sources of water

Dr. S. T. Ramesh / Associate Professor / Civil Engg.

Sources of Water

Dr. S. T. RAMESH, Ph.D.

Associate Professor

Department of Civil Engineering

National Institute Technology,

Tiruchirappalli – 620 015.

E-Mail : [email protected]


HYDROLOGICAL CYCLE

• The hydrological cycle describes the constant movement of

water above, on, and below the Earth's surface.

• The cycle operates across all scales, from the global to the

smallest stream catchment and involves the movement of

water along evapotranspiration, precipitation, surface

runoff, subsurface flow and groundwater pathways.

• In essence, water is evaporated from the land, oceans and

vegetation to the atmosphere, using the radiant energy

from the Sun, and is recycled back in the form of rain or

snow.

• When moisture from the atmosphere falls to the Earth's

surface it becomes subdivided into different interconnected

pathways.


• Precipitation (excluding snow and hail) wets vegetation,

directly enters surface water bodies or begins to infiltrate into

the ground to replenish soil moisture.

• Excess water percolates to the zone of saturation, or

groundwater, from where it moves downward and laterally to

sites of groundwater discharge.

• The rate of infiltration varies with land use, soil characteristics

and the duration and intensity of the rainfall event.

• If the rate of precipitation exceeds the rate of infiltration this

leads to overland flow.

• Water reaching streams, both by surface runoff and

groundwater discharge eventually moves to the sea where it

is again evaporated to perpetuate the hydrological cycle.


• PRECIPITATION: The evaporated water from the

surfaces of streams, rivers, sea, ponds, wet surfaces,

trees and plants etc again returned to the earth surface

by the condensation in the form of rain, hails, dew, sleet

etc is known as precipitation.

• The water of precipitation further goes off in the following

ways.

• RUN-OFF: After precipitation a portion of its water flows

over the ground in the form of rivers and streams and

some water flows towards lakes and ponds and collected

there.


• INFILTRATION: A portion of precipitation percolates in

the ground and it is stored in the form of sub-soil or

ground water.

• EVAPORATION: some portion of the precipitation is

also evaporated from the lakes, rivers, reservoirs and

wet surfaces in the form of vapor due to sun‟s heat is

known as evaporation Water Supply Engineering

• EVAPO-TRANSPIRATION: The roots of the trees sucks

water from the ground and some portion of it evaporates

in the atmosphere through leaves in the form of

transpiration.


Kinds of precipitation

• There are different kinds of precipitation:

– (1) convectional,

– (2) orographic and

– (3) cyclonic.


Orographic Precipitation

• Orographic precipitation results when warm moist air moving

across the ocean is forced to rise by large mountains.

• As the air rises, it cools. Why? A higher elevation results in

cooler temperatures.

• Cold air cannot hold as much moisture as warm air.

• As air cools, the water vapour in the air condenses and water

droplets form.

• Clouds forms and precipitation (rain or snow) occurs on the

windward side of the mountain (see diagram).

• The air is now dry and rises over top the mountain.

• As the air moves back down the mountain, it collects moisture

from the ground via evaporation.

• This side of the mountain is called the leeward side. It receives

very little precipitation.


Orographic Precipitation


Convectional Precipitation

• Convectional precipitation results

from the heating of the earth's

surface.

• The warm ground heats the air over

it.

• As the air warms, the air molecules

begin to move further apart.

• With increased distance between

molecules, the molecules are less

densely packed.

• Thus, the air becomes “lighter” and

rises rapidly into the atmosphere. As

the air rises, it cools.

• Water vapour in the air condenses

into clouds and precipitation.


Cyclonic Precipitation

• Cyclonic or Frontal precipitation results when the leading

edge of a warm, moist air mass (warm front) meets a

cool and dry air mass (cold front).

• The molecules in the cold air are more tightly packed

together (i.e., more dense), and thus, the cold air is

heavier than the warm air.

• The warmer air mass is forced up over the cool air.

• As it rises, the warm air cools, the water vapour in the air

condenses, and clouds and precipitation result.


• This type of system is called Frontal Precipitation

because the moisture tends to occur along the front of

the air mass.

• A cyclonic storm is a large, low pressure system that

forms when a warm air mass and a cold air mass collide.

• This collision often occurs under the polar-front jet

stream which spreads cold, dry arctic air near warm,

moist tropical air.

• The rotation of the earth causes the air to circulate in a

counterclockwise direction around an area of low

pressure


Cyclonic Precipitation


The hydrological cycle


Sources of Water


Sources of water (RAIN)

Surface Sources Ground Sources

Streams Springs

Lakes Infiltration Galleries

Ponds Infiltration Wells

Rivers Wells and Tube wells

Impounded Reservoirs

Oceans


Surface Water

• When rain falls upon the earth, part runs off tostreams, ponds, lakes or the ocean.

• Snow evaporates to some extent, but intemperate climate most of it remains to melt andrun off in the spring, thereby contributing tospring floods.

• In mountainous regions the snow at the higherelevation melts slowly with warm weather andthus tends to maintain the flow of streams and toeffect their summer quality and quantity.


• The quality of water taken from the surface sourcesdepends upon– the character and the area of the water shed,

– its geology and topography,

– the extent and nature of the development by man,

– time of year and

– weather conditions.

• The quality of water taken from the streams is generallymore variable and less satisfactory than that of pondsand lakes.

• Water from lime stone regions is harder but lesscorrosive than water from granite regions.

• Surface sources in heavily polluted areas are affected bysewage and industrial sources.


Streams

• Water flowing in streams consist of direct

precipitation runoff which has flowed over the

surface of the ground or overflow from the lakes

and swamps and water seeping through the

ground from the high land to the valleys.

• The proportion of flows from the several sources

varies from season according to the geology and

development of the drainage area,


• During periods of heavy precipitation, the melting snowand of floods, the stream flow consists largely of surfacerunoff.

• At these times the water may be muddy, relatively softand high bacterial content.

• During extreme floods the dilution may be such that thewater is less muddy and contains fewer bacteria.

• Streams subject to pollution by man or his activities maybecome highly objectionable because of over-loadingwith putrescible organic matter. Finally, betweenmaximum and minimum flows there may be substantialvariations in the quality.


• The quantity and type of surface wash carried intostreams depend upon the character of surface materials,the steepness of the valley slopes, the area and type offorestation, swamps, and the amount and kind ofcultivation.

• Clay soils tend to produce muddy streams cause rapidrun off, resulting in erosion and a change in water qualityeffect by washing of silt into the streams.

• Forests, on the other hand, retard run off and tend toequalize stream flow.

• Other things, being equal, the run off from areas withforests of deciduous trees is more highly colored thanthat from areas with stands of ever green.


• Run off from cultivated land is likely tocarry silt and particles of fertilizer, whereasrun off from pasture lands will carrymanure and other organic debris.

• In the autumn much dead vegetation willbe blown of washed into water courses.

• Thus it is evident that even streams fromrelatively sparsely inhabited water shedswill carry considerable „natural pollution‟.


• Soluble minerals are brought into streams notonly as a result of run off absorbing suchsubstances from the surface of the soil, but asthe result of ground.

• These minerals seep through the ground.

• These soluble minerals increase the alkalinityand hardness of the streams somewhat inaccordance with the relative proportions of theground and surface water as well as with thecharacter of the geological formation.


• From a sanitary stand point, pollution by man or or as aresult of his pursuits is the most significant.

• In sparsely settled regions, human pollution will berelatively indirect, incidental or accidental.

• In populated regions the pollution by sewage andindustrial wastes will be direct.

• Such pollution may carry germs or disease from humanexcreta or toxic substances from the manufacturingwastes.

• The extent of impairment of a stream is roughlyproportional to the ratio of population to the stream flow.


• There are natural causes which also tend to purify polluted streams.

• These cause are physical, chemical and biological.

• Sedimentation removes silt and other suspended matters, oxidationmodifies organic constituents, sunlight bleaches color, and biologicalforces tend to destroy disease organisms.

• The degree of self purification obtained is dependent uponnumerous factors including time, temperature, character of thepollution dilution ratio, hydrography and reaeration.

• Ice covers tends to retard such natural processes which areenhanced by surface aeration, and there is evidence that diseasegerms, such as those of typhoid fever, live longer in cold water thanin warm water,

• Decomposing deposits of organic matter in bottom of streams alsohave an adverse effect on color, taste, iron and carbon dioxidecontents.


• Climatic, geographic and hydrographicconditions are among the factors which affectthe physical, chemical and biologicalcharacteristics of stream water.

• Temperature vary according to season andgeographic location.

• Large streams have less rapidly fluctuatingtemperatures than do small streams.

• Streams in calcareous regions of hard, those insiliceous regions are soft.


• Different sections of the country have streams ofdifferent outstanding characteristics.

• Microscopic flora and fauna are prompted or retarded byvariations in physical and chemical conditions.

• Floods although temporarily the increase turbidity andsuspended matter, tend to scour deposits from streambeds, thereby removing organic matter, which, indecomposing, would impair the quality of water.

• Shallow, rapid streams may undergo self purificationmore quickly than do keep sluggish, although in latersedimentation may reduce sediment and bacteria moreeffectively.


Ponds and Lakes

• What are Lakes and Reservoirs?

– Lakes and reservoirs are oftenreferred to as standing watersand encompass a wide rangeof types and sizes.

– These range from ponds,gravel pits and slow movingcanals to very large naturallakes.

• Lakes

– Lakes are large bodies ofstanding water, either formednaturally or man-made foramenity purposes.

– Water levels tend not tofluctuate to any great extentand gently shelving marginssupport a wide variety of floraand associated fauna.


Ponds and Lakes• A natural large sized depression formed within the

surface of the earth, when gets filled up with water, ifknown as pond or a lake.

• The difference between a pond and a lake is only that ofsize.

• If the size of the depression is comparatively small, itmay be termed as a pond, and when the size is larger, itmay be termed as lake.

• The flow of water in a lake is just like the flow in a streamchannel.

• Generally, the surface runoff from the catchment areacontributing the particular lake, enters the lake throughsmall drains or streams.

• Sometimes, the underground water through somespring, also enters natural depressions and get collectedthere, forming ponds and lakes.


• The quality of water in a lake is generally good and doesnot need much purification.

• Larger and older lakes, however provide comparativelypurer water than smaller or newer lakes.

• Self purification of water due to sedimentation ofsuspended matter, bleaching of color, removal ofbacteria makes the lake‟s water purer and better,

• On the other hand, in still waters of lakes and ponds, thealgae, weed and vegetable growth takes place freely,imparting bad smells, tastes and color to their waters.


• Wave action tends to produce turbid shore water andsome instances, growth of microscopic organisms mayat times be heavy in such waters.

• In the great lakes, gross population occurs along shoresin the vicinity of large centers of population.

• Wind induced currents, flood flows from tributories andice flows may carry pollution many kilometers in thelakes.

• Generally in the large lakes, dilution and self purificationassure good quality in water that are well off shore,except as localize and passing pollution may result fromboat traffic.


• The quantity of water available from lakes is,however, generally small. It depends upon thecatchment area of the lake basin, annual rainfall,the geological formations.

• Due to the smaller quantity of water availablefrom them, lakes are not considered as principalsources of water supplies,

• They are, therefore, useful for only small townsand hilly areas.

• However, when no other sources are available,larger lakes may become the principal sourcesof supplies.


Classifications of Productivity

Oligotrophic Lakes


Eutrophic Systems


Hypereutrophic


Dystrophic Lake


Comparison of Lake System with River

System

• Lakes / Reservoirs

– Lotic / Static

– Vertical stratification

– Wind and Thermal Perturbations

– Pollutant / Nutrient accumulation

• Rivers / Streams

– Lentic / Running

– No stratification

– Mixing by Flow

– Natural dilution / self-purification


Impounded reservoirs

• An impounded reservoir may be defined as an artificiallake created by the construction of a dam across a valleycontaining a water course.

• Impounded reservoirs, formed by dams across thevalleys cut by streams, are subjected to much the sameconditions as are natural ponds and lakes.

• The reservoir essentially consists of two parts

– A dam to hold back water

– A spillway through which excess stream flow maydischarge

– A gate chamber containing the necessary valves forregulating the flow of water from the reservoir.


Reservoirs

• Reservoirs, or dams,are man-made bodiesof open water servingas public water supplysources, as winterstorage for cropirrigation or as floodstorage facilities inassociation with rivercorridors.

• Upland reservoirs arecommonly known asimpounding reservoirssince they are builtacross river valleys.


Impounded reservoirs

• When some of the early reservoir were built, the surfacesoil of the site was stripped of all vegetation and top soilto avoid the effects of decomposing organic matter.

• Normally the good quality of water will be found at aboutmid depth.

• Top water are prone to develop algae.

• Bottom of the water may be high in CO2, Iron,Manganese and an occasion hydrogen sulphide.

• In deep lakes and reservoirs the bottom water remainscold throughout the year, a permanent zone relativestagnation occurring at depths below about six meters.


Forms of Subsurface Water


Ground water

• Part of rain which falls upon the surface of the earthpercolates into the ground and becomes ground water.

• During this passage through the ground, the watercomes in contact with many substances, both organicand inorganic.

• Some are readily soluble in water.

• Others such as those causing alkalinity and hardness,are soluble in water containing carbon dioxide absorbedfrom the air or from decomposing organic matter in thesoil.

• The decomposition organic matter also removedissolved oxygen from the water percolating through it.


• Such water, free from oxygen and high in carbondioxide, dissolves iron and manganese from thesoil.

• Water containing iron and manganese isfavorable for the development of Crenothrix andother similar organisms in collected groundwater supplies.

• Hydrogen sulphide sometimes occurs in groundwater and is associated with the absence ofoxygen the decomposition of organic matter orthe reduction of sulphates.


• Although bacteria and other living organisms onthe surface of the ground may first be picked upby rain falling thereon, percolation into thesubsoil results in the filtering out of theseorganisms.

• An exception occurs where fissured or crackedrock, such as lime stone, is encountered nearthe surface.

• The sanitary conditions in the vicinity of ground water sources are important, particularly where sub surface pollution may be derived from privy pits, leaching cess pools and leaking sewers.


• Generally ground water are clear, cold, colorless andharder than the surface water of the region in which theyoccur.

• In lime stone formations ground waters are very hard, tendto form deposits on water pipes and relatively noncorrosive.

• In granite formation ground waters are soft, low in dissolvedminerals, relatively high in free carbon dioxide, and areactively corrosive.

• Bacterially, ground waters are much better than surfacewaters except where subsurface pollution exists.

• Although changes in the rate of draft from wells may aboutchanges in the quality of water from them, ground watersgenerally of uniform quality.

• Ground water temperatures remain fairly uniformthroughout the year.


• These are further divided into

(i) Infiltration galleries

(ii) Infiltration wells

(iii)Springs

(iv)Wells etc.


Springs

• Ground water that flows naturally from the ground at thesurface is called a spring, and where the flow is diffuse, itmay be called a seep or seepage.

• Many rivers receive water from diffuse seepage.

• The occurrence of most springs is controlled by thestructure of the rock formations.

• The flow rate from a spring may depend on ground waterrecharge conditions, the season, and the water demandsof vegetation.

• Typical geological situations (very simplified) for theoccurrence of springs are shown in the five crosssections:


Springs

• Natural outflow of Ground water at earth‟ssurface.

• Gravity springs : Ground water table rises high &water overflows though the sides of a naturalvalley or depression.

• Surface springs : an impervious obstructionsupporting underground storages becomesinclined causing water table to go up & getexposed to ground surface.

• Artesian Springs : when water flowing throughsome confined aquifer is under pressure.


Saturated soils over impermeable rock

• A spring can occur ifimpermeable bedrockprevents downwardflow.

• The size of upslopearea, the soil thickness,and the frequency ofprecipitation (rain orsnow-melt) willdetermine whether thespring flows year-round.


Permeable and impermeable rock

• Where rock strata havebeen tilted and eroded itis possible forprecipitation falling onone side of a hill tocontribute to spring orseepage flow on theother side!

• Finding the origin ofrecharge to a spring canbe important if thesource is to be protected.


Barrier of intrusive rock

• A spring may result from theoccurrence of impermeableintrusive volcanic rocks.

• In this case, water emergesas a spring, flows as a streamwhere the rock isimpermeable, and then seepsbelow the surface when itreaches permeable rock,before seeping into a streamin the valley.

• In igneous rocks, such asgranites, water moves throughweathered zones, joints andfractures.

• A spring can occur when animpermeable layer causeswater to reach the surface.


Joints and fractures in

granite

Permeable against

impermeable rock


Fault as flow conduit

• In situations where rocksare fractured along theline of a geologic fault, itmay result in a springsupplied from an aquiferin contact with the fault.

• Depending on thetopography of the landsurface there could be aline of springs related tothe same fault.


Infiltration well

• Infiltration well or sunk well is only the inter position of a

masonry or concrete barrel into such a formation so as

to intercept as large a quantity of water as possible.

• Infiltration wells are generally proposed in the river bank,

riverbed or lakebed to tap water from the unconfined

aquifer.

• Infiltration wells are preferred where the minimum

saturated thickness of aquifer is at least 5m.

• Generally, this will provide a very good supply of water

throughout the year.


• Even if the river dries up during times of little rain, water

will be available from the underground.

• Water from the stream passes through the sand and silt

in the river bank and impurities are removed by natural

filtration.

• The degree of purification will depend on the extent of

contamination of the stream and on the soil type.

• In many cases, the purification process in the sub soil

system will be sufficient, and no further treatment is

necessary.


Infiltration well

Plan of Jack Well receiving water

from a number of infiltration wells


Infiltration wells


Infiltration galleries

• To increase the amount of water that can be collected by aninfiltration well, infiltration galleries can be constructed.

• A horizontal tunnel which is constructed through waterbearing strata for tapping underground water near rivers,lakes or streams are called “Infiltration galleries”.

• These trenches are dug in the bank parallel to the stream,below groundwater level, or below the stream bed itself.

• Tile, concrete or perforated plastic collecting pipes are placedin the gravel-lined trenches and connected to a storage well.

• The gravel in the trench filters out sediment and preventsclogging of the pipes.

• The water is pumped from the storage well into thedistribution system in the same way as described forinfiltration wells.


Infiltration Galleries

Porous Pipe Galleries


Infiltration galleries


Wells

• A well is a vertical opening which extends from the

surface of the ground into the water bearing formation.

• The water bearing stratum is termed as the aquifer.

• The three factors which form the basis of theory of wellsare

– Geological conditions of the earth‟s surface

– Porosity of various layers

– Quantity of water, which is absorbed and stored indifferent layers.


Open Wells (Dug Wells)

• Open masonry wells, 2 – 9 m dia, less than 20 m depth.Discharge 5 L/s

• Walls built of brick or stone masonry or precast concretering

• To improve yield of well, 10 cm dia hole at centre of wellis made (Shallow well / Deep Wells)

• Shallow well rests in a pervious strata.

• Deep well rests on an impervious „mota‟ layer & drawsits supply from the pervious formation lying below „mota‟layer.

• A shallow well might be having more depth than a deepwell


Types of wells

• The following are different types of wells

– Shallow wells

– Deep wells

– Tube wells

– Artesian wells


Shallow wells

• Shallow wells are those developed in surface deposits of

pervious materials overlying an impervious stratum.

• Arbitrarily, any well deeper than 20 meters may be

considered a deep well.

• Shallow wells may be large diameter dug wells or small

diameter drivel wells.

• Suction lift is usually employed to obtain water from the

wells.

• The quality of shallow well ground water is largely

determined by the character of the nearby catchment area.

• Properly protected shallow wells in satisfactory pervious

material will yield water of good quality.


Deep wells

• Deep wells are either driven or drilled, depending upon

the strata encountered.

• Often they penetrate impervious strata before reaching

the water bearing stratum desired.

• Just like shallow wells, waters from deep wells possess

characteristics determined by the nature of the tributary

catchment area and the geological formation through

which the waters have passed.

• Deep well waters are likely to be more highly mineralized

than, shallow well waters.


• Deep well water are usually clean and colorless but

often, contain iron and manganese.

• Certain deep wells may contain water with high amount

of hydrogen sulphide, and other may contain mineral

salts such as chlorides, sulphates, and carbonates which

render treatment difficult.

• Deep well waters are usually bacterially.

• In new wells temporary contamination may result during

driving or drilling operations.


Deep wells


Tube Wells

• A tube well is constructed by taking a boring into the

ground and driving with auger or bit by hand or by

machinery.

• Tube well are suitable both for deep as well as shallow

wells.

• They may be constructed in soft, un consolidated soil or

in a rock formations and may accordingly be termed as

bored wells or drilled wells respectively.

• Their sizes ranges widely from 25 mm to 900 mm

diameter.


Tube Wells

• Yield from std. tube well 40 - 45 L/s.

• A long pipe or tube, bored deep into the ground,

intercepting one or more water bearing strata.

• Tube wells in Alluvial soils / Hard Rocky soils.

• Deep tube wells : 70 - 300 m depth, yield 200

L/s.

• Shallow tube wells : 20-70 m depth, 20 L/s yield


Tube Wells


Artesian wells

• Like a pipe full of water, the confined aquifer into which

this well is drilled sustains higher water pressure than in

the unconfined aquifer above it, so that water is forced to

rise higher in the artesian well than the local water table

around it.

• If the water level rises above the top of the well, the well

flows under natural water pressure


Summary of Methods of Developing

Sources of Surface Water

Method Quality Quantity Accessibility Reliability Cost

Springs and

Seeps

Good quality;

disinfection

recommended after

installation of spring

protection.

Good with little

variation for

artesian flow

springs; variable

with seasonal

fluctuations likely

for gravity flow

springs.

Storage necessary

for community

water supply;

gravity flow delivery

for easy community

access.

Good for artesian

flow and gravity

overflow; fair for

gravity depression;

little maintenance

needed after

installation.

Fairly low cost; with

piped system costs

will rise.

Ponds and

Lakes

Fair to good in large

ponds and lakes; poor

to fair in smaller water

bodies; treatment

generally necessary.

Good available

quantity; decrease

during dry season.

Very accessible

using intakes;

pumping required

for delivery system;

storage required.

Fair to good; need

for a good program

of operation and

maintenance for

pumping and

treatment systems.

Moderate to high

because of need to

pump and treat

water.

Streams and

Rivers

Good for mountain

streams; poor for

streams in lowland

regions; treatment

necessary.

Moderate: seasonal

variation likely;

some rivers and

streams will dry up

in dry season.

Generally good;

need intake for both

gravity flow and

piped delivery.

Maintenance

required for both

type systems; much

higher for pumped

system; riverside

well is a good

reliable source.

Moderate to high

depending on

method; treatment

and pumping

expensive.

Rain Catchment Fair to poor;

disinfection necessary

Moderate and

variable; supplies

unavailable during

dry season; storage

necessary.

Good; cisterns

located in yards of

users; fair for

ground catchments.

Must be rain; some

maintenance

required.

Low-moderate for

roof catchments;

high for ground

catchments.

sources of water

Documents

water of precipitation

portion of precipitation

rate of precipitation

precipitation isalso

evaporated water

water flows

surface water bodies

form of rivers