PART I – Hydrology and Hydrologic
Cycle
Hydrology – Lecture
rd
3 Term AY 2022-2023
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Contents
1. Introduction
2. Hydrologic Cycle
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1. Introduction
Hydrology - deals with the occurrence,
distribution, and disposal of water; it is the
science which deals with the various phases
of the hydrologic cycle.
Hydrologic cycle is the water transfer
cycle, which occurs continuously in nature;
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2. HYDROLOGY
SCOPE OF HYDROLOGY
▪ To identify the maximum probable flood that
may occur at a given site and its frequency.
▪ This is required for the safe design of
drainages, dams and reservoirs, and
other flood control structures.
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2. HYDROLOGY
SCOPE OF HYDROLOGY
▪ To identify the water yield from a basin – its
occurrence, quantity and frequency.
▪ This is necessary for the design of
dams, municipal water supply, water
power, and river navigation
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2. HYDROLOGY
SCOPE OF HYDROLOGY
▪ To determine groundwater development for
which a knowledge of the hydrogeology of
the area
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2. HYDROLOGY
HYDROLOGICAL DATA
▪ Climatological data
▪ Hydrometeorological data (temperature,
wind velocity, humidity)
▪ Precipitation records
▪ Stream-flow records
▪ Ground water table
▪ Evaporation data
▪ Cropping pattern and their consumptive use
▪ Water quality data
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2. HYDROLOGY
HYDROLOGIC EQUATION
▪ This is simply the statement for the
conservation of mass when considering
water transfer, given by the basic equation
𝑰𝒏𝒇𝒍𝒐𝒘 = 𝑶𝒖𝒕𝒇𝒍𝒐𝒘
▪ In a realistic system, there are many factors
that affect water transfer that introduces
losses in the system, therefore
𝑰𝒏𝒇𝒍𝒐𝒘 = 𝑶𝒖𝒕𝒇𝒍𝒐𝒘 + ෍ 𝑳𝒐𝒔𝒔𝒆𝒔
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3. HYDROLOGIC CYCLE
HYDROLOGIC CYCLE
▪ Water transfer cycle that occurs
continuously in nature
▪ Three important phases – evaporation,
precipitation, and runoff
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3. HYDROLOGIC CYCLE
Image source: gpm.nasa.gov
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3. HYDROLOGIC CYCLE
Image source: gpm.nasa.gov
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3. HYDROLOGIC CYCLE
Image source: gpm.nasa.gov
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3. HYDROLOGIC CYCLE
Image source: gpm.nasa.gov
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3. HYDROLOGIC CYCLE
Image source: gpm.nasa.gov
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3. HYDROLOGIC CYCLE
Image source: gpm.nasa.gov
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3. HYDROLOGIC CYCLE
Image source: gpm.nasa.gov
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3. HYDROLOGIC CYCLE
Image source: gpm.nasa.gov
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3. HYDROLOGIC CYCLE
Image source: gpm.nasa.gov
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3. HYDROLOGIC CYCLE
Image source: gpm.nasa.gov
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4. BASIC UNIT
WATERSHED
▪ Basic unit of hydrology
▪ Area of land that drains or “sheds” water
into a specific waterbody
▪ Other terms: Catchment area, Drainage
Area, Catchment basin, River basin
Image source: gpm.nasa.gov
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4. BASIC UNIT
Image source: gpm.nasa.gov
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References
• Linsley, R.K., M.A. Kohler and J.L.H. Paulhus (1988).
Hydrology for Engineers; McGraw-Hill
• Applied Hydrology by VenTe Chow (1988), David Maidment
and Larry Mays; McGraw-Hill
• Dela Cruz, K. (2021). ABE 57 - Field Hydrology Lecture
Notes, LWRD Institute of Agricultural and Biosystems
Engineering, CEAT-UPLB
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