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Jun 1, 2017 - TOOL SELECTION. ..... Texas State Soil and Water Conservation Board. TWDB. Texas Water ..... Group at Oregon State University (2012). 2.4.

TECHNICAL SUPPORT DOCUMENT FOR TOTAL MAXIMUM DAILY LOADS FOR INDICATOR BACTERIA IN ARANSAS RIVER ABOVE TIDAL AND POESTA CREEK

Technical Support Document for Total Maximum Daily Loads for Indicator Bacteria in Aransas River Above Tidal and Poesta Creek Segments: 2004 and 2004B Assessment Units: 2004_02 and 2004B_02

TECHNICAL SUPPORT DOCUMENT FOR TOTAL MAXIMUM DAILY LOADS FOR INDICATOR BACTERIA IN ARANSAS RIVER ABOVE TIDAL AND POESTA CREEK

TECHNICAL SUPPORT DOCUMENT FOR TOTAL MAXIMUM DAILY LOADS FOR INDICATOR BACTERIA IN ARANSAS RIVER ABOVE TIDAL AND POESTA CREEK

Technical Support Document for Total Maximum Daily Loads for Indicator Bacteria in Aransas River Above Tidal and Poesta Creek Segments: 2004 and 2004B Assessment Units: 2004_02 and 2004B_02

Prepared for Total Maximum Daily Load Program Texas Commission on Environmental Quality MC-203 P.O. Box 13087 Austin, Texas 78711-3087

Prepared by Michael Schramm Texas Water Resources Institute Texas A&M University College Station, Texas

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TECHNICAL SUPPORT DOCUMENT FOR TOTAL MAXIMUM DAILY LOADS FOR INDICATOR BACTERIA IN ARANSAS RIVER ABOVE TIDAL AND POESTA CREEK

Acknowledgements The U.S. Environmental Protection Agency and the Texas Commission on Environmental Quality provided financial support for this study. The Texas Commission on Environmental Quality was the study’s lead agency.

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Contents ACKNOWLEDGEMENTS ...................................................................................................................................I CONTENTS ........................................................................................................................................................ II LIST OF FIGURES ............................................................................................................................................ IV LIST OF TABLES.............................................................................................................................................. IV LIST OF ACRONYMS AND ABBREVIATIONS ........................................................................................... V SECTION 1. INTRODUCTION ......................................................................................................................1 1.1. 1.1. 1.2.

BACKGROUND .......................................................................................................................................1 WATER QUALITY STANDARDS ...............................................................................................................1 REPORT PURPOSE AND ORGANIZATION .................................................................................................2

SECTION 2. HISTORICAL DATA REVIEW AND WATERSHED PROPERTIES ...................................4 2.1. DESCRIPTION OF STUDY AREA...............................................................................................................4 2.2. REVIEW OF ROUTINE MONITORING DATA FOR TMDL WATERSHEDS .....................................................7 2.2.1. Data Acquisition .......................................................................................................................7 2.2.2. Analysis of Bacteria Data .......................................................................................................7 2.3. WATERSHED CLIMATE AND HYDROLOGY ..............................................................................................8 2.4. WATERSHED POPULATION AND POPULATION PROJECTIONS ..................................................................9 2.5. LAND USE........................................................................................................................................... 10 2.6. SOILS .................................................................................................................................................. 14 2.7. POTENTIAL SOURCES OF FECAL INDICATOR BACTERIA ....................................................................... 15 2.7.1. Permitted Sources .................................................................................................................. 16 2.7.1.1. 2.7.1.2. 2.7.1.3. 2.7.1.4.

2.7.2. 2.7.2.1. 2.7.2.2. 2.7.2.3. 2.7.2.4.

Domestic Wastewater Treatment Facility Discharges.................................................................. 16 Sanitary Sewer Overflows..................................................................................................................... 17 TPDES General Wastewater Permits .................................................................................................. 18 TPDES Regulated Stormwater ............................................................................................................. 18

Unregulated Sources ............................................................................................................. 19 Wildlife and Unmanaged Animal Contributions ........................................................................... 19 Non-Permitted Agricultural Activities and Domesticated Animals ......................................... 20 Failing On-Site Sewage Facilities ........................................................................................................ 20 Bacteria Survival and Die-off............................................................................................................... 22

SECTION 3. BACTERIA TOOL DEVELOPMENT ................................................................................... 23 3.1. TOOL SELECTION ................................................................................................................................ 23 3.1.1. Situational Limitation of Mechanistic Modeling .............................................................. 23 3.1.2. Available Data Resources .................................................................................................... 25 3.1.3. Allocation Tool Selection ...................................................................................................... 26 3.2. METHODOLOGY FOR FLOW DURATION & LOAD DURATION CURVE DEVELOPMENT ............................ 26 3.2.1. Step 1: Determine Hydrologic Period ................................................................................ 26 3.2.2. Step 2: Determine Desired Stream Locations ................................................................... 27 3.2.3. Step 3: Develop Daily Streamflow Records ...................................................................... 27 3.2.4. Steps 4 Through 6: Flow Duration Curve and Load Duration Curve ......................... 28 3.3. FLOW DURATION CURVES FOR TMDL WATERSHEDS.......................................................................... 28 3.4. LOAD DURATION CURVES FOR TMDL WATERSHEDS ......................................................................... 30 SECTION 4. TMDL ALLOCATION ANALYSIS ....................................................................................... 33 4.1. 4.2.

ENDPOINT IDENTIFICATION ................................................................................................................ 33 SEASONALITY ..................................................................................................................................... 33

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4.3. LINKAGE ANALYSIS............................................................................................................................. 34 4.4. LOAD DURATION CURVE ANALYSIS .................................................................................................... 35 4.5. MARGIN OF SAFETY ............................................................................................................................ 36 4.6. LOAD REDUCTION ANALYSIS .............................................................................................................. 36 4.7. POLLUTANT LOAD ALLOCATIONS ....................................................................................................... 37 4.7.1. AU Level TMDL Calculations ............................................................................................... 37 4.7.2. Margin of Safety (MOS) ........................................................................................................ 38 4.7.3. Wasteload Allocation (WLA)................................................................................................. 38 4.7.4. Future Growth (FG) ............................................................................................................... 40 4.7.5. Load Allocation (LA) ............................................................................................................. 41 4.8. SUMMARY OF TMDL CALCULATIONS ................................................................................................. 42 SECTION 5. REFERENCES .......................................................................................................................... 44 APPENDIX A..... EQUATIONS FOR CALCULATING TMDL ALLOCATIONS FOR REVISED WATER QUALITY STANDARDS................................................................................................................................ 47

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List of Figures Figure 1. Total contributing drainage area for the study, including Assessment Units 2004_02 and 2004B_02 ............................................................................................................................................5 Figure 2. “Two Total Maximum Daily Loads for Indicator Bacteria in the Tidal Segments of the Mission and Aransas Rivers” TMDL project boundaries in relation to project watersheds. ...6 Figure 3. SWQM monitoring station and USGS streamflow gage locations in the Aransas River and Poesta Creek watersheds ................................................................................................................7 Figure 4. Beeville normal monthly precipitation by month and normal average, maximum, and minimum air temperature by month from 1981-2010 ....................................................................8 Figure 5. Average annual rainfall (inches) across the study area from 1981-2010 ............................9 Figure 6. 2010 population by Census block............................................................................................. 10 Figure 7. 2011 land use/land cover across the study area ................................................................... 12 Figure 8. Soil hydrologic groups within the project watershed........................................................... 14 Figure 9. WWTF outfall locations across the project watershed ......................................................... 17 Figure 10. OSSF estimates for the project watersheds .......................................................................... 21 Figure 11. Flow duration curve for Aransas River Above Tidal (AU 2004_02) ................................. 29 Figure 12. Flow duration curve for Poesta Creek (AU 2004B_02) ....................................................... 29 Figure 13. Load Duration Curve for Aransas River Above Tidal (AU 2004_02) ............................... 31 Figure 14. Load Duration Curve for Poesta Creek (AU 2004B_02) ...................................................... 32 Figure 15. Distribution of E. coli concentrations by season in (a) Aransas River Above Tidal (AU 2004_02) and (b) Poesta Creek (AU 2004B_02) ............................................................................... 34

List of Tables Table 1. 2014 Integrated Report Summary for Aransas River Above Tidal and Poesta Creek. .......8 Table 2. 2010 population and 2020-2070 population projections in the study area ..................... 10 Table 3. Land Use/Land Cover for the study area .................................................................................. 13 Table 4. Soil hydrologic groups for the study area ................................................................................ 15 Table 5. Permitted domestic wastewater treatment facilities in the project watersheds .............. 16 Table 6. Summary of SSO incidents reported in project watersheds from August 2009 through February 2016 ........................................................................................................................................ 18 Table 7. Monitoring requirements and compliance status for WWTFs in the project watershed 18 Table 8. Summary of land area covered by stormwater permits in project watersheds as of January 20, 2017.................................................................................................................................... 19 Table 9. Estimated deer and feral hog populations in project watershed ........................................ 19 Table 10. Livestock estimates for project watersheds .......................................................................... 20 Table 11. Estimated households and pet populations .......................................................................... 20 Table 12. OSSF estimate for the project watersheds ............................................................................. 21 Table 13. Basic information on USGS streamflow gages in project area ........................................... 25 Table 14. Summary of historical E. coli concentrations ........................................................................ 26 Table 15. Drainage Area Ratios (DARs) used to estimate flow ............................................................ 28 Table 16. Percent reductions for project watersheds ............................................................................ 36 Table 17. Summary of allowable loadings for project watersheds ..................................................... 38 Table 18. Summary of MOS for project watersheds............................................................................... 38 Table 19. Summary of WLAs for WWTFs in the project watersheds .................................................. 39 Table 20. Permitted Stormwater Acreage and FDASWP calculation ....................................................... 40 Table 21. Regulated stormwater calculations for the project watersheds ........................................ 40 Table 22. Wasteload allocation summary for the project watersheds ............................................... 40 Table 23. Future growth summary for the project watersheds ........................................................... 41

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Table 24. Load allocation summary for project watersheds ................................................................ 42 Table 25. TMDL allocation summary for project watersheds .............................................................. 42 Table 26. Final TMDL allocations for project watersheds .................................................................... 42

List of Acronyms and Abbreviations AU CCN cfs DAR DMR DSLP ECHO E coli FDC FG ft I&I LA LDC MGD mL MOS MPN MS4 NLCD NOAA NPDES OSSF SSO TCEQ TMDL TPDES TSSWCB TWDB TWRI USCB USEPA USGS WLA WWTF

Assessment Unit Certificate of Convenience and Necessity Cubic Feet per Second Drainage-Area Ratio Discharge Monitoring Report Days since last precipitation Enforcement & Compliance History Online Escherichia coli Flow Duration Curve Future Growth Feet Inflow and infiltration Load Allocation Load Duration Curve Million Gallons per Day Milliliter Margin of Safety Most Probable Number Municipal Separate Storm Sewer System National Land Cover Database National Oceanic and Atmospheric Administration National Pollutant Discharge Elimination System Onsite Sewage Facility Sanitary Sewer Overflow Texas Commission on Environmental Quality Total Maximum Daily Load Texas Pollutant Discharge Elimination System Texas State Soil and Water Conservation Board Texas Water Development Board Texas Water Resources Institute United States Census Bureau United States Environmental Protection Agency United States Geological Survey Wasteload Allocation Wastewater Treatment Facility

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Section 1. 1.1.

Introduction

Background

Section 303(d) of the federal Clean Water Act requires all states to identify waters that do not meet, or are not expected to meet, applicable water quality standards. States must develop a Total Maximum Daily Load (TMDL) for each pollutant that contributes to the impairment of a listed water body. The Texas Commission on Environmental Quality (TCEQ) is responsible for ensuring that TMDLs are developed for impaired surface waters in Texas. A TMDL is like a budget—it determines the amount of a particular pollutant that a water body can receive and still meet its applicable water quality standards. TMDLs are the best possible estimates of the assimilative capacity of the water body for a pollutant under consideration. A TMDL is commonly expressed as a load with units of mass per period of time, but may be expressed in other ways. In addition to the TMDL an implementation plan is developed, which is a description of the regulatory and voluntary management measures necessary to improve water quality and restore full use of the water body. The TMDL Program is a major component of Texas’ overall process for managing the quality of its surface waters. The program addresses impaired or threatened streams, reservoirs, lakes, bays, and estuaries (water bodies) in, or bordering on, the state of Texas. The primary objective of the TMDL Program is to restore and maintain the beneficial uses—such as drinking water supply, recreation, support of aquatic life, or fishing—of impaired or threatened water bodies. The TCEQ first identified bacteria impairments within Aransas River Above Tidal and within Poesta Creek in the 2014 Texas Integrated Report of Surface Water Quality for the Clean Water Act Sections 305(b) and 303(d) (TCEQ, 2015a). This document will consider bacteria impairments in two water bodies (segments), each consisting of a single assessment unit (AU). The complete list of water bodies and their identifying AU number is shown below: 1. Aransas River Above Tidal 2004_02; and 2. Poesta Creek 2004B_02

1.1.

Water Quality Standards

To protect public health, aquatic life, and development of industries and economies throughout Texas, water quality standards were established by the TCEQ. The water quality standards specifically protect appropriate uses for each segment (water body), and list appropriate limits for water quality indicators to assure water quality and attainment of uses. The TCEQ monitors and assesses water bodies based on the water quality standards, and publishes the Texas Water Quality Integrated Report list biennially. The Texas Surface Water Quality Standards (TCEQ, 2010) are rules that:

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• • •

designate the uses, or purposes, for which the state’s water bodies should be suitable; establish numerical and narrative goals for water quality throughout the state; and provide a basis on which TCEQ regulatory programs can establish reasonable methods to implement and attain the state’s goals for water quality.

Standards are established to protect designated uses assigned to water bodies of which the primary uses assigned in the Texas Surface Water Quality Standards to water bodies are: • • • •

aquatic life use contact recreation domestic water supply general use

Fecal indicator bacteria are indicators of the risk of illness during contact recreation (e.g., swimming) from ingestion of water. E. coli (Escherichia coli) are bacteria present in the intestinal tracts of human and other warm blooded animals. The presence of these bacteria indicates that associated pathogens from fecal wastes may be reaching water bodies, because of such sources as inadequately treated sewage, improperly managed animal waste from livestock, pets in urban areas, aquatic birds, wildlife, and failing septic systems (TCEQ, 2006). On June 30, 2010, the TCEQ adopted revisions to the Texas Surface Water Quality Standards (TCEQ, 2010) and on June 29, 2011, the U.S. Environmental Protection Agency (USEPA) approved the categorical levels of recreational use and their associated criteria. Recreational use consists of four categories: •







Primary contact recreation is that with a significant risk of ingestion of water (such as swimming), and has a geometric mean criterion for E. coli of 126 most probable number (MPN) per 100 milliliters (mL) and an additional single sample criterion of 399 MPN per 100 mL; Secondary contact recreation 1 covers activities with limited body contact and a less significant risk of ingestion of water (such as fishing), and has a geometric mean criterion for E. coli of 630 MPN per 100 mL; Secondary contact recreation 2 is similar to secondary contact 1, but activities occur less frequently. It has a geometric mean criterion for E. coli of 1,030 MPN per 100 mL; and Noncontact recreation is that with no significant risk of ingestion of water, where contact recreation should not occur due to unsafe conditions. It has a geometric mean criterion for E. coli of 2,060 MPN per 100 mL (TCEQ, 2010).

1.2.

Report Purpose and Organization

The TCEQ contracted the Texas Water Resources Institute (TWRI) for the Aransas and Poesta Creek TMDL project. The tasks of this project were to (1) acquire existing (historical) data and information necessary to support assessment activities; (2)

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perform the appropriate activities necessary to allocate E. coli loadings; and (3) assist the TCEQ in preparing the TMDL. This project intends to use historical bacteria and flow data in order to (1) review the characteristics of the watershed and explore potential sources of E. coli for the impaired segments; (2) develop an appropriate tool for development of a bacteria TMDL for the impaired segments; and (3) submit the draft and final technical support document for the impaired segments. The purpose of this report is to provide technical documentation and supporting information for developing the bacteria TMDL for the Aransas River Above Tidal and Poesta Creek watersheds. This report contains: • • • • •

information on historical data, watershed properties and characteristics, summary of historical bacteria data that confirm the State of Texas 303(d) listings of impairment due to presence of indicator bacteria (E. coli), development of load duration curves (LDCs), and application of the LDC approach for the pollutant load allocation process.

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Section 2. Historical Data Review and Watershed Properties 2.1.

Description of Study Area

Both water bodies included in this study are located within the Aransas River watershed shown in Figure 1. Both water bodies are located upstream of the Aransas River Tidal (Segment 2003) and will be added to the existing TMDL, Two Total Maximum Daily Loads for Indicator Bacteria in the Tidal Segments of the Mission and Aransas Rivers (TCEQ, 2016), through a Water Quality Management Plan update. This study incorporates a watershed approach where the drainage area upstream of each AU outlet is considered. The location of Aransas River Above Tidal (AU 2004_02) and Poesta Creek (AU 2004B_02) in relation to the original Mission and Aransas River TMDL project boundaries is shown in Figure 2. The headwaters of Poesta Creek (Segment 2004B) begin in Bee County northwest of Beeville and flow approximately 28.7 miles southeast to Aransas Creek (Segment 2004A) forming the Aransas River Above Tidal (Segment 2004). The Aransas River Above Tidal begins at the confluence of Aransas and Poesta Creeks and flows 34.9 miles to a point just upstream of US 77. The Aransas River Tidal (Segment 2003) begins flow at this point and flows 28.3 miles to Copano Bay. The drainage area for the impaired AU of Poesta Creek (AU 2004B_02) is 52.3 square miles and located entirely within Bee County. The drainage area for the impaired AU of Aransas River Above Tidal (AU 2004_02) includes the drainage area for Poesta Creek and is 314.4 square miles. The drainage area for Aransas River Above Tidal (AU 2004_02) is predominately in Bee County (98% of the watershed); Live Oak County includes approximately 1.5% of the watershed; San Patricio and Refugio counties each include less than 1% of the watershed area. The 2014 Texas Integrated Report (TCEQ, 2015a) provides the following segment and AU descriptions for the water bodies considered in this document: •



Segment 2004 (Aransas River Above Tidal) - From a point 1.6 kilometers (1.0 mile) upstream of US 77 in Refugio/San Patricio County to the confluence of Poesta Creek and Aransas Creek in Bee County o 2004_02 – From the confluence with Papalote Creek to the upstream end of segment at the confluence with Aransas Creek and Poesta Creek Segment 2004B (Poesta Creek) - From the confluence with the Aransas River to the headwaters of the stream about 7.5 km upstream of FM 673 o 2004B_02 –From the confluence with Talpacate Creek to the headwaters of the stream approximately 7.5 km upstream of FM 673

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Figure 1. Total contributing drainage area for the study, including Assessment Units 2004_02 and 2004B_02 Source: TCEQ Assessment Units (TCEQ, 2015b)

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Figure 2. “Two Total Maximum Daily Loads for Indicator Bacteria in the Tidal Segments of the Mission and Aransas Rivers” TMDL project boundaries in relation to project watersheds.

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2.2.

Review of Routine Monitoring Data for TMDL Watersheds

2.2.1. Data Acquisition The TCEQ Data Management and Analysis Team provided ambient E. coli data on 4 January 2017 (TCEQ, 2017a). The data represented all historical ambient E. coli data and field parameters collected in the project area. Data included E. coli collections from July 2002 through July 2016. 2.2.2. Analysis of Bacteria Data Recent environmental monitoring has occurred within AUs 2004_02 and 2004B_02 at two TCEQ monitoring stations (Figure 3). E. coli data collected at these stations over the seven-year period of 1 December 2005 through 30 November 2012 were used in assessing attainment of the primary contact recreation use as reported in the 2014 Texas Integrated Report (TCEQ, 2015a). The 2014 assessment data indicate nonsupport of the primary contact recreation use because of geometric mean concentrations exceeding the geometric mean criterion of 126 MPN/100 mL for Aransas River Above Tidal (AU 2004_02) and Poesta Creek (AU 2004B_02) as summarized in Table 1.

Figure 3. SWQM monitoring station and USGS streamflow gage locations in the Aransas River and Poesta Creek watersheds Source: TCEQ SWQM stations from TCEQ (TCEQ, 2012); USGS stream gage stations from USGS (USGS, 2011)

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TECHNICAL SUPPORT DOCUMENT FOR TOTAL MAXIMUM DAILY LOADS FOR INDICATOR BACTERIA IN ARANSAS RIVER ABOVE TIDAL AND POESTA CREEK

Table 1. 2014 Integrated Report Summary for Aransas River Above Tidal and Poesta Creek. Source: TCEQ, (2015a)

Water Body

Assessment Unit (AU)

Parameter

Station

Date Range

No. of Samples

Aransas River Above Tidal Poesta Creek

2004_02

E. coli Geomean

12952

12/01/2005 – 11/30/2012

50

Station Geometric Mean (MPN/100mL) 166

2004B_02

E. coli Geomean

12932

12/01/2005 – 11/30/2012

21

311

2.3.

Watershed Climate and Hydrology

Figure 4. Beeville normal monthly precipitation by month and normal average, maximum, and minimum air temperature by month from 1981-2010 Source: NOAA (2016)

Monthly normal precipitation, from the Beeville Chase Station USW00012925 weather station (NOAA, 2016), indicate Beeville’s mean annual rainfall from 1981-2010 was 31.96 inches (NOAA, 2016). Rainfall normally peaks in September (4.76 inches) with lowest totals occurring in December (1.55 inches) (Figure 4). Average annual precipitation values across the study area from the PRISM Climate Group at Oregon State (2012) indicate average annual rainfall ranges from 29 to 33 inches per year across the watershed, with a clear east to west decreasing gradient (Figure 5).

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Monthly normal air temperature, also from the Beeville Chase Station USW00012925 weather station (NOAA, 2016), indicate daily mean air temperature was 73.0°F. Minimum average daily temperature reaches a low of 46.3°F in January. Maximum average daily temperature reached a peak of 97.4°F in July.

Figure 5. Average annual rainfall (inches) across the study area from 1981-2010 Source: PRISM Climate Group at Oregon State University (2012)

2.4.

Watershed Population and Population Projections

Watershed population estimates were developed using 2010 US Census block data (USCB, 2010). Because US Census block boundaries are not the same as watershed boundaries, the population was estimated by multiplying the census block population to the percent of each block within the watershed. The population of the AU 2004_02 watershed is approximately 27,972. The population of the AU 2004B_02 watershed is approximately 11,663. The city of Beeville (population 12,863) is the only municipality in the study area. Texas Water Development Board (TWDB) Regional Water Plan Population and Water Demand Projections (TWDB, 2017) were used to estimate population projections for counties and water user groups within the watershed. Population projections from Live

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Oak, Refugio, and San Patricio counties are not included because they account for less than 2% of the total watershed area. Table 2 contains population projections.

Figure 6. 2010 population by Census block Source: USCB (2010)

Table 2. 2010 population and 2020-2070 population projections in the study area Source: TWDB (2017) and USCB (2010)

Group Beeville Bee County

2.5.

2010 12,863

2020 13,516

Projected Population 2030 2040 2050 14,082 14,327 14,351

2060 14,365

2070 14,369

Percent Increase 11.7%

31,861

33,478

34,879

35,579

35,590

11.7%

35,487

35,545

Land Use

Land use and land cover for the watersheds was obtained from the 2011 National Land Cover Database (NLCD) (USGS, 2015), displayed in Figure 7. The following categories and definitions represent land use/land cover in the NLCD database:

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• •























Open Water – Areas of open water, generally with less than 25% cover of vegetation or soil. Developed, Open Space – Areas with a mixture of some constructed materials, but mostly vegetation in the form of lawn grasses. Impervious surfaces account for less than 20% of total cover. These areas most commonly include large-lot single-family housing units, parks, golf courses, and vegetation planted in developed settings for recreation, erosion control, or aesthetic purposes. Developed, Low Intensity - Areas with a mixture of constructed materials and vegetation. Impervious surfaces account for 20% to 49% percent of total cover. These areas most commonly include single-family housing units. Developed, Medium Intensity - Areas with a mixture of constructed materials and vegetation. Impervious surfaces account for 50% to 79% of the total cover. These areas most commonly include single-family housing units. Developed, High Intensity - Highly developed areas where people reside or work in high numbers. Examples include apartment complexes, row houses and commercial/industrial. Impervious surfaces account for 80% to 100% of the total cover. Barren Land (Rock/Sand/Clay) - Areas of bedrock, desert pavement, scarps, talus, slides, volcanic material, glacial debris, sand dunes, strip mines, gravel pits and other accumulations of earthen material. Generally, vegetation accounts for less than 15% of total cover. Deciduous Forest - Areas dominated by trees generally greater than 5 meters tall, and greater than 20% of total vegetation cover. More than 75% of the tree species shed foliage simultaneously in response to seasonal change. Evergreen Forest - Areas dominated by trees generally greater than 5 meters tall, and greater than 20% of total vegetation cover. More than 75% of the tree species maintain their leaves all year. Canopy is never without green foliage. Mixed Forest - Areas dominated by trees generally greater than 5 meters tall, and greater than 20% of total vegetation cover. Neither deciduous nor evergreen species are greater than 75% of total tree cover. Shrub/Scrub - Areas dominated by shrubs; less than 5 meters tall with shrub canopy typically greater than 20% of total vegetation. This class includes true shrubs, young trees in an early successional stage or trees stunted from environmental conditions. Grassland/Herbaceous - Areas dominated by gramanoid or herbaceous vegetation, generally greater than 80% of total vegetation. These areas are not subject to intensive management such as tilling, but can be utilized for grazing. Pasture/Hay - Areas of grasses, legumes, or grass-legume mixtures planted for livestock grazing or the production of seed or hay crops, typically on a perennial cycle. Pasture/hay vegetation accounts for greater than 20% of total vegetation. Cultivated Crops - Areas used for the production of annual crops, such as corn, soybeans, vegetables, tobacco, and cotton, and also perennial woody crops such as orchards and vineyards. Crop vegetation accounts for greater than 20% of total vegetation. This class also includes all land being actively tilled.

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Woody Wetlands - Areas where forest or shrubland vegetation accounts for greater than 20% of vegetative cover and the soil or substrate is periodically saturated with or covered with water. Emergent Herbaceous Wetlands - Areas where perennial herbaceous vegetation accounts for greater than 80% of vegetative cover and the soil or substrate is periodically saturated with or covered with water.

Figure 7. 2011 land use/land cover across the study area Source: National Land Cover Database (USGS, 2015)

The total Aransas River Above Tidal (AU 2004_02) watershed area is 201,226.6 acres and predominately composed of Pasture/Hay (32.5%) and Shrub/Scrub (30.7%) (Table 3). The Poesta Creek (AU 2004B_02) watershed, located within the Aransas River Above

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Tidal watershed, is 33,441.7acres. The majority of land cover in the Poesta Creek watershed is also Shrub/Scrub (42.3%) and Pasture/Hay (32.8%). Urban development comprises less than 8% of the Aransas River Above Tidal watershed and nearly 15% of the Poesta Creek watershed. Table 3. Land Use/Land Cover for the study area Source: National Land Cover Database (USGS, 2015)

Open Water

Aransas River Above Tidal (2004_02) Percent of Acres Total 33.4

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