Sabine River Authority of Texas
To: Interested Parties
From: Environmental Services
RE: October 1998 Water Quality Monitoring Report
This is the Sabine River Authority Water Quality Report for October 1998. Water quality sampling was performed October 13 through October 15. Weather during October can be characterized as warm and wet throughout most of the Basin, heavy rains occurred one week prior to the October Water Quality Monitoring (WQM). These rains caused high flow in the Sabine Basin, which had begun to recede in some locations by the October WQM.
Upper Sabine Basin Above Toledo Bend Including Lake Fork and Lake Tawakoni
Most of the parameter's values seen in the Upper Basin sites are consistent with water of high quality. A few values for pH and dissolved oxygen exceeded stream standards and fecal coliform exceeded the numerical criteria for stream standards. Lake Tawakoni and Lake Fork Reservoir were weakly stratified with respect to dissolved oxygen and temperature at a few sample sites. However, most of the reservoir sites tended to have significantly cooler temperatures and lower dissolved oxygen near the bottom, gradually increasing toward the surface rather than having a distinct thermocline at which temperature and dissolved oxygen change abruptly. LT23A had 4.33mg/l dissolved oxygen at the surface, which, for the third month in a row, is less than the 5.00mg/l surface water quality standard. The low dissolved oxygen at this site was studied last month with additional sampling in September. No explanation was discovered other than the unusually long period of mixing and re-stratification seen this year. The absence of cold fronts and cooler fall weather this year has caused the reservoirs to become weakly mixed and re-stratified numerous times this fall. The markedly lower dissolved oxygen at LT23A can be compared with other reservoir sites this month by examining percent saturation of dissolved oxygen. Other reservoir sites exhibited over 100% saturation of dissolved oxygen while LT23A was only 50.9% saturated. High algal activity leading to super-saturation at most of the reservoir sites was probably responsible for causing pH values at LT23C and LT23D to exceed stream standards criteria with pHs of 9.38 and 9.35 respectively. Water quality parameters tested at river sites were normal for the most part but with fecal coliform counts exceeding 200 colonies/100mls at seven sites. Streptococcal bacteria counts at these sites were also high indicating livestock or wildlife as the source of contamination.
Lower Sabine Basin Including Toledo Bend to Morgan Bluff
Values measured during October Water Quality Monitoring in the Lower Basin were reflective of waters with high quality. Several sites in the Lower Basin demonstrated values outside the normal range. Station TB6N had the lowest dissolved oxygen value, while exhibiting elevated fecal coliform, fecal streptococcus, orthophosphate and conductivity values. These values are an indication of nutrient loading possibly due to a wastewater treatment plant upstream. Station TB6I also showed low dissolved oxygen values but all other parameters at this site were within normal ranges. Station BA4 had elevated conductivity, sulfate and fecal coliform values. Station TB6S had a high ammonia value and Station SR3 had a slightly elevated sulfate value. Fecal Coliform values were elevated at several perimeter sites on Toledo Bend and several river sites below Toledo Bend. Fecal Streptococcus value were also elevated at several locations in the Lower Basin. These elevated fecal values are most likely due to runoff from recent rains. While the Upper Basin and Lower Basin below Toledo Bend were relatively wet, the Toledo Bend area demonstrated normal rainfall. While the lake elevation increased in the month of October, the lake was still 6 ft below normal pool elevation. Most Toledo Bend sites were stratified with respect to dissolved oxygen and temperature. This stratification was not as well defined or as shallow as in previous months.
Tidal Section of the Sabine Basin below Morgan Bluff
Values for stations in the tidal portion of the Sabine Basin were well within ranges for waters of high quality. All fecal coliform values were within the numerical criteria for stream standards. Dissolved Oxygen values while low were also well within these limits. Salinity was measured at four of the five sites in the tidal area of the Basin.
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: