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# CE-235 EH Lec 1

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• assalamualaikum
i am Thailand
Thak u Brother
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• I think that change in storage will be 200ha-cm.
leading to the answer of Loss=418.4hec-cm or 4.184hec-m
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• wa alikum salam dear brother.
The sequence of the solution is as follows.
but I think that you should verify the data again.

Area=600*1000 %1hec=1000 sq m
Time=24*30*24*60*60 %in seconds taking 30 days per month
Rain_fall=100 %cm or hec-cm
I_O=5-4.5 %cubic meter per second
I_O=0.5*Time %in cubic meter
I_O=(0.5*Time)*100/(600*10000) %in hec-cm
deltaS=200 %in hec-cm
Loss=(I_O)+Rain_fall-deltaS %in hec-cm

for hec-m
divide the loss by 100
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• Hello Salaam Alaykum
Could you help me solving this calculation,I am a bit confused because I have little back ground o hydrology:
A 600 ha reservoir receives 100 cm of rainfall during 24 months. During this time, the mean inflow to the reservoir is 5 cumec and mean outflow from reservoir is 4.5 cumec, and an increase in storage is 200 ha-m. Compute Evapotraspiration loss in ha-m as well in cm.
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• 1. NUST Institute of Civil Engineering/Engr Sajjad Ahmad
1
• 2. Engineering Hydrology(CE- 235)
CHAPTER - I
2
INTRODUCTION
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• HYDROLOGY
Hydrology is the science of the waters of the earth and atmosphere.
It deals with
• Occurrence
• 3. Circulation
• 4. Distribution and
• 5. Movements of these waters over the globe
3
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• ENGINEERING HYDROLOGY
Engineering Hydrology deals with:-
• Estimation and analysis of water resources
• 6. The study of processes such as precipitation, runoff, evapotranspiration
• 7. The study of hydrologic problems such as floods and droughts, and strategies to combat them
4
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• Importance of Hydrology in Civil Engineering
It has an important role in design and operation of water resources engineering projects like
Irrigation
Flood control
Water supply schemes
Hydropower projects
Navigation
5
Engineering Hydrology(CE- 235)
These Civil Engineering projects may fail due to improper Assessment of Hydrologic Aspect
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• 6
Engineering Hydrology(CE- 235)
Vs
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• SCOPE
Essential for analysis, design and operation of any hydraulic structure which retains or conveys water (from the simplest culvert to the largest complex of dams, hydroelectric works, barrages and irrigation structures)
Designer needs magnitude of stream flow and their probability of occurrence not only for design of hydraulic structures but also for flood control
Combating the menace of water-logging and salinity in irrigated areas
7
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• SCOPE
Predicting relationship between characteristics of a basin and rate of flow
Probability of occurrence of floods and droughts
Water availability into the reservoir from the basin
Effect of rainfall occurring in basin on the magnitude of flow in streams and predict rainfall-runoff relationship of the basin and probability of its occurrence
8
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• SCOPE
Probable flood flow over a spillway, at a highway culvert or in urban storm drainage system
Reservoir capacity sizing required to assure adequate water for irrigation, hydropower or municipal water supply during droughts
Effect of reservoir, levees and other control works on flood flows in stream
Assessment of reasonable boundaries of floodplain
9
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• MAJOR ASPECTS OF HYDROLOGY
The main jobs of a hydrologist are
Collection of data
Analysis of data
prediction
10
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• COLLECTION OF DATA
• Rainfall Data
• 8. Snowfall and Snowmelt Data
• 9. Runoff Data (Catchment Runoff and Stream Flows)
• 10. Topographic Maps, Satellite Imageries, and
• 11. Groundwater Data
11
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• ANALYSIS OF DATA
Analysis of hydrologic data includes
Checking the data for
Consistency and
Homogeneity
Finding of various statistical parameters
12
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• PREDICTION
Based upon the analysis followings can be predicted
Design values
Maximum possible flood
Maximum outflows from catchments
13
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• DISTRIBUTION OF EARTH’S WATER
14
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• HYDROLOGIC CYCLE
The earth’s water circulatory system is known as Hydrologic Cycle
Total water supply of earth is in constant circulation from earth to atmosphere, and back to earth
15
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• 16
Engineering Hydrology(CE- 235)
Atmospheric phase
Land phase
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• 17
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• 18
Evaporation
Evaporation
Interflow
Runoff = Streamflow
Volcanic outgassing
Infiltration
drainage
Gravity
Groundwater flow
and Baseflow
Subsea outflow
Subduction
Seafloor
vents
Vapor
Flow
Liquid
Atmosphere
The Hydrologic Cycle
(water vapor)
Flow
Precipitation
Evapotranspiration
( ) =
Storage
surface
Land
Streams
Oceans
Lakes
Surface
etc.
(Ice, snow,
depression
storage)
Overland flow =
Compartmentalized
Hydrologic
Cycle
Direct Runoff
(Seawater)
(Surface water)
Infiltration
Vadose Zone
(Soil moisture)
Water Table
NUST Institute of Civil Engineering/Engr Sajjad Ahmad
(Ground water)
• 12. PROCESSES OF HYDROLOGIC CYCLE
Precipitation
Fall of moisture from the atmosphere to earth surface. Precipitation may be:-
Liquid precipitation
Frozen precipitation
Evaporation and Transpiration
Surface Evaporation
Water Surface Evaporation
Plants/Leaves Evaporation (Transpiration)
19
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• PROCESSES OF HYDROLOGIC CYCLE
Runoff
Portion of precipitation that is not evaporated is known as runoff, which ultimately runs to ocean through surface or sub-surface streams. Runoff may be classified as:-
Surface runoff
Interflow or subsurface runoff
Groundwater or base flow
20
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• PROCESSES OF HYDROLOGIC CYCLE
Infiltration
Precipitation falling on the ground, is to some extent, absorbed by the land. This absorption of precipitation water by land from the surface of earth is called infiltration.
21
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• PROCESSES OF HYDROLOGIC CYCLE
Interception
A part of the precipitation is obstructed by vegetation and temporarily remains there. This process is called interception. Later the intercepted water is either evaporated or infiltrated.
22
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• PROCESSES OF HYDROLOGIC CYCLE
Depression Storage
A part of precipitation is stored in depressions on the catchment area. This is called depression storage.
23
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• PROCESSES OF HYDROLOGIC CYCLE
Detention Storage
When the precipitation occurs for a longer duration and at a rate greater than the rate of infiltration some water is collected on the surface of the earth up to a certain depth. On attaining a certain depth, the action of gravity makes this water flow. Before it starts flowing, the water stored on the surface of earth is called detention storage.
24
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• 25
Engineering Hydrology(CE- 235)
HYDROLOGIC EQUATION
inflow
Storage
outflow
inflow
Law of Conservation of Matter
outflow
inflow - outflow = D storage
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• HYDROLOGIC EQUATION
I – O = ΔS (law of conservation of matter)
I = Inflow
O = Outflow
ΔS = Change in storage
In its differential form it states that rate of volume inflow minus the rate of volume outflow is equal to the rate of change of storage. Mathematically
I – O = ΔS / Δt
where
I = Rate of volume inflow (volume/time), (m3/sec or ft3/sec)
O = Rate of volume outflow (volume/time)
ΔS / Δt = Rate of change of storage (volume/time)
26
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• 27
Engineering Hydrology(CE- 235)
CATCHMENT & BASIN
• A Catchment is a portion of the earth’s surface that collects runoff and concentrates it at its furthest downstream point, referred to as the catchment outlet.
• 13. The runoff concentrated by a catchment flows either into a larger catchment or into the ocean
• 14. The terms watershed and basin are commonly used to refer to catchments. Generally, watershed is used to describe a small catchment (stream watershed), whereas basin is reserved for large catchments (river basins)
• 15. NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
28
• 16. HYDROLOGIC EQUATION
Components of Inflow
There are two components of inflow:-
• Precipitation over the catchment and reservoir
• 17. Surface or groundwater flow from other catchment areas
29
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• HYDROLOGIC EQUATION
Components of Outflow
Three components of outflow are:-
• Surface evaporation
• 18. Groundwater seepage
• 19. Direct runoff
30
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• HYDROLOGIC EQUATION
If we fix the time and take the volume units, then the hydrologic equation can be written as:-
Total volume inflow – Total volume outflow =Total change in volume of the system
This is hydrologic or storage equation for a catchment/system
31
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• HYDROLOGIC EQUATION
Inflows and outflows may or may not change during a time interval of Δt
If inflows and outflows changes from ‘I1’ to ‘I2’ and ‘O1’ to ‘O2’ respectively in time ‘Δt’, then the change in storage can be determined by following equation
(I1 + I2) / 2 – (O1 + O2) / 2 = (S2 – S1) / Δt
32
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• WATER BUDGET IN A CATCHMENT
I – O = ΔS
P – (Li + R + Le) = D + F
or R = P – (Li + Le + D + F)
R = P – The Losses
R = P - L
33
Engineering Hydrology(CE- 235)
P=Precipitation
R=Runoff
Li=Loss due to interception
Le=Loss due to evaporation
D=Depression storage
F=storage due to infiltration
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• EXAMPLE # 1
Flow of River Chenab at Marala Barrage varied linearly from 34 cumec (m3/sec) to 283 cumec in 10-hours during a flood. The flow variation at Khanki Barrage, downstream of Marala was observed to be from 28 to 255 cumec during the above mentioned time. Assuming no lateral flow in or out of the reach, find out the rate of change of storage of the river reach between Marala and Khanki. What is the total change in storage of the reach in this period?
34
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• EXAMPLE # 2
Water at a constant rate of 370 cumec was observed to be entering into Tarbela Reservoir in a certain season. If outflow from the reservoir including infiltration and evaporation losses is 280 cumec, find out the change in storage of reservoir for 10 such days. Also convert your answer into Hectare-Meter.
(1hec=10000m2)
35
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• EXAMPLE # 3
A precipitation measuring 125 mm occurred over a catchment. If the infiltration, interception, depression storage and other losses are 50 mm, find direct runoff and total runoff.
36
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• EXAMPLE # 4
A part of catchment area of Hub river measuring 78 km2 received 100 mm of rainfall in 3 hours due to a storm. A drainage stream joins this part of catchment to the Hub river. The stream was dry before rainfall and there was flow in the stream for a period of 2.5 days with an average discharge of 10 cumecs. After the storm runoff, the stream again became dry. Find the losses, direct runoff and total runoff in cumecs and Hectare meter.
37
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• EXAMPLE # 5
Assume that Mangla reservoir has surface area of 39 km2 in the beginning of a certain month and the water depth is 76.20 m for this whole surface of the lake. Further assume that sides of the reservoir are nearly vertical. The reservoir received an average inflow of 226.50 cumec as a direct runoff in the same month, and direct precipitation of 125 mm. The outflow from the reservoir was 170 cumec and evaporation and seepage losses were estimated to be 113 mm during the month. Find out depth of reservoir at the end of that month and total increase or decrease in the storage.
38
Engineering Hydrology(CE- 235)
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
• NUST Institute of Civil Engineering/Engr Sajjad Ahmad
39