Sea level rise and coastal hazards are putting human and natural communities along the coasts at greater risk than ever.
Ground Water
Groundwater is a critical resource on Long Island. The Long Island Aquifer, one of the most productive in the world, provides drinking water for nearly the entire population of the island, some 7.7 million people. In addition to this essential ecosystem service to human populations, groundwater aquifers play an important role in maintaining ecological communities, as outlined below. With sea level rise will likely come saltwater incursion into groundwater aquifers, which will have impacts on both their ecological function and their ability to provide drinking water.
As sea level rises and intrudes into groundwater stores near the coast, some drinking water will no longer be potable. The salinity of freshwater aquifers near the coast will gradually increase as seawater flows toward them underground and as higher salinity water seeps or migrates toward them through pore spaces in the soils or rock fractures. Coastal aquifers generally consist of a fresh water layer overlying a denser, saltwater layer. Pressure from the freshwater layer prevents saltwater from rising in the aquifer. With rising seas, the water table will be raised and saltwater will rise higher and higher in the aquifer. Sewers, drainage systems, other critical infrastructure, and many erosion control structures have been designed with the normal water table in mind. A progressively elevated groundwater table will interfere with these systems causing malfunctions, damages, and incurring major expenses for municipalities and the State.
Sea level rise will lead to a decrease in the depth from the soil surface to groundwater (i.e., a thinning of the “unsaturated zone”), which will likely have a variety of ecological impacts. First, the decrease in distance to groundwater will reduce the interval during which soils experience dry conditions (desiccation interval) in low-lying areas. This would, in turn, substantially alter the vegetation composition of nearby communities, favoring wetland or moisture-tolerant species at the expense of upland species that require drier conditions. In addition, as sea level rises, the freshwater-saltwater interface will migrate upstream in rivers and streams, and inland and upward within coastal aquifers. This would cause a conversion of adjacent vegetation communities from freshwater to brackish or salt-tolerant species. If nearshore riparian habitats convert to primarily salt-tolerant species, the freshwater fish and other fauna that currently use these areas for nesting, spawning and foraging will be unable to continue to do so.
