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Water: Nonpoint Source Success Stories

Colorado: Box Canyon Creek

Better Management of Unpaved Roads and Cattle Grazing Reduces Sediment Loads

 

Waterbody Improved

  Sediment from unpaved roads and poorly controlled cattle grazing impaired the assessment unit comprising Colorado's Box Canyon Creek and its unnamed tributaries. As a result, Colorado added the assessment unit to its 1998 Clean Water Act (CWA) section 303(d) list. The U.S. Forest Service (USFS) completed a number of watershed restoration projects and changed land management practices to address sediment sources. Sediment levels dropped, and Box Canyon Creek and its unnamed tributaries now attain their designated aquatic life uses. Colorado determined that this assessment unit is no longer impaired as of 2010.

 

Contact:

Joan Carlson
(jycarlson@fs.fed.us)
USFS Rocky Mountain Region
303-275-5097


 
This pre-project photo shows a dirt road with incised tire tracks.

Figure 1. Before restoration efforts, unmaintained forest roads like this one contributed sediment to the creek.

 
This post-project photo shows grass growing on a decommissioned dirt road.

Figure 2. Many unpaved roads, such as this one, were closed to vehicular traffic and reseeded.

 

Problem

The watershed of Box Canyon Creek, a tributary of the West  Mancos River, is entirely within the San Juan National Forest in southwestern  Colorado's Montezuma County. The watershed includes approximately 5.8 total  stream miles; the mainstem, which is perennial, is approximately 3 miles long.  Sediment from disturbed areas such as unpaved roads (Figure 1), off-road  vehicle use areas, and livestock grazing areas entered the creek. The presence  of excessive fine sediment prevented the creek from supporting its cold water  class I aquatic life use designation. Consequently, Colorado added the  assessment unit that includes Box Canyon Creek and its unnamed tributaries to  the 1998 CWA section 303(d) list of impaired waters.

  Colorado completed a total maximum daily load (TMDL) for Box  Canyon Creek in June 2000 with a goal of restoring the macroinvertebrate  community throughout the mainstem. Three metrics were used to describe the  macroinvertebrate community: total taxa richness, EPT index, and EPT:C ratio.  The total taxa richness indicates the diversity of the macroinvertebrate  community and is determined by counting the total number of different taxonomic  groups (e.g., families, genera or species) within a sample. The EPT index  measures the richness of genera and species from the three aquatic insect  orders most sensitive to pollution—Ephemeroptera (mayflies), Plecoptera  (stoneflies), and Trichoptera (caddisflies). A third biological metric used to  evaluate stream health is the EPT:C ratio, which compares the number of  individuals from the sensitive Ephemeroptera, Plecoptera and Trichoptera (EPT)  orders in the sample to the number of individuals from the pollution-tolerant  family Chironomidae (e.g., non-biting midges). Streams that have an EPT:C ratio  above 0.5 are considered unimpaired.

The TMDL set two additional water quality  targets: (1) a maximum of 25 percent sediment fines of 8.0 millimeters  (mm) or smaller diameter deposited on the surface of the streambed and (2) a  road density no greater than 1.8 total road miles per square mile within the  5-square-mile Box Canyon Creek watershed. The TMDL study found a baseline road  density of 6.9 miles per square mile.

Project Highlights

After the TMDL was approved, the USFS implemented watershed  restoration projects and changed land management practices to address sediment  sources. Unmaintained native surface roads used for off-road vehicle use were a  primary source of sediment. Because motorized vehicle use previously had been  unrestricted, the road density in the watershed included many unauthorized,  user-created and unmaintained recreational use roads. The Bureau of Land  Management (BLM) and USFS implemented travel management plans for the  surrounding area, specifying which roads would be added, maintained or closed.  Each travel management plan outlined travel designations, specifying what types  of vehicles would be permitted on each designated route and in what season.  Travel management decisions set restrictions limiting the use of motorized  vehicles (including off-road and four-wheel-drive vehicles) to designated  routes on roads maintained or added under the travel management plans.  Implementation of the travel management plans also included permanently closing  and reclaiming many roads (Figure 2).

Additional sediment control measures included  better management of permitted livestock grazing. The specific measures used  included reducing the number of cattle and the duration of grazing, as well as  constructing drift fences (typically of barbed wire) to guide cattle away from  sensitive areas. Changing grazing practices increased vegetative cover in the  watershed and reduced cattle access to riparian areas, thereby reducing the  potential for accelerated erosion from grazing.  

     

Results

In July 2006 the U.S. Environmental Protection Agency  (USEPA) Region 8, the Colorado Department of Public Health and Environment  (CDPHE), and the USFS partnered to collect post-restoration data on substrate  particle size, macroinvertebrate community, stream habitat and water chemistry  at four sites in the Box Canyon Creek watershed. The data showed that the TMDL  target for fine sediment—a maximum of 25 percent fines of 8.0 mm or smaller  diameter—had not been achieved in any of the four reaches of Box Canyon Creek;  however, efforts to meet the TMDL goal for macroinvertebrate diversity (Table  1) and the target for road density had been successful.

  The data showed a macroinvertebrate community with a greater  richness of species, specifically the more sensitive EPT species, throughout  the entire stream length than before the project began. The EPT:C ratio for all  reaches was above the target of 0.5, and therefore all four reaches could be  considered unimpaired.

  Post-project road density was calculated in September 2006  using field verification of the existing geographic information system (GIS)  roads layer. The total length of open roads (system, secondary system and  non-system roads) was 5.689 miles, and the total watershed area was 4.64 square  miles. These figures gave a current road density of 1.23 miles of road per  square mile, well below the initial density of 6.9 miles per square mile in  2000.

  Because of these results, the Colorado Water Quality Control  Commission reports that Box Canyon Creek fully meets its aquatic life  designated use and is no longer impaired as of 2010.

Partners and Funding

Restoration partners included the USFS, in conjunction with  livestock grazing permittees and the off-road recreation community in the Box  Canyon watershed. BLM and USFS developed travel management plans for watershed  areas. USFS, USEPA Region 8, and the CDPHE's Water Quality Control Division  conducted post-restoration monitoring and documented watershed improvements  using approximately $15,000 in federal funding; CDPHE and USEPA Region 8  personnel provided additional in-kind assistance.

         
Table 1. Macroinvertebrate Survey* in Box Canyon Creek (July 11–12, 2006)
  Reach  1 Reach  2 Reach  3 Reach  4
Total Taxa Richness 44 34 34 30
EPT  Richness 20 17 11 11
Chironomids  (%) 15.14 6.45 9.6 18.43
EPT  (%)75.0380.8227.9053.40
EPT:C  ratio 0.83 0.93 0.74 0.74
* Streams with an EPT:C ratio above 0.5 are considered unimpaired.

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