Groundwater monitoring for the impacts of geothermal energy development, conversion and waste disposal is similar to groundwater monitoring for other purposes except that additional information is needed concerning the geothermal reservoir. The research described here developed a six-step methodology including failure analysis and computer-based contaminant transport and geochemical models to design groundwater monitoring plans. Failure data analyses indicate that production and injection wells have the highest probability of failure and should be the focal points for groundwater monitoring. Groundwater monitoring techniques fall into four categories: (1) monitoring the injection/production well, (2) monitoring in the saturated zone, (3) monitoring in the unsaturated zone, and (4) monitoring on or above the ground surface. Location of the monitoring wells and what to measure in them may be determined with the aid of computer contaminant transport and geochemical models. POLLUTE is a nondispersing contaminant transport groundwater computer model that enables the user to locate a contaminant plume at a given time. Prediction of resultant fluid chemistries from a leaked geothermal fluid may be essential to unambiguous evaluation of geothermal fluid impact at remote groundwater monitoring sites.