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Introduction 2 Description of the storm Hydrologic effects of storm runoff on streamflow, reservoir contents, and water quality Double Mountain Fork Brazos River and Salt Fork Brazos River Clear Fork Brazos River and tributaries Main stem Brazos River and tributaries from South Bend to Whitney Dam Main stem Brazos River from Whitney Dam to mouth : Effects of flood on water quality in selected reservoirs Reservoir water quality (general considerations) Hubbard Creek Reservoir-Temperature Dissolved oxygen 37 Specific conductance, dissolved solids, dissolved chloride, dissolved sulfate, and hardness 37 Possum Kingdom Lake 40 Temperature-40 Di ssol ved oxygen 40 Specific conductance, dissolved solids, dissolved chloride, dissolved sulfate, and hardness 42 Lake Granbury 43 Temperature* 43 Dissol ved oxygen. 46 Specific conductance, dissolved solids, dissolved chloride, dissolved sulfate, and hardtiess 46 Lake Whitney-47 Temperature 47 Di ssol ved oxygen-49 Specific conductance, dissolved solids, dissolved chloride, dissolved sulfate, and hardness "-51 Summary and conclusions 52 References 57-m-14. Discharge hydrograph for Brazos River near Glen Rose, Texas (08091000), October 12-27, 1981 26 15. Reservoir-contents hydrograph for Lake Whiterry near Whitney, Texas (08092500), October 10-24, 1981 27 16. Graphs showing variations in mean daily discharge and dissolved-solids concentrations and loads for Brazos River near Highbank, Texas (08098290), Brazos River near College Station, Texas (08109500), and Brazos River near Richmond, Texas (08114000), October 1981 17. Map showing location of water-quality data-collection sites on Hubbard Creek Reservoir 18. Map showing location of water-quality data-collection sites on Possum Kingdom Lake 19. Map showing location of water-quality data-collection sites on Lake Granbury 20. Map showing location of water-quality data-collection sites on Lake Whitney 21. Graphs showing temperature, dissolved-oxygen, and specific-conductance profiles for Hubbard Creek Reservoir, August 4 and October 27, 1981 36 22. Graphs showing variations in volume-weighted-average concentrations of dissolved solids, dissolved chloride, dissolved sulfate, and hardness in Hubbard Creek Reservoir, 1978-81 39 23. Graphs showing temperature, dissolved-oxygen, and specific-conductance profiles for Possum Kingdom Lake, August 5-6 and October 28, 1981 £4. Graphs showing variations in volume-weighted-average concentrations of dissolved solids, dissolved chloride, dissolved sulfate, and hardness in Possum Kingdom Lake, 1978-81 25. Graphs showing temperature, dissolved-oxygen, and specific-conductance profiles for Lake Granbury, August 6-7 and October 29, 1981 26. Graphs showing variations in volume-weighted-average concentrations of dissolved solids, dissolved chloride, dissolved sulfate, and hardness in Lake Granbury, 1978-81 27. Graphs showing temperature, dissolved-oxygen, and specific-conductance profiles for Lake Whitney, August 12 and October 30, 1981 28. Graphs showing variations in volume-weighted-average concent...

Thermal stratification in Lake Conroe usually begins to develop in March and persists until October. Thermal stratification has resulted in significant seasonal and area! variations in the concentrations of dissolved oxygen, dissolved iron, dissolved manganese, total inorganic nitrogen, and total phosphorus. Volume-weighted-average concentration of dissolved solids generally were less than 120 milligrams per liter, those of dissolved chloride generally were less than 22 milligrams per liter, and those of dissolved sulfate were less than 10 milligrams per liter in Lake Conroe during the 1973-82 water years. The concentrations of each of these constituents usually were largest during the summer. The water was moderately hard (hardness greater than 60 but less than 120 milligrams per liter as calcium carbonate). The average concentrations of dissolved oxygen at most sites in the downstream one-half of the lake averaged 3.2 milligrams per liter during summer stratification and more than 9 milligrams per liter during winter circulation. The concentrations at most sites in the headwaters of the lake averaged less than 4.3 milligrams per liter during the summer and less than 7.9 milligrams per liter during the winter. Water below depths of 25 to 35 feet usually contained less than 1 milligram per liter dissolved oxygen during the summer. The concentrations of dissolved iron and dissolved manganese in water throughout the reservoir during winter circulation and in water near the reservoir surface during summer stratification were less than 100 micrograms per liter. The greatest concentration occurred during summer stagnation near the reservoir bottom at site Ac , a deep site near Lake Conroe Dam. The concentrations of total inorganic nitrogen and total phosphorus were greatest during summer stratification in water near the reservoir bottom at deep sites. No accumulation of these constituents within the reservoir was detected during the study. The densities and composition of algal populations varied seasonally. Algal densities were greatest during the summer with blue-green algae being the predominant phylum. I2 13 concentrations of dissolved winter surveys.