NB_290_19_7 - NB 290-19-7 INV – Conservation Effects Assessment Project (CEAP) Science Note on “Assessing Cumulative Impacts of Wetlands on Watershed Hydrology Using an Improved Hydrologic Modeling Approach”
NB 290-19-7 INV – Conservation Effects Assessment Project (CEAP) Science Note on “Assessing Cumulative Impacts of Wetlands on Watershed Hydrology Using an Improved Hydrologic Modeling Approach”
National Bulletin: 290-19-7      Date: September 10, 2019 
Subject: INV – Conservation Effects Assessment Project (CEAP) Science Note on “Assessing Cumulative Impacts of Wetlands on Watershed Hydrology Using an Improved Hydrologic Modeling Approach”  


 
Purpose.   To announce the availability of a new CEAP-Wetlands Science Note, “Assessing Cumulative Impacts of Wetlands on Watershed Hydrology Using an Improved Hydrologic Modeling Approach.”     
 
Expiration Date.   September 30, 2019
 
Background.   CEAP Conservation Insights are reports of studies that summarize CEAP findings and that have program implications. Conservation Insights are available on the CEAP website at http://www.nrcs.usda.gov/wps/portal/nrcs/main/national/technical/nra/ceap/.    
 

Explanation.   Historically, over 60 percent of wetlands have been lost in the Chesapeake Bay Watershed. Degradation of the Chesapeake Bay Watershed ecosystem by increasing agricultural nutrient loads has drawn attention to the importance of wetland conservation and protection as a potential cost-effective management practice. As a result, wetland restoration and enhancement are considered important conservation practices in the region.

 
Despite the importance of ecosystem services provided by wetlands in the Coastal Plain of the Chesapeake Bay Watershed, current understanding of wetland functions is mostly limited to individual sites. Overall catchment-scale wetland functions have rarely been investigated.

This study coupled the Soil and Water Assessment Tool (SWAT) with two improved wetland modules for enhanced representation of riparian wetlands (RWs) and geographically isolated wetlands (GIWs) to better show the cumulative impacts of wetlands on hydrology in an agricultural watershed within the Coastal Plain of the Chesapeake Bay Watershed.

 
Simulation results show that GIWs play a significant role in controlling hydrological processes in up gradient areas and downstream flow. GIWs increase groundwater flow while decreasing surface runoff, subsequently leading to increased stability of stream flow. Simulated removal of GIWs has the opposite effect, increasing surface runoff by 9 percent, decreasing groundwater flow by 7 percent, and decreasing groundwater recharge by 14 percent.

GIWs provide greater hydrological impact in controlling downstream flow than RWs, likely because GIWs have a much greater water storage volume than RWs. Increased emphasis on protecting GIWs is critical for enhanced hydrological resilience to extreme flow conditions in this region.

 
Contact.   If you have questions, please contact Michael Carlo, acting CEAP-Wetlands component leader, at michael.carlo@usda.gov.   
 
 


 /s/


DAVID HOOVER
Acting Deputy Chief for Soil Science and Resource Assessment

 
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