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

Abstract

Coastal wetlands represent an ecotone between ocean and terrestrial ecosystems, providing important services, including flood mitigation, fresh water supply, erosion control, carbon sequestration, and wildlife habitat. The environmental setting of a wetland and the hydrological connectivity between a wetland and adjacent terrestrial and aquatic systems together determine wetland hydrology. Yet little is known about regional-scale hydrological interactions among uplands, coastal wetlands, and coastal processes, such as tides, sea level rise, and saltwater intrusion, which together control the dynamics of wetland hydrology. This study presents a new regional-scale, physically based, distributed wetland hydrological model, PIHM-Wetland, which integrates the surface and subsurface hydrology with coastal processes and accounts for the influence of wetland inundation on energy budgets and evapotranspiration (ET). The model was validated using in situ hydro-meteorological measurements and Moderate Resolution Imaging Spectroradiometer (MODIS) ET data for a forested and herbaceous wetland in North Carolina, USA, which confirmed that the model accurately represents the major wetland hydrological behaviours. Modelling results indicate that topographic gradient is a primary control of groundwater flow direction in adjacent uplands. However, seasonal climate patterns become the dominant control of groundwater flow at lower coastal plain and land-ocean interface. We found that coastal processes largely influence groundwater table (GWT) dynamics in the coastal zone, 300 to 800 m from the coastline in our study area. Among all the coastal processes, tides are the dominant control on GWT variation. Because of inundation, forested and herbaceous wetlands absorb an additional 6% and 10%, respectively, of shortwave radiation annually, resulting in a significant increase in ET. Inundation alters ET partitioning through canopy evaporation, transpiration, and soil evaporation, the effect of which is stronger in cool seasons than in warm seasons. The PIHM-Wetland model provides a new tool that improves the understanding of wetland hydrological processes on a regional scale. Insights from this modelling study provide benchmarks for future research on the effects of sea level rise and climate change on coastal wetland functions and services.

Rapid deforestation of a coastal landscape driven by sea‐level rise and extreme events

“…Instead, the spatial distribution of forested wetland loss appears more consistent with saltwater intrusion, and the timing suggests that extreme events are leading to forest mortality. In this landscape of low topographic relief and shallow groundwater, all hydrologically connected areas are potentially vulnerable to saltwater intrusion (Bhattachan et al 2018, Zhang et al 2018, 2019). Marine salts move inland as a result of diffusion and wind tides during droughts as well as during hurricane storm surges (Manda et al 2014, 2018, Tully et al 2019).…”

Plant–soil feedbacks in mangrove ecosystems: establishing links between empirical and modelling studies

“…Numerical models that investigate feedback mechanisms between vegetation and porewater salinity in mangrove ecosystems can be categorized by the spatial scale of the model and the level of detail incorporated within the models. There are regional models (Zhang et al 2018;Liu et al 2019), site-specific models (Sternberg et al 2007;Teh et al 2008Teh et al , 2013Teh et al , 2015 and models which describe the interactions on the scale of individual plants (Bathmann et al 2020). Different scales of the models tend to incorporate different levels of detail.…”

“…This can help to understand the impacts of regional changes in water availability, which are predicted to vary as a consequence of climate change on ecosystem processes. For example, Zhang et al (2018) used a detailed hydrological model to connect hydrological processes on the surface and the subsurface to inform how hydrological regimes in coastal wetlands influence the energy budgets and evapotranspiration of vegetated patches. The model developed by Liu et al (2019) extended this idea through the incorporation of abiotic transport and accumulation processes to understand the dynamics of porewater salinity within the soil of coastal wetlands.…”

Rivers’ Temporal Sustainability through the Evaluation of Predictive Runoff Methods

“…They have implemented simulation models for being applied to hydrographic basins and then are compared to observational data records to get a good calibration. Those models follow the traditional hydrological scheme of procedure of routing for getting the final product of hydrographs [25][26][27][28].…”