TPWD 1972 F-2-R-19 #1433: Region 2-B Fisheries Studies: The Effects of a Thermal Effluent on the Seasonal Criteria of Decker Lake, Job Progress Report, Federal Aid Project No. F-2-R-19

--- Page 1 --- JOB PROGRESS REPORT As Required By FEDERAL AID IN FISHERIES RESTORATION ACT TEXAS Federal Aid Project No. F-2-R-19 REGION 2-B FISHERIES STUDIES Job No. B-27: The Effects of a Thermal Effluent on the Seasonal Criteria of Decker Lake Project Leader: Darrell W. Butler Clayton T. Garrison Executive Director Texas Parks and Wildlife Department Austin, Texas Lonnie J. Peters Robert J. Kemp Chief, Inland Fisheries Director, Fish and Wildlife January 18, 1973 --- Page 3 --- JOB PROGRESS REPORT State of Texas Project No. _ F-2-R-19 Name: Region 2-B Fisheries Studies Job No. B-27 Title: The Effects of a Thermal Effluent on the Seasonal Criteria of Decker Lake pen ESO anal Period Covered: February 1, 1971 to January 31, L972 Objectives: 1. To review existing literature relative to the effects of a thermal effluent to aquatic life. 2. To determine the seasonal changes in the physical, chemical, and biotic parameters of the waters of Decker Lake. Procedures: This job was scheduled to begin February 1, 1971. However, since the project was involved with plans and preparations to renovate Lake Lyndon B. Johnson and all time and manpower was devoted to this renovation, the first collections anc samplings of Decker Lake was postponed until July, 1971. The generating plant was in test opera- tion at this time and discharging into the lake. This was completed during November and no generation will be carried out until April 1972. Existing literature was reviewed concerning the effects of temperature on aquatic life and is continuing throughout the job. In June, 1971, seven water sampling stations were selected for measuring physical and chemical water criteria (Figure 1). These stations were marked with styrofoam bouys to insure sampling at the same site each time. Water samples were collected at the surface and bottom at each station monthly and the following criteria was measured: Temperature at five-feet intervals, dissolved oxygen, alkalinity, pH, water transparancy, and specific conductance. Temperature profiles were also measured at five-feet inter- vals at the 32 bottom sampling stations. Temperatures were measured with an electric thermometer and the dissolved oxygen determined by the Winkler Method. The alkalinity was determined by the indicator method. The pH was measured by the use of the Hach wide range comparator and the conductivity with a Beckman model RA-2A conductivity meter. A Secchi disc was used to determine water transparancy. Benthos samples were collected monthly with a 6 in. X 6 in. Ekman dredge from four transects, two located on the inlet side and two on the discharge side (Figure II). Eight samples were collected from each of the transects. These samples were first collected from the seven water sampling sites but were changed in September to transects to collect more meaningful data. The samples were washed in the field and preserved in 80% alcohol until they could be separated and identified. The organisms --- Page 4 --- -2- were taxonomically classified to genera in the laboratory and recorded for future computations. Netting surveys were conducted quarterly since the job began. Ten stations were sampled in each survey with 150 feet experimental gill nets. The fish collected were weighed, measured and examined to determine sexual development. The composite of these netting surveys is included in this report (Table I). Seining collections were also made at various stations. Due to the time spent on other jobs during this segment and a shortage of per- sonnel, it was not possible to carry out the food habit study as planned. The process of collecting and examining the stomach samples would have required more time than was available to do justice to the study. It was also the plans to use the Carbon-14 method to determine productivity. However, the equipment needed could not be obtained in time to use on this job. It was decided by project and department personnel that plankton collections should be made although an extensive study in this area would not be possible. Plank- ton samples will be collected during the next segment as soon as the necessary equip- ment can be obtained. These samples will be collected at one station in the cool water and one station in the area of the thermal influence in an attempt to observe . any drastic change that might take place. Findings: Since only six months of data has been collected this segment, no conclusions or definite findings can be made at this time. More complete analysis of the data will be made for the next segment when more data has been collected and available for analysis Water Quality From July to November of this segment, the power plant was in operation. This discharge had some affect on the water quality in the areas of stations #1 and #2 in the form of higher temperatures at these two stations and slightly lower dissolved oxygen readings as a result of these higher temperatures. The surface temperatures at station #1, approximately 100 yards from the discharge, ranged from a high of 88 degrees F. in August to a low of 55 degrees in February when the generation had stopped. During the time the plant was generating the influence of this discharge was not carried past station #2 during most sampling periods. The data indicates a cooling of the water past station #2 and a warming trend of the water in the shallower, cool side during the warmer months. A three degree temperature change was observed between the discharge and intake areas during July, one degree in August, six degrees in September and October, and an equalization of temperatures in these areas after generation was stopped. Other project activities prohibited sampling during the month of November. Decker Lake was stratified at the date of the first sampling in July. During this month the thermocline was observed at 25-30 feet with a depletion of dissolved oxygen below 30 feet. This decreased in depth in August to a thermocline at 20 feet and zero oxygen below 25 feet. Destratification began in September and the thermo- cline had dropped to between 35 and 40 feet and dissolved oxygen as deep as 35 feet. By December high concentrations of dissolved oxygen were measured at all stations and depths as a result of destratification and lack of thermal discharge. This condition --- Page 5 --- -3- continued through February. Only carbonate alkalinity was found in all samplings remaining relatively con- stant except during stratification. Both the high and low readings were observed during the months of August at different depths. The low of 109 mg/1 was measured at the surface and the high of 198 mg/1 at 60 feet. Carbonate alkalinity averaged approximately 120 mg/1 increasing slightly with depth during periods of stratifica- tion. Dissolved oxygen ranged from a low of 6.8 ppm at station #1 in July to 10.6 ppm in December also at station #1. The lower reading was most likely due to the warmer water from the discharge layering out on the surface at this station having a lower saturation potential due to the increased temperature. A summary of the temperature readings on the surface and bottom is included in this report (Figures III-IX) as are the oxygen readings (Table II). Like the alkalinity, the lowest and highest pH readings were also recorded during August with a pH of 8.0 at the surface and 7.0 at 60 feet. [In other sampling months the pH was consistantly around 7.2 units. Benthos Benthic samples were collected at thirty-two stations, eight in each transect. Collections from this segment were separated and classified to genus. Calculations will be made when more data have been collected and the results statistically analyzed to compare different areas of the lake and the different seasons. Community diversity (H), diversity per individual (H), maximum diversity (Hpax)> minimum diversity er ), and redundancy (R) will becalculated using equations pre- sented by Patten (19 ae m n, H=- 2 ny log 9 i=1 _ m a! ny H=-2 logo —_—__ ot N N Hiax= log2 N i- mlog9 (-~>-— : Hin = log, N : = logs [N- (m-1)] : R= Hnax 7 H Hnax 7 Hmin where N is the total number individuals, (n, ) the number of individuals of the i-th species, and m the number of species. --- Page 6 --- -4- Indices of diversity (d) and heterogenity (IH) will be calculated using equations given by Margalef (1958): m-1 d= 1nN IH = Se ae where (m) is the number of species, (N) the total number of organisms, [a¢A)] the diversity at station A, fa(B)] the diversity at station B, and [4(A+B)] the diversity of the pooled samples A and B. A great diversity of organism has not been observed in the samples collected thus far but rather a large number of a few species. The most predominant species collected were Hexagenia sp., Chaoborus sp., and Tendipes sp. Other species found regularly but not in as great a number are Pentaneura sp., and various species of Tricoptera, Odonata, and scuds. Netting Results Gill netting surveys were conducted during May, August and December of 1971. The predominant rough fishes in Decker Lake are smallmouth buffalo, Ictiobus bubalus, and gizzard shad, Dorosoma cepedianum. These species will most likely remain a con- stant problem since the water lost to evaporation in the lake is replaced by pumping from the Colorado River. These species and the river carpsucker, Carpiodes carpio, are management problems in all of the lakes in the Colorado chain. A composite of the netting results can be found on Table I of this report. Fish collected on the discharge were tabulated separately from those collected from the in- take and will be analyzed as such when enough data have been collected to statistically analyze the data. Literature is now being reviewed to determine the best method to statistically treat the data collected. Decker Lake was impounded in 1968 and the frequency distributions reflect the presence of five age classes of channel catfish and largemouth bass although the sample size was smaller than preferred. This indicates excellent reproduction since the hatchery stocking of this lake in 1968. The netting results also reflect a large population of sunfish with an average of over 10 sunfish caught per 100 feet of net. Since the job began in July, 1971, no data could be collected concerning spawning times. However, efforts will be made during the next segment to collect fishes from different areas of the lake with electro-fishing equipment to determine if early sexual development occurs in the area influenced by the heated discharge. If time and man- power permits, scale samples will be collected in an attempt to correlate the influx of heated water on the growth of certain species. --- Page 7 --- -5- Conclusions and Recommendations: The data collected this segment represent a catagorizing of the waters of Decker Lake from July to February, before the introduction of a substantial heated effluent. This data will be collected through April when the power plant will begin full operation and then through the next segment while the plant is operating. With the increasing use of impounded waters for use as cooling waters, it is recommended that this job be carried to completion next segment to determine what affect, if any, a thermal effluent of this magnitude may have on the chemical, phys- ical, and biotic parameters influencing a sport fishery. Prepared by: Darrell W. Butler Approved by: Project Leader Date: __ January 18, 1973 Robert L. Bounds Regional Director of Inland Fisheries --- Page 9 --- Table I Decker Lake Netting Results 1971 Collection Periods: May-10 nets August-10 nets December-10 nets Number Species Number 100 ft. net Weight Dorosoma cepedianum 214 4.76 149.90 Ictiobus bubalus 102 2.27 1234.04 Carpiodes carpio 8 0.18 32.27 Notemigonus chrysoleucas 15 0.33 4.58 Ictalurus punctatus 160 3.56 542.53 Ictalurus melas 117 2.60 45.59 Micropterus salmoides 49 1.09 59.29 Chaenobryttus cyanellus 42 0.93 6.95 Lepomis microlophus 72 1.60 26.26 Lepomis macrochirus 332 7.38 54.32 Lepomis megalotis 42 0.93 6.31 Pomoxis annularis 30 0.67 35.34 1184 2204.63 Per cent rough fish - 38.51% by number 66.51% by weight Per cent game fish - 72.49% by number 44.49% by weight Weight lbs. 100 ft. 3s 27 QO. 0. 12, 33 42 72 10 06 OL «2 15 -58 21 .14 -79 net --- Page 10 --- Table IT Dissolved Oxygen - mg/1 Aazenige,y Azenuer Jequeseq 19q0290 Zequejzdes jsngny Arne Station #1 a0) .0 -6 -7 10.6 8 7.8 7. 7.4 6.1 6.8 Surface 9 9.2 8.0 PaO Bottom 10' Station #2 oo lonmon ™ 9.0 8. 7 7.4 3 7 0.0 Surface Bottom 30' Station #3 oo am CON ee am 8.0 6.0 7.9 0.0 8.1 0.0 7.4 0.0 Surface Bottom 45' Station #4 Oe CON am oo lonmee) oo oo nO ~O oo ~O oo Surface Bottom 60' Station #5 oo am nO a oO 9. 9 7. 7 7.6 3.8 0.0 7 0.0 Surface Bottom 35' Station #6 oo ov 0 oO ~t nv NW oe oo com wo wn ™~ Oo cow oe ™ re Surface Bottom 25' Station #7 TON loon’ wz fon aon) oo co 0 oo ~nN oO xt nN ON Surface Bottom 10' --- Page 11 --- Figure | ® discharge Ko) ee ® DECKER LAKE WATER SAMPLING STATIONS --- Page 12 --- Figure II e i e @ discharge I ee Power Plant DECKER LAKE BOTTOM SAMPLING STATIONS --- Page 13 --- Figure III Temperature-Degrees F. OOT i (o) 9 L 08 06 ui oO jo) oO July August September October November aoeyans T# woTaeaS December January (°33 O1) woz 30g February Figure IV Temperature-Degrees F. wn ON ~ oO j=) oO OOT ~ jo) 08 06 July August September October November aoryans Z# UOTIBIS December January (°33 GZ) woz}0g --- February --- Page 14 --- Figure WV Temperature-Degrees F. uw Oo ~ [e) je) oO oO Oo 06 OOT Lf (=) July August September October Ef UOTIeIS November aoeyans December January ('33 0%) woz30g --- February Figure VI Temperature-Degrees F. uw ON ~ (oe) o oO o oO 06 OOT oO July August September October November aoeyans yy UOTICIS December January February (*3F ¢¢) wozI0g --- Page 15 --- Figure VII / Temperature-Degrees F. uw oa ~ [oe] oO jo) oO jo) 06 OOT + oO July August September October November aoejyains — G# uot BIS December January (*33 0€) Woqjog --- February Figure VIII Temperature-Degrees F. mn fon ~ [) (jo) [=) i=) oO OOT + io) 06 July August September October gy woT3eIS November aoejzans December January (°33 GZ) worq0g --- February --- Page 16 --- Figure IX Temperature-Degrees F. 08 06 OOT “I =) jo) jo) July August September ' n t i |g ww UW ct Octob ae ct tt Fh Oo e November ae a o~N 2; December oO +h ct January —_ February