Summary of statistical and trend analyses of selected water-quality data collected near the Big Thicket National Preserve, southeast Texas

Statistical and trend analyses of selected water-quality data collected at three streamflow stations in the lower Neches River basin, Texas, are summarized in order to document baseline water-quality conditions in stream segments that flow through the Big Thicket National Preserve in southeast Texas. Dissolved-solids concentrations in the streams are small, less than 132 milligrams per liter in 50 percent of the samples analyzed from each of the sites. Dissolved-oxygen concentrations in the Neches River at Evadale (08041000) generally are large, exceeding 8.0 milligrams per liter in more than 50 percent of the samples analyzed. Total nitrogen and total phosphorus concentrations in samples from this site have not exceeded 1.8 milligrams per liter and 0.20 milligram per liter, respectively.

Trend tests for dissolved solids and major ions indicate that small downtrends in total alkalinity, dissolved calcium, and hardness occurred in the Meches River at Evadale (08041000) and Pine Island Bayou near Sour Lake (08041700). Small uptrends in dissolved sulfate were detected at all three stations in the study area.