Beaucoup Creek Watershed Data Review
within a map unit, soil layer depths, hydrologic soil groups, and soil texture among
other soil properties.
5.1.9 Cropping Practices
Tillage practices can be categorized as conventional till, reduced till, mulch-till, and
no-till. The percentage of each tillage practice for corn, soybeans, and small grains by
county are generated by the Illinois Department of Agriculture from County Transect
Surveys. Data specific to the Washington County Lake Watershed were not available;
however, the Washington County NRCS office recommended percentages of each
tillage practice for application to the Washington County Lake Watershed as shown in
Table 5-22 (NRCS 2002a).
Table 5-22 Tillage Practices in Washington County (NRCS 2002a)
Tillage Practice Corn Soybeans Small Grains
Conventional Till 0% 0% 0%
Reduced Till 60% 15% 10%
Mulch-Till 10% 30% 60%
No-Till 30% 55% 30%
Crop rotation practices in the Washington County Lake Watershed were obtained from
the Washington County NRCS office (2002a). The typical rotations in the watershed
are a two-year rotation of corn and soybeans; a three-year rotation of corn, soybeans,
and wheat; and a four-year rotation of corn, soybeans, wheat, and meadow.
5.1.10 Reservoir Characteristics
Reservoir characteristics were obtained from GIS analysis, the Illinois EPA, the
Washington County Lake Resource Plan, and USEPA water quality data. The resource
plan reports the surface area of Washington County Lake as 242 acres (Washington
County Lake Resource Plan [WCLRP] 1997). The value from the resource plan was
used to validate the surface area of 260 acres obtained from GIS analysis. For
modeling analyses, the area obtained through GIS analysis was scaled to equal the area
from the resource plan.
The water quality dataset described in Section 188.8.131.52 was used to determine the
average depth of Washington County Lake. On each date sampled for water quality
constituents, the total depth at the site was measured. Table 5-23 lists the average
depth calculated for each water quality site in Washington County Lake for each year
of available data after 1990.
Table 5-23 Average Depths for Washington County Lake
RNM-1 RNM-2 RNM-3 Lake Average
1990 19.9 15.5 7.5 14.3
1995 19.1 13.7 6.5 13.1
2001 18.4 13.8 6.4 12.9
Reservoir characteristics that were unavailable were flows into and out of the reservoir.
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