This book provides an overview of the current state of knowledge on the occurrence and distribution of arsenic and iron problems in water supplies in North Lakhimpur sub-division of Lakhimpur district, Assam. With groundwater-based water supply and irrigation projects being implemented across India, this book is an attempt to address the groundwater contamination of arsenic and iron in a regional context. A comprehensive analytical and statistical analysis of distribution of pH, arsenic and iron in groundwater in seven development blocks of North Lakhimpur sub-division of Lakhimpur district, Assam has been presented in this book. The water sources, selected for this study, have been in use for a long time for meeting drinking water needs and other domestic purposes. The focus of the study is on the rural areas rather than urban areas, due to the particular difficulties associated with applying mitigation measures in scattered rural communities. Sporadic occurrence of arsenic in groundwater has been observed in the study area. It is hoped that the book can be used as a reference while carrying out regional-scale studies of groundwater quality in near future.