Sabine River Authority of Texas

To: Interested Parties

From: Environmental Services

RE: JuLY 1999 Water Quality Monitoring Report

This is the Sabine River Authority Water Quality Report for July 1999. Water quality sampling was performed July 13 through July 15. The Sabine Basin received greater than average rainfall in the Lower Basin and the Tidal Area. The Upper Basin however, received lower than normal rainfall amounts. Due to problems with laboratory equipment values for ammonia and orthophosphate were not obtained. Total alkalinity and total hardness values were obtained at only a few locations.

Upper Sabine Basin Above Toledo Bend Including Lake Fork and Lake Tawakoni

Most values measured in the Upper Basin were consistent with water of high quality. Temperature and dissolved oxygen profiles indicate most of the reservoir sites were thermally stratified. Lake Fork sites were strongly stratified with 4.4 - 12.9C of difference from surface to bottom. Lake Tawakoni sites were weakly stratified with about 2.4C of difference. High photosynthetic activity at both reservoirs caused the percent saturation of dissolved oxygen to exceed 100% at all Upper Basin reservoir sites. The pH at these sites was also elevated, conceivably due to the consumption of carbon dioxide and release of oxygen through photosynthesis. Dissolved oxygen was slightly below Texas Surface Water Quality Standards (Stream Standards1) at SR21 and the secchi depth was unusually low. USGS flow records indicate a peak of flow at this site from a rainfall event five days previous. Fecal coliform bacteria exceeded Stream Standards at SR17, SR15, and SR14.

Lower Sabine Basin Including Toledo Bend to Morgan Bluff

Values measured during the July WQM were indicative of water with high quality. Stations TB6N, TB6I, TB6M, TB6J and TB6 all had low dissolved oxygen values, these values were below the numerical criteria for dissolved oxygen according to Stream Standards. Stations TB6N, BA4 and BCC1 had elevated fecal coliform values. BA4 also had a high turbidity value, elevated conductivity (for this reach of the River) and elevated sulfate. Station BCC1 had elevated fecal coliform, low pH, and low conductivity. This is most likely due to runoff from a rain event just prior to the sampling. Lake Stations at Toledo Bend showed stratification of dissolved oxygen at depths from 3 to 8 meters and temperature at depths greater than 10 meters.

Tidal Section of the Sabine Basin below Morgan Bluff

Values for stations in the tidal portion of the Sabine Basin were also consistent with water of high quality. All values were within the Stream Standard and TNRCC screening criteria. Salinity values were detected at BB1 and SRT1. Releases from Toledo Bend along with the rainfall just prior the sampling were most likely the reason for the lower salinity.

 

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:

 

1 The TNRCC sets surface water quality standards in an effort to maintain the quality of water in the state. This document is currently under revision and can be found at the following URL. http://www.tnrcc.state.tx.us/water/quality/standards/index.html

Printed Wednesday, February 23, 2000