Recreational water quality analyses of the Colorado River corridor in Grand Canyon

Abstract

We intensively examined the recreational water quality of the Colorado River and 26 tributaries in Grand Canyon National Park over four consecutive summers. Highly ephemeral precipitation cycles and arid watershed hydrologies were the principal factors influencing water quality. Fecal coliforms (FC) in the river and in most tributaries were '10 FC 100 ml-' and s20 FC 100 ml-', respectively, during drought cycles. During rainfall cycles, FC densities were highly variable and often exceeded recreational contact standards. FC were not found to vary significantly in response to diurnal fluctuations in river stage height which resulted from hydroelectric stream flow regulation. River and tributary bottom sediments harbored FC in densities averaging 10 to 100 times those in the overlying waters. Sediment FC densities were not found to be reliable indicators of overlying water quality when storm flow and nonstorm flow periods were compared.

Climate change and waterborne and vector-borne disease

“…Heavy rainfall leads to storm water runoff into surface water sources, which has high counts of indicator bacteria as well as potential pathogens (Doran and Linn 1979;O'Shea and Field 1992). Heavy rainfall is also associated with high counts of indicator bacteria in river waters (Tunnicliff and Brickler 1984) and marine waters (Crowther et al 2001). Given the well described relationships between counts of indicator organisms in surface water and the subsequent risk of predominantly gastrointestinal illness (Kay et al 1994) it should be expected that people swimming in untreated surface waters after heavy rain would be at increased risk of illness.…”

“…Heavy rainfall leads to storm water runoff into surface water sources, which has high counts of indicator bacteria as well as potential pathogens (Doran and Linn 1979; O'Shea and Field 1992). Heavy rainfall is also associated with high counts of indicator bacteria in river waters (Tunnicliff and Brickler 1984) and marine waters (Crowther et al . 2001).…”

Factors affecting Escherichia coli concentrations at Lake Erie public bathing beaches

“…In contrast, in a study of canals along the Texas Coast (Goyal and others, 1977), investigators found no statistically significant relation between fecal-indicator concentrations and temperature, pH, turbidity, or suspended solids concentrations. Tunnicliff and Brickler (1984) found a statistically significant correlation between turbidities and fecal-coliform concentrations in samples collected during storm events but not for samples collected during base flow.…”

Fecal-indicator bacteria in the Newfound Creek watershed, western North Carolina, during a high and low streamflow condition, 2003

“…Bacteria attach to sediment particles and survive in the nutrient-rich environment of the streambed where they are deposited (Gerba and McLeod, 1976;Burton and others, 1987). Lake and streambed sediments can contain densities of fecal-indicator bacteria several times those of the overlying water column (Bromel and others, 1978;Tunnicliff and Brickler, 1984). Streambed sediments in Newfound Creek may provide a reservoir of fecal-indicator bacteria that are deposited from point or non-point sources and then resuspended by physical disturbances, such as high flow.…”