Serial : 01. SK_J+B_CE_Irrigation_090918 CLASS TEST (GATE) Delhi Noida Bhopal Hyderabad Jaipur Lucknow Indore Pune Bhubaneswar Kolkata Patna Web: E-mail: info@madeeasy.in Ph: 011-451461 CLASS TEST 018-19 CIVIL ENGINEERING Subject : Irrigation Date of test : 09/09/018 Answer Key 1. (c) 7. (c) 1. (b) 19. (a) 5. (b). (d) 8. (d) 14. (c) 0. (a) 6. (a). (d) 9. (a) 15. (d) 1. (c) 7. (c) 4. (b) 10. (a) 16. (a). (b) 8. (b) 5. (c) 11. (b) 17. (a). (a) 9. (c) 6. (d) 1. (c) 18. (a) 4. (a) 0. (d)
CT-018 CE Irrigation 7 Detailed Explanations. (d) Water depth required at canal Volume of water required for 10 hectare (10 10 4 m ) field Water depth required in the field η η a c 10 1.89 cm 0.8 0.9 4. (b) Scour depth 1.89 105 m 1,890 m 1,890 kl 1/ 1/ q 1.5 1.5.64m f 1. 5. (c) Required discharge (mean) in the field 0.4 cumecs 6. (d) Peak discharge required mean discharge 0.4 0.5cumecs capacity factor 0.8 Design discharge for distributary Required discharge for crops 0.5 1 cumecs Time factor 0.5 15 5 60 60 Water depth applied to fields 0.7714 m 4 5 10 Water depth actually stored in root zone 0.4 m Water application efficiency, η a 0.4 51.85% 0.7714 7. (c) d max 11RS 0 Where, R By y B+ y [ B y] d max 11(0.75) 0.008 0.015 m 1.5 mm 8. (d) The discharge (Q) in canal remains the same. Duty for rice, D 1 150 ha/cumec Q Duty for wheat, D A Q ha/cumec
8 Civil Engineering D Now 1 1 B1 A B or 1 1 1 D B A B A 1 140 150 58 ha 150 60 9. (a) Gross commanded area (G.C.A) 6000 ha Culturable commanded area (C.C.A.) G.C.A. Area reserved for forests and roads 0 6000 6000 4800ha Pastures and fallow lands are included in culturable commanded area. So, it will be a part of culturable commanded area. Area to be irrigated Intensity of irrigation CCA 60 4800 880ha 10. (a) Given, B days; D 178 ha/cumec Delta, 8.64 B D 8.64 0.5m 50 cm 178 11. (b) The limiting height of a low concrete gravity dam without considering uplift force is given by f H max γ w ( G + 1) 4.16 10 1.915 m 9.81(.45 + 1) 1. (c) Depth of water required in the field during transplantation 600 mm Useful rainfall during this period 150 mm Depth of water required to be supplied by the water course (600 150) 450 mm 0.45 m D 8.64B Duty of water on the field is 8.64 0 D 0.45 84 hectares/cumec Since the losses of water in the water course are 5%, a discharge of 1 cumec at the head of the water course will be reduced to 0.75 cumec at the head of the field, and hence will irrigate
CT-018 CE Irrigation 9 84 0.75 88 hectares Duty of water at the head of the water course 88 hectares/cumec Total area under rice plantation 0.75 900 hectares Discharge at the head of water course 900.15 cumec.1 cumec 88 1. (b) From the figure tanθ 1 1.5 θ 0.588 radians.69 A y (θ + cot θ).4 (0.588 + 1.5) 1.0 m V 8 1.0.8 m/sec. m/sec 1.5 θ 1.4 m 14. (c) The deficiency created due to fall of moisture from 5% to 17% is 16 75 (0.5 0.17) 0.0979 m 9.81 So, 0.0979 m is the net irrigation requirement. Quantity of water required to be supplied to the field irrigation requirement is FIR NIR η a 0.0979 0.105 m 1.05 cm 0.75 15. (d) where, H 1 G E d π λ H Total head 1.5 m 1+ 1+ α λ d Depth of d/s cutoff m α λ b 1 6.5 d 1+ 1+ 6.5 1.5 1 G E π.79 G E 0.1 0.1.79
10 Civil Engineering 16. (a) 17. (a) Total available moisture holding capacity of soil (in terms of depth, mm) 1.5 0.8 10 cm mm 50 Moisture which must be added to the soil through irrigation 50mm Moisture added 50mm Frequency of irrigation 10days Consumptive use 5mm/day 18. (a) For no scouring, d 11 RS d or R max 11 S V but, N V 1 R / S 1/ N 1/6 ( d) 4 4 1/ 6 R S d / 1/ (Strickler's formula) V max 4 1/ 6 R S d / 1/ max 4 d 1/ V max S 1/ 6 d 11S 4.85 d 1/ S 1/6 (where d is in m) when d is in cm i.e. d cm, then dcm d 1/ dcm 1/6 V max 4.85 S V max 0.485 d 1/ S 1/6 / 19. (a) Discharge required for crop x Area under crop x 0.0 000 0.91m /s Duty for crop x 0 8.64 17.5 Area under crop y 0.4 000 Discharge required for y 0.8m /s Duty for crop y 15 8.64 9 Total discharge (0.91 + 0.8) 1.74 m /s 0. (a) 1. (c) Culturable command area 5 75 10 75000 hectares
CT-018 CE Irrigation 11 50 for Kharif crop, Area under Kharif crop 75000 7500hectares Duty for Kharif crop hectares/cumecs Required discharge for Kharif crop 7500 1.5cumecs 55 for Rabi crop, Area under Rabi crop 75000 4150hectares Duty for Rabi crop 1400 hectares/cumecs Required discharge for Rabi crop 4150 9.46 cumecs 1400 Discharge of the canal at the head of the field should be 1.5 cumecs (as it is maximum). Now, considering 0% provision for losses, Required discharge at the head of canal 1.5 /0.8 9.06 cumecs. (b) Given: H m S c. C 0.75 Case (i): No Tension H B min Sc C Case (ii): No sliding H B min µ c Note: µ is not given so solve by case (i), B min ( S C). 0.75 80.m. (a) Volume of total water applied 750 m Volume of water got wasted 1% of 750 m 90 m Water used in raising moisture content up to field capacity 750 90 660 m Depth of water used in raising moisture content up to field capacity from the existing 10% 4. (a) 660 0.44 m 1500 But water depth required in root zone to increase moisture content of soil to field capacity is given by, 1.47 0.44 1.75 [ F.C 0.1 ] 1 FC 0.710 Hence, field capacity 7.10% H 1 Exit gradient, G E d π λ H 6.5 m b 60 m d 6.5 m
1 Civil Engineering where λ and α 1+ 1+α b 60 9. d 6.5 λ 1+ 1+ 9. 5.14 6.5 1 G E 0.1407 0.14 6.5 π 5.14 5. (b) 6. (a) Given, Initial bulk unit weight, γ 1 0.4 kn/m Water content, w 1 0% 0.0 Dry unit weight, γ d1 Final bulk unit weight, γ 18.7 kn/m γ1 0.4 17kN/m 1+ w 1+ 0.0 1 Gγw γ d 1 + e G and γ w are similar for a particular type of soil. So, if e remains unchanged, γ d will also remain unchanged. Hence, γ d d 1 γ 17kN/m γ d γ 1+ w 7. (c) 18.7 17 1 w 1.1 w 0.1 10% 1+ w + water depth requied in the field Water depth required at canal η η a. c 8 1.77 cm 0.7 0.87 Volume of water required 8 10 4 1.77 10 1016 kl 8. (b) According to Bligh s creep theory, the total creep length is given by L ( 5) + ( ) + 5 + ( 10) 61 m
CT-018 CE Irrigation 1 Length of creep upto point A ( 5) + ( )+10 6 m Residual seepage head at point A is 6 h A 5 1.87 m 61 Required thickness of floor at point A 9. (c) 4 ha 4.87 or t (G 1) (.5 1) 4.87.55 m 1.5 1 θ r y.5 m r θ 1.5 B 5 m For a lined trapezoidal channel, corners are rounded, due to which A and P are computed by the following equations A y(b + y θ + y cot θ) P B + y θ + y cot θ Here for 1.5 (H) : 1 (V) side slope, we have tan θ 1 1.5 cot θ 1.5, θ 0.588 radians y.5 m, B 5 m A.5 (5 +.5 0.588 +.5 1.5) 5.55 sq.m P (5 +.5 0.588 +.5 1.5) 15.44 m R A 5.55 1.655 P 15.44 Q 1 A R / S n 1 / 1 5.55(1.655) 70.65 m /s 0.016 0 During kor period of 10 days, volume of water which can be supplied by the channel 70.65 (10 4 60 60) m 61.0416 10 6 m Area which can be irrigated (A) Depth of water required Volume of water available A 0.15 m 61.0416 10 6 m or A 6 61.0416 10 m 406.944 10 6 m 406.94 sq. km 0.15
14 Civil Engineering 0. (d) Depth of water in root zone at field capacity per metre depth of soil, d w1 0.5 m Depth of water in root zone at permanent wilting point per metre depth of soil, d w 0. m Depth of soil, d 1 m, γ d 1.5 kn/m γ w 10 kn/m Field capacity γ w dw1 10 0.5 0.40 40% γ d 1.5 1 d Permanent wilting point Field capacity 0. 0.16 16% 0.5