Coastal Groundwater Management in the Presence of Positive Stock Externalities

Coastal Groundwater Management in the Presence of Positive Stock Externalities

National Institute for Water Resources, Water Resources Research Institute Program

9/1/2005 - 8/31/2008

The nearshore marine environment of Hawai‘i is a major recreational and ecological resource that supports indigenous fish and marine vegetation. Freshwater discharge from groundwater aquifers mixes with seawater along the coast to create an ecological system with salinity less than that of the ocean water. Onshore extraction of freshwater affects the salinity of the nearshore ecosystem since lower aquifer-head levels produce less freshwater discharge into the ocean. In other words, the state of the aquifer is directly linked to the cultural, recreational, and economic values of the community.

Thus our research objective was to determine the optimal management scheme in Hawai‘i for groundwater resources—taking into consideration both the benefits of water consumption and the environmental consequences of freshwater extraction.

Understanding the environmental consequences of freshwater extraction requires an assessment of the linkages between submarine discharge and the nearshore ecosystem. Native marine algae, identified by the Hawaiian word limu, play an important role as primary producers in a food web of endemic and other organisms. They can therefore serve as an appropriate indicator of the surrounding environment’s overall health.

To gain a better understanding of how groundwater discharge affects the nearshore marine environment we monitored, in a controlled laboratory environment, the physiological response of a selected species of limu to varied levels of salinity and nutrients. We chose to use the edible endemic species of marine algae Gracilaria coronopifolia for our study.

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