4. DATABASE AND METHODOLOGY
Digital data IRS 1A LISS II, October 1990, Path 29 Row 48 A1,
Geocoded FCC (band 2,3,4) ofIRS 1B LISS II, October, 1992 and
March, 1993 satellite imagery and panchromatic B/W aerial
photographs, 1988 (1:50,000 scale) have been used in the above
study. Based on monoscopic interpretation of satellite imagery,
bytakinginto consideration various image interpretation elements
such as color, tone, texture, size, shape, shadow and association
etc., stereoscopic interpretation of aerial photographs and
information extracted from field observations on depth to water
level and water quality and digital image processing, the following
thematic maps were prepared on 1:50,000 scale.
* Geological map
* Geomorphological map
* Lineament map
* Slope map
* Drainage map
* Drainage density map
* Depth to water level map
(Nov. 1994)
* Water level fluctuation map
(June to Oct. 1993)
* EC based quality map
All the above thematic maps were digitized by reducing these
maps on 1:131,578 scale to fit the size of the digitizer (20 cm x
20cm). IDRISIGIS software package was used to integrate all the
above thematic maps. À standard grid cell size of 200X200 has
been selected by considering a number of factors like size of
minimum interpretable unit and appropriate format for the screen
display. All these digitized maps were rasterized by the process
of lineras and polyras. A rating weightage factor system has been
developed for the integration ofthese thematic maps. A numerical
rating system ranging between 0 to 10 have been assigned to
various classes of individual theme maps based on the degree of
influence of individual categories on ground water regime of the
region. Secondaly all these thematic maps have been assigned a
weightage factor, this is called equal wieghtage integration method
aimed at reducing subjectivity in the analysis, however it can not
remove subjectivity in rating/coding, completely from the analysis.
Two composite maps one based on integration of satellite based
information and another integrated field observation map, were
prepared. These were further overlayed and a composite map was
prepared. By integrating this map with EC based quality map,
hydromorphogeological map was finally prepared showingutility
map for ground water prospects.
S. RESULTS AND DISCUSSION
Hydromorphogeological map of the area is shown in map -2.
Utility map showing ground water prospects in various zones is
shown in map -3. Hydromorphogeological characteristics and
ground water prospects of various geomorphic units are discussed
below:
5.1 HILLS
5.11 Low structural hills: The area is traversed by two parallel
ridges bordering the N-S Sohna valley, known as Harchandpur
and Sohna ranges. These are composed of Alwar group of rock
formations of Delhi super group. Lithological composition is
20
essentially quartzites with pegmatite veins and schist intercalations
with subordinate bands of arsenopyrite and graphite. Five set of
joints have been demarcated. In the vicinity of pegmatite bodies
the quartzites are often sheared. Joints allow limited infiltration
into them. However by and large “low structural hills" acts as a
Zone of surface run off and is negligible from ground water point
of view.
5.12 Valley fills: It consists ofunconsolidated material, coarseto
fine sand, silt and clay. Water level was observed as 6 to 12
meters below ground level (bgl) with fresh quality. It is good from
ground water prospects point of view. It harbours limited water
hence dug wells/ shallow tubewells are suggested in this zone.
5.2 PEDIMENT
A narrow zone immediately bordering the hills is pediment,
representing partly an undulating rocky surface sloping away
from the hills and partly a surface with very shallow weathering
and a thin veneer of soil. It is composed of weathered quartzites
with gravelly soil and is found at few places in the study area.
Water level in this zone varies from 15 to 20 metres (bgl).
Pediments with joints or fractures yield limited extent of ground
water. This zone is poor from ground water exploration point of
view.
5.3 PIEDMONT PLAIN
This zone is constituted of both piedmont aeolian plain and
piedmont alluvial fan plain. It is composed of coarse to fine sand,
silt and clay and is highly porous and permeable. Dendritic
drainage pattern observed. This is a fresh water zone with water
level ranging from 16 to 21 metres (bgl). EC in this zone varies
from 0-2,000 micromhos/cms. It falls under fairly moderate to
good ground water prospective zone.
S.4 AEOLIAN PLAINS
Large area in western side is covered by sand of aeolian origin
with presence of scattered sand dunes/sand mounds. The color of
sand varies from light brown to tan/buff. Lithological composition
is medium to fine sand with little clay. It is porous and permeable.
There is no surface drainage in this zone, but small drains which
originate from hill sides die out in this area, hence it is good from
ground water recharge Point of view. Depth to water level varies
from 17 to 27 meters. EC in this geomorphic unit varies from 0-
2000 micromhos/cms. Average discharge of tubewells in this unit
ranges from 150 to 350 ltrs per minute (lpm). This is good to
moderate from ground water point of view. Moderately deep to
deep tubewells are recommended in this area. Artificial recharge
should be considered by constructing check dams/waterharvesting
structures or erthen dams at suitable locations after due
investigations.
S.S ALLUVIAL PLAIN
5.51 Paleochannels/channel remnants: Two paleochannels of
probably Yamuna River have been demarcated in the area. Few
channel remnants have also been identified. These are composed
of coarse to medium sand with silt and clay, forming good
aquifers. These are highly porous with water level varying from
4-9 meters (bgl). Shallowto deep tubewells are feasible. This unit
is excellent from ground water point of view. Pump test results
showtubewell discharge of 632 Ipm near village Isaqi in this unit.
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B6. Vienna 1996
