This document discusses various concepts related to water resource engineering. It covers topics like precipitation, runoff, infiltration, evaporation and evapotranspiration. It describes different methods to measure these parameters, like using infiltration tests, pan evaporation, empirical equations and water or energy budget methods. Factors affecting each process are also listed. Various formulas to calculate runoff, evaporation and infiltration rate are presented.

1. WATER RESOURES ENGINEERING -I
Presented By
Srikanth Samudrala
Department of CIVIL ENGINEERING
KAMALA INSTITUTE OF TECHNOLOGY AND SCINCE, SINGAPUR

2.  Precipitation – Surface runoff= Total loss
 Run off
 Total loss= Interception + Transpiration
+Infiltration +Depression storage
+Watershed leakage + Evaporation

3.  Run off measured by
 Centimeters of water over a catchment
 Total water in cubic meter
 Run off classified into three types
i. Surface runoff
ii. Sub-surface runoff
iii. Base flow

5. 1. Precipitation characteristics
2. Shape and size of the catchment
3. Topography
4. Geological characteristics
5. Meteorological characteristics
6. Character of the catchment surface
7. Storage characteristics

6. 1) By linear or exponential regression
2) By empirical equation and tables
3) By infiltration method
4) By unit hydrograph
5) By rational method

7. a. Straight line regression between P and R
R=aP+b
a & b are the constants representing abstractions.
𝑎 =
𝑁 𝞢𝑃. 𝑅 − (𝞢𝑃)(𝞢𝑅)
𝑁 𝞢𝑃2 − (𝞢𝑃)2
b=
𝞢𝑅−𝑎𝞢𝑃
𝞢𝑁
b. Exponential regression between P and R
R=β𝑃 𝑚
β and m are the constants
log 𝑒 𝑅 = mlog 𝑒 𝑃 + log 𝑒 β

8. a. Runoff coefficient
b. Strange’s table and curves
c. Inglis’s formula

9. d. Lacey’s formula
e. Khosla’s formula
f. ICAR formula

10.  Evaporation is defined as the process of a
liquid changing into a gas

12. 1. Nature of evaporating surface
2. Area of water surface
3. Depth of water in water body
4. Humidity
5. Wind velocity
6. Temperature of air
7. Atmospheric pressure
8. Quality of water

14. 1. Measurements using evaporation pans
2. Use of empirical equations
3. Water budget method
4. Energy budget method

15.  E = u ( es-ea )
E= Evaporation loss (mm/day)
u: function of wind speed,
u=a+vb
a, b are constants
ea : current vapor pressure of the air above
es : saturation vapor pressure at the water surface
temperature

16.  Types:
◦ Livingstone atmometer
◦ Piche Atmometer

17.  Pan evaporation is a measurement that combines or
integrates the effects of several climate elements:
temperature, humidity, rain fall, drought dispersion, solar
radiation, and wind

18.  ISI Standard Pan
◦ Specified by IS:5973 and known as the modified
Class A Pan
◦ A pan of diameter 1220mm and depth 255mm
◦ The pan is made of copper sheet 0.9mm thick,
tinned inside and painted white outside
◦ The pan is placed on a square wooden platform of
width 1225mm and height 100mm above ground
level to allow free air circulation below the pan
◦ A fixed point gauge indicates the level of water

20.  Class A Evaporation Pan

22.  A square pan of 900mm sides and 450mm
deep
 Supported by drum floats in the middle of a
raft of size 4.25m x 4.87m, it is set afloat in
a lake with a view to simulate the
characteristics of a large body of water
 Water level in the pan is maintained at the
same level as that in the lake, leaving a rim of
75mm

24.  Lake evaporation =pan coefficient*pan
evaporation
◦ pan coefficient =
Lake evaporation
pan evaporation
Sl. No. Types of Pan Average Value Range
1 Class A Land Pan 0.70 0.60 – 0.80
2 ISI Pan (Modified Class A) 0.80 0.65 – 1.10
3 Colorado Sunken Pan 0.78 0.75 – 0.86
4 USGS Floating Pan 0.80 0.70 – 0.82

25.  WMO recommends the following values of
minimum density of evaporimeters
◦ Arid Zones – 1 station for every 30,000 sq.km
◦ Humid Temperate Zones – 1 station for every
50,000 sq.km
◦ Cold regions – 1 station for every 1,00,000 sq.km

26. (1) Meyer’s Formula

27. The wind velocity assumed to the 1/7 power law
𝑉ℎ = 𝐶ℎ(
1
7
)
𝑉ℎ1
𝑉ℎ2
=
ℎ1
ℎ2
(
1
7
)

29. Surface runoff -
Subsurface
runoff
Inflow-
Outflow-
Evaporation- E
surface losses
Precipitation -
P

30.  Hn = Ha + He + Hg + Hs + Hi
Where, Hn = net heat energy received by the water surface
= Hc (1- r) - Hb
Hc (1 – r) = incoming solar radiation into a surface of reflection coefficient
(albedo) r
Hb = back radiation (long wave) from water body
Ha = sensible heat transfer from water surface to air
He = heat energy used up in evaporation = ρ L E
where ρ = density of water
L = latent heat of evaporation and
E = evaporation in mm
Hg = heat flux into the ground
Hs = heat stored in water body
Hi = net heat conducted out of the system by water flow (advected energy)

31.  The sensible heat term Ha can be estimated
by using Bowen’s ratio by the following
expression

33. The process by which water vapour escapes
from the living plant , principally through the
leaves and enters the atmosphere
Air enters and water exit through Stomata

34.  a) Temperature;
 b) Solar Radiation;
 c) Wind;
 d) Soil Moisture;
 e) Plant type

35.  Use of empirical equations
 WBM
 EBM
 By field experiments
Potometer
Lysimeter

36.  combination of evaporation and transpiration =
consumptive use = Evapotranspiration (ET)
 The process by which water is evaporated from
wet surface and transpired from plants, i.e.
sum of evaporation and transpiration.
Potential Evapotranspiration (PET)
 The evapotranspiration (ET) that would occur if
there was an adequate soil-moisture supply at
all time.
Evapotranspiration

37. 𝑐 𝑢 = 𝑘. 𝑓

45. The downward movement of water from soil surface, into
the soil mass through the pores of the soil.

46. 1. Condition of entry surface
2. Permeable characteristics of soil
3. Moisture conditions in soil
4. Temperature
5. Intensity and duration of rainfall
6. Movement of man and animals
7. Human activities
8. Quality of water
9. Presence of ground water table
10. Size and characteristics of soil particles
11. Catchment parameters

48. Infiltration by Horton’s method

50.   kt
cc effff 
 0

51.  Single tube(ring) infiltrometer
 Double tube(ring) infiltrometer

52. Single Ring Double Ring

53. 1. Average infiltration rate or W-index
Run off coefficient ‘k’