In April the river appears turbid at Grants Pass in the lower Rogue Valley.
To comply with section 303(d) of the federal Clean Water Act, the EPA or its state delegates must develop a list of the surface waters in each state that do not meet approved water-quality criteria. To meet the criteria, the DEQ and others have developed
Total Maximum Daily Load (TMDL) limits for pollutants entering streams and other surface waters.
[n 4] The Oregon 303(d) list of pollutants for 2004–06 indicated that some
reaches of the surface waters in the Rogue River Basin did not meet the standards for temperature, bacteria,
pH and nuisance weeds and
algae. All of the listed stream reaches were in Oregon; none in the California part of the basin was listed as impaired on that state's 303(d) list in 2008.
The EPA approved temperature TMDLs for three Rogue River tributaries: Upper Sucker Creek in 1999, Lower Sucker Creek in 2002, and Lobster Creek in 2002. It approved temperature, sedimentation, and biological criteria TMDLs for the Applegate River basin in 2004, and temperature, sedimentation,
fecal coliform, and
Escherichia coli (E. coli) TMDLs for the Bear Creek watershed in 2007. In 1992 it had approved pH, aquatic weeds and algae, and dissolved oxygen TMDLs for the Bear Creek watershed. In December 2008, DEQ developed two TMDLs for the Rogue River basin (except the tributaries with their own TMDLs); a temperature TMDL was meant to protect salmon and trout from elevated water temperatures, and a fecal contamination TMDL was intended to safeguard people using surface waters for recreation.
The DEQ has collected water-quality data in the Rogue basin since the mid-1980s and has used it to generate scores on the Oregon Water Quality Index (OWQI). The index is meant to provide an assessment of water quality for general recreational uses; OWQI scores can vary from 10 (worst) to 100 (ideal). Of the eight Rogue basin sites tested during the water years 1997–2006, five were ranked good, one was excellent, and two—
Little Butte Creek and Bear Creek, in the most populated part of the Rogue basin—were poor. On the Rogue River itself, scores varied from 92 at RM 138.4 (RK 222.7) declining to 85 at RM 117.2 (RK 188.6) but improving to 97 at RM 11.0 (RK 17.7). By comparison, the average OWQI score for the Willamette River in downtown
Portland, the state's largest city, was 74 between 1986 and 1995.