Identification, characterization, and threat assessment of groundwater dependent ecosystems in the northeastern United States with an integrated GIS- and field survey-based approach
Dates
Start Date
2017-10-01
End Date
2020-09-30
Summary
Problem statement: Groundwater is an important source of freshwater for human populations worldwide, and management of this resource typically is focused on ensuring quality and quantity for human use. Many aquatic systems receive groundwater as a portion of base water flow, and in some systems (e.g., springs, seepages, subterranean streams, fens) the connection with groundwater is significant and important to the system’s integrity and persistence. Groundwater management decisions for human use often do not consider ecological effects of those actions on groundwater dependent ecosystems (GDEs), which rely on groundwater to maintain ecological function (Brown et al. 2010, USDA 2012). This disconnect between management and ecological [...]
Summary
Problem statement:
Groundwater is an important source of freshwater for human populations worldwide, and management of this resource typically is focused on ensuring quality and quantity for human use. Many aquatic systems receive groundwater as a portion of base water flow, and in some systems (e.g., springs, seepages, subterranean streams, fens) the connection with groundwater is significant and important to the system’s integrity and persistence. Groundwater management decisions for human use often do not consider ecological effects of those actions on groundwater dependent ecosystems (GDEs), which rely on groundwater to maintain ecological function (Brown et al. 2010, USDA 2012). This disconnect between management and ecological needs potentially results in damage to these resources that have repercussions for both GDEs and human populations that rely on them (Blevins and Aldous 2011, Kreamer et al. 2015).
Groundwater inflow affects flow volume, temperature, and chemical composition of GDEs, and creates a hydrological environment that supports unique biotic assemblages. Groundwater may stabilize
aquatic environments by cooling water in summer, maintaining minimum flows during drought, and providing consistent sources of dissolved minerals that vary with seasonal precipitation and surface water influx. Disruptions in groundwater flow timing, volume, temperature, and composition can be adverse for obligate or facultative species associated with GDEs (Humphreys 2009, Brown et al. 2010, Klove et al. 2014). The environmental conditions of a GDE reflect its geological setting, climate conditions, and landscape position that influence the associated biodiversity (Brown et al. 2009, Blevins and Aldous 2011). For example, springs and seeps occur where groundwater flow discharges, creating an environment with relatively constant temperature, oxygen, and water chemistry that provides habitat for amphibians (salamanders), invertebrates (amphipods, isopods, Tennessee heelsplitter), and fish that are spring and seep specialists. Fen and wet meadow wetlands receive groundwater input that maintains saturation, creating habitat for drought-sensitive species, including plants (Hall’s bulrush, Bog spicebush, Boykin’s lobelia, swamp pink), host rare butterflies (Clayton’s copper, Hessel’s hairstreak, Spicebush swallowtail butterfly) and dragonflies (Arrowhead spiketail, swamp darner), and provide habitat for amphibians (northern leopard frog, blue-spotted salamander) and hibernating reptiles (bog turtle, eastern massasauga). Similarly, groundwater discharge to lakes, streams, and rivers during late summer ensures persistent inflow of cool water into fish spawning habitat (Bluestone sculpin, brook trout, Atlantic salmon) and freshwater mussel beds (dwarf wedge mussel) during infrequent precipitation when water otherwise would warm to lethal temperatures (Klos et al 2014, Rosenberry et al. 2016). Maintaining the biodiversity of GDEs requires conserving the volume, timing, composition, and quality of groundwater discharging into these systems and understanding the sensitivity of the inhabiting biota to changes in these environments, both locally and throughout the surrounding watershed (Brown et al 2009, 2010, Blevins and Aldous 2011, Klove et al. 2014).
Understanding sensitivities of a GDE depends on knowledge about its context, including the landscape setting, groundwater source and flow path, and natural or human-caused conditions that may affect groundwater quality and volume between the source and discharge zones. Threats to groundwater quality include contamination from the byproducts of industrial use, agricultural processes, and domestic waste. Threats to groundwater quantity include excessive withdrawal that disrupts flow volumes (for irrigation, industrial, or residential uses), timing, and alters flow paths (Reilly et al. 2008, Kreamer et al. 2015). Despite the importance of groundwater resources to both human and wildlife populations, GDEs remain largely unmapped and poorly studied in the northeastern United States. Management of GDEs requires that the extent of influence of human activities on their groundwater source be identified, a difficult task given the uncertainty of the distribution and abundance of GDEs as well as knowledge of connections between a GDE’s hydrology and its watershed. Similarly, knowledge about GDE biodiversity and species’ sensitivities to groundwater alterations are important for effective conservation of these systems.
Implications of the work:
Our proposed research addresses 2018 USGS-SSP RFP Theme #6 Assessment of Groundwater-Dependent Species and Risks of Groundwater Development. The northeastern U.S. is anticipated to experience up to a 50% increase in water resource usage owing to population growth and climate change in the upcoming decades. Water resource stress will be localized by increased population concentration in expanding urbanizing areas (USDA-Forest Service 2010). The northern Atlantic coastal plain (NACP) aquifer region, comprising ~10% of the USFWS Region 5 and spanning coastal land area from Virginia to Long Island, NY, is one of the smallest aquifers in the U.S., yet the aquifer’s groundwater withdrawals are ranked in the top 20% in the nation, and groundwater currently provides ~40% of the drinking water consumed by the human population in this region (Masterson et al. 2016). Approximately 9% of the land in conservation management in this region falls within this aquifer, as does ~48% of the land managed by the USFWS in Region 5. In addition to growing pressure on the groundwater supply from increasing withdrawals for drinking water with increasing human population density, other threats to the region’s water resources are expected to increase. The region's water resources also are chemically affected by contamination from waste disposal, accidental spills, and pesticides and fertilizer applications that will continue to stress the region's aquifers and associated GDEs.
Approximately 17% of species with ESA listing status in the continental United States are associated with GDEs (Blevins and Aldous 2011). Many of these species occur in areas designated by state Natural Areas Programs as rare community types (e.g., in Maine: Hardwood Seepage Forest, Atlantic White Cedar Swamp, Riverside Seep, Circumneutral Fen, Pocket Swamp). The northeastern U.S. contains at least 3 known threatened or endangered species that depend on GDEs (swamp pink, bog turtle, Madison Cave isopod) and recent research (Rosenberry et al 2016) suggests a fourth, dwarf wedge mussel, can also be associated with GDEs. In addition to listed species, there are 23 non-federally listed at-risk groundwater dependent species, including several isopods, amphipods, freshwater mussels, stoneflies, dragonflies, crayfish, salamanders, snakes, turtles, plants, and fish found in a variety of GDEs such as springs, seeps, streams, cave pools, ponds, and wetlands. Many priority conservation species in the region (e.g brook trout, Atlantic salmon) are found in spring-fed streams in the Appalachians and coastal plain wetlands and streams that receive both surface and groundwater discharge to maintain their hydrology. Given the terrestrial focus of most conservation lands, it is likely that GDEs in the northeastern U.S., including those containing these at-risk species and communities, are underrepresented in the region’s natural resources conservation network (Herbert et al. 2010). The distribution of GDEs in the northeastern U.S., and specifically on conservation management lands in the region (e.g., National Wildlife Refuges, state and national parks and forests, land trusts, etc.), is not well known, nor have these systems been surveyed systematically to document hydrological conditions and biota. Similarly, specific threats to the region’s GDEs are unknown. There is a critical need to identify areas in the landscape where GDEs are likely to be found, their key threats, and those systems likely to contain at-risk species (including at least 23 identified in Region 5), so that their conservation may be prioritized. These are overarching objectives of our proposed research.
Objectives:
The goal of our research is to increase our knowledge about the distribution, biological communities, and threats to GDEs in the northeastern United States, and increase our knowledge about the hydrologic conditions that support high priority GDE types. Our research is proposed in stages, initially applying spatial analysis tools to identify areas likely to contain GDEs, followed by field-based assessment of selected areas predicted to contain high quality GDEs or GDE clusters, to better understand their landscape context and watershed-level threats, characterize hydrologic conditions, and describe the species they support. Specific project objectives are:
Create a cell-based surface to predict landscape “suitability” for GDE presence with spatial data describing hydrogeologic, ecological, and climate conditions in USFWS Region 5.
Evaluate relationships between known GDEs in the study region compiled from surveys of state and federal biologists, land managers, and literature review and HUC12 watersheds identified in Objective 1 that are predicted to be suitable for GDEs or GDE clusters.
Determine vulnerability of GDEs and their watersheds identified in Objectives 1 and 2 to threats, combining factors affecting exposure, sensitivity, and adaptive capacity (e.g., Magness et al. 2011) and threats to groundwater quantity and quality (e.g., Brown et al. 2009), to identify both the at-risk systems and the most significant threats.
Select a subset of HUC 12 watersheds with high predicted suitability for GDEs (Objectives 1, 2) for surveys, combining remote reconnaissance and on-site rapid assessment, to evaluate model predictions and characterize GDE type.
Select a subset of sites surveyed in Objective 4 to further characterize the hydrology, ecological setting, and to survey for groundwater-dependent biota. Sites will be selected in consultation with USFWS staff and other federal or state land managers to balance conservation value of the high-resolution information and survey cost. For example, GDEs in Nulhegan Basin Division (VT), Aroostook (ME), and Cape May (NJ) National Wildlife Refuges (NWR) provide examples associated with different aquifer types (valley-fill, carbonate rock, and coastal plain, respectively) to be instrumented for continuous hydrologic data collection.
Develop a user guide for deploying continuous hydrologic monitoring equipment for characterizing conditions of GDEs on conservation land, targeting sites surveyed in Objective 5.
