WSP10010

• File Number: 8449.700
• Description: Cherry Creek
• State: CO
• Basin: South Platte
• Date: 9/1/1995
• Author: Halepaska & Assoc.
• Title: Phase 1 Baseline Water Quality Data Collection Study for the Upper Cherry Creek Basin - Final Report
• Water Supply Pro - Doc Type: Publication

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JCHA

flDaI Reoort. _ I P- .' Ie W..... 0uaIitv Data Collectioo StudY

~iPnIber 1995

vs. non-point sources of phosphorus contributions to the upper Cherry Creek Basin are
evaluated, the study data for the one-year study indicate that the bulk of the phosphorus being
input to the reservoir is from non-point sources, and that the percentage of phosphorus
contributions related to non-point sources has generally been increasing over the course of the
study. During the study period, non-point sources have represented 80 to 99 percent of the total
phosphorus being input to Cherry Creek Reservoir from the main stem of Cherry Creek (Table
6 and Figure 15).

The flow and water quality data that have been collected as part of the first year of the Phase
I baseline study generally indicate increases and decreases in both nitrogen and phosphorus
concentrations and loads throughout the study reach, with very little correlation of changes in
concentrations in load based on point discharges that are currently being made in the upper
Cherry Creek Basin. This may be related to the adsorptive capacity of the system, or it may
simply be related to the relatively minor percent of overall flow that is represented by direct
discharges at this point in time. As point discharges increase in the upper Cherry Creek Basin,
a more direct correlation may develop. Currently, nitrate-nitrogen loading to the reservoir is
greater than the phosphorus loading (23,575Ibs. vs. 3,440 Ibs.). The phosphorus loading from
the main stem of Cherry Creek represents approximately 24 percent of the overall allowable
phosphorus loading to the reservoir (14,270 lbs.).

Stream channel sediment data collected during the Phase I baseline study has indicated only
minimal transport of ammonia-nitrogen concentrations and relatively low phosphorus
concentrations. Based on the data collected to date, suspended sediment transport of nitrogen
and phosphorus species to the reservoir appears to be a relatively minor component of the
overall loading to the reservoir.

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