'In Bihar Plains, ground water is the most important source of drinking and irrigation water. The purpose of this interdisciplinary study, undertaken along the levee of river Ganga in the Mid Ganga Plain, was to determine the existence and intensity of arsenic contamination in aquifers being tapped for direct and indirect ingestion of the properties of the region’s ground water, in the four districts of Bihar [India], i.e., Patna, Bhojpur, Vaishali and Bhagalpur. The methodology involved formulation of a protocol for arsenic detection in ground water, use of Field Test Kits for initial detection, obtaining GPS coordinates of arsenic hotspots for spatial analysis of the problem, and confirmatory testing of  arsenic hot samples by U.V., and Atomic Absorption Spectrophotometry. Water samples of 28000 private and government owned hand pumps were tested. Many arsenic hotspots were detected in all the four districts, the coordinates of which were recorded by GPS. Arsenic contamination up to 1861 ppb. was found in the western district of Bhojpur, against the W.H.O. permissible limit of 10 ppb. The greatest frequency of contaminated hand pumps was noted in the eastern district of Bhagalpur. Sharp spatiotemporal variations of contamination levels were detected in this densely populated study belt.