IRS-1A AND LANDSAT DATA IN MAPPING DECCAN TRAP FLOWS AROUND PUNE, INDIA : 
IMPLICATIONS ON HYDROGEOLOGICAL MODELLING 
VIVEK S. KALE and HIMANSHU KULKARNI 
Department of Geology, University of Poona, PUNE 411 007, INDIA. 
ABSTRACT 
Hardcopy multispectral data from IRS-1A and LANDSAT were used in conjunction with aerial photographs 
and field verification for mapping the Deccan Trap basaltic lava flows in the region around Pune. 
a part of the Deccan Trap Volcanic Terrain of Western India, is perpetually drought-prone 
region, 
This 
and 
the groundwater from the basaltic aquifers is the prime source of water during summer. 
The 
the bedrock can be interpreted from the FCCs. 
as lineaments. 
the basalts. 
IRS-1A and LANDSAT data not only allow the extrapolation of individual basaltic flows across 
of kilometres, but also brings out their irregular geometry. 
tens 
The amygdaloidal and compact nature of 
The extension of regional fracture zones can be traced 
These and other related factors have a direct 
influence on the groundwater potential of 
It is therefore concluded that the IRS-1A and LANDSAT multispectral data are extremely useful tools for 
rapid extrapolations 
terrain around Pune. 
KEY WORDS : 
modelling. 
INTRODUCTION 
The major asset of remote sensing, namely its, 
capability of rapid and accurate areal coverage, 
becomes crucial during the groundwater exploration 
in water-scarce regions. Unfortunately its 
populist publicity has raised expectations of this 
tool far beyond its real capability, often ending 
up in criticism that it fails to satisfy these 
(hyperinflated) expectations. The experience. of 
groundwater exploration in the Deccan Trap 
basaltic terrain of Western India could be cited 
as a typical example of this problem. 
Several strategies such as "soil moisture 
estimation using MSS data", "lineament 
intersection loci contouring" and so on were 
proposed for exploring groundwater in this pile of 
basaltic flows. Not that any of these strategies 
were complete failures, rather they did succeed in 
their test sites. However, their  extrapolations 
to adjoining sectors often proved disastrous. The 
failure lay, not with the remotely  sensed data, 
but with its handling without  appreciating the 
vagaries of the Deccan Trap basaltic aquifer 
systems and without making due allowances for the 
complexities of these basaltic flows themselves. 
An appropriate understanding of such factors would 
allow a more efficient use of the remotely sensed 
data in exploration of the groundwater resource. 
DECCAN TRAPS OF WESTERN INDIA 
The Deccan Trap Volcanic Province of Western India 
(Fig. 1) occupies more than 500,000 sq.km. in a 
tropical - subtropical region. This stack of 
subhorizontal basaltic flows with an estimated 
thickness of over 1500 m, which erupted around 65 
+ 10 million years ago, has been classified on the 
basis of chemical composition and petrological 
variations, into 12 Formations (Subbarao, 1988). 
The constituent flows, primarily of basalts, with 
thicknesses varying from less than a metre to 
almost 100 m individually, are presumed to have a 
flat, tabular geometry and have been traced to 
and efficient targetting of groundwater resources 
Multispectral data; Deccan Trap basaltic flows; Mapping; 
429 
in the Deccan Trap basaltic 
Groundwater exploration and 
extend across long distances (Mitchell and Cox, 
1988). In the field, they are classified into 
"gimple flows and compound flows" or as "compact 
basalts and amygdaloidal/vesicular basalts" or as 
the analogs of the Hawaian "aa-type and  pahoehoe- 
type flows". These field classifications are 
besides the petrological and chemical 
classifications of the Deccan Trap flows. 
  
o 
    
68°E 72 
  
  
  
  
  
  
  
FIG.l]  : The Deccan Trap volcanic province of western 
India. The close spaced shading is the sector of 
dominant compound flows, while simple flows dominate 
in the wide spaced shaded region (after Deshmukh, 
1988). The three major zones of known post-Trappean 
structural disturbances, characterised by 
proliferation of fracture zones and dykes are the 
ENE-WSW trending Narmada Son Structure (along the 
Narmada river valley), the NW-SE Kurduwadi Lineament 
(along which the Bhima river valley is aligned) and 
the roughly N-S trending Konkan Coastal Belt (along 
the western edge of this province). [adapted from 
Kale,et al.,1992]. The rectangle marks the study 
area.