SECONDARY BENEFITS OF USFWS WETLAND MANAGEMENT: 
SEDIMENT AND NUTRIENT CAPTURE AND REMOVAL AT THE HALFWAY 
CREEK MARSH COMPLEX, HOLMEN, WISCONSIN

William Richardson1, Joe Schubauer-Berigan2, Peter Hughes3, Lynn  Bartsch1, Jennifer 
Cavanaugh1, and James Nissen4
1US Geological Survey, Upper Midw. Envir. Sci. Ctr., La Crosse, WI,  2US EPA, ORD, 
Cincinnati, OH,  3US Geological Survey, Wisconsin Water. Sci. Ctr., Middleton, WI, 
4UMR National Wildlife & Fish Refuge, Onalaska, WI.
				
The Halfway Creek Marsh Complex (HWCM) (Holmen, WI) is managed by the US Fish 
and Wildlife Service as a waterfowl feeding and loafing site.  Portions of the HWCM 
were restored from agricultural use while the remainder is in a relatively natural 
condition.  The restored portions are linked to the Halfway Creek through an inlet 
structure used to fill the restored marsh during floods.  A secondary function of the 
restored marsh is to capture sediments and nutrients from floodwaters to reduce 
downstream flux to the Mississippi River.  The Environmental Protection Agency has 
interest in understanding the effectiveness of such wetland function and funded 
collaborative research, with the USGS, to determine 1) loads of sediments and nutrients 
entering the Mississippi River through HWC; 2) the percentage of  sediment and nutrient 
load captured by the HWCM complex during normal management practices; 3) 
biological and biogeochemical processes important in transformation and removal of 
nitrogen (N) and phosphorus (P) captured by the Marsh (both restored and natural areas).  
During 2004 the total load of suspended sediments entering the restored marsh was 4,417 
metric tons (mt), N was 37.7 mt, and P was 7.7 mt.  Of this load 10 % of the sediment, 5 
% of the N, and 10 % of the P was captured in the wetland.  We also evaluated rates of 
nitrification, denitrification, sediment N and C and moisture to determine how well the 
restored wetlands performed as processors of N relative to natural wetlands.  
Denitrification (enzyme activity) was greatest in water-saturated areas (2.2 ug-N cm2 hr-1) 
and lowest in the restored marsh (0.5 ug-N cm2 hr-1).  Nitrification rates were highest in 
the drier areas (7.85 ug-N cm2 hr-1), whereas the restored marsh was lowest (4.8 ug-N 
cm2 hr-1).  N-removal capacity in the restored and natural marsh areas was correlated with 
sediment moisture and nitrate concentrations, which are determined by water 
management practices.  Microbial removal of N was minuscule relative to the total load 
entering the marsh.  Excavation and removal of sediments in the restored marsh is the 
most effective method of sediment and nutrient management in this stream-wetland 
complex.  

Keywords:  wetland management restoration nutrient sediment retention