Surface water quality of the major drainage basins of Big Thicket National Preserve

Surface water quality was monitored at 19 stations (2-4 week intervals) in six drainage basins of Big Thicket National Preserve of east Texas between 1996 and 1999. The parameters monitored were temperature, dissolved oxygen, pH, conductivity, current speed, light attenuation, chlorophyll a and concentrations of ammonium, ortho-phosphate, nitrate and nitrite. The best water quality (low nutrients and chlorophyll a; no hypoxia) was found in the Big Sandy Creek, Turkey Creek and Village Creek systems. Water quality in the Neches River was also generally good except for instances of moderate algal blooms. The Pine Island Bayou system, however, typically showed poor water quality. Very low current velocities and high concentrations of nutrients promoted massive spring plankton blooms (chlorophyll a in excess of 100 μg L-1) and subsequent hypoxia/anoxia (dissolved oxygen less than 5 mg L-1). In this system, hypoxia occurred as early as April and as late as December.