Remote sensing is one of the modern tools used for quick investigations of a country's natural resource potentialities with particular reference to the occurrence of the rocks, soils, water and vegetation. Remote sensing studies of aerial photographs and satellite imageries have proved to be very important in providing data on parameters that are essential in judging the water resources of a particular region. Several authors have used remote sensing for the investigation of field studies permitted the study of structures and correlated them with lineament interpretations [1-9]. Hydro-geological setting of springs and wells were investigated in the field from well logs and pumping test data. All thematic layers were integrated and analysed in a GIS. The parameters include the nature and distribution of vegetation, soil-moisture, drainage patterns and their frequency. Also the other important aspects are the nature of rock types and their structural attitudes and the geomorphologic features of the area. The geology of the area is quite complex and there are major tectonic disturbances with four major cycles of depositions and erosions (diastrophism) during last one billion years . The basement is Vindhyan super group of the Kaimur series followed by erosion; then Rajpur and Mohanpur formations occur and followed by erosion. Next formation is Hanumannagar which is bare formation between two erosion unconformities . The study area covers several districts: Bhojpur, Rohtas, Patna, Jahanabad, Aurangabad, Ballia and Chapra of the Uttar Pradesh. In this paper, we investigated two lineaments alongside of the river Ganga in northwest parts of the area in Ballia district, which may play a very vital role in groundwater monitoring in the area. A detailed analysis of geomorphology and geology of the Lower Son valley on the basis of photo-interpretation techniques for surface features, drainage pattern and density, and drainage texture has been carried out to determine alluvial type, permeability, tributary, etc. As there have been wide varieties of material exogeny with varying drainage patterns, textures and densities, the materials are found to have different hydrologic properties. The Darcy velocity analysis enab- led to find the flow pattern of ground water. Thus, we find that the water potentiality of the entire Lower Son valley is very high, and there is a very good prospect for its exploitation in future.
2. Location of the Study Area
2.1. Imagery of the Study Area
The satellite imagery used is IRS LISS 1 B1 (index no. 62PO22-R50), taken on 29th January 1991 at 10:01:24 AM. The scale of the imagery is 1:250000 in the band -1 (Figure 1).
2.2. Coverage of the Study Area
The area under investigation is about 13000 [km.sup.2] covering 44 administrative blocks and located between 24.5[degrees]26[degrees] N latitude and 83.5[degrees]-84.8[degrees] E longitude (Figure 2). The area of interest is covered by the Survey of India toposheet No. 72 C & D (1:250000) and extends over seven districts, namely Bhojpur, Rohtas, Patna, Jahanabad, Aurangabad, Ballia and Chapra.
The basin lies in a zone of average rainfall of 1250 mm. About 88% of the annual precipitation occur during the four monsoon months June-September, of which 60% is recorded in only two months, July and August. During summer, the rainfall is about 3% of the total precipitation with the air temperature as high as 45[degrees]C and the relative humidity of the basin is 38%. In winter, the minimum air temperature is 6[degrees]C and the relative humidity is 63%. The daily mean wind speed in December is 4.2 km/hr, which rises to 8.5 km/hr in May. The average annual wind speed is 6.5 km/hr.