Sabine River Authority of Texas
From: Environmental Services division
RE: september 1999 Water Quality Monitoring Report
This is the Sabine River Authority Water Quality Summary for September 1999. Water quality sampling was performed September 21 through September 23. Daytime high air temperatures during the seven days prior to the sampling dates have been in the 80's and 90's with nighttime lows 20-30 degrees cooler. Dry weather prevailed in the basin, and reservoir and river conditions were impacted little to none by the most recent rainfall. Due to failure of laboratory equipment, values for ammonia and orthophosphate were not obtained.
Upper Sabine Basin Above Toledo Bend Including Lake Fork and Lake Tawakoni
For the September sample run, most of the parameter's values seen at the Upper Basin sites were consistent with water of high quality. The most recent rainfall was a 0.6 inch rain eight days prior to sampling. Lake Tawakoni recorded 0.99 inches of rain since September 1st and Lake Fork recorded 2.11inches during the same period. Cooler weather and wind caused most of the reservoir sites to mix this month after having been stratified through the summer months. Only the deepest sites, LF2 and LF4, were still stratified, with LF2 stratified at 12m and LF4 at 9m. A new station was added at the request of the TNRCC and monitored for the first time this month. This site is on the Lake Fork Creek arm of Lake Fork Reservoir up-lake from the LF4 site. Water quality parameters at this site were consistent with water of high quality. LT23C and LT23D exceeded stream standards for pH. SRA believes stream standards for pH on Lake Tawakoni are set too low for a reservoir in the Blackland Prairie ecoregion with higher natural hardness and alkalinity. Dissolved oxygen was slightly less than 5mg/l at LF3 and several other parameters at this site were outside of screening ranges. No stream standards exist for these parameters, but nitrate/nitrite, chloride, and sulfate were elevated above recommended screening levels. The water color at LF3 was brown and small suspended particles were observed during sampling. These are signs of recent lake turnover and may have attributed to the lower dissolved oxygen and elevated nutrients. For the most part, data at river sites reflected good water quality conditions with good clarity and low fecal coliform counts. Dissolved oxygen was slightly under 5mg/l at SR14 and Sulfate was elevated at SR11 as has been observed during other low-flow periods.
Lower Sabine Basin Including Toledo Bend to Morgan Bluff
September WQM sampling results were indicative of water of high quality at most sites. Toledo Bend Reservoir exhibited drought conditions at the time samples were taken. The surface of Station TB6N was completely covered with duckweed, a floating aquatic plant, and had higher values for fecal coliform, chloride and sulfate than other sites sampled. Deep water stations sampled at Toledo Bend Reservoir did not exhibit thermal stratification but did exhibit anoxic conditions below 10 meters. Compared to other sites sampled during the September WQM, Station BA4 had higher fecal coliform, sulfate,TDS, and conductivity values. Station BA4 is sampled downstream from a paper mill discharge. At the time the sample was taken, the bayou was very low with dark, almost black, water and had an odor similar to sewage.
Tidal Section of the Sabine Basin below Morgan Bluff
Stations sampled in the tidal portion of the Sabine Basin had values that were consistent with water of high quality. All surface water values measured were within stream standards criteria. Deep water oxygen values measured at Station SRT2 became anoxic at approximately 6 meters. A definite salt water wedge was detected as far north as the Interstate 10 bridge. Salinity readings ranged from 2 ppt at surface to 21 ppt at a depth of 9 meters. No tidal action was observed at the time of sampling.
This Report and additional data for these monitoring stations are available on our World Wide Web site (www.sra.dst.tx.us). If you have any questions or comments concerning this report, please contact:
Printed Tuesday, May 02, 2000