Water-quality, streamflow, and meteorological data for the Tualatin River Basin, Oregon, 1991-93

Plankton communities and summertime declines in algal abundance associated with low dissolved oxygen in the Tualatin River, Oregon

“…Previous modeling of Chl-a in the Tualatin River (Rounds and others, 1999) found that, at times, the simulated biomass was higher than that measured in the river, and attributed this to losses from zooplankton grazing. A comparison of zooplankton taxa from 2006-08 with previous data from 1991-93 (Doyle and Caldwell, 1996) showed that many of the same Genera (Daphnia, Ceriodaphnia, and Bosmina) were dominant in all years.…”

“…In addition, the large degree of annual variability in algal populations (figs. 4 and 6) and lack of a consistent successional pattern in the algal species composition (Doyle and Caldwell, 1996) has made it difficult to incorporate interspecies differences in buoyancy, nutrient requirements, growth rates, or susceptibility to grazing by zooplankton, for example, into the models.…”

“…The dominant types of algae in the Tualatin River during summer, based on a limited number of past studies, included planktonic diatoms (Stephanodiscus, Cyclotella, Aulacoseira, Melosira, and others), Chlamydomonas and other green algae, and occasional blooms of potentially toxic blue-green algae, including Anabaena and Microcystis (Carter and others, 1976;Rinella and others, 1981;Oregon Department of Environmental Quality and Unified Sewerage Agency, 1982;Doyle and Caldwell, 1996).…”

Water-quality and algal conditions in the North Umpqua River Basin, Oregon, 1992-95, and implications for resource management

“…The sample, prepared in the ODL as part of an established quality control program with the United Sewerage Agency (Doyle and Caldwell, 1996) contained known concentrations of nutrients in water that was previously certified to be free of inorganic constituents at the microgram per liter level. Concentrations of nutrients were deliberately chosen to reflect the concentrations previously observed in the North Umpqua River Basin.…”

Water-temperature, specific-conductance, and meteorological data for the Tualatin River basin, Oregon, 1994-95

“…Hourly and half-hourly water temperature, specific-conductance, and meteorological data from the fixed-station sites, along with 16-minuteinterval water-temperature data from the synoptic surveys, are also available in digital American Standard Code for Information Interchange (ASCII) file format from the USGS Oregon District Office upon request. Additional water-quality data and analyses concerning the Tualatin River are available in Doyle and Caldwell (1996) and Kelly (1995), which were products of a separate cooperative water-quality study of the USA and the USGS.…”