This revised edition has been written to provide the reader with a general understanding of the principles involved with groundwater, its movement and character, and the subsequent impact these characteristics have on the design, construction, and maintenance of groundwater well systems for water utilities. The contents of this edition include two major changes from prior editions: the incorporation of the well construction standards formerly attached to Standard A100 Water Wells and sustainability of groundwater supplies in light of competition, lack of regulatory limitations, overdrafting, and climate changes. This manual will provide operators and engineering staff with an understanding of groundwater principles that will help them to make decisions on design, installation, phasing, and repair needs when problems or the need to expand supplies arise.