Mapping the landscape-level hydrological connectivity of headwater wetlands to downstream waters: a geospatial modeling approach - Part I

Authors: YEO, I.Y. - University Of Newcastle; LANG, M.W. - Us Fish And Wildlife Service; LEE, S. - University Of Maryland; HAUNG, C. - University Of Maryland; McCarty, Gregory; Sadeghi, Ali; YETEMEN, O. - University Of Newcastle

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2018
Publication Date: 12/15/2018
Citation: Yeo, I., Lang, M., Lee, S., Haung, C., McCarty, G.W., Sadeghi, A.M., Yetemen, O. 2018. Mapping the landscape-level hydrological connectivity of headwater wetlands to downstream waters: a geospatial modeling approach - Part I. Science of the Total Environment. 653:1546-1556. https://doi.org/10.1016/j.scitotenv.2018.11.238.
DOI: https://doi.org/10.1016/j.scitotenv.2018.11.238

Interpretive Summary: Headwater wetlands have been shown to influence downstream water quality. However, many wetlands, because of being isolated without apparent connection to larger wetland systems, continue to be at risk and not protected by state and federal regulations. This study evaluates how isolated wetlands are hydrologically connected by using remotely sensed maps developed from satellite information. Results of this study indicated that there exists a strong and positive relationship between the seasonal inundation patterns of isolated wetlands and hydroperiods. This mapping technique demonstrates the feasibility of using annual patterns of inundation to infer wetland function and shows the connectivity between hydroperiod and wetland function. Information regarding wetland functions is increasingly being sought and used to support natural resources decision-making about wetland protection at multiple scales, from local to national. The availability of inundation maps and other satellite data products measuring land surface properties provides valuable information to relate wetland hydrological connection with downstream water over multiple time scales and to infer wetland function in a timely manner.

Technical Abstract: Headwater wetlands affect ecosystem integrity of downstream waters; however, many wetlands - particularly geographically isolated wetlands (GIWs) - continue to be at risk. Current regulations in the U.S. require a clear demonstration of the surface water connectivity of wetlands to and their cumulative impacts on downstream waters for their protection. Moreover, while future US federal regulations for wetlands are in flux, wetland-stream connections and their cumulative influence on downstream waters will likely continue to be crucial to the future jurisdictional status of wetlands. We present a novel geospatial modelling method to help elucidate the hydrological relationship between GIWs and downstream waters at the landscape scale. The approach used inundation maps derived from time series remotely sensed data, weather and hydrological records, and ancillary geospatial data including information from the US Fish and Wildlife Service National Wetlands Inventory (NWI) between 1985 and 2015. The study site was a headwater catchment (292 km2) of the Choptank River Basin, located in the Mid-Atlantic region of USA. The results from the geospatial analysis showed inundation extent within GIWs varied, in aggregate, in response to weather variability (r = 0.58; p-value =0.05), and was well correlated with streamflow (r = 0.81; p-value < 0.01) and base flow (r = 0.57; pvalue < 0.1) conditions. The relationship between inundation patterns and stream discharge also varied with National Wetlands Inventory (NWI) geospatial dataset hydrologic modifiers. The GIWs with longer hydroperiods exhibited stronger correlations with stream discharge. However, inundation in saturated wetlands (which are inundated seldom or only for a very short period) were less correlated with stream discharge. This analysis suggests the mutual reliance (i.e., connection) of wetlands and streams on groundwater. GIWs appeared to function in aggregate, and it is likely that the combined effect of these wetlands significantly influenced downstream waters.