Canal Irrigation & Canal Design

Classification of Irrigation canal

Irrigation canal can be classified in different ways on the following basis

(1)    Based on nature of source of supply

                (a) Perennial canal / बारहमासी नहर

                (b)  Non-Perennial canal / गैर-बारहमासी नहर

                (c) Inundation Canal or Flood Canal / बाढ़ नहर

(2) Based on discharge and relative importance in given network

                (a) Main Canals – Principal canal of canal network

                (b) Branch canal – off takes from main canal on either sides, Q > 5 cumecs

                (c) Major Distributaries – off take from branch canal, Q = 0.25 to 5 cumecs

                (d) Minor Distributaries – off take from major distributaries, Q < 0.25 cumecs

                (e) Water Course or field channels – channels which carries water from outlets of major or minor distributaries to the filed

(3) Based on soil through which it is constructed

                (a) Alluvial Canal – Excavated in alluvial soil

                (b) Non- Alluvial canal – Excavated in non- alluvial soil.

(4) Based on the lining

                (a) Lined Canal

                (b) Unlined canal

(5) Based on Canal alignment

(a)    Ridge Canal / रिज नहर

• Also known as Watershed canal.  वाटरशेड नहर के रूप में भी जाना जाता है।

• Aligned along the ridge or natural watershed line.

        रिज या प्राकृतिक वाटरशेड लाइन के साथ संरेखित होती हैi

• Can irrigate lands of both sides of ridge.

                रिज के दोनों किनारों की भूमि की सिंचाई कर सकते हैं।

• No cross drainage work required

(b)   Contour canal / कंटूर नहर

• Aligned parallel to contours of the land
• Can irrigate areas only on one side of ridg.भूमि के समोच्च के समानांतर संरेखित। रिज के केवल एक तरफ के क्षेत्रों की सिंचाई कर सकते हैं।

• Cross drainage works are required

(c)    Side slope canal / साइड ढलान नहर

• It is aligned right angles to the contour of land
• It also irrigate land on one side

Design of Unlined alluvial canal/channel

• In India Alluvial canal carry a certain amount of sediments.
• These channels are designed on the basis of hypothetical theories  given by Kennedy and Lacey.
• Main problems of alluvial canal is silting(settling of particles) and scouring (erosion of surface).
• Excess s silting reduces the discharge carrying capacity.
• Excessive scouring – bed eroded so that cross section increases and irrigate less command area.
• A channel is said to be stable or in regime condition if there is no problem of silting and scouring.
• Non –silting & Non – Scouring channels are known as channels in regime conditions.

(1)    Kennedys Theory (1895)

• Carried extensive investigation  on some of canal in upper Bari Doab canal system in Punjab. पंजाब में ऊपरी बारी दोआब नहर प्रणाली में कुछ नहरों पर व्यापक जांच की गई।
• He concluded that

a)      Silt supporting power of channel depends upon generation of eddies from base of the channel.

b)      These eddies are generated due to the friction of flowing water with channel surface.

c)       Generation of eddies are responsible for keeping silt in suspension.

d)      Kennedy defined critical velocity (V₀) in a channel as the mean velocity which will just keep the channel free from silting or scouring, and related to the depth of flow

                                                V₀ = 0.55 my^0.64 

                                where V₀  = Critical velocity in the channel in m/sec

                                              y  =  depth of water in channel in m

                                             m  = critical velocity ratio. (CVR) ( depends upon the silt grade)

Design steps for Keneddys theoy –

1. Assuming a trial depth of ‘y’ find the critical velocity V₀  which keep sediments in suspension.         V₀ = 0.55 x my^0.64
2. Find the cross – sec area of channel for given discharge    A = Q/ V₀
3.   find the channel dimensions by assuming it to be trapezoidal channel having side slope of 1V : 0.5H
4. Calculate hydraulic radius     R = P/A         ( P = perimeter of channel)
5. Using value of R find actual velocity by using chazey’s 0r Manning’s formula but Kennedy recommends Kutter’s formula.

                Chezy’s  Equation             V = C. R^1/2 S^1/2       

                   Manning’s Equation         V = (1/n). R^2/3 S^1/2

                    Kutter’s  formula           

       

                                                                                                              ^{where n = roughsity coefficient (0.002 to 0.003)}

6. If  V₀  = V, then our assumed depth of water is satisfactory. Otherwise change the depth and repeat the above procedure till we have V₀  ≈  V
7. Recommended ranges of slope 1 in 3500 to 1 in 5000.
8. Dimensions of channel using Kennedy’s theory is also determined using Garret’s Diagram.

Limitations of Kennedy’s theory

1)      According to Kennedy eddies are generated from bottom but in actual practice it is generated from sides and bottom. केनेडी के अनुसार एड्डीज़ नीचे से उत्पन्न होते हैं लेकिन वास्तविक व्यवहार में यह पक्षों और नीचे से उत्पन्न होते हैं।

2)      Value of ‘m’ was decided arbitrarily.

                ‘m' का मान मनमाने ढंग से तय किया गया था।

3)    Not given his own equation to find actual velocity so limitations of Kutter’s theory becomes                its limitation. वास्तविक वेग ज्ञात करने के लिए उसका अपना समीकरण नहीं दिया गया है,                 इसलिए कुटर के सिद्धांत की कमियां इसका दोष बन जाती हैं।

4)    Not given formula to find channel bottom slope. नहर के निचले ढलान के लिए सूत्र नहीं          दिया गया है।

5)    Did not noticed the importance of b/d ratio.  बी / डी अनुपात के महत्व पर ध्यान नहीं दिया।

6)    Did not account concentration the silt concentration and bed load.गाद की सांद्रता और बेड         लोड पर ध्यान नहीं दिया।

(2) Lacey’s  Theory (1939)

• Lacey found many drawbacks in Kennedy’s theory and gave his own theory.
• Lacey gave more general applicable theory.
• According to him , even a channel showing no silting or no scouring may actually not be in regime.
• According to him perfect regime conditions will not exist and there are 3 regime conditions in general.

                (a) Initial Regime              (b) Final Regime               (c) True Regime

(a)    Initial Regime

• After in service 1^st regime condition obtained by channel.
• When only bed slope & depth of channel varies than a condition of non – silting and non – scouring may exists which is called initial regime condition.
• Constant quantities are discharge, silt grade & charge, width of the channel.
• Lacey’s design theory is not valid for initial regime condition. ( for subsequent flow conditions regime condition may changed if site conditions change)

(b)   Final Regime

• Ultimate stage of regime attained by channel.
• If all the variables such as perimeter, depth, slope, etc. are equally free to vary and finally get adjusted according to discharge and silt grade, then the channel is said to have achieved permanent stability, called final regime.
  यदि परिधि, गहराई, ढलान आदि जैसे सभी चर समान रूप से भिन्न होते हैं और अंत में निर्वहन और गाद ग्रेड के अनुसार समायोजित हो जाते हैं, तो चैनल को स्थायी स्थिरता प्राप्त final regime कहा जाता है।

• Considered Semi- elliptical section.

(c)    True Regime ( ideal condition)

• There can be only single channel section and single bed slope at which a channel carrying a given discharge, silt charge and silt grade would be in regime.
  केवल एकल चैनल अनुभाग और एकल बेड ढलान हो सकता है, जिस पर दिए गए डिस्चार्ज, गाद चार्ज और गाद ग्रेड का एक चैनल स्थिरता में होगा।

• Hence , an artificial constructed channel having a fixed cross section and a fixed slope can behave in true regime if it satisfies the conditions of constant discharge, uniform flow, constant silt grade & Charge and canal is flowing through incoherent alluvium.

 एक कृत्रिम क्रॉस चैनल जिसमें एक निश्चित क्रॉस सेक्शन और एक निश्चित ढलान होता है, स्थिर चैनल के रूप में व्यवहार करता है। यदि यह निरंतर निर्वहन, एक समान प्रवाह, निरंतर गाद ग्रेड और चार्ज की स्थितियों को संतुष्ट करता है और नहर असंगत जलोढ़ के माध्यम से बह रही है।

Soil Water Relationship

• The water below the water table is known as ground water and above the water table is known as soil – moisture or soil – water.
•  Soil provides the necessary medium the plants to the water through which water gets used by the plants.
•  Soil moisture can be classified as following.

1)      Gravity water

2)      Capillary water

3)      Hygroscopic water

4)      Structural water

1)      Gravity water – Gravitational water is that water which is not held by the soil as this water drains out freely under the action of gravity. गुरुत्वाकर्षण पानी वह पानी है जो मिट्टी द्वारा धारण नहीं किया जाता है क्योंकि यह पानी गुरुत्वाकर्षण की क्रिया के तहत स्वतंत्र रूप से बाहर निकलता है।

2)      Capillary water –

• Capillary water is that water which is retained in the soil.
  केशिका पानी वह पानी है जो मिट्टी में बरकरार रहता है।
• Water is held in the soil by force of surface tension against the force of gravity.
  गुरुत्वाकर्षण बल के विरुद्ध सतह के बल द्वारा मिट्टी में पानी का रुक जाना।
• This water is most beneficial for plant growth.
• It is also known as available water.

3)      Hygroscopic water –

• Hygroscopic water is that water which is absorbed by the particles of dry soil and is held as a very thin film on the surface of particles due to adhesion.
  हाइग्रोस्कोपिक पानी वह पानी है जो सूखी मिट्टी के कणों द्वारा अवशोषित किया जाता है और आसंजन के कारण कणों की सतह पर बहुत पतली फिल्म के रूप में आयोजित किया जाता है।
• It can not removed easily from the soil particles.
• It is not available for plant growth.
• It can be removed only at very high temperature.

4)      Structural water –

• It is that water which is present in the chemical bonds between the molecules.
  यह वह पानी है जो अणुओं के बीच रासायनिक बंध में मौजूद होता है।
• It is not removed but if removed it changes the soil properties.

Basic Definitions –

1. Field Capacity ( F.C ) –

• It is the amount of water content held in the soil after excess water gets drained off due to gravity. यह गुरुत्वाकर्षण के कारण अतिरिक्त पानी के बह जाने के बाद मिट्टी में बची जल की मात्रा है।
• It is expressed the ratio of the weight of water contained in the soil to the weight of dry soil retaining that water.
• In medium textured soils, field capacity is about 50% of pore volume.

      II  Saturation capacity -

• It may be defined as the total water content of soil when 100% of pores are filled with water.
  100% छिद्र पानी से भर जाने पर इसे मिट्टी की कुल जल सामग्री के रूप में परिभाषित किया जा सकता है।
• It is the maximum water holding capacity of soil.

    III  Permanent wilting point/ स्थायी विल्टिंग पॉइंट –

• Water content at which plant is no longer able to extract water from the soil for its growth.
• At PW Pont, films of water are held very tightly and hence plant roots not able to extract sufficient water.

     IV  Available moisture (AM) –

•  AM = F.C – P.W.P

     V    Readily Available moisture (RAM) –

• It is the portion of available moisture which can be most easily extracted by the plants. यह उपलब्ध नमी का हिस्सा है जो पौधों द्वारा सबसे आसानी से निकाला जा सकता है।
• In general, RAM is 75% of the available moisture.

Depth of water stored in root zone of soil (d_w)

Let d be the depth of root zone , dw be the depth of water stored in root zone & Fc be the field capacity.

If we consider 1 m2 area of soil of depth of root zone d.

Volume of soil = d x 1 cubic meter

If the dry unit wt. of soil is ɣ_d  & ɣ_w is unit wt of water

                      Wt. of water retained in soil = ɣ_w x d_w  x 1

Wt. of dry soil having same volume = ɣ_d x d x 1

                         Field capacity (F.C) = (ɣ_w x d_w)/(ɣ_d x d)

                                                    d_w = (ɣ_d x d) x F.C/ ɣ_w

                                                   d_w  = (ɣ_d x d) x (F.C – P.W.P)/ ɣ_w

Irrigation requirements

Consumptive use/ Epavapotranspiration (Cu) –

                 Consumptive use for a particular crop is defined as the total amount of water used by plants in transpiration and evaporation from adjacent soils, in any specified time.

                किसी विशेष फसल के लिए उपभोग का उपयोग किसी भी निर्दिष्ट समय में, निकटवर्ती मिट्टी से वाष्पोत्सर्जन और वाष्पीकरण में पौधों द्वारा उपयोग किए जाने वाले पानी की कुल मात्रा के रूप में परिभाषित किया गया है।

(1)    Consumptive irrigation requirement (C.I.R) - 

• It is water required through irrigation for consumptive use.
  यह जल के माध्यम से सिंचाई के लिए आवश्यक है।
• C.I.R =  Consumptive water requirement – Effective rainfall

(2)          Net Irrigation Requirement ( N.I.R) –

• It is the amount of irrigation water required in the field to meet the needs of consumptive use as well as other requirement such as leaching.
  यह खेत में सिंचाई के लिए आवश्यक पानी की मात्रा का उपयोग करने के साथ-साथ अन्य उपयोग जैसे कि लीचिंग के लिए आवश्यक है।
• N.I.R = C.I.R + Other req/ Leaching Req

(3)          Field Irrigation Requirement (F.I.R) –

• It accounts for losses occurring in the field.
• F.I.R = N.I.R/ Application Efficiency

(4)          Gross Irrigation Requirements (G.I.R) –

• It is the total quantity of water which is required by taking into account conveyance losses.
• G.I.R = F.I.R/ Conveyance Efficiency

Important questions

Q01 Wheat is to be grown in field having field capacity 27% and permanent wilting point is 13%. Find the storage capacity in 80 cm depth of soil, if the dry unit wt of the soil is 1.5 g/cc. If the irrigation water is to be supplied when the average soil moisture falls to 18%, find the water depth required to be supplied to field.

Solution – Given values

                F.C = 27%, P.W.P = 13% , R.A.M = 18% , ɣ_d = 1.5g/cc

                (a) Maximum storage capacity = d_w  = (ɣ_d x d) x (F.C – P.W.P)/ ɣ_w

                                                                                                           d_w  =  (1.5 x 80) x ( 0.27 – 0.13)/1

                                                                       d_w  = 16.8 cm

                (b) Depth of irrigation water required to be supplied to the field

                                                                      d_w  = (ɣ_d x d) x (F.C – R.A.M)/ ɣ_w

                                                                                                        d_w  = (1.5 x 80) x ( 0.27 – 0.18)/1

                                                                      d_w  = 10.8 cm

Q02 Depth of water in root zone at filed capacity and permanent wilting point are 0.5 m & 0.2 m per meter depth of soil respectively. Find the F.C & P.W.P. Take ɣ_d = 13.73 kN/cubic meter.

Solution – Given values

                d = 1 m , d_w1 (at F.C)= 0.5 m , d_w2 (at P.W.P)= 0.2 m

(a)     F.C = Wt. of water retained in root zone corresponding to F.C/ Wt. of dry soil

                        = ɣ_w  x (d_w1 x 1)/ ɣ_d x ( d x 1)

                                 = 9.81 x (0.5 x 1) / 13.73( 1 x1 )

                                 = 0.3573 = 37.52%

(b)  P.W.P = Wt. of water retained in root zone corresponding to P.W.P/ Wt. of dry soil

                        = ɣ_w  x (d_w2 x 1)/ ɣ_d x ( d x 1)

                                 = 9.81 x (0.2 x 1) / 13.73( 1 x1 )

                                = 0.1429 = 14.29%

                      

Water Requirement of crops

Topics

1)      Introduction

2)      Important definitions

3)      Duty, Delta & base period relationship

4)      Crop seasons and  Indian Agriculture

5)      Irrigation Efficiencies

Introduction

• Every crop requires a certain quantity of water after a certain fixed interval thought its period of growth. हर फसल को निश्चित अवधि के बाद पानी की एक निश्चित मात्रा की आवश्यकता होती है।
• In a tropical country like India, the natural rainfall is either insufficient, or the water does not fall regularly. भारत जैसे उष्णकटिबंधीय देश में, प्राकृतिक वर्षा या तो अपर्याप्त है, या पानी नियमित रूप से नहीं गिरता है।
• The area where irrigation is must for agriculture is called Arid region. जिस क्षेत्र में कृषि के लिए सिंचाई होनी चाहिए वह शुष्क क्षेत्र कहलाता है।
• The area in which inferior crops can be grown without irrigation is called semi-arid region.
  जिस क्षेत्र में सिंचाई के बिना निम्न स्तरीय फसलों को उगाया जा सकता है उसे अर्ध-शुष्क क्षेत्र कहा जाता है।
• The term ‘water requirements of a crop’ means the total quantity and way in which a crop requires water, from the time it is shown to the time it is harvested.
  'फसल की पानी की आवश्यकता' शब्द का अर्थ कुल मात्रा और जिस तरह से एक फसल को पानी की आवश्यकता होती है, फसल की बुवाई से लेकर फसल कटाई तक.
• Water requirement, will vary with the crop as well as with place.
  पानी की आवश्यकता, फसल के साथ-साथ जगह के साथ अलग-अलग होगी।

Certain Important Definitions

(1)    Crop Period - The time period that elapses from the instant of its sowing to the instant of its harvesting is called crop period. फसल बुवाई के तुरंत बाद से फसल कटाई के समय तक समय अवधि को फसल अवधि कहा जाता है।

(2) BASE Period –The time between first watering of a crop at the time of its sowing to its last watering before harvesting is called Base period of the crop.
फसल की पहली बुवाई के समय इसकी कटाई से पहले इसकी आखिरी पानी की कटाई के बीच के समय को फसल का आधार काल कहा जाता है।

NOTE-  Crop period is slightly more than base period, but for practical purposes, they are taken same , generally expressed in days and represented by B. 

फसल अवधि आधार अवधि की तुलना में थोड़ा अधिक है, लेकिन व्यावहारिक उद्देश्यों के लिए, उन्हें समान लिया जाता है, आमतौर पर दिनों में व्यक्त किया जाता है और B द्वारा दर्शाया जाता है।

(3) Frequency of irrigation/Rotation period – The time interval between two consecutive watering. सिंचाई की आवृत्ति दो लगातार पानी के बीच का समय अंतराल
कहा जाता है।

• Rotation period is inversely proportional to climatic temperature.

(4) Kor-Watering - The first watering which is given to a crop, when the crop is a few centimeters high is called kor-watering. पहला पानी  जो एक फसल को दिया जाता है, जब फसल कुछ सेंटीमीटर ऊँची होती है उसे कोर-वाटरिंग कहा जाता है।

• Depth of water applied is max.
• Ex. Rice – 19 cm , Wheat – 13.5 cm, Sugarcane – 16.5 cm.

(5) Paleo Irrigation- In the initial stages before the crop is sown, the soil is moistened with water, so as to help in sowing of crops is known as Paleo irrigation.
फसल बोने से पहले शुरुआती चरणों में, मिट्टी को पानी से सिक्त किया जाता है, इसलिए फसलों की बुवाई में मदद करने के लिए पैलियो सिंचाई के रूप में जाना जाता है।

(6)    Crop Ratio – The ratio of proposed areas, to be irrigated in Kharif season to that of Rabi season is called crop ratio/ Kharif – Rabi ratio. खरीफ मौसम तथा रबी मौसम के अनुसार सिंचित होने वाले क्षेत्रों के अनुपात को फसल अनुपात / खरीफ - रबी अनुपात कहा जाता है।

Note- This ratio is generally 1:2 i.e. Kharif area is one-half that of Rabi area.

(7) Delta (∆) – It is the total depth of water required  during its base period for full growth of crop.

(8) Duty (D)– Duty of water is defined as the number of hectares of land irrigated for full growth of a given crop by supply of 1 m³/sec of  water continuously during the entire base period (B) of that crop.
पानी की ड्यूटी को उस फसल की संपूर्ण आधार अवधि (B) के दौरान लगातार 1 m3 /sec पानी की आपूर्ति द्वारा दी गई फसल की पूर्ण वृद्धि के लिए सिंचित भूमि की हेक्टेयर की संख्या के रूप में परिभाषित किया गया है।

Unit of Duty – hectare/ cumec

Relation between Duty, Delta & Base period

                Let there be a crop of base period B days . Let 1 cumec of water be applied to this crop on the field for B days.

                So, volume of water applied during B days

                                                V = discharge x time = (1 x B x 60 x 60 x 24) m³

                                                V = 86,400 B  (m³)

                By the definition of duty (D), one cubic meter supplied for B days matures D hectare of land.

                B total depth of water applied on this land = Volume / Area

                                                                         D = A/ Q                      [ Q = 1 cumec]

                                                                         A = D hectare

                                                                       ∆ = 86,400 x B/ 10⁴ D

                                                                       ∆ = 8.64 B/D (meters)

                                                                                                       ∆ = 864 B/D   ( cm.)

                Where B in days and D is in hectare/ cumec

Different types of Duty

1)      Flow duty    -  at the head of flowing channel 

2)       Storage Duty  - at the head of storage channel

3)       Lift Duty – At the head of lifting channel

Flow Duty

• Duty at the head of flowing channel is known as flow duty.
•  Types of flow duty

• Duty at head of field is called Net Quantity (N.Q) – at sec.4
• Duty at head of water- course is called Outlet Factor (O.F) – at sec 3
• Duty at the head of distributaries/ laterals is called Lateral Quantity (L.Q) – at sec 2
• Duty at head of main canal is called as Gross Quantity (G.Q) – at sec 1

Duty at various places –

• In irrigation system , the water from its source, first of all flows into the main canal ; from main canal it flows into branch canal; from branch canal it flows into distributary ; from the distributary it flows into minor; and then into field channel and finally into the field. सिंचाई प्रणाली में, अपने स्रोत से पानी, सबसे पहले मुख्य नहर में बहता है; मुख्य नहर से यह शाखा नहर में बहती है; शाखा नहर से यह वितरण में बहती है; वितरण से यह छोटे चैनल में बह जाता है; और फिर फील्ड चैनल में और अंत में फील्ड में।
• During passage of water from these irrigation channels, water is lost which are called conveyance losses.
• Duty of water increases as one moves downstream from the head of main canal towards the head of branches  or water courses. पानी की ड्यूटी बढ़ जाती है जब पानी मुख्य नहर से नीचे की ओर बढ़ता है।’
• Note - Duty N.Q>O.F>L.Q>G.Q

Crop Seasons & Indian Agriculture

•  More Than 70% of Indian Population is directly or indirectly connected with agriculture.
• Avg. rainfall in India is about 125 cm.
• From the agriculture point of view, the year is divided into three principal cropping seasons.

(1)    Rabi season –

• This season starts from 1^st October and ends on 31^st March.
• Crops of this season is known as ‘winter crops’.
• Ex. – wheat, barley, gram , linseed, mustered, potato, etc./ गेहूं, जौ, चना, अलसी, सरसों, आलू, आदि।

(2)  Kharif season –

• This season starts from 1^st April and ends on 30^th September.
• Crops of this season is known as ‘summer crops’.
• Ex. – rice, bajra, jowar, maize, cotton, tobacco, groundnut etc./ चावल, बाजरा, ज्वार, मक्का, कपास, तंबाकू, मूंगफली आदि।

(3)  Zaid season –

• Short season between kharif and Rabi crops in month of March to July is known as Zaid.
• Ex. – Seasonal vegetables and fruits etc.

Special type of crop

• Perennial Crops – The crops which require more than one season for their growth
• Ex – Sugarcane, strawberry etc.

               

Important terms-

1)      Gross command area/ सकल कमांड क्षेत्र ( GCA) –

• The total area of land irrigated by a canal if there is unlimited supply of water is available. यदि पानी की असीमित आपूर्ति हो तो नहर द्वारा सिंचित भूमि का कुल क्षेत्र उपलब्ध है।
• It is total Cultivable and non- cultivable area covered by a canal. यह कुल कृषि योग्य और गैर कृषि योग्य क्षेत्र है जो नहर द्वारा कवर किया जाता है ।

2)      Cultivable command area / खेती योग्य कमांड क्षेत्र (CCA) –

• It is the part of GCA on which cultivation is possible.
  यह सकल कमांड क्षेत्र का वह हिस्सा है जिस पर खेती संभव है।
• CCA = GCA – uncultivable areas

3)      Intensity of irrigation ( IOI) –

• It is that part of CCA on which irrigation is done in given period of time. यह खेती योग्य कमांड क्षेत्र का वह हिस्सा है जिस पर सालाना सिंचाई की जाती है।

4)      Total Intensity of irrigation –

• It the intensity of irrigation for whole year
• IOI of rabi season + IOI of kharif season

5)  Optimum water depth –

•  It is the maximum quantity of water for any crop at which crop yield is maximum.
  यह किसी भी फसल के लिए पानी की अधिकतम मात्रा है जिस पर फसल की पैदावार अधिकतम होती है।
• Crop yield increases with water, reaches a certain maximum value and then falls down.

6)  Warabandi System/ वारबंदी सिस्टम -

• It is a rotational water allocation system in which can fulfill the requirement of equality. यह एक घूर्णी जल आवंटन प्रणाली है जिसमें समानता की आवश्यकता को पूरा किया जा सकता है।

7)  Capacity Factor -

• It  is the ratio of actual  discharge  in canal to design discharge of canal. यह नहर के डिस्चार्ज को डिजाइन करने के लिए नहर में वास्तविक निर्वहन का अनुपात है।

Irrigation Efficiencies

• Efficiency is the ratio of the water output to the water input, is usually expressed as percentage.
• Efficiency is inversely proportional to the losses.
• Different Irrigation efficiencies are -

1. Water Conveyance Efficiency
2. Water Application Efficiency
3. Efficiency of water use
4. Water Storage Efficiency
5. Water Distribution Efficiency

I) Water Conveyance Efficiencies / जल संवहन क्षमता (η_c )

• It is the ratio of  the water delivered  into the fields to the water entering into the channel at its starting point. यह अपने आरंभिक बिंदु पर चैनल में प्रवेश करने वाले पानी में खेतों में वितरित पानी का अनुपात है
• It takes conveyance losses into consideration.                                                                                       

II) Water Application  Efficiencies/ जल अनुप्रयोग दक्षता (η_a )

• It is the ratio of the water stored into the root zone of crops to the water delivered into the field. यह फसलों के जड़ क्षेत्र में जमा पानी का अनुपात है जो पानी को खेत में पहुंचाता है।
• Also called farm efficiency,
•  It takes into consideration the water lost in the farm. 

III Efficiency of water use / पानी के उपयोग की क्षमता (η_u )

• It is the ratio of the water beneficially used by plant to the water delivered into the field. यह पौधे द्वारा पानी के लिए इस्तेमाल किए गए पानी का अनुपात है जो खेत में पहुँचाया जाता है।

IV) Water Storage Efficiency/ जल संग्रहण क्षमता(η_s)

• It is the ratio of the water stored in the root zone during irrigation to the water needed in to the root zone prior to irrigation. यह सिंचाई से पहले रूट ज़ोन के लिए आवश्यक पानी को सिंचाई के दौरान रूट ज़ोन में संग्रहीत पानी का अनुपात है।

IV) Water Distribution Efficiency/ जल वितरण क्षमता(η_d)

• This efficiency represents the extent to which the water has penetrated to a uniform depth, thought the field. यह क्षेत्र में क्षेत्र के माध्यम से जड़ क्षेत्र में समान रूप से पानी के प्रवेश की डिग्री का मूल्यांकन करता है।

    Important questions       

                                                

Q01  The base period of paddy is 120 days. If the duty for this crop is 900 hectare per cumec, the delta of paddy is.

a)      1.15 cm                                 

b)      11.5 cm

c)       115 cm

d)      None

Q02 If delta of wheat is 36 cm and its base period is 140 days then the outlet factor at the head of field is?

a)      3.360 ha/cumec

b)      33.6 ha/cumec

c)       336 ha/cumec

d)      3360 ha/cumec

Q03 Transplantation of rice requires 10 days and total depth of water required during transplantation is 48 cm. During transplantation there is an effective rainfall of 8 cm. The duty of irrigation water in hectare/cumecs is?

a)      612

b)      216

c)       300

d)      108

 Q04 A canal was designed to supply the irrigation needs of 1200 hectares of land growing rice of 140     days base period having a delta of 134 cm. If this canal water is used to irrigate wheat of base period 120 days having a delta of 52 cm, the area in hectares that can be irrigated is?

a)      543

b)      850

c)       2650

d)      3608

Q05 The culturable command area for a distributary is 400 hectares out of which 40% is culturable, if intensity of  winter crop is 60% , then area under crop is?

a)      240 hectares

b)      160 hectares

c)       136 hectares

d)      96 hectares

Q06 The culturable command area for a distributary is 20,000 hectares. Wheat is grown in the entire area and the intensity of irrigation is 50%. The kor period for wheat is 30 days and kor depth is 120 mm. The outlet discharge for distributary should be in cumecs?

a)      2.85

b)      3.21

c)       4.63

d)      5.23

Q07 In an irrigation project, in a certain year , 70% and 46% of the culturable command area in kharif and Rabi, respectively, remained without water and rest of the area got irrigation water. The intensity of irrigation in that year for project was?

a)      30%

b)      54%

c)       84%

d)      116%

Q08 The gross command area for a distributary is 5000 hectares, 80% of which is culturable. The intensity of irrigation for Rabi is 50% and for Kharif is 30%. The average duty at the head of the distributary for Rabi season is 2000 hectares/cumec and that of Kharif season is 900 hectare/cumec. The discharge ( in cumec )required at the head of distributary is?

a)      1

b)      1.33

c)       2.33

d)      3.33

Q09 One cumec of water is pupmed into a farm distributio system. 0.8 cumec is delivered to from outlet 1 km from well. Conveyance efficiency of irrigation is?

a)      70%

b)      80%

c)       85%

d)      90%

Q10 A field measures 40 hectares. When 8 cumecs of water was supplied for 6 hours, 30 cm of depth was stored in the root zone. The field app;ication efficiency is nearly?

a)      70%

b)      80%

c)       85%

d)      90%

Q11 One cumec of water is pupmed into a farm distributio system. 0.8 cumec is delivered to from outlet 1 km from well. The depth of water penetration varied linearly from 1.7 m at the head end of field and 1.1 m at the tail end. The water distribution efficiency of irrigation is?

a)      58%

b)      68%

c)       78%

d)      88%