Integrating isotopic tracers and field protocols for the conceptual characterization of geothermal exploration and production areas

Characterizing geothermal fields and their associated hydrological and hydrogeological systems requires precise environmental tracer data to define subsurface processes and recharge mechanisms. To do so, a technical training program was introduced in the Tipitapa and Momotombo geothermal sites (Managua, Nicaragua), focusing on the application of stable isotopes (δ¹⁸O and δ²H) to standardize protocols for the collection, handling, and storage of samples from diverse sources. The scope of this study included the collection of precipitation, surface water, and high-mineralization geothermal brines, which were prepared for isotope content analysis using laser infrared spectrometry. The methodology included specialized theoretical modules with intensive field training. The theoretical component addressed isotopic fractionation theory, the construction of local meteoric water lines, and the comparative analysis of geothermal systems across various geological settings (geothermal fields in Mexico). Fieldwork was conducted in a geothermal exploration area and an active production plant. Sampling protocols included in situ measurements of physicochemical parameters and alkalinity, followed by the collection of 14 representative water samples. Filtration techniques were required, using 0.45-micron nylon filters, implemented for small-volume vials (5 ml and 30 ml), ensuring the complete exclusion of air bubbles to prevent isotopic fractionation during storage. The technical execution established best practices for sampling complex sources, such as lake-river interfaces, groundwater wells, hot springs, and high-temperature production wells. By implementing preservation standards and duplicate sampling at sites of interest, a reliable workflow was established for capturing the isotopic signatures of geothermal brines, surface water (lake and river samples), and groundwater (urban wells). The integration of chemical and isotopic data enabled a detailed characterization of the connectivity between surface bodies and the underlying thermal systems. The program successfully unified technical procedures for water sampling, bridging the gap between field collection and laboratory analysis. Strengthening these competencies ensures that isotopic data from exploration and exploitation areas are representative and robust. This precision is essential for developing accurate conceptual models of geothermal reservoirs and ensuring the sustainable management of groundwater and energy resources.