Written by Neven Kresic, author of several best-selling books on groundwater, Hydrogeology 101 is a college textbook introducing basic concepts in groundwater science and engineering with 16 lectures, the duration of a typical one or two-semester course at American universities. With hundreds of full color figures and photographs, it covers Introduction to Hydrogeology, Groundwater Use, Porosity and Hydraulic Characteristics of Porous Media, Groundwater Flow, Aquifers and Aquitards, Groundwater Recharge and Discharge including Springs, Flow in Unsaturated Zone, Groundwater Chemistry, Groundwater Contamination and Remediation, Field Investigations, Groundwater in Water Supply, and Groundwater Drought in California Case Study by Alex Mikszewski.This college textbook is available for free download, and reposting for non-profit uses by all interested.