Table 3 provides a listing of monitored lakes, rivers, streams, and creeks in the LTBB reservation, a water quality data summary, and notes on impairments. Note that presentation of the water quality monitoring data in a summarized format does not include the more detailed analyses and information that are presented in the text. Water quality in monitored lakes ranged from impaired to excellent (Table 3). The most significant issues are fish tissue concentrations of mercury and PCBs and temperature in some of the shallower lakes. Elevated conductivity in some lakes may be linked to disturbance of natural marl substrates by boat motors and other activity.
Water quality in rivers and streams was found to be generally good to excellent, with scattered impairments. Water quality on tribal lands is affected by hydromodification and habitat alteration (i.e., alteration of channels and riparian areas), nonpoint source pollution (i.e., polluted runoff) from roadways and other developed areas, temperature, and fish tissue concentrations of mercury and PCBs. Tribal staff have documented that roadway stream crossings and channel modifications, in the form of culverts, bridges, or dredging, are causing erosion, obstructing fish passage, and resulting in warm temperatures and elevated nutrient concentrations at some locations. Channel modification and high temperatures affect river and stream fisheries because fish cannot find spawning and hiding places in streams with thick deposits of sediment, nor can they survive and reproduce above threshold temperatures.
A total of 152 river and stream impairments on and adjacent to tribal lands were noted, with approximately half resulting from alteration of channels and riparian areas. Stormwater runoff from urban areas is the second leading cause of impairment, followed by transportation infrastructure (including road maintenance), atmospheric deposition, agriculture/aquaculture, and marinas/boating (Table 3). The Crooked River watershed, which flows toward Lake Huron, has the most impairments, with 33 impaired reaches.