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Water and nutrient discharge to a high‐value terrace–floodplain fen: resilience and risk
Author(s) -
Schilling Keith E.,
Jacobson Peter J.
Publication year - 2016
Publication title -
ecohydrology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.982
H-Index - 54
eISSN - 1936-0592
pISSN - 1936-0584
DOI - 10.1002/eco.1718
Subject(s) - terrace (agriculture) , water table , hydrology (agriculture) , groundwater , environmental science , transect , floodplain , aquifer , riparian zone , streams , geology , ecology , geography , oceanography , habitat , geotechnical engineering , computer network , computer science , archaeology , biology
While fens provide a host of ecosystem services, those located at the base of river terraces are under threat from upgradient agricultural activities. We investigated a fen located along the boundary of the highly agricultural terrace and modern floodplain of the Cedar River in southeast Iowa using a transect of groundwater and surface water monitoring points. During the three‐year monitoring period, the water table level in the terrace fluctuated 55 cm in the terrace, but hydraulic head in the fen varied only 18 cm during a severe drought that occurred in the region. Fen water table levels were significantly related to those measured in the adjacent terrace but groundwater flow to the fen from regional aquifer sources appeared to provide resilience against large fluctuations in fen water table levels. Terrace groundwater discharging into the fen from a spring at the terrace base had NO 3 –N concentrations as high as 16 mg/l, averaging approximately 8 mg/l during the study. Concentrations were significantly lower in fen groundwater, likely due in part to denitrification occurring in the organic‐rich fen deposits. PO 4 –P concentrations were less variable (ranging from 0.04 to 0.1 mg/l) but were significantly higher (1.2 mg/l) in the low‐redox fen groundwater. Conservation of these unique and high‐value terrace–fen ecosystems should be made a priority through additional hydrologic investigation and local land management. Copyright © 2015 John Wiley & Sons, Ltd.