C150240 Vegitation Montioring Analysis

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EXECUTIVE SUMMARY Vegetation monitoring was performed by WestWater Engineering (WestWater) during four seasons to evaluate vegetation trends following the increase of storage capacity at Bull Creek Reservoir #4 in 2011. The intent of the vegetation monitoring was to assess potential secondary impacts to wetland functions as a result of increasing the water level. Functions such as flood- flow attenuation, sediment entrapment, shoreline stabilization, wildlife and aquatic habitat, and nutrient export can be influenced by the vegetation present at a site. Regression analysis was used to describe change in percent cover, species richness, and species diversity between 2010 and 2014. WestWater was unable to detect any statistically significant change in percent cover, species richness, or species diversity within the various elevations (zones) or sites during the monitoring period. One potential trend noted is species richness may have decreased over the monitoring period. This ' trend is described by a weak linear relationship. Natural variation from year to year is expected and could be explained by some other variable not measured. Wetland has increased in size within the inundated zone from 3.38 acres to 6.49 acres. Function has increased, propelled by the increase in wetland acres. Total wetland (functional) value has increased 67% from a value of 2.91 in 2010 to a value of 4.45 in 2014. Secondary impacts to vegetation cover, richness, and diversity in the newly inundated zone were not detected. INTRODUCTION WestWater was requested by Bull Creek Reservoir, Canal and Power Company (BCRCPC) to perform vegetation monitoring at Bull Creek Reservoir #4. The area of interest is the newly inundated zone between the restricted water level elevation (9,857.5 ft) and the high water level elevation (9,864 ft). Bull Creek Reservoir #4 is located southwest of the town of Mesa, Colorado. The reservoir is located on federal lands managed by the U.S. Forest Service (USFS) within the Grand Mesa National Forest within Sections 20 and 29, Township 11 South, Range 95 West, 6th Principal Meridian (Figure 1). The State Engineer's Office (SEO) placed a year round restrictive water level on Bull Creek Reservoir#4 in 1984 until dam maintenance could be conducted. Because BCRCPC did not have the financial resources available to conduct the maintenance, Bull Creek Reservoir #4 has not been fully utilized for agricultural water storage. During this period, wetland vegetation grew between the historical and the restricted water levels. In 2008, work to the dam, spillway, and access roads was authorized by a permit (SPK-2008- 00722). BCRCPC conducted maintenance on the dam at Bull Creek Reservoir #4 to remove restrictions placed by the SEO, and restore the reservoir to historic water levels. WestWater Engineering Page 1 of 14 February 2015