1. Engineering Hydrology (ECIV 4323)
Chapter 1:
Introduction
Instructor:
Dr. Yunes Mogheir
2015

2. 1.1 Introduction
- Hydrology is the science of water:
It is the science that deals with the occurrence, circulation, and distribution of water of the earth and earth’s atmosphere.
It is concerned with water in streams and lakes, rainfall and snowfall, snow and ice on the land, and groundwater.
It is of inter-disciplinary nature.

3. … 1.1 Introduction
In general, hydrology deals with
Estimation of water resources.
The study of processes such as precipitation, runoff, evapotranspiration and their interaction.
The study of problems such as floods and droughts and strategies to combat them.

4. 1.2. Hydrologic Cycle

6. - Hydrologic Cycle Processes
Atmospheric water
Precipitation
Evaporation
Infiltration
Surface Runoff
Groundwater Recharge
(Percolation)
Baseflow
Land Surface
Surface Water
Soil water
Groundwater
System

7. Catchment Area or Watershed?
1.3. Water Budget
Catchment Area or Watershed?
Catchment area or drainage basin or river basin or watershed is defined as: The area drained by a stream or a system of connecting streams such that the surface runoff originating in this area leaves the area in concentrated flow through a single outlet.
Stream Outlet A
Or Station A
Catchment boundary or watershed or divide for
the site At A
Stream Outlet B
Catchment boundary for
the site At B
Tributary

8. Wadi Gaza:
Estimated average annual flow =
15 MCM / yr

10. Water budget equation System Concept Vi – V0 =  S
Hydrologic analysis for various applications and models begins with the system concept.
SYSTEM
OPERATORS
INPUTS
OUTPUTS
System Boundary
Vi – V0 =  S
I - Q =  S/ t (change in storage with respect to time)
I = inflow volume per unit time
Q = outflow per unit time

11. Typical Water Budget System Components
P = precipitation
E = evaporation
T = transpiration
R = Surface runoff
G = net groundwater flow
 S = change in storage
P - R - G - E - T =  S
- Example 1.1 and 1.2

12. Example 1.1
A lake has a surface elevation of 103.2m above a datum at the beginning of a certain month. In that month the lake received an average inflow of 6.0 m3/s from surface runoff. In the same period the outflow from the lake had an average value of 6.5 m3/s. In that month the lake received a rainfall of 145 mm and the evaporation from the lake surface was 6.10cm. The average area of the lake is 5000 ha and assume no contribution from or to the groundwater storage.
Write the water budget equation for the lake and calculate the water surface elevation at the end of that month.

13. 1.4. World Water Balance Oceans 96.5 % of total
Saline water on land 1% of total
Fresh: % of total
Groundwater 30.1 % of fresh water
Polar Ice % of fresh water
Lakes & Rivers % of fresh water
Check tables 1.1 and table 1.2 in your text book

14. Global Water Balance (Table 1.2 in textbook)
Global Average Precipitation (per year):
Ocean (70.8 %) and Land (29.2%)
127 cm x cm x = cm/yr
Global Average Evaporation (per year):
140 cm x x = cm/yr

15. 1.6. Application in Engineering
►We need hydrology in the design and operation of water resources engineering projects such as those for irrigation, water supply, flood control, water power and navigation.
More specific examples:
The capacity of storage structures such as reservoirs
The magnitude of flood flows to enable safe disposal of excess flow
Floodplain analysis and delineation
The minimum flow and quantity of flow available at various seasons
Erosion and sediment control
The interaction of the flood wave and hydraulic structures, such as levees, reservoirs, and bridges
►The hydrologic study should of necessity precede structural and other detailed design studies.

16. 1.7. Sources of Data The data normally required:
Weather records ( temperature, humidity, wind velocity)
Precipitation data
Stream-flow records
Evaporation and transpiration data
Infiltration characteristics of the area
Groundwater characteristics
Physical and geological characteristics