TPWD 1955 F-2-R-2 #131: Job Completion Report: Basic Survey of the Remaining Portions of the San Gabriel River and Brushy Creek within Region 2-B

STATE Texas PROJECT Fn2~R-2, Job A». PERIOD We fl re ll II J. I”: |'\" 1; j r h on; Job Completion Report ~m - 3; by Kenneth C, Jurgens and Billy D. Cooper Basic survey of the remaining portions of the San Gabriel River and Brushy Creek within Region o-B, which were not covered in JOb A-2, Project F~2anl, OBJECTIVES To gather fundamental data on the above waters in regard to their physw ical, chemical and biological aspects. METHODS Seven stations were selected on the North San Gabriel River and the Roam sel Fork of the North San Gabriel River in Burnet County, Texas, Seven other stations on the San Gabriel River and Brushy Creek,in Milan County,were also see lasted, These fourteen stations, combined, were considered sufficient to complete the overall survey of the San Gabriel River and its principal tributaries as how gun under Job A~2, Project Fm2~R~l. The locations of these stations are shown in Table l and on the accompanying maps, Each of the stations selected were visited at least once during the course of the jobo On these occasions the following data were gathered: average width and depth; turbidity; volume of flow (wherever possible); pool size, type and free quency; bottom types, both in the pools and on the riffles; kinds and abundance of aquatic vegetation, a description of the surrounding country and the immediate shoreline; a notation of the larger tributaries and evidences of pollution where indicated, I FINDIBES Since the work done under the present job was a continuation of work done under an earlier job, the findings of this job must be reported upon in two sepm arate sectionso The first section deals with that portion of the North San Gab“ riel River which lies in Burnet County. The remainder of the report is concerned with those portions of the San Gabriel River and Brushy Creek within Milan County, Texas. The San Gabriel River, Burnet County: _ The North San Gabriel River heads in Burnetwfiofinty, approximately ten miles north of the town of Burnet. From its source, the river flows in a southeasterly direction to the Williamson County line and continues on, as described in the report for Jab Aw2, Project Fufi-R-l, in a ”southeasterly direction to the vicinity of Georgetown where it is joined by the South and Middle San Gabriel Riveni” _ The North San Gabriel and Russel Fork of the North San Gabriel River, the only tributary of consequence in Burnet County, flow through country which is char» acterised by thin to medium bedded, hard, continuous limestone strata, alternatm 2. ing with marls or marly limestones. The hesdwater sections of both streams flow through country with rough, rolling type of topography, with soils on the hills limited to a thin mantle of calcareous soils. Further east in hornet County, the topography becomes more gently rolling with.tillable valleys and flood plzins. Soils in this area are grayublack calcareous clays with thin seams of bedded limes stone. Both the North San Gabriel and Russel Fork are intermittent, running only - during periods of prolonged rainfall. Above the confluence of the North San Gabw rial and Russel Fork, both streams have bad rock bottoms with shallow to non~ existent banks. Below the confluence, the river has a tendency to become more _deeply entrenched in the deeper soils and has medium to deep cut banks with sandy to silty gravel bottoms on both the riffles and in the pools. Very scanty aquatic vegetation; composed principally of filamentous green algae, musk grass (Chara E24) and coontail (Ceratophyllum demersum);is limited to the small pools. Due to the extreme drouth, which this part of the country has undergone during recent years, these streams no longer flow. Water temperatures in the North San Gabriel River and Russel Fork varied from 79°F to 82°F during the study period. The pH in this portion of the San Gab- riel River system ranged from 8.0 to 8.3. The fish populations of the San Gabriel River in Burnet County were found to be very limited not only in numbers but in species, occurring in the small pools, isolated by drouth conditions, and prayed upon by both animals and man. Fish kills in these pools, due to oxygen deficiencies caused by low water, almost never occur because the pools are cleared of fish by predation before the deficiency can come about. In the total of approximately 3h stream miles covered by this survey in Burnet County, 12 species, representing h fish families, were found in the North San Gabriel River and Russel Fork. A checklist of these species is given in Table lll. The San Gabriel River and Brush _Creek, Milam_Count“: - After entering Milan County, the San Gabriel River and Brushy Creek flow through three geologw ical formations: the Taylor, the Navarro and the Midway. - Taylor and Navarro formations are similar in that they consist of chalks, marls and sandy clays which have weathered into waxy, black soils which are used mostly for farming and for the most part, are gently rolling. Along a line running approximately NNE and ssw between the towns of San Gabriel and Thorndale, in Milam County, both the San Gabriel River and Brushy Creek enter the third of the three formations, the Midway. This formation differs from the other two in that it concise of sands and sandy clays and the soils derived from it are chocolate brown in color and are lighter, since they contain more sand . All three of these formations have provided soils which are easily erod- able and as a result the stream beds of both the San Gabriel River and Brushy Creek are progressively more deeply entrenched as the streams flow toward their confluence with each other and with the Little River about six miles northeast of Rockdale. . The streams themselves consist of relatively deep pools, averaging from four to six feet in depth, with maximum depths up to ten feet. Bottom types in the pools are mostly silt with some gravel and the more infrequent riffles have bottoms U.) of sand and gravel with some silt. 0n the San Gabriel River, towards the confluence with the Little R:ver, the stream bottom changes slightly in that some sandstone rubble occurs on some of the riffles and in some of the pools. What vegetation occurs in these streams is limited to filamentous green algae, on the riffles, and musk grass (Chara sp;) in the pools. Some arrows head (§§ggitaria platyphylla) occurs on the edges of some of the pools on the San Gabriel River. Physically, Brushy Creek differs only in that it is narrower and more deeply entrenched than is the San Gabriel River. It is also more heavily shaded. As a result, water temperatures in Brushy Creek were found to be somewhat cooler than those of the San Gabriel, averaging about TYOF. While the San Gabriel had temperatures ranging from 820E to 87 F. The pH in the San Gabrielianged from 7.2 to 7.9 and in Brushy Creek from 7.t to 7.6. (Table 11). Fish populations in the San Gabriel River and in Brushy Creek are concen- trated into the larger pools because of the lack of flowing surface water. There are indications that these populations are out of balance due to silt pollution and predation. Many of the clearwater forms were reduced in numbers because of the necessity of their having to live in turbid pools. Thirtywone species, representing 8 families of fish, were found to be present in the 17 miles of the San Gabriel Biver_surveyed in Milam County during the study period. A smaller number, only 18 species representing 7 families, were found in Brushy Creek during the survey. Approximately 15 miles of Brushy Creek were covered by the survey in Milam County. A checklist of the species found to occur in Brushy Creek and in the San Gabriel River in Milam County are also given in Table 111. Since neither Brushy Creek nor the San Gabriel River were flowing during the study period, data concerning the rate of flow was not obtained. Furthermore, the U. S. Geological Survey records do not include stream flow data for either stream in Milan County. The only evidences of pollution encountered during the course of the sure vey were instances of pollution due to silt which is a direct result of the poor land management practices which were common in this area during the last fifty to oneuhundred years. Some positive efforts are being made at present to remedy this situation by farmers and ranchers. Perhaps in time these streams will once more become favorable habitats for the desired game species which, we are told, were once so abundant. SUNWMRY l. The work was divided between those portions of the North San Gabriel River in Burnet County and the remaining poruons of the San Gabriel River and Brushy Creek, notcnvered previously, in Milam County. 2. The North San Gabriel and Russel Fork are typically small, shallow bedrock streams with a tendency to become more or less deeply entrenched with sand, silt and gravel bottoms belOW'their confluence. 1+9 3. The San Gabnnl River and Brushy Creek in Milan County are very deepn ly entrenched with silt and gravel bottoms and have long, deep pools and short, shallow riffles. h. Aquatic vegetation occurs infrequently and in scant amounts in both the streams of Burnet County and those of Milan County covered in this survey. 5. Prolonged drouth has all but dried these streams up and during most of the survey period very little flow was Observed and none could be measured. 6. A total of 33 species, representing 10 families, were found to occur in these waters. Of these, only 12 species were found in the North San Gabriel in Burnet County, all but one species was found in the lower San Gabriel in Milan County and 17 species were found in Brushy Creek. 7. Other than pollution due to silt, no evidences of pollution were encountered during the survey. North San Gabriel River (Burnet County) Station No. Location Russell Fork North San Gabriel, 6 mi. NE Bertram Russell Fork North San Gabriel 5 mi. N Burnet on Farm Road 963 North San Gabriel River, 5 mi. SE Lake Victor North San Gabriel River, 3 mi. NNW’Tamega North San Gabriel River, crossing at Joppa Russell Fork North San Gabriel, 2 mi. 8. Joppa North San Gabriel River, 4 mi. SW Mhhomet on Farm Road 2M3 San Gabriel River (Milan Station No. Location é-mi. s town or San Gabriel, Farm Road 486 6 mi. SE town of San Gabriel on county road 7 mi. NW Rockdale on county road 6 mi. N. Rockdale on Farm Road #87 Brushy Creek (Milam County)- % Station No. Location 12. 1 mi. E Thorndale on Texas Highway 79 13. ' 6 mi. E Thorndale on county road 1h. 5 mi. NW Rockdale on county road Table 1. Locations of Survey Stations Used During Study Period under Job A-H, Project F-2-R-2, Basic Survey of the Remaining Portions of the San Gabriel River and Brushy Creek Within Region 6-B, Which Were Not Covered in Job A—E, Project F—Q-R—l. 6. Temperature and pH Conditions, San Gabriel River and Brushy Creek in Burnet and Milan Counties - Air Tempni water Temp.- ‘Station_No. Date 0F _ _ __ _ 9F _ pH. 1. June ll 89 8o 8.l a. June ll 9o 81 . 8.1 3. June ll 92 ' 82 . 8.2 a. June ll 9H ' 82 8.1 9. June ll 96 79 8.3 6. June ll 94 1 81 8.1 7. June ll 93 81 8.0 8. July 7 86 82 :7.2* 8. Aug. 9 8t 86.5 7.6 9. July 7 no water I 10. July 16 no water ll. July 16 95 85 ' 7.6 ll. Aug. 10 85 f. 87 7.9 12. July 16 no water 13. Sept. 15 92 76.5 7.h ls. Sept. 16 88 77 7.6 Table ll. 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