Introduction to irrigation

Introduction to irrigation

1. Programme - Civil Engineering Course - Water Resource Engineering Code - 22501 Lecture - 2 Unit Outcome – 1h(i) :Compute the maximum flood discharge using the relevant method from the given data

2. UNIT – I : INTRODUCTION TO IRRIGATION AND HYDROLOGY CO – 1 : Estimate hydrological parameters. 04 JULY 2020 Mr. N . H. Telang Sr. Lecturer , Civil Engineering, G. P., Gadchiroli

3. Sub-Topics: Maximum flood discharge Methods of calculating maximum flood discharge 04 JULY 2020

4. UO – 1h(i) : Compute the maximum flood discharge using the relevant method from the given data

5. Content: 1.Maximum Flood Discharge Measurement: Rational Method and Empirical Methods 2. Simple Numerical Problems

6. Concept Map Flood Maximum Flood Discharge Runoff (surface & Subsurface) Discharge Dickens formula Empirical Formulae Formula involving rainfall intensity and drainage area Ryve’s formula Boston Society of Civil Engineers Inglis formula Involving drainage area only Involving drainage area & its shape Design of Water Retaining structure (Dams, Spillways, Barrages etc.) Involving drainage area variables Nawab Jangbahadur formula Jarvis formula Modified Myers formula Involving drainage area only

7. 1.6 Maximum flood discharge Maximum flood discharge MFD is the maximum discharge of river during flood. The maximum concentration of flow from a catchment area at the outlet in a small period. It is very important to estimate it accurately as it is the basis of the design of spillway. It is expressed as volume per unit time i.e. cumec (m 3 /s)

8. Maximum flood discharge measurement

9. Maximum flood discharge measurement Methods of calculating maximum flood discharge a) Rational method Where, Q = Peak flow in cumec ; i = Rainfall intensity in cm/ hr A = catchment area in hectares; K = runoff coefficient  

10. Maximum flood discharge measurement b) Empirical Formulae i ) Dicken’s formula Q = C x A ¾ Where, Q = Discharge in cumec A = catchment area in sq.Km C = A constant value considered as Region Value of C Northern India 11.4 Central India 13.9 to 19.5 Western India 22.2 to 25

11. Maximum flood discharge measurement ii) Ryve’s formula Q = C x A 2/3 Where, Q = Discharge in cumec A = catchment area in sq.Km C = A constant value considered as 6.8 iii ) Inglis formula Where , Q = Discharge in cumec A = catchment area in sq.Km  

12. Maximum flood discharge measurement iv) Nawab Jung Bahadur formula – Q = C A’ ( 0.92-1/14 log A ) Where, Q = Discharge in cumec A = catchment area in sq.Km C = A constant varies from 48 to 60 A’ = 0.39A

13. Numericals Ex 1 . Estimate MFD for a catchment of a proposed reservoir of 245 km 2 in western Maharashtra using Inglis formula. Ans : Given Data, Catchment area A = 245km 2 MFD = ? By Inglis formula = 1886.239 m 3 /sec ( Ans )  

14. Numericals 2. Calculate the maximum flood discharge for a catchment area 1500km 2 using Dicken’s formula. Assume Dicken’s coefficient as 28. Ans : Given Data, Catchment area A = 1500km 2 Dickens constant C = 28 MFD = ? By Dickens’ formula Q = C x A ¾ = 28 x 1500 ¾ = 6748.799 m 3 /sec ( Ans )

15. Numericals 3. Compute the MFD of a stream over a catchment area of 150 km 2 using: ( i ) Dicken’s formula (C = 27) (ii) Inglis formula. Ans : Given Data, Catchment area A = 150km 2 Dickens constant C = 27 MFD =? ( i ) By Dickens’ formula : (ii) By Inglis formula Q = C x A ¾ = 27 x 150 ¾ = 1157.263 m 3 /sec ( Ans ) = 1457.508 m 3 /sec ( Ans )  

16. Summary Today we learnt Maximum flood discharge Various methods of calculating MFD Numerical on MFD