Galapagos Islands: Integrated Water Study (GIIWS). A Trans-Disciplinary Approach to Quantify Water Resources and their Impact on Natural Ecosystems

Abstract:

The GIIWS program was started in 2003 to understand the hydrological functioning of the Galapagos Islands and provide scientifically based information to allow the local institutions to carry out management in view of maintaining the integrity of the ecosystems and reduce mismanagement of the natural resources. To serve those critical needs, our scientific program aims at the: i) quantification of recharge rates, ii) analysis with an hydrogeological approach of the morphology, geometry and physical properties of volcanic formations, and iii) assessment of the consistency of the whole data collection and the conceptual model with numerical groundwater flow modeling. To this end, a multi-disciplinary approach has been used, which is based on the combination of experimental and modeling methods throughout the implementation of experimental sites along the windward side of the Islands. One of the most determining factors in hydrogeology is the input from precipitation (and eventually cloud water interception by the canopy) that will not be evaporated, nor transpired, nor stored in the soil, but infiltrated to the underground and recharge deep aquifers. Then, it flows down in the unsaturated volcanic formations, possibly supply perched aquifers while impervious layers occur, and finally it reaches the basal aquifer, in equilibrium with seawater. The dynamic of groundwater flow is investigated with numerical flow models based on mass conservation and the constitutive equation of flow, the Darcy law. Because we miss accurate data on rocks hydraulic properties and calibration data from drill holes, we are not being able to obtain accurate predictive simulations. Nevertheless, we obtain from our investigations quantitative data on recharge rates and an extensive characterization of volcanic formations. Finally modeling approach will let us test our hypotheses on groundwater occurrence on tropical Islands