20-09-2016, 11:16 AM
Ground water potential in a semi-arid region of
Andhra Pradesh - a geographical information
system approach
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Abstract. Continuous and adequate supplies of potable water from ground
reservoirs are important for sustained agriculture, industry and domestic use
throughout huge semi-arid regions of India. The present paper describes an
approach to investigating groundwater potential over extensive geographical areas and illustrates its potential with reference to watershed planning in the large Varaha River Basin (VRB), Andhra Pradesh, India. The method involves the
creation of a systematic database of information from satellite data for reconnais- sance survey before going for eld exploration. Colour composite images from
Landsat Thematic Mapper and Indian Remote Sensing (IRS) satellite were used
to interpret various thematic maps of the Varaha river basin. SPOT 1 MLA data of band 3 on a 1:250 000 scale was used for improving the accuracy of interpretation
of topographic units due to its higher resolution and stereo coverage. Slope and other coverages were derived from topographic maps. The thematic and
topographic information was digitized and ERDAS Imagine GIS software was used to analyse this information. Groundwater potential zones were delineated
through subjective weights assigned to interpreted thematic and derived topo- graphic units according to their likely in ltration capacities. Seven categories of
groundwater potential ranging from very good to poor were derived automatic- ally. Field measurements were then made within a selection of these categories
to check the groundwater potential at selected sites. The validity and eŒectiveness
of using remote sensing and GIS techniques for improving the targeting of eld
observations for groundwater for a huge river basin is shown by comparing the
inferred groundwater potential with the eld measurements.
Introduction
A scienti c approach for the management of natural resources like water requires
a periodical revision of the database. Revision involves checking and changing
information to re ect the situation in the eld. Recent advances in computer software
have lead to the development of a Geographical Information System (GIS). These
enables a quantitative assessment of the consequences of heterogeneity in ecological
systems over a broad range of spatial and temporal scales. Integration of several
surface features that indicate groundwater potentialities in a systematic way is an
important aspect in water management studies. A database designed to support
water resource decisions must contain a variety of thematic information because of
the interdisciplinary nature of water problems. Conventional methods of exploration
do not always take into account the diverse factors aŒecting the presence of ground- water. The regions or locations selected by these methods are therefore not as reliable
as they could be. The technology of Geographical Information Systems (GIS) provides a means of
introducing information and knowledge from other data sources into the decision
making process and helps the handling and manipulating of classi ed remotely
sensed data (Adinarayana and Ramakrishna 1996). Many scientists have shown that
integration of multi-thematic maps of the Earth, remote sensing and GIS is useful
for identifying accurate water zones for exploration and for the development and
management of groundwater resources (Sidhu and Mehta 1989, Mattikalli et al.
1995, Kamaraju et al. 1996). Lynn (1989) developed a hydrologic run-oŒ/rainfall
model using GIS. A number of studies have been carried out to prove the capability
of remote sensing and GIS technologies in natural resource studies and development
planning (Smith and Blackwell 1980, Hellden et al. 1982, Trotter 1991, Kushwaha
1993). The rst pilot study in India using remote sensing and GIS was done in
Karnataka state (NRSA 1987). In the present paper, an attempt has been made to
locate groundwater potential zones in the Varaha river basin using remote sensing
and geographical information system techniques.
2. Study area
The VRB is located between the geographical coordinates 82ß30¾–82ß53¾ E longitude
and 17ß23¾–17ß55¾ N latitude in the Visakhapatnam district of Andhra Pradesh
( gure 1). The total area of the basin is 1132.70 km2 and the upper reaches are
covered with hilly tracts with steep slopes of > 31ß and the lower part of the basin
is a large ood plain. The area is drained by many ephemeral streams joining the
main river Varaha. This ows over a length of 62 km towards the east and debouches
in the bay of Bengal at Bangarammapalem. The most prominent soils in the basin
are hills (unconsolidated silty soils), sandy silty clay, sandy silty gravel, sandy soil, marine clay, and coastal sands. The temperature varies from 15ß C to 25ß C in winter
and 32ß C to 38.8ß C in summer and the average annual rainfall is about 1230.70 mm
showing a semi-arid type of climate. The chief rock types exposed in the study area
are khondalites (quartz-perthite-plagioclase-sillimanite-garne t gneisses), felsic char- nockites (orthopyroxene-plagioclase-perthite-garnet-quartz) , calc-silicate granulites
(Salite-scapolite-plagioclase-Wollastonite) rocks.
3. Data used
The following data were used for the study:
E Landsat TM, False Colour Composite of bands 4, 3, 2 of scale 1:50 000;
IRS 1A (LISS II), Geo-coded, FCC of bands 4, 3, 2; SPOT 1, HRV 2, MLA
band 3 of scale 1:250 000. E The Survey of India topographic maps 65 K/9 to K/15 of scale 1:50 000 and
census reports obtained from State Government departments. E Non spatial data like temperature, rainfall data were collected from Indian
Meteorological Department.
4. Importance of base maps in the context of hydrology
Six thematic coverages were generated for the study. The coverages include land
use/land cover, soils, hydrogeomorphology , iso-drainage density, slope and rainfall. The basic properties of all thematic maps were considered in the classification.