IWRA Proceedings

< Return to abstract list

Monitoring and methods to assess the groundwater quality degradation risk in karstic island aquifers (Bantayan Island, Cebu Province, Philippines)

IWRA 2020 Online Conference - Addressing Groundwater Resilience under Climate Change
THEME 1. Groundwater Natural Resouces Assessment Under Climate Change
Author(s): Robert M. DiFilippo, Professor Lee Bosher, Tom Dijkstra

Mr. Robert DiFilippo
Loughborough University, School of Architecture, Building and Civil Engineering
United Kingdom


Professor Lee Bosher
Loughborough University, School of Architecture, Building and Civil Engineering
United Kingdom

Dr. Tom Dijkstra
Loughborough University, School of Architecture, Building and Civil Engineering
United Kingdom

Keyword(s): Anthropogenic Climate Change, Karst. Freshwater Lens, Saltwater Intrusion


Karst islands such as those found in the Philippine Archipelago present extreme challenges for stakeholders to manage their water resources in a sustainable manner. Anthropogenic climate change, an increasing population and changes in land use and industry have all combined to alter the water balance on these fragile islands. Karst features (in particular the potential for dissolution), the combination of point source pollution with a shallow depth to groundwater and saltwater intrusion contribute greatly to the challenges for
sustainable water resource development.

Bantayan Island (Cebu Province, Philippines) was selected as the study area. The single freshwater lens of this island is vulnerable to salt water intrusion due to several factors including karts geology and abstraction well discharge.

A multi-methodological approach for the assessment of the quality of the freshwater lens is proposed based upon field monitoring and spatio-temporal analysis of groundwater quality changes. The tools to provide suitable data to users are modest and inexpensive. The chief purpose is to obtain a groundwater surface coupled with a groundwater quality assessment of the freshwater lens. The spatial and multi-temporal analysis of typical chemical and physical data is used to establish a spatial vulnerability of the aquifer to salt water intrusion. The multi-parameter field data collection provides a nimble methodology for rapid groundwater quality classification for each monitoring location. This study introduces the water quality trends expressed in terms of salinity and derives salinity thresholds to evaluate intrusion of brackish water into the freshwater lens. Water quality impacts resulting from sea water intrusion are a result of a combination of upconing in areas of concentrated abstraction, coastal boundary zones affected by tidal forcing, and structural geological features where enhanced groundwater flow along long-linear discontinuities (faults, major joints) provides inland connections
with the coastal zone.

The approach allows consideration of the current abstraction management schemes and the ability to improve design by instituting more realistic and science-based targets. A management instrument relative to the development of an island-wide observational model of the freshwater lens is proposed.

IWRA Proceedings office@iwra.org - https://www.iwra.org/member/index.php