Freshwater lens assessment of karst island water resources: towards an interdisciplinary protocol

Abstract

: Fresh groundwater lenses on karstic oceanic islands form a vital resource sustaining local populations. However, this resource is susceptible to saltwater intrusion through human drivers (over-abstraction) and natural processes (variable precipitation and storm surges). There is a paucity of means to assess the risks that freshwater lenses are exposed to. This is partly driven by a poor understanding of the root causes of saltwater intrusion, which leads to potentially inappropriate freshwater management strategies. Thus, effective management of these freshwater lenses requires a baseline understanding of the processes that drive saltwater intrusion and the degradation of freshwater lenses, and the temporal and spatial variability of these processes. Dynamics of such freshwater lenses involve an interplay between physical, chemical, and socio-economic processes; therefore, finding a solution necessitates an interdisciplinary approach and a range of data collection strategies. This approach was formalized in a Freshwater Lens Assessment Protocol (FLAP). Results from the research developed and tested on Bantayan Island in the Philippines reveals a sufficient freshwater lens to support the current and projected population; however, local officials are operating abstraction wells from the wrong locations on the island. Such locations are utilized due to ease of access to existing infrastructure and government boundaries, but do not consider technical factors that influence saltwater intrusion. FLAP is an appropriate, cost-effective, interdisciplinary tool that uses a pragmatic approach to data collection, interpretation, and integration into an observational model. Continuous adjustments are possible through ongoing monitoring of the model, offering opportunities to evaluate the efficacy of resource management strategies. compelling island-wide observational model intended to have a positive impact on the management of the freshwater lens. The island-wide observational model, therefore, becomes an island asset. The careful application of appropriate empirical data sets to complement local data sources was intended to minimize any potential uncertainty in the island-wide observational model, providing a complete image of the natural system, with wider utilization of the data sets by stakeholders. The model’s limitations can be attributed to the frequent paucity and incompleteness of regional and local data sources. Despite this, this research provides stakeholders with an island-wide observational model, and guidance on the required data sets to take it forward. effective application as it is informed by local data sets and an understanding of stakeholder attitudes regarding water resources in their communities. The goal of this research was to be translational to local stakeholders to improve capacity and understanding of freshwater lens management. This was demonstrated by the local stakeholder workshops conducted at the close of the research. These dissemination and communication activities are vital mechanisms for knowledge exchange to improve understanding of this fragile water resource.