Contents preface (VII) introduction 1—37

Example 5.4 Determine the location of closed tile drains below ground for the following
data:

Root zone depth	= 1.5 m
Capillary rise in soil	= 0.3 m
Coefficient of permeability of soil	= 1.5 × 10^–4 m/s
Drainage capacity	= 0.11 m^3/s/km^2
Spacing of drains	= 200 m
Depth of impervious stratum below ground	= 10.0 m
Solution:
From Eq. (5.29)

q	=	4k [(H + d)^2	− d^2 ]
B
		d

224				IRRIGATION AND WATER RESOURCES ENGINEERING
where	q = 0.11 × 200 × 1/10^6 m^3/s/m
	d
	H + d = 10 – (1.5 + 0.3) m
			= 8.2 m
	B = 200 m
and	k = 1.5 × 10^–4 m/s
∴	0.11 × 200		= 4 × 1.5 × 10 ^−^4 [(8.2) ^2 − d^2 ]
	10^6
			200

d = 7.74 m
Hence, the drains should be located at 10 – 7.74 = 2.26 m below the ground.

EXERCISES

1. 
   Write a brief note on the planning of canal alignments.
   

2. 
   What is meant by the ‘duty’ of canal water ? Obtain an expression for ‘duty’ in terms of water depth. Distinguish between ‘duty’ and ‘outlet discharge factor’.
   

3. 
   Describe different types of outlets mentioning their suitability for different sets of field condi-tions.
   

4. 
   In what possible ways can irrigation water be delivered to various farms once it has been brought up to the watercourse ? Discuss the salient features of these methods.
   

5. 
   How is water distribution managed in the warabandi system?
   

6. 
   What are the causes of waterlogging ? How can a waterlogged land be made useful for cultiva-tion?
   

7. 
   An outlet is required to serve 6000 ha of CCA. Determine the discharge for which the outlet should be designed for the following data:
   

	Wheat	Rice
Intensity of irrigation	20%	10%
Kor period	3 weeks	2 weeks
Kor water depth	90 mm	250 mm

8. 
   An outlet has a gross command area of 500 ha out of which only 80 per cent is culturable. The intensity of irrigation for the Rabi season is 65 per cent while it is 30 per cent for the Kharif season. Assuming losses in the conveyance system as 6 per cent of the outlet discharge, deter-mine the discharge at the head of the irrigation channel. Assume outlet discharge factor for Rabi season as 1500 ha/m³/s and for the Kharif season as 800 ha/m³/s.
   

8. 
   The maximum discharge available at an outlet of an irrigation channel is 1.33 m³/s. The culturable command area for the outlet is 8000 ha. What percentage of this area can be irrigated for wheat if the kor period is 3 weeks and the kor water depth is 13.5 cm?
   

8. 
   Closed drains at a spacing of 16 m are located 2 m below the ground surface and the position of
   

the water table is 1.7 m below the ground surface. Find the discharge carried by a drain if the coefficient of permeability of the soil is 2 × 10^–2 cm/s and the depth of the pervious stratum is 8 m.

REFERENCES

1. 
   Bharat Singh, Fundamentals of Irrigation Engineering, Nem Chand and Bros., 1988.
   

2. 
   Etchevery, BA, and ST Harding, Irrigation Practice and Engineering, McGraw-Hill Book Co., 1933.
   

CANAL IRRIGATION	225
3. ...... IS 7986-1976, Code of Practice for Canal Outlets.

4. 
   Malhotra, SP, The Warabandi System and its Infrastructure, ‘CBIP Publication No. 157, April, 1982.
   

4. 
   Ranga Raju, KG and GL Asawa, Viscosity and Surface Tension Effects on Weir Flow, J. of Hy-draulics Division, Proc. ASCE, Oct. 1977.
   

4. 
   Rnaga Raju, KG and GL Asawa, Comprehensive Weir Discharge Formulae, Proc. of IMEKO Sym-posium on Flow Measurement and Control in Industry, Tokyo, Japan, Nov. 1979.
   

4. 
   Range Raju, KG, R Srivastava and PD Porey, Scale Effects in Modelling of Flow over Broad-Crested Weirs, CBIP J. of Irrigation and Power, July 1992.
   

4. 
   Ranga Raju, KG, GL Asawa, SK Gupta and SJ Sahsrabudhe, Submerged Broad-Crested Weirs, Proc. of IMEKO Symposium on Flow Measurement of Fluids, Groningen, The Netherlands, Sept. 1978.
   

4. 
   Ackers, P, WR White, JA Perkins and AJM Harrison, Weirs and Flumes for Flow Measurement, John Wiley and Sons, 1978.
   

4. 
   Parshall, RL, Discussion of Measurement of Debris-Laden Stream Flow with Critical Depth Flumes, Trans. ASCE, Vol. 103, 1938.
   

4. 
   Parshall, RL, Measuring Water in Irrigation Channels with Parshall Flumes and Small Weirs, Soil Conservation Circular No. 843, US Department of Agriculture, May 1950.
   

4. 
   Parshall, RL, Parshall Flumes of Large Size, Bulletin 426A, Colorado Agricultural Experimental Station, Colorado State University, March 1953.
   

4. 
   Hansen, VE, OW Israelson and GE Stringham, Irrigation Principles and Practices, John Wiley & Sons, USA, 1987.
   

14. ......, I.S. 3873-1987, Code of Practice for Laying in-situ Cement Concrete Lining on Canals. 15. ...... IS 5331-1969, Guide for Selection of Type of Linings for Canals.

16. ...... IS 7873-1975, Code of Practice for Lime concrete Lining for Canals. 17. ...... IS 4515-1967, Code of Practice for Boulder Lining for Canals.
18. ...... IS 7113-1973, Code of Practice for Soil-Cement Lining for Canals.

19. 
    Luthin, J.N., Drainage Engineering, John Wiley & Sons, U.S.A., 1966.
    

19. 
    Prasad, RS, Integration of Drainage, Flood Control, and Water Management in Alluvial Plains in India, Proc. of 8^th ICID International Drainage Workshop held at New Delhi, 2000.