Characterization and Modeling of a Tropical Groundwater System: La Villa Watershed, Panama

Groundwater plays an important role in runoff generation in the humid tropics,both as subsurface stormflow during rain events and sustaining baseflow during dry periods. Yet groundwater fluxes in tropical areas, particularly groundwater/surface-water (GW-SW) interactions, are not very well characterized at regional scales, thus preventing us from estimating how climate change and anthropogenic activities will affect future groundwater availability. In the case of Panama, abundance of water resources has caused its misuse and thus groundwater is exploited without previous knowledge of its distribution and availability. However, regions of the country such as the Central Pacific Region suffer from water scarcity during periods of extended drought, when streamflow reduces significantly and shallow wells get dry. Understanding groundwater dynamics, especially GW-SW interactions, is crucial for government authorities to make informed decisions in order to secure water availability for current and future generations. This work presents advances on the characterization of the La Villa groundwater basin, located in the Central Pacific Region of Panama. By building a groundwater conceptual and numerical model, and a surface water model, potential recharge areas and groundwater flow patterns were identified. Also, the model reveals that groundwater feeds the rivers, not only during dry periods, but throughout the year. Although this preliminary model is not yet capable of predicting the total amount of groundwater stored, and neither can be used to inform management decision, it can inform us of which features have the greatest influence on groundwater flow and it can tell us what types of data are necessary to improve the results of the simulation. The development of these models is the first step towards the development of an integrated hydrologic simulation that can be used to test different climate change and/or management scenarios.