Application of Remote Sensing and Geographic Information System in Groundwater Resource Management: A Case Study from Ladakh, Jammu & Kashmir

INTRODUCTION

Proper management of groundwater is essential for the development of any country. Ground water is a major source of drinking water to the rural population in India. There are still, a large number of habitations in the country which are either non-covered (NC) or partially-covered (PC) due to the non availability of suitable drinking water sources. The spatio-temporal variations in rainfall and regional / local differences in geology and geomorphology have led to uneven distribution of groundwater in different regions across the country. Systematic estimation and budgeting of groundwater resource based on its spatio-temporal distribution & its allocation are required for meeting the competing demands for irrigation, industrial and domestic usage.

Groundwater study involves analysis and integration of large volume of data from various sources. Remote Sensing and GIS technology offers effective and meaningful solutions to the problem. NRSC has taken up a project to create a scientific database on ground water in the form of ground water prospects maps based on the interpretation of Indian Remote Sensing (IRS) Linear Imaging Self Scanning (LISS) III data having spatial resolution 23.5 meter with limited ground checks, in GIS environment. The database facilitates scientificsource finding of ground water for all the habitations in the country besides providing necessary information for selection of sites for construction of recharge structures to improve the sustainability of drinking water sources.

The groundwater prospects hitherto are evaluated considering only the rock type, i.e., the primary porosity and permeability of the rock formations. Hence in most of the groundwater maps, rock type forms the basic unit. However, the secondary porosity and permeability contributed by fracture network and geomorphological setup also significantly controls the occurrence and movement of groundwater particularly in hard rock area. Geomorphology in terms of its topographic variations plays an important role in understanding the surface runoff and infiltration. It also influences the groundwater flow and quality to a certain extent. Then, it percolates into the ground, comprising of different rock formations having differenthydrogeological properties (Sankar, 2002 and Bahuguna 2003; Rao, etal, 2001). Satellite data in conjunction with limited ground truth data provides cost & time effective accurate data on all these parameters. Similarly, GIS forms an effective tool for integration and analysis of the data on groundwater controlling parameters. Taking the advantage of the availability of satellite data and GIS technology, an innovative methodology hasbeen developed for assessment of groundwater prospects more effectively.

ADVANTAGE OF SATELLITE DATA IN GROUNDWATER STUDY

The satellite images acquired using Remote Sensing technology provides diagnostic signatures on the parameters i.e rock types, geomorphology, geological structures and recharge conditions which control the occurrence and distribution of groundwater. Using these signatures, all these parameters can be studied and mapped accurately avoiding detailed field survey which is time taking, particularly in hilly terrains where the area is inaccessible, the satellite data is highly useful (Mather, 1987; Lillesand and Kiefer, 2004). The study of ground water demands a systematic inventory of all the details of the parameters for drawing meaningful conclusions. It is time taking to bring out all the details pertaining to the parameters by field work using conventional methods. Further, the occurrence and distribution of groundwater at a given location cannot be assessed just based on the consideration of parameters only at that location. They have to be considered in their totality.

The synoptic view of the image derived due to large area coverage, provides information about the parameters on regional scale thereby facilitating the understanding of the ground water regime as a whole. The groundwater regime is a dynamic system governed by the combination of several parameters. For the proper understanding of the system, the role of each parameter in forming the aquifer and the degree of its influence on the groundwater prospects need to be evaluated. The satellite data provides information about the parameters in an integrated form, so that, the role and influence of each parameter can be studied with respect to the other parameters there by a quick evaluation of groundwater conditions can be made. The three dimensional view provided by the satellite data facilitates to study of the terrain conditions and geomorphology more effectively.

STUDY AREA

Leh district is situated at 32^° 20’ to 35^° 15’ North latitude and 76^° 20’ to 79^° 40’ East Longitude (Figure 1). It has an area of 45100 sq. km, major part of which is rugged hilly terrain occupied by glaciers and snowfields. The elevation varies from 5900 m to 8500 m above mean sea level. Regionally, the study area forms part of a major Himalayan mountain belt comprising Proterozoic to Recent formations. The soil type is characterised by sandy soil and hilly soils.

GEOLOGY

Geologically the area covers formations from igneous, sedimentary and metamorphic rocks of sub-recent to Proterozoic age in nature. Important among area –Nidar Ophiolites, Shyok formation,Shergol Ophiolite melange, Khardung volcanics, Ladakh Plutonic complex, Indus formation etc. The lithological map of Leh district is shown in Figure 2.

GEOMORPHOLOGY & LANDFORM

The area is very rugged and mountainous terrain with little or no vegetation. The area is occupied by glaciers and snow fields. Siachen glacier, Shyok glaciers are some of the major glaciers present in this region. Main geomorphology is the large ‘U’ shaped glacial valleys developed by glacial erosion and moraine deposits. Glacial outwash plains, Linear Ridges, Eolian Plain, Talus cones, Intermontane Valleys ,Valley Fills and Denudations Hills are the other landforms types in the region. Figure 3 depicts the geomorphology map of theregion.

GEOLOGICAL STRUCTURES

The area is characterised by various major thrust systems like Indo-Tsango Suture zone. Besides these thrusts there are various lineaments and fractures present in the region. Many of the springs are located in the fault/fracture zones. Figure 4 shows the geological structure map of the region.

HYDROLOGY

The region is well drained by water from snow-melt runoff and perennial rivers such as Indus,Shyok, Nubra rivers. The main source of irrigation is through canals and an area of nearly 10,000 hectares is drained through canal irrigation. Groundwater irrigation is nil in the district. The major crops are wheat, barley, pulses and fruits and all these crops are irrigated by canals. Figure 5 showing the hydrology map of the district.

METHODOLOGY & RESULTS

In the first step, all the above maps /layers on groundwater controlling parameters have been mapped based on the onscreen interpretation of satellite data with limited ground checks. In the second step, the data on the parameters have been integrated in GIS environment to delineate homogenous hydrogeomorphic units having unique combination of lithology, geomorphology, structure and recharge conditions. The hydrogeomorphic units are considered as aquifers for all practical purposes. Based on the weighted index overlay method considering the Hydrogeological characteristics of the parameters, the groundwater prospects are evaluated and drawn meaningful conclusions on the occurrence and distribution of groundwater. Figure 6 shows the groundwater potential map of Leh district.

Major aquifer systems in the district are consolidated sediments / hard rocks, unconsolidated sediments and recent alluvium deposits. The denudational hills with consolidated sediments having very less potential of groundwater. Many cases ground water occurs in the fractures / lineaments in the hilly terrains. The yield varies from 50 – 100 litre per minute (LPM).

Valley Fill Shallow(VFS), Talus, Glacial Valley (GV), Glacial outwash plains (GOWP) and moraine deposits constituted by unconsolidated sediments forms aquifers having moderated yield (200-400 LPM). The maximum yield of >600 LPM of groundwater is expected from the unconsolidated alluvium of river / drainage channels. Most of the habitations are located along the alluvial plains near to river channels.

Groundwater development in the district is in moderate scale and restricted to valley portions only. Many of the drinking water sources depend on the natural springs, rivers and nalas. As Leh is part of the Ladakh Cold Desert’, freezing of water is a major concern during winter season. Snow water harvesting is also an artificial recharge technique which can be adopted in the district for augmenting the water. Spring development along major fracture zones can provide more groundwater in many hilly terrains. Check dam type recharge structures are suggested along the foot hill zones for recharging the groundwater. Valley fill deposits, riverterraces and moraine deposits are the highly productive zones for construction of tube wells for water supply. Due to the high elevation and snow-melt runoff hydropower generating sites can be constructed at appropriate locations and the arrested water can be used for irrigation.

RECOMMENDATIONS

- Natural springs data has to be collected and necessary spring development activities needs to be carried out.
- Snow water harvesting practices must be adopted in many areas.
- Drilling of suitable wells in moraine deposits needs to be carried out.

ACKNOWLEDGEMENTS

The authors are thankful to Dept. of Drinking Water Supply (DDWS), Ministry of Rural Development (MoRD) Govt. of India for financial support to RGNDWM project under which the study was carried out. Authors are also thankful to Director, NRSC and Dy. Director, RS&GIS-AA, NRSC for their encouragement in carrying out this work. The help provided by colleagues from Hydrogeology Division of NRSC in preparing this manuscript is gratefully acknowledged.

REFERENCES
- Bahuguna, I. M., Nayak, S., Tamilarsan, V. and Moses, J., 2003. Groundwater prospective zones in Basaltic terrain using Remote Sensing. Jour. of the Indian Soc. of Remote Sensing, 31 (2) : 107–118.
- Lillesand, T. M. and Kiefer, R. W., 2004. Remote Sensing and Image Interpretation (4th edition). John Wiley & Sons, New York, USA, 725 pp.
- Mather, P. M., 1987. Computer processing of remotely sensed images: An Introduction John Wiley & Sons, NY, 352 p.
- Rao N. S., Chakradhar, G. K. J. and Srinivas, V., 2001. Identification of groundwater potential zones using Remote Sensing techniques in and around Guntur Town, A. P. J. of the Indian Soc,. of Remote Sensing, 29 (1 & 2) : 69–78.
- Sankar, K. 2002. Evaluation of Groundwater potential zones using remote sensing data in Upper Vaigai river basin, Tamilnadu, India. Jour. Indian Soc. Remote Sensing, 30 (3) : 119– 129.

K. Babu Govindha Raj, Paritosh Singh Chauhan & S.K. Subramanian
Hydrogeology Division, RS & GIS Application area, National Remote Sensing Centre (NRSC)
Indian Space Research Organisation (ISRO)