Development of Chlorophyll-a Criteria to Support Recreational Uses of Texas Reservoirs Exploratory Data Analysis - Year 1 of a 2-Year Study William W. Walker, Jr., Ph.D. Environmental Engineer wwwalker.net presented at "Lakes: Habitat for Fish, Habitat for People" North American Lake Management Society Victoria, British Columbia November 5, 2004
Abstract Numerical nutrient criteria can based upon a variety of factors, including linkage to other water quality standards for protection of aquatic life (dissolved oxygen, ph), support of specific water uses (fisheries, recreation, water supply), anti-degradation concepts, and regional comparisons with minimally impacted water bodies. This presentation describes an exploratory analysis of data from the first of a two-year study undertaken by regional water authorities in conjunction with Alan Plummer Associates, Inc. to support the development of chlorophyll-a criteria for protecting recreational uses of reservoirs. The study is designed to assess relationships among eutrophication-related water quality conditions, aesthetic qualities, and suitability for recreational uses, as gauged by reservoir user surveys. Similar studies have supported development of regional and lake-specific nutrient criteria in Minnesota, Vermont, New York, Florida, and other states using similar survey forms. This study also collects information on several factors that may influence relationships between algal density and perceived impairment, including: site type (cove vs. open lake), optical properties (relative importance of algae vs. inorganic suspended solids as factors controlling water transparency), trophic state (overall level of enrichment), observer category (lay public vs. sampling crew), type of water use (swimming, boating, fishing, hiking, etc.), and observer visit frequency. The study involves 8 reservoirs and 16 sites reflecting a wide range of nutrient and turbidity levels and biweekly water quality sampling events paired with an average of 7 user survey forms per event. Ranges and patterns in the preliminary data are explored using simple cross-tabulation and graphical techniques. Results indicate the potential power and limitations of the full survey dataset to support statistical modeling and development of chlorophyll/nutrient criteria.
Texas Water Conservation Association Investigation to Support the Development of Nutrient Criteria Based on Recreational Uses of Reservoirs Interim Report - Year 1 of a 2-Year Study May 2004 prepared by Brazos River Authority Guadalupe-Blanco River Authority Lower Colorado River Authority Sabine River Authority San Antonio River Authority Tarrant Regional Water District Trinity River Authority in association with Alan Plummer Associates, Inc. William W. Walker, Jr.
Exploratory Data Analysis
Cast of Characters Travis Georgetown Granger Bridgeport Fork Cedar Creek Canyon Livingston 'IOURe 1-1 CI<l.OROPIm.l... C " ~CREA T IOIW,. u.n ITUO't' IIUI_.
Bases for Nutrient & Chlorophyll-a Criteria Regional Reference Lakes Pre-Development Condition Limnological Concept - "Trophic State" Linkage to Numeric Water Quality Stds DO, ph, Ammonia, Secchi Ecological - Fishery Water Supply Concerns Taste & Odor, THM's, Treatment Cost Support of Recreational Uses Swimming, Boating Aesthetic Enjoyment Anti-Degradation
Statistical Basis for Mean Chlorophyll-a Criteria Frequency of Severe Nuisance Blooms vs. Mean Chl-a 5 Vermont Lakes CE Reservoirs SA Reservoirs Percent > 30 4 3 Threshold Log-Normal Distribution 1 0 10 20 30 40 Mean Chlorophyll-a (mg/m 3 ) Based upon Log-Normal Frequency Distribution Models Calibrated to Various Datasets Walker, W., "Statistical Bases for Mean Chlorophyll-a Criteria", Lake & Reservoir Mgt, 1985
Previous Applications of the Concept Regional Criteria Minnesota New York Vermont Florida new!!! Lake-Specific Criteria Cherry Creek Reservoir Lake Champlain Lake Okeechobee Vadnais Lake Lake Pepin Onondaga Lake Colorado Vermont/New York Florida Minnesota Minnesota New York Communicating to Public Meaningful Expression of Lake Condition Gain Support for Restoration & Management Programs
Study Design 8 Reservoirs, 2 Sites Each ( Main Lake, Cove ) Criteria for Site Selection Depth >= 10 Feet Adjacent to Use Areas (Beaches, Marinas, etc) No Significant Stands of Aquatic Vegetation Biweekly Sampling, June-Sept (April-Sept in 2004) 0, 3, 6 Foot Composite Samples Nutrient Species, TSS, VSS, Turbidity, Field Param Chl-a & Phaeophytin Analyzed by a One Lab (LCRA) ~ 7 Survey Forms Completed on Sampling Date Target ~ 5 Lay Users Target ~ 2 Sampling Crew 5 Survey Questions : Appearance Suitability for Use Green vs. Muddy Visit Frequency User Type
Recreational User Survey Questions 1 & 2 1) Please circle the one response that best describes the physical condition of the lake water today: a) No algae, or crystal clear water b) A little algae visible c) Definite algal greenness d) Very green; some scum present and/or mild odor apparent e) Pea-soup green with one or more of the following: massive floating scums on lake or washed up on shore, strong foul odor, or fish kill 2) Please circle the one response that best describes your perception of how suitable the lake water is for recreation and aesthetic enjoyment today: a) Beautiful, could not be any nicer b) Very minor aesthetic problems; excellent for swimming, boating enjoyment c) Swimming and aesthetic enjoyment slightly impaired d) Desire to swim and level of enjoyment of the lake substantially reduced e) Swimming and aesthetic enjoyment of the lake nearly impossible
Recreational User Survey Questions 3-5 3) If you circled c, d, or e in Question No. 2 above, please indicate the factor that most affected your answer: a) Muddiness b) Algae/greenness c) Other (please specify) 4) How many times a year do you visit the lake? (Circle one response) a) Permanent resident b) More than six times per year c) Two to six times per year d) Typically every year e) This is my first visit 5) Please circle the activity that best describes your primary recreational activity today: a) Swimmin d) Skiing/Windsurfing b) Fishing e) On-Shore Activity (camping, picnicking, etc.) c) Boating f) Other or non-recreational (Please specify)
Survey Cross-Tabs Question 1 - Appearance Question 4 - Type of Use Count of Date Question1 Count of Date Question4 ResLabel ove_ma a b c d e rand Total Re Cove_Main a b c d e rand Total Bridgeport Cove 5 32 14 3 54 Bri Cove 4 26 10 3 11 54 Main 11 40 4 1 56 Main 7 29 13 1 6 56 Bridgeport Total 16 72 18 4 110 Bridgeport Total 11 55 23 4 17 110 Canyon Cove 16 17 12 1 46 Ca Cove 16 15 9 1 5 46 Main 8 31 6 1 46 Main 12 15 7 5 7 46 Canyon Total 24 48 18 2 92 Canyon Total 28 30 16 6 12 92 Cedar Creek Cove 1 27 27 2 1 58 Ce Cove 26 29 3 58 Main 6 36 13 1 56 Main 17 25 3 4 7 56 Cedar Creek Total 7 63 40 3 1 114 Cedar Creek Total 43 54 6 4 7 114 Fork Cove 3 14 14 3 34 Fo Cove 21 5 4 4 34 Main 12 20 18 50 Main 26 9 5 2 8 50 Fork Total 15 34 32 3 84 Fork Total 47 14 9 2 12 84 Georgetown Cove 20 12 1 33 Ge Cove 3 22 4 2 2 33 Main 20 18 1 39 Main 16 18 3 2 39 Georgetown Total 40 30 2 72 Georgetown Total 3 38 22 5 4 72 Granger Cove 2 6 5 13 Gr Cove 9 3 1 13 Main 6 32 21 59 Main 8 25 14 6 6 59 Granger Total 8 38 26 72 Granger Total 8 34 17 6 7 72 Livingston Cove 3 33 19 6 61 Liv Cove 39 15 3 1 3 61 Main 11 24 26 2 63 Main 18 18 9 6 12 63 Livingston Total 14 57 45 8 124 Livingston Total 57 33 12 7 15 124 Travis Cove 8 23 9 1 41 Tra Cove 4 34 3 41 Main 14 29 6 49 Main 5 27 10 7 49 Travis Total 22 52 15 1 90 Travis Total 9 61 13 7 90 Grand Total 146 394 196 20 2 758 Grand Total 206 319 118 34 81 758 Question 2 - Use Impairment Question 5 - Visit Frequency Count of Date Question2 Count of Date Question5 ResLabel ove_main a b c d e rand Total Re Cove_Main a b c d e f and To Bridgeport Cove 13 29 9 3 54 Bri Cove 9 7 5 14 19 54 Main 33 20 3 56 Main 4 33 8 3 23 71 Bridgeport Total 46 49 12 3 110 Bridgeport Total 13 40 13 17 42 125 Canyon Cove 15 27 4 46 Ca Cove 4 4 22 3 1 20 54 Main 22 23 1 46 Main 10 4 6 4 4 20 48 Canyon Total 37 50 4 1 92 Canyon Total 14 8 28 7 5 40 102 Cedar Creek Cove 8 35 13 2 58 Ce Cove 8 20 16 2 1 21 68 Main 14 37 5 56 Main 1 2 19 21 3 2 16 64 Cedar Creek Total 22 72 18 2 114 Cedar Creek Total 1 10 39 37 5 3 37 132 Fork Cove 7 12 12 2 1 34 Fo Cove 3 12 4 2 16 37 Main 17 27 6 50 Main 2 32 4 1 15 54 Fork Total 24 39 18 2 1 84 Fork Total 5 44 8 1 2 31 91 Georgetown Cove 19 13 1 33 Ge Cove 15 2 1 16 34 Main 17 20 2 39 Main 5 6 6 1 13 15 46 Georgetown Total 36 33 3 72 Georgetown Total 20 8 6 1 14 31 80 Granger Cove 3 8 2 13 Gr Cove 1 12 13 Main 6 27 21 5 59 Main 11 17 15 1 12 21 77 Granger Total 6 30 29 7 72 Granger Total 11 18 15 1 12 33 90 Livingston Cove 1 2 43 12 3 61 Liv Cove 1 16 14 10 4 12 16 73 Main 11 36 15 1 63 Main 10 24 10 4 18 17 83 Livingston Total 1 13 79 27 4 124 Livingston Total 1 26 38 20 8 30 33 156 Travis Cove 16 23 2 41 Tra Cove 8 3 16 3 2 19 51 Main 24 24 1 49 Main 1 14 5 13 4 7 15 59 Travis Total 40 47 3 90 Travis Total 1 22 8 29 7 9 34 110 Grand Total 1 224 399 114 19 1 758 Grand Total 3 121 203 156 47 75 281 886
10 8 4 Q5 - Use Type Other Shore Fishing Boating Skiing Swimming % of Responses Georgetown Travis Canyon Granger Bridgeport Fork Livingston Cedar Creek All Increasing Mean Chlorophyll-a
Exploratory Analysis Bloom Frequency vs Seasonal Mean Chl-a Statistical Model Survey Responses vs. Sample Chl-a Within Reservoirs Across Reservoirs Responses vs. Observer Category Sampling Crew Contact Users Noncontact Users
Calibration of Bloom Frequency Model Log-Normal Freq. Distribution Temporal Coef. of Variation This Study ~ 0.37 Historical Data (Same Res.) ~0.67 Other Lakes & Reserv. 0.4 0.7
Observed & Predicted Bloom Frequencies vs Mean Chl-a Mean Threshold ~ 0.5 x Bloom Criterion 10 10 Freq > 10 ppb (%) 8 4 Main Cove Predicted 0 20 40 60 Mean Chl-a (ppb) Freq > 20 ppb (%) 8 4 Main Cove Predicted 0 20 40 60 Mean Chl-a (ppb) Freq > 30 ppb (%) 10 8 4 Main Cove Predicted Freq > 40 ppb (%) 10 8 4 Main Cove Predicted 0 20 40 60 Mean Chl-a (ppb) 0 20 40 60 Mean Chl-a (ppb)
Response Frequencies by Site, Sorted by Mean Chl-a Mean Chl-a + Phaeophytin (ppb) Question 1 - Physical Appearance 10 8 4 Bloom Frequencies Question 2 - Use Impact 10 8 4 <5 5-10 10-20 20-40 >40 a b c de Georgetown - Main Georgetown - Cove Travis - Main Travis - Cove Canyon - Main Canyon - Cove Granger - Main Granger - Cove Bridgeport - Main Bridgeport - Cove Fork - Main Fork - Cove Livingston - Main Livingston - Cove Cedar Creek - Main Cedar Creek - Cove Percent of Responses Georgetown - Main Georgetown - Cove Travis - Main Travis - Cove Canyon - Main Canyon - Cove Granger - Main Granger - Cove Bridgeport - Main Bridgeport - Cove Fork - Main Fork - Cove Livingston - Main Livingston - Cove Cedar Creek - Main Cedar Creek - Cove Georgetown - Main Georgetown - Cove Travis - Main Travis - Cove Canyon - Main Canyon - Cove Granger - Main Granger - Cove Bridgeport - Main Bridgeport - Cove Fork - Main Fork - Cove Livingston - Main Percent of Responses Livingston - Cove Cedar Creek - Main Cedar Creek - Cove 10 9 8 7 5 4 3 1 a b c de Georgetown - Main Georgetown - Cove Travis - Main Travis - Cove Canyon - Main Canyon - Cove Granger - Main Granger - Cove Bridgeport - Main Bridgeport - Cove Fork - Main Fork - Cove Percent of Responses Livingston - Main Livingston - Cove Cedar Creek - Main Cedar Creek - Cove 100 Mean & Range 10 Mean Chl-a + Phaeo (ppb) 1
Data Screening Based upon Non-Algal Turbidity Secchi (meters) 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 y = 2.14e -0.02x R 2 = 0.65 0 20 40 60 80 Chl-a (ppb)
Data Screening Based upon Non-Algal Turbidity 1/Secchi (m) 5 5 4 4 3 3 2 2 y = 0.03x + 0.41 R 2 = 0.72 TSS (mg/l) 60 50 40 30 20 y = 0.19x + 2.08 R 2 = 0.68 1 1 10 0 0 20 40 60 80 0 0 50 100 150 Chl-a (ppb) Chl-a (ppb) 70 18 Turbidity (ntu) 60 50 40 30 20 10 y = 0.14x + 2.07 R 2 = 0.56 VSS (mg/l) 16 14 12 10 8 6 4 2 y = 0.41x R 2 = 0.55 0 0 0 50 100 150 0 20 40 60 Chl-a (ppb) TSS (mg/l)
100 10 1 Question 1 - Appearance Question 2 - Use Impact Beautiful OK Slight Imp Impacted Mean Chl-a (ppb) Georgetown Georgetown Travis Canyon Granger Bridgeport Fork Livingston Cedar Creek All Travis Canyon Granger Bridgeport Fork Livingston Cedar Creek All 100 10 1 Mean Chl-a vs. Survey Response by Reservoir No Algae Some Definite High Mean Chl-a (ppb)
Chl-a Frequency Distribution Samples 20 18 16 14 12 10 8 6 4 2 0 Most Sensitive Range For User Perception 0 8 16 24 32 40 48 56 64 72 80 88 96 Chl-a + Phaeophytin (ppb)
Responses vs. Reservoir & Observer Category 10 Crew Contact Non-Contact Q1 = c, d, e 8 4 Cedar Creek Livingston Fork Bridgeport Granger Canyon Travis Georgetown 8 Crew Contact Non-Contact Q2 = c, d, e 4 Cedar Creek Livingston Fork Bridgeport Granger Canyon Travis Georgetown Use Impacted Algae Visible
Survey Responses vs Chl-a Interval Sampling Crews & Contact Users Survey Responses vs Chl-a Interval Non-Contact Water Users 10 10 Question 1 8 4 No Algae Some Definite High Question 1 8 4 No Algae Some Definite High <5 5-10 10-20 20-40 >40 <5 5-10 10-20 20-40 >40 Chl-a Interval (ppb) Chl-a Interval (ppb) 10 10 Question 2 8 4 Beautiful OK Slight Imp Impaired Question 2 8 4 Beautiful OK Slight Imp Impaired <5 5-10 10-20 20-40 >40 Chl-a Interval (ppb) <5 5-10 10-20 20-40 >40 Chl-a Interval (ppb)
Survey Responses - Lake Champlain vs. Texas Reservoirs Question 1 - Appearance Question 2 - Use Impact Lake Champlain Lake Champlain 10 8 4 a b c de 10 8 4 a b c de Texas Reserv - Crew or Contact User 10 8 4 a b c de 0-2 2-4 4-6 0-2 6-8 2-4 8-12 4-6 12-18 6-8 >18 8-12 12-18 >18 0-2 2-4 4-6 6-8 8-12 12-18 Texas Reserv - Crew or Contact User 10 8 4 a b c de 0-2 2-4 4-6 6-8 8-12 12-18 >18 >18 Texas Reserv - Other Observer Texas Reserv - Other Observer 10 10 8 4 a b c de 8 4 a b c de 0-2 2-4 4-6 6-8 8-12 12-18 >18 0-2 2-4 4-6 6-8 8-12 12-18 >18 Chl-a Interval (ppb) Chl-a Interval (ppb)
Factors Potentially Influencing Correlations Between Survey Responses & Chlorophyll-a Exploratory Analysis - First of Two Survey Years yes Level of Enrichment (Oligo-Meso vs. Hypereutrophic) yes Observer Category (Sampling Crew vs. Lay Observer) yes Water Use ( Contact vs. Noncontact) yes Non-Algal Turbidity (Low-Moderate vs. Extremely High) yes Site Type (Cove vs. Open Lake) yes Spatial/Temporal Variance in Reservoir (High vs. Low) no Observer Visit Frequency no Season (June-July vs.. Aug-Sept) no Include or Exclude Phaeophytin