What is Water Resources Engineering?
includes the design of systems to control the
quantity, quality, timing, and distribution of
water to meet the needs of human habitation
and the environment.
feasibility from legal, economic, financial,
political, and social viewpoints must generally
be considered in the development process.
successful operation of an engineered system
usually depends as much on nonengineering
analyses (e.g., economic and social analyses) as
on sound engineering design.
include domestic, commercial, and industrial
water supply, wastewater treatment, irrigation,
drainage, flood control, salinity control,
sediment control, pollution abatement, and
hydropower-generation systems. Practical Hydraulics & Water Resource
Engineering by Kay, Melvin
The Nature and
Importance of Water
Topics to be covered…
❑Physical and Chemical Nature of Water
❑Uses and Importance of Water
❑Hydrologic Cycle
❑Factors Affecting Water Cycle
Physical and Chemical Nature of Water
• most abundant substances on Earth without which life cannot exist
• covers more than 70% of the earth’s surface
• considered as the universal solvent because of its ability to dissolve almost all
organic and inorganic solids and gases
• For this reason, pure water is never found in nature
• Even rainwater, the purest natural water, contains chemicals dissolved from the air
• Pure water is obtained only by special methods of distillation and by chemical
action in laboratories
From Practical Hydraulics and Water Resource
Engineering by Kay, Melvin
From Water Resources Engineering by David Chin, page 3
Physical and Chemical Nature of Water
• Pure water is a tasteless, odorless and colorless liquid.
• Water in liquid form is most dense at 4° C (used as a standard of comparison
for expressing the density of other liquids and solids)
• At 4° C, one liter of water weighs 1 kilogram (a density of 1 gram/cc).
• In its gas form as a vapor, water is lighter than air, thus, it rises in the
atmosphere.
Physical and Chemical Nature of Water
Other important properties of water are the following:
At 4°C pure water has a specific gravity of 1.
The density of pure water is a constant at a particular temperature and does not depend on the
size of the sample (intensive property).
Its density however, varies with temperature and impurities.
Water is the only substance on Earth that exists in nature in all three physical states of matter:
solid, liquid and gas.
When water freezes it expands rapidly adding about 9 % by volume..
The specific heat of water in the metric system is 1 calorie – the amount of heat required to raise
the temperature of one gram one degree Celsius. Water has a higher specific heat than almost any
other substance. The high specific heat of water protects living things from rapid temperature
change.
Uses and Importance of Water
Uses of fresh water can be categorized as consumptive and non-
consumptive.
Consumptive water use is water removed from available supplies without return to a water resource
system (e.g., water used in manufacturing, agriculture, and food preparation that is not returned to a
stream, river, or water treatment plant).
Non-consumptive water use refers to a water use that can be treated and returned as surface water.
A great deal of water use is non-consumptive, which means that the water
is returned to the earth as surface runoff.
Uses and Importance of Water
1. Domestic Uses
Small water utilities are primarily concerned with water for potable use,
Aside from drinking, other domestic uses include: washing, bathing, cooking,
cleaning, tending and watering of home gardens, and the upkeep of domestic
animals.
According to the National Water Resources Board (NWRB), the average
consumption was 118 L/d/c in 2004. The highest consumption was recorded in
the East Zone of Metro Manila as 232 L/d/c.
Uses and Importance of Water
2. Other Uses
Other use categories for water
supplied by water utilities
include:
Irrigation,
Power Generation,
Fisheries,
Livestock Raising,
Industrial and Photo taken from The Software Industry's "Clean Water Act"
Recreational uses. Alternative by Robert A. Martin and Steven M. Christey (2012)
28.52 B m3 of water were withdrawn from various sources in the Phils in 2000:
➢ 74% (21.10 billion m3) was used for agricultural purposes,
➢ 9% (2.57 billion m3) for industrial processes,
➢ and 17% (4.85 billion m3) for domestic consumption.
From Practical Hydraulics and Water Resource Engineering by Kay, Melvin
Hydrologic Cycle
• describes the storage and
movement of water on, above and
below the surface of the Earth.
• Water occurs in one of its three
forms as it moves through this
cycle.
• consists primarily of precipitation,
vapor transport, evaporation,
evapo-transpiration, infiltration,
groundwater flow, and runoff.
Hydrologic Cycle
1. Water in the Atmosphere
The sun, which drives the water cycle, heats water in oceans and seas.
Water evaporates as water vapor into the air.
Ice and snow may melt into liquid or sublimate directly into water vapor.
Evapo-transpiration is water transpired from plants and evaporated from the soil.
The water vapor rises in the atmosphere where cooler temperatures cause it to
condense into clouds.
As the air currents pick up and move the water vapor, cloud particles collide, grow, and
fall out of the sky as precipitation.
Hydrologic Cycle
2. The Bodies of Water
Most water falls back as rain into the oceans or onto land, where it flows over the
ground as surface runoff.
A portion of runoff enters rivers in valleys, where the stream flow moves the water
towards the oceans.
Some of the runoff and groundwater is sequestered and stored as freshwater in lakes.
But not all the runoff flows into rivers or lakes; much of it soaks into the ground as
infiltration.
Hydrologic Cycle
3. Water in the Earth
Some of the water infiltrates deep into the ground and replenishes aquifers, which
store freshwater underground for long periods of time.
Some infiltration stays close to the land surface and can seep back into surface-water
bodies as groundwater discharge.
Some groundwater finds pathways that eventually lead to openings in the land
surface, where it comes out as springs.
Over time, the water returns to the ocean, where the water cycle started.
Hydrologic Cycle
4. The Phenomena in the Water Cycle
The various phenomena that characterize the water cycle are as follows:
Evaporation – Evaporation is the process by which liquid water is converted into a gaseous state. It takes place
when the humidity of the atmosphere is less than the evaporating surface (at 100% relative humidity there is no
more evaporation).
Condensation – Condensation is the change in state of water from vapor to liquid when it cools. This process
releases latent heat energy to the environment.
Precipitation – Precipitation is any aqueous deposit (in liquid or solid form) that develops in a saturated
atmosphere (relative humidity equals 100%) and falls to the ground. Most precipitation occurs as rain, but it also
includes snow, hail, fog drip, and sleet.
Infiltration – Infiltration is the absorption and downward movement of water into the soil layer. Once infiltrated,
the water becomes soil moisture or groundwater.
Hydrologic Cycle
4. The Phenomena in the Water Cycle
Continuation….
Runoff – This is the topographic flow of water from the area on which it precipitates towards stream channels
located at lower elevations. Runoff occurs when the capacity of an area's soil to absorb infiltration has been
exceeded. It also refers to the water leaving a drainage area.
Evapo-transpiration – This covers the release of water vapor from plants into the air.
Melting – Melting is the physical process of a solid becoming a liquid. For water, this process requires
approximately 80 calories of heat energy for each gram converted.
Groundwater Flow – This refers to the underground topographic flow of groundwater because of gravity.
Advection – This is the movement of water in any form through the atmosphere. Without advection, water
evaporated over the oceans could not precipitate over land.
Factors Affecting Water Cycle
• Many factors have an impact on the normal workings of the water cycle.
• Some of these are either man–made, such as
• extent of agricultural and industry activities,
• deforestation and forestation,
• the construction of dams,
• the amount of water abstracted from surface and groundwater, and
• the effects of urbanization in terms of consumption and obstruction of the topographic
flow of groundwater.
Factors Affecting Water Cycle
• The other factors are those that influence climate change, which is basically manifested as a
perceptible distortion of climate patterns.
• A large degree of uncertainty governs the understanding on how precipitation and
temperature change leads to changes in runoff and river flows, flooding and drought
patterns.
• The earth’s climate has always changed, but it is the fast rate of change that is causing
concern.
• As an example, there has been an increase of 0.61° C in the measured temperature in the
Philippines from the 1950s to 2005.
Factors Affecting Water Cycle
About 86% of the global evaporation occurs from the oceans, which reduces their
temperature by evaporative cooling.
Without the cooling effect of evaporation, the earth would experience a much higher
surface temperature.
The rising temperatures will increase evaporation and result in increased rainfall.
This situation may cause more frequent droughts and floods in different regions due to
their variations in rainfall.
The Philippines suffered a severe drought in 1999 and two milder dry spells in 2004 and
2007.
Droughts in the Philippines have destroyed millions of pesos worth of crops, reduced the
country’s water supply, and threatened widespread blackouts as power companies
contend with low water levels in hydroelectric dams.
Assignment:
Disadvantages of Desalination
Identify the Climate Change Effects to the Water Cycle & Water Supply
Strategies to Mitigate Risks from Climate Change
