DEDICATION: This technical paper is published in memory of our senior author, Dr. Donald B. Aulenbach, who worked closely with Professors Lawrence K. Wang, Mu-Hao Sung Wang, Nazih K. Shammas, William A. Selke, Milos Krofta and Daniel Guss from 1981 to 2019 for developing a humanitarian engineering program at the Lenox Institute of Water Technology (LIWT; formerly Lenox Institute for Research), teaching/researching there as an Adjunct Professor for almost two decades, and publishing many research papers and textbooks for academic contribution to the humanity. We salute and will forever remember Don. ———-ABSTRACT: This chapter introduces the basic hydrology, water resources and a dissolved air flotation (DAF) boat plant for lake water treatment. Specific coverage includes: special features of water and their relationship to life on earth, hydrology, evaporation, transpiration, evapotranspiration, infiltration, percolation, runoff, ground water, impact of pollution on lakes, thermal impacts on the aquatic environment, toxics in water resources, goals of water pollution control, dissolved air flotation boat plant for lake restoration, glossary, and a list of senior author’s recent publications