My research for my thesis pertains to the entire Basin Group C for the state of Texas. Basin Group C consists of the San Jacinto River Basin, the San Jacinto-Brazos Coastal Basin, the Trinity-San Jacinto Coastal Basin, the Neches-Trinity Coastal Basin, and 21 Bay and Estuary Water Quality Segments. For the focus of this project, I chose to apply my research to the San Jacinto-Brazos Coastal Basin. This basin is located along the Southeast Coast. It is approximately 1725 square miles, and is bordered by the San Jacinto River and the Gulf of Mexico.
The San Jacinto-Brazos Coastal Basin is comprised of two Hydrologic Cataloging Units (HUCs). Austin-Oyster, HUC #12040205, is approximately 630 square miles and contains Brazoria, Fort Bend and Waller Counties. West Galveston Bay, HUC #12040204, is 1095 square miles and contains Brazoria, Chambers, Fort Bend, Galveston, and Harris Counties. Metropolitan areas in the San Jacinto-Brazos Coastal Basin include Brazoria, Galveston/Texas City, and Houston.
To understand what my research encompasses, the phrases in the title must first be defined. TMDL stands for Total Maximum Daily Load, which is " the calculation of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards, and an allocation of that amount of the pollutant's sources." This definition is still confusing, and I better understand the concept of TMDL by thinking of it as it's acronym, the total, maximum, daily load. Therefore, it is the sum of all the allowable loads of one pollutant from all of the point and nonpoint sources of that pollutant, into a designated water body. The value of the TMDL also includes a factor of safety, to ensure that the waterbody is safe for the purposes designated by the state.
The specified uses that the waterbody must be safe for are:
Aquatic Life Support: The waterbody must be at the optimum conditions to support aquatic life.
Contact Recreation: Swimming, and direct contact water sports in the waterbody must be free from risk of any bacteria or viruses in the waterbody.
Public Water Supply: The waterbody can be used as a source of public water supply for surface water treatment.
Fish Consumption: Any fish or shellfish from the waterbody, consumed by the public, are not contaminated.
The TMDL initiative began with the 1972 Federal Clean Water Act (CWA) Section 303(d), requiring all states to develop TMDL programs for any waterbody not meeting these standards.
The TMDL development process is placed in the hands of states, territories, and authorized tribes. The Environmental Protection Agency Office of Water also designates TMDLs for waterbodies. The Texas Natural Resource Conservation Commission (TNRCC) is responsible for TMDL designation for the State of Texas.
A waterbody with a TMDL is designated in the form of a "TMDL segment" on the Clean Water Act Section 303(d) List: The State of Texas List of Impaired Water Bodies. The List contains waterbodies which do not meet the standards for use or are expected not to in the future, pollutants responsible for causing the standards failure, and waterbodies with clean-up activities in the next two years. These pollutants can be anything from metals, organics, fecal coliform bacteria, dissolved oxygen or dissolved solids. For the San Jacinto-Brazos Coastal Basin, there are 11 different segments.
From the State of Texas 1999 Clean Water Act Section 303(d) List from June 25, 1999, the following segments apply to the San Jacinto-Brazos Coastal Basin:
Geospatial Data Development
The other term in my title is Geospatial Data Development. This process consists of collecting pertinent GIS data layers and putting them in the same projection. For the TNRCC TMDL project, this projection is the Texas State Mapping System, Albers Equal Area Projection. The projection parameters are as follows:
The data layers needed can be placed into categories:
Hydrology: including TMDL water quality segments, National Hydrography Dataset network, Hydrologic Cataloging Unit boundaries
Coverages: including STATSGO and SSURGO soil coverages, Land Use layers, Vegetation layers
Point Layers: including discharge points, USGS gage locations, locations of hydraulic structures, water quality monitoring stations
Political/Municipal Information: County boundaries, City boundaries, transportation networks, legislative districts
Basically, Geospatial Data Development includes any sort of information that can be represented spatially. The purpose of this data is to facilitate the Watershed Action Plan used by the State in implementing the TMDL clean-up activities. Watersheds for each TMDL segment are used as management regions to assess the water quality issues of a segment. By have the spatial data available, the process of identifying pollutant sources and responsible parties, and knowing who to notify makes formulating the corrective actions easier.
After assessing the tasks, I decided to set the scope of this project as developing the river network and delineating watersheds for the San Jacinto-Brazos Coastal Basin, and the TMDL segments within it. The Data and Procedure sections outline the steps I followed.
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