Water quality problems caused by sediment can affect stream habitats and the aquatic life that depends on them. In southeastern Idaho, Rapid Creek provides an example of how agricultural best management practices (BMPs), monitoring, and cooperation among landowners and watershed partners can contribute to measurable improvements. After sediment impairment was identified in the watershed, a series of projects focused on reducing soil erosion and limiting sediment entering streams.Rapid Creek is located in southeastern Idaho, where rangeland is the predominant land use. Livestock grazing, streambank erosion, sheet and rill erosion, and erosion from roads contributed excess sediment that negatively impacted water quality.Biological assessments discovered that several streams within the Rapid Creek watershed did not support cold water aquatic life. Based on IDEQ’s Section 305(b) water quality assessment report, the U.S. Environmental Protection Agency (EPA) added Upper and Lower Rapid Creek to the CWA Section 303(d) list in 1994 for sediment impairment.In 1995, the Idaho Department of Environmental Quality (IDEQ) conducted a Beneficial Use Reconnaissance Program (BURP) wadeable streams rapid bioassessment on Rapid Creek to confirm the impairment. BURP analyzes stream health through multimetric indices spanning biological, physical, and chemical conditions, using a scale from 0.0, the lowest score, to 3.0, the highest.Both North Fork Rapid Creek and Lower Rapid Creek obtained a stream macroinvertebrate index (SMI) score of 0, below the minimum threshold levels. The sites therefore automatically failed and were considered not to support advantageous uses. The stream segments remained on the CWA Section 303(d) list for sediment impairment.At that time, Lower Rapid Creek and West Fork Rapid Creek were listed as Water Quality Limited Segment #2334. West Fork Rapid Creek was listed as impaired based on the failing scores measured at Lower Rapid Creek. In 2002, however, the segment was divided into the assessment units used today.Agricultural Projects Targeted Soil ErosionAttempts to address the sediment concern began with agricultural water-quality projects. From 1989 to 1999, the Portneuf Soil and Water Conservation District (SWCD) implemented a State Agricultural Water Quality Program (SAWQP) grant-funded project across the 16,195-acre Upper Rapid Creek watershed.With assistance from SAWQP, landowners implemented BMPs on almost 3,839 critical upland acres to minimize soil erosion.Additional work followed from 2001 to 2007, when the Portneuf SWCD led the Upper Rapid Creek Section 319 project. The project helped landowners implement BMPs on 2.8 miles of impaired stream segments and was established on the earlier 1989–1999 SAWQP effort.In the initial inventory, the SWCD found 4,800 acres of the watershed as critical. Landowners subsequently implemented agricultural BMPs on 1,085 of those acres with CWA Section 319 funding, 1,251 acres through Conservation Reserve Program (CRP) funding, and 506 acres through Environmental Quality Incentives Program (EQIP) funding.Watershed partners also used a Conservation Innovation Grant (CIG) to help finish a Section 319 project. Together, these four funding sources supported treatment of 59% of the critical acres.Monitoring Recorded ImprovementsMonitoring conducted after BMP implementation featured improvements in water quality. The Idaho Association of Soil Conservation Districts (IASCD) monitored the West and North Forks of Rapid Creek in 2006–2007. Sites were selected above and below the CWA Section 319 project area, enabling upstream-downstream comparisons.The monitoring showed that the suspended solids load declined by an estimated 26 pounds per day, or 8%. Escherichia coli and nitrogen concentrations also declined.IDEQ collected water samples at the mouth of Rapid Creek under high-flow conditions in 2007. The samples averaged 23.6 milligrams per liter (mg/L) of total suspended solids (TSS), meeting the 80 mg/L high-flow sediment TMDL target.Biological Assessments Showed Stronger Stream ConditionsIDEQ remained conducting BURP bioassessments to evaluate whether stream conditions had improved. Assessments were conducted on North Fork Rapid Creek in 2011, West Fork Rapid Creek in 1998 and 2011, and Lower Rapid Creek in 2001, 2004, and 2012.The 2011 North Fork Rapid Creek assessment produced an average BURP score of 2, which is the minimum average score indicating complete support of cold water aquatic life. West Fork Rapid Creek also supported cold water aquatic life in 2011, getting an average score of 2.67.Lower Rapid Creek received an average score of 2.67 in 2012. That assessment was the first since 1995 to analyze all three multimetric indices—SMI, SFI, and SHI—and the resulting score was regarded as fully supporting.Percent fines data offered additional proof. At all sites, less than 30% of the substrate consisted of material less than or equal to 2.5 millimeters in size. As per the IDEQ’s Guide to Selection of Sediment Targets for Use in Idaho TMDLs, this indicated a lack of fine sediment impairment.Three Rapid Creek Assessment Units Were DelistedThe monitoring and biological assessments offered multiple lines of evidence that water quality and stream conditions had enhanced. Based on these findings, IDEQ removed three assessment units from the state’s lists of impaired waters for sediment impairment.The delisted regions included the 4.87-mile-long North Fork Rapid Creek, the 6.58-mile-long West Fork Rapid Creek, and the 5.62-mile-long Lower Rapid Creek. Lower Rapid Creek was removed from the state’s 2012 list, while the North and West Forks of Upper Rapid Creek were removed in 2014.A Long-Term Example of Watershed ImprovementRapid Creek’s progress followed years of work involving landowners, the Portneuf SWCD, IDEQ, IASCD, and other watershed partners. Beginning with the identification of sediment impairment and continuing through agricultural BMP implementation and repeated monitoring, the effort provided evidence of improving water quality and aquatic habitat.The results feature the significance of combining on-the-ground conservation practices with monitoring data. In Rapid Creek, reductions in suspended solids and improved biological and habitat scores were followed by the removal of three assessment units from Idaho’s impaired-waters lists for sediment impairment.Source: U.S. Environmental Protection AgencyFAQs:Q1. What caused sediment problems in Rapid Creek?Livestock grazing and several forms of erosion contributed excess sediment. These sources negatively affected water quality.Q2. When was Rapid Creek listed for sediment impairment?Rapid Creek was added to Idaho’s CWA Section 303(d) list in 1994. The listing was based on sediment impairment.