Modeling the Potential Impacts of Climate Change on the Hydrology of Selected Forested Wetlands in the Southeastern United States

Abstract

Abstract. Riverine floodplains and coastal margins of the southeastern United States host extensive forested wetlands, providing myriad ecosystem services including carbon sequestration, water quality improvement, groundwater recharge, and wildlife habitat. However, these ecosystems, which are closely dependent on wetland hydrology, are at risk due to human-made climate change. This study develops site-specific empirical hydrologic models for five forested wetlands with different characteristics by synthesizing long-term observed meteorological and hydrological data. These wetlands represent typical Cypress Ponds/Swamps, Carolina Bays, Pine Flatwoods, and Wet Pine, and natural Bottomland Hardwoods ecosystems. The validated empirical models are then applied at each wetland to predict future water table changes using climate projections from 20 General Circulation Models (GCMs) participating in the Coupled Model Inter-comparison Project 5 (CMIP5) under both Regional Concentration Pathways (RCP) 4.5 and RCP 8.5 greenhouse gas emission scenarios. We show that projected combined changes in precipitation and potential evapotranspiration would significantly alter wetland groundwater dynamics in the 21st century. Compared to the historical period, all five studied wetlands are predicted to become drier by the end of this century. The water table depth increases vary from 4 cm to 22 cm due to global warming. The large decrease in water availability (i.e., precipitation minus potential evapotranspiration) will cause a drop in the water table in all the five studied wetlands by the late 21st century. Among the five examined wetlands, the depression wetland in hot and humid Florida appears to be most sensitive to climate change. This modeling study provides quantitative information on the potential magnitude of wetland hydrological response to future climate change for typical forested wetlands in the southern U.S. Study results suggest that the ecosystem functions of southern forested wetlands will be substantially impacted by future climate change due to hydrological changes that are the key control to wetland biogeochemical cycles, vegetation distribution, fire regimes, and wildlife habitat. We conclude that climate change assessment on wetland forest ecosystems and adaptation management planning in the southeastern U.S. must first evaluate the impacts of climate change on wetland hydrology.

Understanding coastal wetland hydrology with a new regional‐scale, process‐based hydrological model

“…To date, many hydrological models have been developed to describe coastal wetland hydrology (Dai et al, ; La Torre Torres, Amatya, Sun, & Callahan, ; Li, Barry, & Pattiaratchi, ; Li, Barry, Stagnitti, & Parlange, ; Lu, Sun, McNulty, & Amatya, ; Robinson, Gibbes, & Li, ; Sun, Riekerk, & Comerford, ; Yu et al, ; Yuan, Xin, Kong, Li, & Lockington, ; Zhu et al, ). Some of these models have physically based representations of hydrological processes (Dai et al, ; Li et al, ; Li et al, ; Robinson et al, ; Sun et al, ; Yu et al, ; Yuan et al, ).…”

“…For example, Richards's equation and Darcy's law have been used for modelling subsurface and surface water flow (La Torre Torres et al, ; Yu et al, ). Alternatively, statistical models have been used to simulate and predict hydrological variables (e.g., groundwater table [GWT] depth) using empirical relationships between meteorological variables and hydrological states from site‐specific measurements (La Torre Torres et al, ; Lu et al, ; Zhu et al, ). These wetland hydrological models were often developed for specific types of wetland ecosystems.…”

“…For example, coastal marshes have been intensively studied using small‐scale models (e.g., spatial scale of tens to hundreds of metres from the shoreline) to understand the variation of surface and subsurface flow under the microtopographic control, and how water flow influences the distribution and transport of salt water and nutrients (Li et al, ; Li et al, ; Oude Essink, Van Baaren, & De Louw, ; Yu et al, ; Yu et al, ; Yuan et al, ). Watershed‐scale models (e.g., spatial scale of thousands of square metres) have been employed to understand variation in ET and the GWT of forested wetlands under climate variability/change (Dai et al, ; La Torre Torres et al, ; Lu et al, ; Sun et al, ; Zhu et al, ). However, coastal marshes and forested wetlands are not hydrologically isolated.…”