Geothermal Systems of Low Temperature in Mexican Highlands: Alternative Uses and Associated Risks

Abstract

Groundwater of geothermal systems of low temperature located in the Mexican Highlands is used as urban water supply due to water scarcity in the area. Juventino Rosas, Irapuato, Cuitzeo and Jocotitlan in Guanajuato and Mexico States, are some of the areas supplied with geothermal water. These aquifer systems are formed mainly by volcanic rocks of the Sierra Madre Occidental and the Trans Mexican Volcanic Belt. The groundwater of these systems contains some risk elements like arsenic and fluorine. Radon has been also detected in all the studied zones. Tectonic and subsidence faults and fractures allow a fast migration of Radon to surface. In Juventino Rosas the radon content range is 12,000 – 40,000 Bq/m3. Health affectations related to radon exposure has not been reported. Geothermal water is also used for irrigation and cattle breeding. Arsenic can be absorbed by some crops. Some cheese producers reported low arsenic concentration in their products. The highest well temperature is 50°C. Most of hot waters have temperatures between 27 and 33°C. The groundwater temperature calculated with geothermometers in Juventino Rosas is higher than 100°C. The water temperature can be used in some home-biased industrial processes. These systems cannot be used for big energy generation systems, but can increase the efficiency of solar energy systems. Water for human consumption is distributed directly from wells. The maximum arsenic concentrations were found in Cuitzeo and Irapuato, 3.8mg/L and 0.30mg/L respectively. In Juventino Rosas the fluorine content is causing dental fluorosis. In Irapuato there are a few cases of keratosis, one of the first health affectations related to arsenic ingestion. Water treatment could be one of the solutions. Only one small community in Irapuato has a treatment plant.