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George A. Irwin

Publications and source records attributed to George A. Irwin.

9 recordsLinked to original sources
USGS1976

Water-quality investigation, Salinas River, California

Concentrations of dissolved solids in the Salinas River are variable and range from 164 to 494 milligrams per liter near Bradley and from 170 to 1,090 milligrams per liter near Spreckels. Higher concentrations near Spreckels are caused mainly by sewage inflow about 150 feet (50 meters) upstream. Concentrations of nitrogen, phosphorus, total organic carbon, selected trace elements, and pesticides also generally increase downstream from Pozo to Spreckels and are related to sewage effluent; however, high concentrations occur elsewhere in the river. Specific conductance and water discharge regression results indicate that relations were all significant at the 1-percent probability level at Paso Robles, Bradley, and Spreckels, with the explained variance ranging from 66 to 74 percent. Concentrations of nitrogen, phosphorus, total organic carbon, and trace elements are only infrequently related to water discharge.

California↗
USGS1976

Water-quality investigation, Eel River, California

This report summarizes selected water-quality data collected in the Eel River, Calif., during a reconnaissance study from November 1971 through January 1975. It also includes a summary of the major inorganic chemical data collected near Dos Rios, at South Fork, and at Scotia since the early 1950's. The recent reconnaissance involved data collection for nitrogen, phosphorus, total organic carbon, trace elements, and pesticide compounds in the river at Van Arsdale Dam, near Dos Rios, at Fort Seward, and at Scotia. The number of samples collected during the special reconnaissance is somewhat limited, and therefore the data are only an estimate of conditions that presently exist at selected sites in the river. Results indicate that most of the constituents were low in concentration; although some variability was measured for some constituents. Sampling was designed so that samples collected at each site would represent a large range in discharge. Results indicate that discharge was not the singular factor controlling the concentration variance for most constituents. However, the concentrations of total ammonia, phosphorus, arsenic, chromium, copper, and zinc indicated a direct relation with discharge at some sites. Statistical analysis indicates that the past sampling program has been adequate to estimate the major chemical constituents of the river. Specific conductance in the river near its headwaters ranges from 110 to 300 micromhos about 98 percent of the time; and at Scotia, near the mouth, the specific conductance ranges from 110 to 340 micromhos about 98 percent of the time. Results of regression analyses indicate that between 83 and 88 percent of the variance in specific conductance can be explained by discharge.

California↗
USGS1975

A summary of selected chemical-quality conditions in 66 California streams 1950-72

Water from California streams has been analyzed for concentrations of selected chemical constituents since the early 1950's. This summary includes about 1,200 water years of data from 88 sampling sites on 66 streams. Results of this summary show that about 80 percent of the sites had a mean dissolved-solids concentration of 400 milligrams per litre or less. All the sites that had mean concentrations ranging from 601 to 800 milligrams per litre were in either the South Coastal or Central Coastal subregions. Results of regression analysis between specific conductance and calcium, magnesium, sodium, bicarbonate, dissolved solids, and hardness usually indicated a high percentage of explained variance. Other constituents, such as potassium, sulfate, chloride, and particularly nitrate, were not as frequently highly associated with specific conductance. At sites where the water discharge was highly regulated, the variation in specific conductance that was explained as a function of discharge ranged from 0 to more than 90 percent. Whereas at the unregulated sites, the explained variance ranged from 50 to more than 90 percent.

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USGS1974

A water-quality reconnaissance of Big Bear Lake, San Bernardino County, California, 1972-1973

A water-quality reconnaissance study of the Big Bear Lake area in southern California was made by the U.S. Geological Survey from April 1972 through April 1973. The primary purpose of the study was to measure the concentration and distribution of selected primary nutrients, organic carbon, dissolved oxygen, phytoplankton, and water temperature in the lake. Estimates of the nitrogen, phosphorus, and silica loading to the lake from surface-water tributaries and precipitation were also made. Results of the study indicate that Big Bear Lake is moderately eutrophic, at least in regard to nitrogen, phosphorus, and organic content. Nitrate was found in either trace concentrations or below detectable limits; however, ammonia nitrogen was usually detected in concentrations greater than 0.05 milligrams per liter. Orthophosphate phosphorus was detected in mean concentrations ranging from 0.01 to 0.05 milligrams per liter. Organic nitrogen and phosphorus were also detected in measurable concentrations. Seasonal levels of dissolved oxygen indicated that the nutrients and other controlling factors were optimum for relatively high primary productivity. However, production varied both seasonally and areally in the lake. Primary productivity seemed highest in the eastern and middle parts of the lake. The middle and western parts of the lake exhibited severe oxygen deficits in the deeper water during the warmer summer months of June and July 1972.

California↗
USGS1972

Limnological studies of Big Bear Lake, California

Big Bear Lake exhibited seasonal changes in physical, chemical, and biological variables from June 1968 to June 1969. Dissolved-oxygen concentrations were depressed during the summer resulting in anaerobic conditions near the bottom of the lake. Water temperature decreased with depth in spring and summer, although classical thermal stratification was not observed. The nutrient standing crop was sufficient to maintain two distinct seasonal phytoplankton blooms. There were phytoplankton growth periods during the winter of 1968 and the summer of 1969, but the maximum populations that were observed were not excessive. During the study Big Bear Lake exhibited periods of biochemical stress symptomatic of organically enriched lakes; however, no attempt was made to determine the magnitude or rate of the eutrophicational processes occurring in the lake.

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