WRP studies at Ray Roberts yield information for improved
management practices
Ray Roberts Reservoir, Denton County, TX, was a demonstration site
for three WRP studies.
Non-Point Source Pollution (NPSP) Management
Storm flows and nonpoint source pollutant concentrations in storm
flows entering and leaving the Spring Creek wetland at the Ray
Roberts wetlands complex were monitored during the 1993
spring/summer runoff season. Suspended solids removals were
significant but other pollutant removals were minor. Removal
efficiencies were low due to a very low hydraulic retention time
for storm flow events.
The study indicates that constructed wetlands that provide storm
flow retention times of only several hours do not effectively
remove nonpoint source pollutants. In addition, when planning for
off-channel constructed wetlands that rely on stream bank overflow
for filling, careful attention should be paid to hydrologic
analysis during the design phase. Otherwise, dike elevations and
control structures may be undersized, resulting in virtually no
retention of storm flows due to complete inundation.
Point of contact for additional information is Mr. Tommy Myers at
(601) 634-3939 or Mr. Chuck Downer at (601) 634-2473,
downer@hl.wes.army.mil.
Sediment Management
Ray Roberts Reservoir also served as a demonstration site for
sediment management. The objectives of the study were monitoring
and documenting suspended sediment removal and sedimentation
patterns in a constructed wetlands complex. Storm flows and
suspended sediment concentrations entering and leaving the wetland
were monitored during the spring/summer runoff period of 1993.
Sedimentation patterns in the wetland were measured with plexiglass
disks. It was found that the wetland was able to reduce peak
suspended sediment concentrations by approximately one-third.
Storm flows overtopped the wetland dikes and resulted in very short
detention times. These short detention times resulted in
relatively poor treatment efficiency. Although treatment
efficiency was low, the high flows resulted in significant sediment
deposition. Sediment accretion in the wetland averaged 2.2 mm/yr.
The areal accumulation in the wetland was 1.4 kg per square meter. The
sediments were 19 percent organic (volatile) material.
The study documented that hydrologic analysis during the
planning phase for a wetland constructed for water quality
benefits, such as sediment retention, is critical to success of the
project. Hydraulically overloading the wetland results in short
hydraulic retention times and low suspended sediment removal.
Complete inundation of the project results in damage to control
structures and requires continuing repairs.
Point of contact for additional information is Mr. Chuck Downer at
(601) 634-2473,
downer@hl.wes.army.mil.
Natural Communities/ Biodiversity Management
Projects on Corps land have historically been managed predominantly
for target game species, especially waterfowl. There is an
increasing need to improve wetland areas for nongame species and
entire communities in an effort to maximize biological diversity.
Demonstration studies were conducted at several locations,
including Ray Roberts Lake, TX.
Work accomplished included (1) a background survey of literature
on biological diversity, emphasizing interior wetlands of the
United States, (2) evaluation of strategies for biodiversity
management in wetland systems, and (3) specific studies on
biological diversity of wetlands at field demonstration sites.
Guidance developed based on the results of biodiversity studies has
widespread application for improving the diversity and quality of
wetland habitats for a variety of species on Corps project lands
and has extensive application on other federal, state, and private
lands as well.
Point of contact for additional information is Mr. Chester P.
Martin at (601) 634-3958.
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