Development Response of the Moana Geothermal System, Reno, Nevada

Abstract

The Moana geothermal system in Reno, Nevada is a low to moderate temperature (<150°C) geothermal resource that is exploited for space and water heating purposes. The geothermal system is believed to be a fault controlled, hydrothermal convection system under confined conditions with lateral and vertical leakage. Most of the geothermal wells are used for residential heating. Over 90 percent of the residences intermittently pump off geothermal water to maintain high temperatures in the wells. A well monitoring program was implemented in January 1989 to assess the state of the geothermal reservoir. Water levels and vertical temperature profiles were measured on a monthly basis for 13 months. A comparison of historic static water levels to those collected for this study indicates that in the most heavily used portion of the geothermal aquifer, the hydraulic heads have declined. This decline in hydraulic heads may induce additional leakage of cooler water from the overlying unconfined aquifer, thus leading to the decreased temperatures as well locations in the geothermal aquifer. Groundwater chemistry sampling at selected geothermal wells was also used to evaluate mixing of thermal and non thermal waters.