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WATER RESOURCES WATER RESOURCES ENGINEERINGENGINEERING

WHAT IS WATER WHAT IS WATER RESOURCES RESOURCES

ENGINEERING?ENGINEERING?

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It is concerned with the analysis It is concerned with the analysis and design of systems to control and design of systems to control water quantity, quality, timing water quantity, quality, timing and distribution to meet the and distribution to meet the need of human habitation and need of human habitation and the environment.the environment.

Typically, water resources is Typically, water resources is related to water supply.related to water supply.

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Disciplines within water resources:Disciplines within water resources:Hydrodynamics - Hydrodynamics - the area of fluid dynamics that is the area of fluid dynamics that is concerned with the study of liquids.concerned with the study of liquids.

Hydraulics - Hydraulics - the study of water or other fluids at rest the study of water or other fluids at rest or in motion, especially with respect to engineering or in motion, especially with respect to engineering applications.applications.

Hydrology - Hydrology - the scientific study of the properties, the scientific study of the properties, distribution, use, and circulation of the water on distribution, use, and circulation of the water on Earth and in the atmosphere in all of its forms.Earth and in the atmosphere in all of its forms.

AtmosphericAtmosphericSurface waterSurface waterGroundwater (Subsurface)Groundwater (Subsurface)Contaminant hydrologyContaminant hydrology

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WATER RESOURCEWATER RESOURCE

Any of the entire range of natural waters (vapor, Any of the entire range of natural waters (vapor, liquid, or solid) that occur on the Earth and that liquid, or solid) that occur on the Earth and that are of potential use to humans.are of potential use to humans.

These resources include the waters of the These resources include the waters of the oceans, rivers, and lakes; groundwater and oceans, rivers, and lakes; groundwater and deep subsurface waters; and glaciers and deep subsurface waters; and glaciers and permanent snowfields.permanent snowfields.

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MODULE 1: PRINCIPLES OF WATER MODULE 1: PRINCIPLES OF WATER RESOURCES ENGINEERINGRESOURCES ENGINEERING

Lesson 1: Surface and Ground Water Lesson 1: Surface and Ground Water ResourcesResources

Lesson 2: Concepts for Planning Water Lesson 2: Concepts for Planning Water Resources Development Resources Development

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Lesson 1: Surface and Ground Water Lesson 1: Surface and Ground Water ResourcesResources

Water in our planet is available in the Water in our planet is available in the atmosphere, the oceans, on land and within the atmosphere, the oceans, on land and within the soil and fractured rock of the earth’s crust.soil and fractured rock of the earth’s crust.

Moisture circulates from the earth into the Moisture circulates from the earth into the atmosphere through evaporation and then back atmosphere through evaporation and then back into the earth as precipitation.into the earth as precipitation.

In going through this process, called the In going through this process, called the Hydrologic Cycle (Figure 1), water is conserved Hydrologic Cycle (Figure 1), water is conserved – that is, it is neither created nor destroyed.– that is, it is neither created nor destroyed.

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HYDROLOGIC HYDROLOGIC CYCLECYCLE

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The earth’s total water content in the hydrologic cycle is not equally distributed (Figure 2).

The oceans are the largest reservoirs of water, but since it is saline it is not readily usable for requirements of human survival. The freshwater content is just a fraction of the total water available (Figure 3).

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Figure 3. Global fresh water distribution

Again, the fresh water distribution is highly Again, the fresh water distribution is highly uneven, with most of the water locked in uneven, with most of the water locked in frozen polar ice caps.frozen polar ice caps.

The hydrologic cycle consists of four key The hydrologic cycle consists of four key componentscomponents

1. Precipitation1. Precipitation

2. Runoff2. Runoff

3. Storage3. Storage

4. Evapotranspiration4. Evapotranspiration

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1.1.1 PRECIPITATION1.1.1 PRECIPITATIONPrecipitation occurs when atmospheric moisture becomes Precipitation occurs when atmospheric moisture becomes too great to remain suspended in clouds. too great to remain suspended in clouds.

It denotes all forms of water that reach the earth from the It denotes all forms of water that reach the earth from the atmosphere, the usual forms being rainfall, snowfall, hail, atmosphere, the usual forms being rainfall, snowfall, hail, frost and dew. frost and dew.

Once it reaches the earth’s surface, precipitation can Once it reaches the earth’s surface, precipitation can become surface water runoff, surface water storage, become surface water runoff, surface water storage, glacial ice, water for plants, groundwater, or may glacial ice, water for plants, groundwater, or may evaporate and return immediately to the atmosphere.evaporate and return immediately to the atmosphere.

Ocean evaporation is the greatest source (about 90%) of Ocean evaporation is the greatest source (about 90%) of precipitation.precipitation.

Rainfall is the predominant form of precipitation and its Rainfall is the predominant form of precipitation and its distribution over the world and within a country.distribution over the world and within a country. 12

1.1.2 RUNOFF1.1.2 RUNOFFRunoff is the water that flows across the land Runoff is the water that flows across the land surface after a storm event. surface after a storm event.

As rain falls over land, part of that gets As rain falls over land, part of that gets infiltrated the surface as overland flow. infiltrated the surface as overland flow.

As the flow bears down, it notches out rills and As the flow bears down, it notches out rills and gullies which combine to form channels. gullies which combine to form channels.

These combine further to form streams and These combine further to form streams and rivers.rivers.

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1.1.3 STORAGE1.1.3 STORAGEPortion of the precipitation falling on land Portion of the precipitation falling on land surface which does not flow out as runoff gets surface which does not flow out as runoff gets stored as either as surface water bodies like stored as either as surface water bodies like LakesLakes, , ReservoirsReservoirs and and Wetlands or as sub-Wetlands or as sub-surface water bodysurface water body, usually called , usually called Ground Ground waterwater..

Ground water storageGround water storage is the water infiltrating is the water infiltrating through the soil cover of a land surface and through the soil cover of a land surface and traveling further to reach the huge body of traveling further to reach the huge body of water underground. water underground.

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1.1.3 STORAGE1.1.3 STORAGEAs mentioned earlier, the amount of ground As mentioned earlier, the amount of ground water storage is much greater than that of lakes water storage is much greater than that of lakes and rivers. and rivers.

However, it is not possible to extract the entire However, it is not possible to extract the entire groundwater by practicable means. groundwater by practicable means.

It is interesting to note that the groundwater It is interesting to note that the groundwater also is in a state of continuous movement – also is in a state of continuous movement – flowing from regions of higher potential to flowing from regions of higher potential to lower.lower.

The rate of movement, however, is The rate of movement, however, is exceptionally small compared to the surface exceptionally small compared to the surface water movement.water movement.

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The following definitions may be useful:The following definitions may be useful:

LakesLakes: Large, naturally occurring inland body : Large, naturally occurring inland body of waterof water

ReservoirsReservoirs: Artificial or natural inland body of : Artificial or natural inland body of water used to store water to meet various water used to store water to meet various demands.demands.

Wet LandsWet Lands: Natural or artificial areas of : Natural or artificial areas of shallow water or saturated soils that contain shallow water or saturated soils that contain or could support water–loving plants.or could support water–loving plants.

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1.1.4 1.1.4 EVAPOTRANSPIRATIONEVAPOTRANSPIRATION

Evapotranspiration is actually the combination Evapotranspiration is actually the combination of two terms – evaporation and transpiration.of two terms – evaporation and transpiration.

The first of these, that is, The first of these, that is, evaporationevaporation is the is the process of liquid converting into vapor, through process of liquid converting into vapor, through wind action and solar radiation and returning to wind action and solar radiation and returning to the atmosphere. the atmosphere.

EvaporationEvaporation is the cause of loss of water from is the cause of loss of water from open bodies of water, such as lakes, rivers, the open bodies of water, such as lakes, rivers, the oceans and the land surface. oceans and the land surface.

It is interesting to note that ocean evaporation It is interesting to note that ocean evaporation provides approximately 90 percent of the provides approximately 90 percent of the earth’s precipitation.earth’s precipitation.

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TranspirationTranspiration is the process by which water molecules is the process by which water molecules leaves the body of a living plant and escapes to the leaves the body of a living plant and escapes to the atmosphere. atmosphere.

The water is drawn up by the plant root system and part The water is drawn up by the plant root system and part of that is lost through the tissues of plant leaf (through of that is lost through the tissues of plant leaf (through the stomata). the stomata).

In areas of abundant rainfall, transpiration is fairly In areas of abundant rainfall, transpiration is fairly constant with variations occurring primarily in the constant with variations occurring primarily in the length of each plants growing season. length of each plants growing season.

However, transpiration in dry areas varies greatly with However, transpiration in dry areas varies greatly with the root depth. the root depth.

Evapotranspiration, therefore, includes all evaporation Evapotranspiration, therefore, includes all evaporation from water and land surfaces, as well as transpiration from water and land surfaces, as well as transpiration from plants.from plants. 18

DEVELOPMENT OF WATER DEVELOPMENT OF WATER RESOURCESRESOURCESDue to its multiple benefits and the problems Due to its multiple benefits and the problems

created by its excesses, shortages and quality created by its excesses, shortages and quality deterioration, water as a resource requires deterioration, water as a resource requires special attention.special attention.

Requirement of technological/engineering Requirement of technological/engineering intervention for development of water intervention for development of water resources to meet the varied requirements of resources to meet the varied requirements of man or the human demand for water, which are man or the human demand for water, which are also unevenly distributed, is hence essential.also unevenly distributed, is hence essential.

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The development of water resources, though a The development of water resources, though a necessity, is now pertinent to be made necessity, is now pertinent to be made sustainable. sustainable.

The concept of sustainable development The concept of sustainable development implies that development meets the needs of implies that development meets the needs of the present life, without compromising on the the present life, without compromising on the ability of the future generation to meet their ability of the future generation to meet their own needs. own needs.

This is all the more important for a resource This is all the more important for a resource like water. Sustainable development would like water. Sustainable development would ensure minimum adverse impacts on the ensure minimum adverse impacts on the quality of air, water and terrestrial environment.quality of air, water and terrestrial environment.

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