This book is an attempt to test the spatial analyst tool of Arc/ GIS 9.3 to map hydrogeochemical mapping in the part of Gadilam River basin especially to develop hydro geochemical spatial information,to determine the cause for water table fluctuation and to identify the groundwater recharge zones for the above basin. Sulphate concentration is found to be poor in South central and North west part of the study area around Thiruvamur and Alagappasamudram. Source of sulphate can be attributed to weathering of sulpher from Terteary upland in the south.Concentration of alkalies in groundwater was...