Coastal Groundwater Management with Nearshore Resource Interactions

This paper develops a regional hydrologic-ecologic-economic model of groundwater use and a nearshore ecosystem. Particularly, we model coastal groundwater management and its effects on discharge, nearshore water quality, and marine biota (e.g., indigenous marine algae). We show that incorporating the external effects on nearshore resources increases the optimal steady-state head level. Numerical simulations are illustrated using data from the Kuki’o region on the island of Hawaii. Two different approaches for incorporating the nearshore resource are examined. We find that including algae’s market value directly in the objective function calls for lower, albeit slightly lower, water extraction rate in all periods. If a minimum constraint is placed on the stock of the keystone species, greater conservation may be indicated. The constraint also results in non-monotonic paths of water extraction, head level, and water price in the optimal solution.