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

Table 4. Description of geomorphology and habitat, irrigation diversions, tributary and agricultural returns, light availability, aquatic plant growth, and nutrient concentrations in three reaches of the lower Yakima River, Washington, 2004–07.

[Abbreviations: RM, river mile; ft, foot; ft/s, foot per second; ft/100 ft, foot per 100 feet; µg/L, microgram per liter; mg/L, milligram per liter; g/m², gram per square meter; na, not applicable; –, no data]

Parameter and unit of measure	Measurement	Reach
Parameter and unit of measure	Measurement	Zillah (RM 116 – 72)	Mabton (RM 72 – 47)	Kiona (RM 47 – 4)
Geomorphology and habitat
River gradient (ft/100 ft)	Longitudinal profile	1.8	0.3	1.1
Geomorphic units from June 2004 survey	Qualitative	Mostly runs with some short pools	Two long pools	Mostly run with one short pool
Maximum water depths from June 2004 survey (ft)	Mean	4.5	7.9	5.4
Maximum surface water velocities from June 2004  survey (ft/s)	Mean	2.2	1.3	2.3
Dominant substrate type from June 2004 survey	Qualitative	Cobble	Fines	Cobble
Diversions and tributary input
Water diversions during 2004 synoptic sampling (percent)	Proportion of total streamflow	90	¹ 0	17
Tributary and agricultural drain inflow during 2004 synoptic sampling (percent)	Proportion of total streamflow	41	50	30
Light availability
Maximum depth of plant colonization, 2005 (ft)	Median	5.7	6.8	12.2
Aquatic plant growth
Frequency of macrophyte presence from June 2004 survey (percent)	Proportion of stations where macrophytes were present	41	48	86
Macrophyte biomass (dry weight), August–September 2005 (g/m²)	Median	0	0	1,020
Phytoplankton abundance (as chlorophyll a),  2004-07 (µg/L)	Median	4.6	13.1	4.4
Nutrients
Surface-water concentration of dissolved nitrite plus nitrate, July–September 2005 (mg/L)	Mean	0.30	1.00	0.91
Surface-water concentration of dissolved orthophosphate, July–September 2005 (mg/L)	Mean	0.033	0.080	0.126

¹The diversion for Chandler Canal is at the end of Mabton reach, but does not affect streamflow in the reach.

Assessment of Eutrophication in the Lower Yakima River Basin, Washington, 2004–07