The 14.5-mile segment of Cattle Creek between Bowers Gulch to the confluence with the Roaring Fork River is listed on Colorado’s Regulation 93 303(d) list of impaired waters due to observed impacts to aquatic macroinvertebrate communities. Roaring Fork Conservancy (RFC) implemented water quality monitoring in 2015 with the support of Garfield County and other stakeholders in order to understand potential sources of impairment. Within a reasonable timeframe, Colorado Department of Public Health and Environment, with input from stakeholders, must make determinations on causes of stream impairments and develop a plan to address water quality issues. Monitoring in 2015 produced targeted data suitable for use in state-level regulatory proceedings.
Water chemistry sampling in Cattle Creek at 7 sites indicates increased levels of nutrients, bacteria, and total dissolved solids in the lower watershed sites. A small number of total phosphorus observations exceeded interim aquatic life standards. E. coli levels frequently exceeded recreational contact standards at multiple sites. Macroinvertebrate sampling indicates increased levels of stress and disturbance at downstream sites relative to upstream sites. Land use analysis identifies gradients of land use change that correlate with water quality findings. The upper reaches of the Cattle Creek watershed are largely undeveloped and forested, producing excellent water quality. A gradient of increasing impacts from irrigated rangeland/pasture and ranching activities occurs in the middle watershed. Increasing nutrient and bacteria levels most likely link to impacts from cattle and ranching activities. Near-stream development including light-density residential units and limited irrigation of pasture impact stream reaches in the lower watershed. Near Cattle Creek’s mouth, commercial development and Highway 82 influence the creek.
Analyses of estimated septic system density at the watershed and sub-reach scales show a correlation between nitrate levels and septic tank density, indicating a potential human component to nutrient issues. However, the nested nature of sites and overall small number of data points reduces the statistical strength of these relationships.
Although riparian conditions and flow stress from significant trans-basin diversions to the Missouri Heights area are suspected to play a role in the stream health conditions of Cattle Creek, those factors were beyond the scope of monitoring. Altered or degraded riparian conditions from near-stream livestock activities or residential development may alter food webs, reduce the ability of natural vegetation to attenuate sediment and nutrient impacts from surface runoff, and overall provide less cover and habitat complexity for aquatic life.
Continued chemistry and macroinvertebrate monitoring will add depth, reliability, and increased statistical power to the dataset for Cattle Creek. Exploration of additional factors such as flow stress and fish communities may also shed additional light on stream impairments. Roaring Fork Conservancy plans to continue Cattle Creek monitoring in 2016.