Development Development, India State-Wise Wise Ground Water Resources Availability, Utilization and Stage of Development Development, India Basinwise Ground water Potential and Utilisation in India (km3/Year)  STATES/UTs. 2013-14 2014-15 2015-16 2013-14 to ANDHRA PRADESH 3014 2927 2743 ARUNACHAL PRADESH 57 56 56 ASSAM 303 296 297 BIHAR 2933 2987 2958 CHHATTISGARH 1462 1468 1476 wise details of net irrigated area from 2013 GOA 38 39 39 GUJARAT 4233 4233 4233 HARYANA 2931 2974 2956 HIMACHAL PRADESH 114 117 120 JAMMU & KASHMIR 323 325 356 JHARKHAND 217 207 213 KARNATAKA 3556 3589 3243 KERALA 397 414 414 MADHYA PRADESH 9455 9584 9284 MAHARASHTRA 3248 3244 3215 MANIPUR 69 69 73 2015-16 MEGHALAYA 68 81 80 MIZORAM 16 16 16 2015 NAGALAND 91 97 104 ODISHA 1245 1259 1230 PUNJAB 4143 4118 4137 RAJASTHAN 7650 7882 7938 SIKKIM 13 12 16 TAMIL NADU 2679 2726 2833 TELANGANA 2289 1726 1486 TRIPURA 78 79 81 UTTARAKHAND 328 330 330 UTTAR PRADESH 14027 14389 14231 WEST BENGAL 3099 3102 3105 State-wise ANDAMAN & NICOBAR ISLANDS 0 0 0 CHANDIGARH 0 0 0 DADRA & NAGAR HAVELI 4 4 5 DAMAN & DIU DELHI 22 22 22 LAKSHADWEEP PUDUCHERRY 13 13 13 ALL INDIA 68117 68384 67300 Per cent net irrigated to net sown area and per cent canal irrigated & per cent groundwater irrigated to net irrigated area (Source: DES, 2017-18) NIA %: Net Irrigated area to net sown area, GW %: Groundwater share in net irrigated area, SW %: Surface water share in net irrigated area Million ha India at a glance: Net sown area: 141 million ha Rainfed area: 86 million ha Cropped area: 190 million ha Irrigation potential: 140 million ha Average annual precipitation: 4000 km3 Average annual surface flow: 1869 km3 Water resources utilizable is about 690 km3 (about 36%) Ground water resources: 432 km3 Available ground water resource for irrigation: 361 km3 Net utilizable ground water resource for irrigation: 325 km3 Various means to enhance water resources potential Water Conservation and Management Prevention of Water Pollution Recycle and Reuse of Water Watershed Management Rainwater Harvesting SOIL MOISTURE MEASUREMENT Irrigation Engineering (IDE-222) Dr. S. K. Raul, Assoc. Prof. (SWCE) CAET, OUAT, Bhubaneswar Soil Matrix: In a soil, the solid phase usually controls the form or spatial distribution of the liquid and the gas phases. The solid phase is therefore called the soil matrix. Interaction between the soil matrix and the water are basically due to the forces of adhesion and cohesion. Adhesion is the attraction of soil particle surfaces for water. It is due to surface tension Cohesion is the attraction of water molecules for each other. By adhesion water is held tightly at the soil water interface. Pore Size Distribution: Micropores: Size less than 30 µm (3 to 30 µm dia) Mesopores: 30 to 100 µm dia Macropores: >100 µm dia Large pores induce aeration and infiltration, medium-sized pores facilitate capillary conductivity, and small pores induce greater water holding capacity Soil water (moisture): There are three forms of soil water: gravitational water capillary water hygroscopic water The irrigationist is concerned with gravitational and capillary water only, since the hygroscopic water is not available to the plants. Capillary water refers to the part of water present in the capillary spaces in the soil and held by forces of surface tension and hence, always moves in the direction of the greatest tension. It is held between tensions of about 31 atm and 1/3rd atm. Gravitational water moves downward freely under the influence of gravity and drains out of the soil. It is also referred to as free water. It is held at tensions of 1/3rd atm or less. Hygroscopic water refers to the water that held totally to the surface of soil particles by adsorptive forces. This part of the soil water is not available for plant use. It is held at tensions of more than 31atm. Methods of Soil Moisture Measurement Direct method Indirect method (Measurement of (Measurement of water potential or moisture content in the stress or tension or suction under which soil, wetness) water is held by the soil) Gravimetric method Appearance or Feel method Volumetric method Neutron probe Tensiometer Resistance blocks/ Gypsum block Time domain reflectometre (TDR) Pressure plate/membrane apparatus 1. Gravimetric Method  Basic measurement of soil moisture is made on soil samples of known weight or volume  The soil samples are weighed and they are dried in an oven at 105 C for about 24 hours  Then cooled it on room temperature and weighed  The difference in weight is the amount of moisture in the soil Hot Air Oven 2. Volumetric Method  Soil sample is collected using a core sampler or with a tube auger whose volume is known  The amount of water present in soil is estimated by drying it in the oven and calculating by the formula  The method is though accurate and simple, it is used mainly for experimental purpose  Sampling, transporting and repeated weighing give error.  It is also laborious and time consuming.  The errors of the gravimetric method can be reduced by increasing the size and number of samples  However, the sampling disturbs the experimental plots and hence many workers prefer indirect methods  Resistance blocks  Nylon units are most sensitive at a tension of less than 2 atm  Plaster of paris blocks function most efficiently at a tension between 1 and 15 atm  Fibre glass units operate satisfactorily over the entire range of available moisture  Nylon and fibre glass blocks cannot be used in saline conditions whereas gypsum blocks work well because of buffering action Limitations:  While placing the gypsum block in soil, care should be taken that the blocks must have close contact with undisturbed soil  After placing the blocks get wet with soil moisture due to capillary movement  Pure gypsum block sets in about 30 minutes  The gypsum block is sensitive to soil moisture from 1.0 atm tension to 20.0 atm  However, the gypsum blocks are not reliable in wet soils 2. Tensiometer  It is also called irrometer  It provides a direct measure of tenacity (tension) with which water is held by soil  It consists of (i) A ceramic or clay cup (7.5 cm); (ii) A cap for closure; (iii) A vacuum gauge; and (iv) A hollow metallic tube  At the time of installation, the system is filled with water from the opening at the top and rubber corked when set up in the soil  Moisture from cup moves out with drying of soil, creating a vacuum in the tube which is measured with the gauge  When desired tension is reached, the soil is irrigated  Tensiometer continues to record fluctuations in soil moisture content unless the tension exceeds about 0.85 atm  They are satisfactory for sandy and sandy loam soils where tensions are low, but they are not so well adapted to clay soils where tensions normally are high, or where the soils crack badly  Tensiometers measure matric or capillary potential Merits: Demerits:  It is very simple and easy to read  Sensitivity of a tensiometer is only soil moisture up to 0.85 atm while available soil  It is very useful instrument for moisture range is up to one atm scheduling irrigation to crops  Hence is useful more on sandy which require frequent irrigations soils wherein about 80% of at low tension available water is held within 0.85 ranges  1 atm = 10.36 m of water = 76.39 cm of Hg = 1.0127 bar 1 bar = 1 N/m2 = 106 dyne/cm2 = 10.23 m of water Soil moisture tension at field capacity are: sandy soils = 0.06 atm; loamy sand = 0.3 atm; clay soils = 0.6 atm Soil Moisture Characteristics Curve or Moisture retention curve 3. Neutron Probe  Works on the principle of neutron scattering method  Principle: The method is based on the use of radioactive material for measuring soil moisture  The principle is based on the measurement of the number of hydrogen nuclei that are present in a unit volume of soil, their number being a direct function of the number of water molecules contained in that same volume Working:  The probe contains fast neutron source, which may be a 2-5 milli curie mixture of radium and beryllium or Americium and beryllium  Access tubes are aluminum tubes of 50 to 100 cm length and are placed in the field where moisture is to be estimated  Neutron probe is lowered into access tube to the desired depth  Fast neutrons are released from the probes, which scatter into the soil  When neutrons encounter nuclei of hydrogen atom of water, their speed is reduced  The scalar or the rate meter counts the number of slow neutrons, which are directly proportional to water molecules  Moisture content of soil can be known from the calibration curve with counts of slow neutrons Count Ratio: ratio of count at a given depth to the standard count Advantages:  Soil moisture can be estimated quickly and continuously another with neutron moisture meter without disturbing the soil  Another advantage is that soil moisture can be estimated from large volume of soil Limitations:  It is expensive and moisture content from shallow top layers cannot be estimated  The fast neutrons are also slowed down by other source of hydrogen, present in the organic matter  Other atoms such as chlorine, boron and boron also slow down the fast neutrons, thus overestimating the soil moisture content 4. Time Domain Reflectometre (TDR):  It is a device capable of producing a series of precisely timed electrical pulses in a wide range of high frequency, e.g., 0.02 – 3.0 GHz by different devices, which travel along a transmission line that is built with a coaxial cable and a probe.  The high frequency provides a response less dependent on soil properties such as texture, salinity or temperature 5. Pressure membrane and pressure plate apparatus:  It generally used to estimate field capacity, permanent wilting point and moisture content at different pressures  The pressure plate extractor functions in the range of 0 to 5 bars of soil column, hence used for determining the field capacity. The pressure membrane apparatus is used for suctions up to 100 bars and therefore useful for determining the wilting point. 6. Appearance and Feel Method:  A practical estimate of moisture content is obtained by the feel and appearance of soil samples taken from the desired depths  The soil sample is squeezed in the hand and its feel and appearance are taken into consideration Determination of Moisture Content of Soil by Gravimetric method AIM: To determine the moisture content of soil by oven-drying method APPARATUS: 1. Hot-air oven 2. Weighing balance 3. Moisture can 4. Gloves THEORY AND APPLICATION: This test is performed to determine the water (moisture) content of soils. The water content is the ratio, expressed as a percentage, of the mass of “pore” or “free” water in a given mass of soil to the mass of the dry soil solids. PROCEDURE: Record the moisture can and lid number. Determine and record the mass of an empty, clean, and dry moisture can with its lid (M1) Place the moist soil in the moisture can and secure the lid. Determine and record the mass of the moisture can (now containing the moist soil) with the lid (M2). Sample M1 in gm M2 in gm M3 in gm Water content, w (%) Number 1 2 3 Sampling depth (cm) Weight of moist soil sample (g) Weight of oven dried soil sample (g) 0-25 132.48 125.86 25-50 134.56 126.42 50-75 123.50 115.25 75-100 109.85 101.73 MEASUREMENT OF IRRIGATION WATER Irrigation Engineering (IDE-222) Dr. S. K. Raul, Assoc. Prof. (SWCE) CAET, OUAT, Bhubaneswar1 The science and practices of water measurement is called as Hydrometry Velocity-Area Method  Float method  Current meter  Tracer method  Radio-isotope method Direct Measurement of Discharge  Weirs  Notches  Orifice  Mouth piece  Flumes  Parshall flumes  Cutthroat flumes Measurement of Flow in Pipes Meters for Measuring Cumulative Flow Dr S K Raul, Assoc. Prof. (SWCE), CAET 2 Velocity-Area Method Float method Mean velocity of flow in open channels (𝑣𝑚 ) is obtained by applying a coefficient 0.80 to the surface velocity (𝑣𝑚 = 0.80𝑣𝑠 ). The area of cross-section multiplied by the average velocity gives the rate of flow (𝑄 = 𝑣 × 𝐴). Current meter Where the depth of flow id too small (