Arsenic contamination of the groundwater poses a major threat to millions of people living in the fertile plains of the Ganga river basin. In the Indian state of Bihar, which is located in the Ganga river basin and has a population of more than 100 million, millions of groundwater wells remain to be tested to estimate the scale of arsenic contamination. In this study, a geostatistical model is developed based on the measured arsenic concentration in the aquifers (samples collected from hand tube-wells) and hydro-geomorphological factors for one out of 38 districts in Bihar, namely Vaishali. Maps of arsenic concentration in the fresh water fetched from hand tube-well of different depths were prepared. The results reveal that high spatial variability of the arsenic concentration can be modeled well based on hydro-geomorphological parameters, most importantly proximity to river, and depth of hand tube-wells. The model might be adapted to estimate the arsenic risk in groundwater in entire Bihar.