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1. WATER
Among the five elements of life viz. Fire, Air, Earth, Water
and Space our attempt is to concentrate over one of the important elements of life i.e. water. Thus it is necessary
to know about the Earth’s distribution of water.
Earth's water distribution:
Where is Earth's water located and in what forms does it exist?
we can see how water is distributed by viewing these bar charts. The left-side bar shows where the water on Earth exists;
about 97 percent of all water is in the oceans. The middle bar represents the 3 percent of the "other" part of the left-side
bar (that portion of all of Earth's water that IS NOT in the oceans). Most, 77 % , is locked up in glaciers and icecaps mainly
in Greenland and Antarctica, and in saline inland seas. Twenty-two percent of this portion of Earth's water is ground water.
The right-side bar shows the distribution of the "other" portion of the middle bar (the remaining one percent). Notice how
rivers make up less than 4/10th of one percent of this remaining water -- yet this is where we get most of the water for our
everyday uses!
Water cycle:
Earth's water is always in movement, and the water cycle, also known as the
hydrologic cycle, describes the continuous movement of water on, above, and below the surface of the Earth. Since the water
cycle is truly a "cycle," there is no beginning or end. Water can change states among liquid, vapor, and ice at various places
in the water cycle, with these processes happening in the blink of an eye and over millions of years.
Although the balance of water on Earth remains fairly constant over.For a
detailed explanation of where Earth's water is, look at the data table below. Notice how of the world's total water supply
of about 326 million cubic miles of water, over 96 percent is saline. And, of the total freshwater, over 68 percent is locked
up in ice and glaciers. Another 30 percent of freshwater is in the ground. Thus, surface-water sources (such as rivers) only
constitute about 300 cubic miles (about 1/10,000 th of one percent of total water), yet rivers are the source of most of the
water people use.
TABLE 1
|
One estimate of global water
distribution: |
|
Water source |
Water volume, in cubic miles |
Water volume, in cubic kilometers |
Percent of fresh water |
Percent of total water |
|
Oceans, Seas, & Bays |
321,000,000 |
1,338,000,000 |
-- |
96.5 |
|
Ice caps, Glaciers, & Permanent Snow |
5,773,000 |
24,064,000 |
68.7 |
1.74 |
|
Groundwater |
5,614,000 |
23,400,000 |
-- |
1.7 |
|
Fresh |
2,526,000 |
10,530,000 |
30.1 |
0.76 |
|
Saline |
3,088,000 |
12,870,000 |
-- |
0.94 |
|
Soil Moisture |
3,959 |
16,500 |
0.05 |
0.001 |
|
Ground Ice & Permafrost |
71,970 |
300,000 |
0.86 |
0.022 |
|
Lakes |
42,320 |
176,400 |
-- |
0.013 |
|
Fresh |
21,830 |
91,000 |
0.26 |
0.007 |
|
Saline |
20,490 |
85,400 |
-- |
0.006 |
|
Atmosphere |
3,095 |
12,900 |
0.04 |
0.001 |
|
Swamp Water |
2,752 |
11,470 |
0.03 |
0.0008 |
|
Rivers |
509 |
2,120 |
0.006 |
0.0002 |
|
Biological Water |
269 |
1,120 |
0.003 |
0.0001 |
|
Total |
332,500,000 |
1,386,000,000 |
- |
100 |
Thus it seems that to meet the requirement of adequate water
for household, drinking and industrial purposes one should make use of the ground water but in limits.
Ground Water
Ground water is an important part of the water cycle. Ground water is the part of precipitation that seeps down through the soil until it reaches rock material that is
saturated with water. Water in the ground is stored in the spaces between rock particles (no, there are no underground rivers
or lakes). Ground water slowly moves underground, generally at a downward angle (because of gravity), and may eventually seep
into streams, lakes, and oceans.
Here is a simplified diagram showing how the ground is saturated
below the water table (the purple area). The ground above the water table (the pink area) may be wet to a certain degree,
but it does not stay saturated. The dirt and rock in this unsaturated zone contain air and some water and support the vegetation
on the Earth. The saturated zone below the water table has water that fills the tiny spaces (pores) between rock particles
and the cracks (fractures) of the rocks.
A couple of important factors are responsible for the existence
of ground water:
(1) Gravity
Gravity pulls water toward the center of the Earth. That means that
water on the surface will try to seep into the ground below it. The effect of gravity depends upon the property of the soil
or rock viz. porosity also other conditions like factures ,fissures which becomes the channel for the flow under gravity.
(2) The Rocks Below Our Feet
The rock below the Earth's surface is the bedrock. If all bedrock consisted of a dense material like solid granite, then even gravity would have a hard time pulling
water downward. But Earth's bedrock consists of many types of rock, such as sandstone, granite, and limestone. Bedrocks have
varying amounts of void spaces in them where ground water accumulates. Bedrock can also become broken and fractured, creating
spaces that can fill with water. And some bedrock, such as limestone, are dissolved by water which results in large
cavities that fill with water.
In many places, if we try to look at a vertical cross-section of
the earth we will see that rock is laid down in layers, especially in areas of sedimentary rocks. Some layers have rocks that are more porous than others, and here water moves more freely (in a horizontal manner)
through the earth. Sometimes when building a road, the layers are revealed by road cuts, and water can be seen seeping out through the exposed layers.
Try as it might, gravity doesn't pull water all the way to the center
of the Earth. Deep in the bedrock there are rock layers made of dense material, such as granite, or material that water has
a hard time penetrating, such as clay. These layers may be underneath the porous rock layers and, thus, act as a confining
layer to retard the vertical movement of water. Since it is more difficult for the water to go any deeper, it tends to pool
in the porous layers and flow in a more horizontal direction across the aquifer toward an exposed surface-water body, like
a river.
Water in the ground is part of the water cycle
Large amounts of water are stored in the ground. The
water is still moving, possibly very slowly, and it is still part of the water cycle. Most of the water in the ground comes
from precipitation that infiltrates downward from the land surface. The upper layer of the soil is the unsaturated
zone, where water is present in varying amounts that change over time, but does not saturate the soil. Below this layer is
the saturated zone, where all of the pores, cracks, and spaces between rock particles are saturated with water. The term ground
water is used to describe this area. Another term for ground water is "aquifer" .although this term is usually used to describe
water-bearing formations capable of yielding enough water to supply peoples' uses. Aquifers are a huge storehouse of Earth's
water and people all over the world depend on ground water in their daily lives.
around the same way in all rocks. Thus, the characteristics
of ground-water recharge vary all over the world.
2.
GROUND WATER VENTURE
It is seen that about 31% of total area of Rajasthan consists of saline groundwater. Thus it is very
essential to locate the areas of adequate fresh groundwater and to extract it one can follow the steps :
- To get a overview of the area of interest from a hydrometeorologist in
order to get the possible presence of adequate ground water.
- Regional geological overview of that area suggested.
- Reconnaissance survey and interpretation.
- Detailed survey and interpretation.
- Drilling methods.
- Pumping test.
- Hydro chemical study.
Hydro meteorological study:
The main activities in this discipline are continuous built up of rainfall
statistics, hydro meteorological studies for different river catchments with a view to estimate Standard
Project Storm (SPS), probable Maximum precipitation (PMP), Time distribution of rainfall storm, Intensity-frequency Analysis
of rainfall which is used by design engineers for construction of Dams, railways and road bridges and geophysicists for
different central and state organizations.
It also provides meteorological support for flood warning and flood control
operation by the field units of Central Water Commission. Hydromet Division also participates regularly in glacier expedition
to take meteorological observations to conduct snowmelt glaciological studies. There is a Hydrology Section at Pune for rainfall
registration and rainfall climatology and five small Hydromet Units at the five Regional Centers for organization and inspection
of rain gauge stations.
The Hydro meteorological Division consists of different units like :-
1) Rainfall Monitoring Unit
2) Design Storm Unit
3) Storm Analysis Unit
4) Glaciology Unit
5) Flood Met. Unit
6) Water Balance Unit etc.
The formulation of rainfall data statistics, hydrometeorology analysis of
different catchments for the benefit of project authorities and meteorological support for draught as well as flood warning
and flood control operation of the Central Water Commission are being continued.
The information provided by hydromet cell about the recharge areas , rainfall
statistics and catchments is very helpful to determine the areas of possible ground water resources.
Regional geological study:
A regional geological study
is necessary along with the predictions of hydromet cell to find the best match for locating the target aquifer.
If the area is not
a virgin land then geologists uses their past records ,observation wells and other surveys conducted earlier in nearby areas
that efficiently maps, tracks, and monitors groundwater resources. To support effective decision-making geological study reveals
the formations in subsurface. Moreover, geological studies reveals that the formations that may contain fresh water or saline
water.
- Geologic Mapping
An understanding
of the subsurface can be important for numerous other reason specific to each site and objective. Subsurface geologic mapping
using geophysical methods can provide this information. Generally, the selection of the appropriate geophysical method or
methods must be tailored to the expected site geology and many other factors.
With these knowledge a geophysicist can select a site for reconnaissance survey.
This cell carry out the satellite data interpretation
for preparation of geological and structural map including lineament for in house projects, Geo statistical and GIS based
applications for mineral and ground water exploration . It is equipped with visual interpretation equipments like PROCOM-2,
AVIOPRET Stereoscope for aerial photo interpretation etc as well as PC based Digital Image Analysis System.
Geophysical Section:
This section carries out geophysical survey (reconnaissance and detailed survey) for departmental projects as well as for
private entrepreneurs to identify the sub surface location of the ore body and its extension through Resistivity, SP, IP,
Seismic and Gravity survey. But in GWB of Rajasthan the main aim is to find the sub surfaces presence of aquifers, fractures
containing fresh water which can be supplied for household purposes and also for the industrial use.
Geophysical section deals with :
- Typically, organizations drill
wells and conduct resistivity / electromagnetic (EM) surveys to assess the location of subsurface water. However drilling
numerous wells is expensive and invasive, while resistivity / EM is rarely able to penetration to sufficient depths to support
effective decision-making.
- Aquifer and groundwater mapping
- Locate subsurface leaks and the paths that they take;
Mine infiltration, control, and remediation .Pipeline, reservoir, canal leak detection and location
- Delineate contaminated groundwater and reaction fronts;
and Determine the location of valuable subsurface resources, such as areas of hot water, steam, oil and gas.
- Landfill seepage mapping and Resource Mapping .
- Integrated GW Management Studies
Geophysical section also equipped with drilling tools by which
they carry out drilling for their target after the interpretation of the detailed survey. The litho logs obtained from the
drilling site is analyzed in the laboratory by geo chemist. Further this section with SP, Resistivity and radioactive logging
methods such as neutron, gamma-gamma, natural gamma interprets the subsurface formations.
ASPECT OF HYDROMETEOROLOGY
– A
METHODOLOGICAL APPROACH
The main source of ground water is rainfall. Rainfall is a natural phenomenon and to locate fresh water aquifer in a any region
the rainfall activity has to be thoroughly studied. In the arid region like Rajasthan the aerial, surface and subsurface condition
authorizes the need of a meteorologist who can precisely estimate the amount of water that can be accumulated in aquifers
of the concerned region after having a detailed look on the rainfall data of the past year and its behavior in the present
climatic scenario. The area is kept under close scrutiny to check the rise of water level during the monsoon and how much
the water level has depleted post monsoon.
As intensity of rainfall and runoff is directly proportional to each other
therefore it is very important to analyze Frequency of rainfall data.
Frequency analysis of Rainfall data :
 The frequency analysis of rainfall data is an important part of hydrological design procedures.
Analysis of rainfall data from single stations is often unreliable, is not temporally or spatially consistent and should generally
not be used for design purposes. Instead a set of accurate, consistent intensity-frequency-duration (IFD) design
rainfall data has been derived for the whole of Rajasthan.
For identification of effective recharge area in Rajasthan, probable maximum
precipitation (PMP) estimation is produced:
Generalised Methods of estimating PMP use data from all available storms
over a large region and include adjustments for moisture availability and differing topographic effects on rainfall depth.
The adjusted storm data are enveloped by smoothing over a range of areas and durations. Generalised methods also provide design
spatial and temporal patterns of PMP for the catchment.
Rain fall pattern:
The annual rainfall in the state varies significantly. The general trend
of Isohytes is from north-west to south-east. There is a very rapid and marked decrease in rainfall west of the Aravalli range
making western Rajasthan the most arid part. The average annual rainfall in this part ranges from less than
RAINFALL PATTERN IN RAJASTHAN
TABLE
1
|
Area (Sq.km) |
3,42,239 |
|
Rainfall (mm) |
504 |
|
Total Districts / Blocks |
32 districts 236
Blocks |
RAINFALL MAP OF RAJASTHAN
JODHPUR
 Jodhpur, the second largest city of Rajasthan. Geographically,
it is located at 26o N 18' latitude and 73o E 02' and at an average altitude of 240m above mean sea level.
GENERAL INFORMATION
Area : 22,850 Sq.km. (is 6.68 per cent of the State)
Altitude : 240 metres
Climate : Mean Max. Mean Min.
Summer : 42.2 degree C 27.3 degree C
Winter : 27.5 degree
C 9.5 degree C
Rainfall : 31 cms.
Jodhpur has an extreme climate. Rainfall is scanty and erratic, averaging
at 31 cm annually. The minimum temperature in summer is 20°C and maximum temperature varies between 45°C to 49°C. The
winter temperatures hover between the mid twenties at the max to 5-6°C at the lowest.
At CAZRI, the Central Arid Zone Research
Institute, which is an internationally recognized centre for research pertaining to problems of arid and semi-arid zones,
basic as well as applied researches are carried out on almost every conceivable area related to arid region.
Simultaneous joint surveys by the units
of hydrometeorology, geology, hydrology and meteorology reveal that:
- The soils are mostly sandy, low in organic matter (0.1-0.45 per cent), with
poor moisture-holding capacity (25-28 per cent) and a high infiltration rate. The pH values vary from 7.0 to 9.0, and the
moisture deficiency is the chief limiting factor on agriculture. Ground water is very deep, generally brackish and saline,
and there are no perennial rivers. Soil salinity and alkalinity further complicate the situation.
- The climate is characterized by high temperatures, with a mean diurnal variation
of 14°C, the mean maximum being 32.7°C and the mean minimum 18.8°C. The mean relative humidity is 41 per cent. The region
has a high solar radiation of 450-550 cal/cm² /day, and a mean wind velocity of between 10 and 20 kph, resulting in a high
evapotranspiration of 6 mm/day and consequently a high mean aridity index ranging from 76 to 78 per cent.
- The southwest monsoon which has its beginning in the last week of June in
the eastern parts, may last till mid-September. Pre-monsoon showers begin towards the middle of June and post-monsoon rains
occasionally occur in October. In the winter season also, there is sometimes, a little rainfall associated with the passing
western distribution over the region. At most places, the highest normal monthly rainfall is during July and August.
- Integrated survey of natural resources including land forms,
soils, flora, fauna, surface and ground water, present land use and land degradation status have been undertaken using the
concept of Major Land Resource Units (JLRUs). Burried courses of river in the desert were mapped using satellite imagery,
confirmed through geophysical depth soundings and successfully used for ground water exploration.
· Based on satellite imagery, maps of processes leading to desertification and common property resources
(PCRs) have been developed
From the satellite imagery the lineaments
of the images shows presence of moisture at subsurface, satellite imagery from microwave and infrared gives the details of
subsurface within five to seven kilometers of depth. With this knowledge the effective
area for ground water exploration is selected.
4.
GENERAL GEOLOGY
Geologically Rajasthan comprises rocks from oldest Archean rocks to recent alluvium formations
. The oldest formations are known as Banded Gneissic Complex exposed in central and southern Rajasthan.
The Aravalli hill range dividing the State diagonally is made up of Precambrian rocks of
Aravalli and Delhi Super group comprising the metamorphosed gneisses, schists, marble, quartzite, calc silicate and ultra
basic and acidic intrusive rocks, trending NE-SW and dipping 30° to 70° easterly. This is known as Delhi fold belt and is
an important horizon for base metals, other metallic and non-metallic minerals.
The eastern and southeastern parts of the State are occupied by rocks of Vindhyan Super group
mainly forming a plateau of sandstone, shale's and limestone. In the southern part Deccan trap formation of cretaceous age
are exposed.
Mineral Potentiality: The State is geologically so endowed that it become a veritable repository
of minerals. Rajasthan is fortunate enough to have a wide spectrum of mineral deposits. There are about 64 different kind
of major and minor minerals produced in the State, contributing an annual revenue of more than 300 crores.
Rajasthan is the sole producer of garnet (gem variety), jasper and wollastonite. Almost entire
production of zinc (concentrate), calcite, asbestos and gypsum in the country was reported from Rajasthan. Besides, Rajasthan
is the leading producer of ball clay (40%), feldspar (70%), and fluorite (graded) (59%), Kaolin (44%), lead concentrate (80%),
ochre (72%), phosphorite (79%), silver (54%), steatite (85%), barytes (53%), copper (34%), quartzite (33%) and silica sand
(21%).
STATE PROFILE RAJASTHAN-A GEOLOGICAL OVERVIEW
GEOLOGICAL
MAP OF RAJASTHAN
GROUND
WATER MEDIUM (Hydro geological Conditions)
The State
can be divided into three hydro geological units namely unconsolidated sediments; semi-consolidated sediments and consolidated
rocks. The unconsolidated sediments are of two types alluvial sediments and Aeoline deposits. The Alluvial deposits are confined
to Barmer, Jalore and Jodhpur district, consisting of sand, clay, gravel and cobbles. Valley fills have been reported from
Jhunjhunu, Ajmer, Bhilwara and Udaipur district. The Aeoline sediments constitute one of the major aquifers east of major
fault, east of Bikaner. It occupies an area of 1400 sq.km. The aquifer thickness is 40 to 80m.The yield of wells ranges from
100 to 150m3/hr. Semi-consolidated formation include sandstones, lime stones and Aur beds, covering Jaisalmer and Barmer districts.
The dugwells in Jaisalmer limestones yield 13 to 68 m3/day. The yield of wells in Lathi sandstne varies from 50-150 m3/hr.
The consolidated rocks includes gneiss, granites, schist, phyllites, marble and Vindhyan sandstones, limestone, quartzite
and basaltic flows, mostly restricted to eastern part of the State. The yield prospect is limited unless the well is located
near major lineaments or any other weak planes. The ground water quality is in general poor (brackish to saline) at deeper
levels.
Hydrogeological Surveys
Ground Water Board carries out regional hydrogeological studies which provide information on ground water occurrence in different
terrains and are essential for future planning of ground water development and management. First level (Systematic) surveys
on 1:50,000 scale has been completed for the entire country by March, 1991.This has generated basic information on various
hydrogeological parameters. Ground water being replenishable and dynamic in nature, it becomes essential to conduct periodic
hydrogeological studies (Reappraisal hydrogeological surveys) to assess the qualitative and quantitative changes in the ground
water regime in time and space. Approximately 2 lakh sq.km. area in different parts of the country is covered under periodic
studies every year. These studies help in reassessing changes in ground water scenario consequent to various development activities.
Photogeological and remote sensing data is extensively used
for hydrogeological purpose viz. source finding to demarcate the area and sites suitable for ground water development. Areas
remaining hitherto inaccessible have also been surveyed and these techniques have proved very useful in understanding ground
water scenario on regional scale. Advanced surface geophysical methods are used as source finding technique. In hard rock
terrains, this technique has proved indispensable to decipher sub-surface saturated fractures or situations suitable for ground
water occurrence.
GWB renders assistance to various urban, defence and public sector establishments to solve their immediate water supply problems
by selecting suitable sites for construction of ground water abstraction structures. The Board has carried out detailed surveys
in Lakshwadeep and Andaman and Nicobar Islands to delineate shallow fresh ground water lenses and deep ground water zones
in an otherwise saline water environment.
Remote Sensing
Remote Sensing is broadly classified into two categories;
(a) Active Remote Sensing: It uses its own source of EM energy which is directed
towards the object and return energy is measured.
(b) Passive Remote Sensing: It uses sun as a source of EM energy and records the energy
that is naturally radiated or reflected from the objects.
Basic Principles of Remote Sensing:
Remote Sensing to a great
extent relies on the interaction of electromagnetic energy with the matter (object). It refers to the sensing of EM radiation,
which is reflected, scattered or emitted from the object.
The organization has well equipped remote sensing
laboratories with opto- mechanical instruments, digital image processing systems, scanners, printers, plotters
and expertise in processing, enhancements, geo-referencing, interpretation and thematic map generation.
The remote sensing data inputs include B&W
aerial photographs, hard copies and transparencies of FCC satellite images and digital data of various satellite sensors like
IRS-WIFS, LISS-II, LISS-III, PAN, LANDSAT-MSS, TM and SPOT-VHRR. Golden Software Surfer, ERDAS Imagine, Ilwis
and ENVI Softwares are used for the image generation and enhancement. All the Regional Headquarters are equipped with
remote sensing laboratories. GIS(Geographical Information System) and use of Remote Sensing
in groundwater exploration.
From Remote Sensing we can study:-
1) Geomorphology
2) Lithology
3) Structures
4) Slopes
5) Hydrology
6) Soil
covers
7) hydrogeology
We can delineate the structure from the satellite data. She told us about the
software used for processing of satellite pictures such as
1) ERDAS
2) ENVI
3) ARCVIEW
4) GEOMETRICA
5) MAPINFO
The resolution of different satellite pictures are different such as LISS-3
data have the resolution of 23.5 m whereas panchromatic data have 5m resolution .The resolution of WIFS data is 1.5 km
|
SATELLITE |
SENSOR |
RESOLUTION |
|
IRS 1A/1B |
LISS-I & LISS-II |
72.5m |
|
IRS 1C/1D |
LISS-III & PAN |
23.5/5.8m |
|
LANDSAT |
THEMATIC MAPPER |
30m |
|
SPOT III & IV |
MLA &PLA |
20/10m |
|
ERS I & II |
C-BAND RADAR |
15m |
|
