USGS Scientific Investigations Report 2009–5078Assessment of Eutrophication in the Lower Yakima River Basin, Washington, 2004

Table 1. Potential factors affecting algal biomass given adequate-to-high nutrient supply and nontoxic conditions.

[Table modified after U.S. Environmental Protection Agency, 2000a.Abbreviations: ft/s, foot per second; >, greater than; <, less than]

Periphyton biomass
High		Low
	High current velocity (>0.33 ft/s)	Low current velocity (<0.33 ft/s)
	Low turbidity/color	High turbidity/color
	Open canopy	Closed canopy
	Shallow stream depth	Greater stream depth
	Minimal scouring	High scouring
	Limited macroinvertebrate grazing	High macroinvertebrate grazing
	Gravel or larger substrata	Sand or smaller substrata
	Smaller depth to width ratio
Phytoplankton biomass
High		Low
	Low current velocity (<0.33 ft/s)	High current velocity (>0.33 ft/s)
	Long detention time (>10 days)	Short detention time (<10 days)
	Low turbidity/color	High turbidity/color
	Open canopy	Closed canopy
	Greater stream depth	Shallow stream depth
	Greater depth to width ratio