Coastal Environments and Global Change

6 Coastal Groundwater

William P. Anderson, Jr.

Department of Geology, Appalachian State University, Boone, NC, USA

6.1 Introduction

Coastal groundwater is an important component of the global hydrological cycle. In general, it is water that begins as recharge to land-based aquifers and ends as discharge to marine waters. This water can take a variety of paths that result in residence times of days to weeks for wave- and tide-induced circulation to thousands of years for deeper circulations, such as those on the continental shelf. Although river discharge to the oceans has long been considered to be the dominant contributor of water and nutrients to the nearshore and continental-shelf environments, studies have demonstrated that the coastal groundwater zone may also serve as a significant contributor of water and nutrients (Moore, 1996). In some locations, groundwater flux to the oceans, known as ‘submarine groundwater discharge’ (SGD), may exceed riverine discharge (Moore, 2010).

The terrestrially derived groundwater of the coastal zone flows seaward under natural conditions because of its high elevation relative to the oceans. In locations affected by human activities, such as pumping for water supply, this natural circulation may be modified and flow may be landward. The shallow coastal groundwater originates as precipitation-derived recharge to shallow aquifers, and it circulates at relatively short temporal scales. Because of its origin on land, this water is ...