Statistical, graphical, and trend summaries of selected water-quality and streamflow data from the Trinity River near Crockett, Texas, 1964-85

Statistical and graphical -.summaries of selected water-quality and'" streamflow data collected between 1964 and 1985 at the Trinity River near" Crockett are presented to document the baseline water quality of the Trinity River at this location. Dissolved oxygen exceeded 7.0 milligrams per liter in more than 50 percent- of the samples analyzed. The mean value of pH'was 7.4 units; the mean values of specific conductance and temperature were 619 microseimens per centimeter at 25 degrees Celsius and 20.5 degrees Celsius, respectively.

As part of the statistical summaries, trend tests were conducted. Several small uptrends were detected for total nitrogen, total organic nitrogen, total ammonia nitrogen, total nitrite nitrogen, total nitrate nitrogen, total organic plus ammonia nitrogen, total nitrite plus nitrate nitrogen, and total phosphorus. Small downtrends were detected for biochemical oxygen demand and dissolved magnesium.