The information on LCRA's water quality data site is the principally designed for use by water quality experts, scientists and other professionals. As a result, casual readers may need assistance in understanding the information.

Below are some general questions and answers about the water-quality data. If you have more specific questions about the information, contact watershed@lcra.org.

How is the information generated?
Water quality professionals from throughout the Colorado River basin collect the data and it is entered into a central database. The information comes from LCRA, the Colorado River Municipal Water District, the Upper Colorado River Authority, the Texas Commission on Environmental Quality, and the City of Austin.

TCEQ contracts with LCRA to collect and distribute the information as part of the Clean Rivers Program in the Colorado River basin. See LCRA's Clean Rivers Program for more information.

How many water-quality parameters are measured?
Several hundred parameters are monitored -- everything from alkalinity and arsenic to water temperature and zinc. Each of these factors is referenced by a "parameter code."

However, water-quality monitors don't measure all parameters at each site. Often, streams and lakes located in areas with high population or special considerations, such as the presence of endangered species, may have more parameters measured than locations in more remote areas.

How can I tell if a water body is polluted?
The answer depends on many factors, including what you intend to use the water for, such as drinking, fishing or boating. For example, if you swim after a heavy rainfall, the water may be unsafe for close human contact. That's because heavy rain will increase the amount of runoff, potentially causing a spike in bacteria and pollutants.

Under the federal Clean Water Act and the Texas Water Code, the TCEQ has the authority to develop and enforce statewide surface water quality standards. For each water body, TCEQ defines how the water will be used based on four categories: protection of aquatic life; fishing; contact recreation such as swimming; public water supply. (A water body may be assigned more than one of these uses.) For each water body, upper and lower limits for common water quality criteria are established.

Bodies of water that don't meet state water quality standards are found on the state's 303(d) List, which refers to a section in the Clean Water Act. See the latest draft of the 303(d) List is found on TCEQ's site.

What are the most common measures of water quality?
There are many measurements used to determine a water body's health. Some of the most common:

• pH: a measure of the water's acidity. Readers will notice numbers ranging from 0 to 14. A number of 7 is neutral. A pH of less than 7 indicates acidity.
• Water temperature: the water temperature (measured in degrees centigrade) is important not only for swimmers, but for fish and industries such as power plants that use water for cooling. Temperature also can affect the ability of water to hold oxygen as well as the ability of organisms to resist certain pollutants.
• Turbidity: the amount of particulate matter suspended in water. Turbidity is measured by shining a light through the water. Typically, the cloudier the water, the higher the turbidity value. The lower the number, the clearer the water. Turbidity is reported in nephelometric turbidity units (NTUs).
• Dissolved oxygen: Aquatic life can have a hard time surviving in stagnant water that has a lot of rotting, organic material in it. During summer, low flows in streams can cause dissolved oxygen levels to dip below the state standard of 5 miligrams per liter.
• Nutrients: Includes nitrate, phosphorus, nitrogen and ammonia. Measuring these nutrients helps determine whether a stream or lake exhibits excessive plant growth, which can lead to eutrophication and problems with dissolved oxygen.
• Bacteria: Includes E. coli and fecal coliform. These are bacteria found in the intestinal tracts of mammals and, therefore in fecal matter. Their presence is an indicator of pollution and possible contamination by agents that cause disease.
• Toxic substances: These are measured in water, sediment and fish tissue in areas where the impact on water quality is deemed most likely. These include metals such as lead and arsenic and organic chemicals such as known carcinogens benzene and pesticides like DDT.

Other parameters that experts use relate to physical conditions, such as how soon after a rainfall was the measurement taken and the general flow level of the water. These factors can significantly impact water quality.

For more information on water-quality terms, see the Water Quality Association's water glossary. For more information on the methods used to collect the data, see the TCEQ's Surface Water Quality Procedures Manual. (This document requires the free Adobe Acrobat Reader to view.)

How often is the data collected?
It depends on the location. Some sites are monitored every few weeks, while others are measured a few times a year. A sudden event, such as an industrial spill, may spark additional monitoring.

LCRA's routine water quality monitoring program samples more than 70 locations on the Highland Lakes, the Colorado River and its tributaries every other month.

Is the historic data most important, or just the most recent data?
It's important to understand that water quality can vary greatly simply because local conditions may change greatly. In fact, the results of a single measurement of a water's properties are actually less important than looking at how the properties vary over time.

What is a stream "segment"?
These are streams and water bodies that have been individually defined by TCEQ and assigned unique identification numbers. Because they have relatively similar chemical, physical and hydrological characteristics, segments provide a basic unit for assigning site-specific standards and for applying water quality management programs.

This site supplies more information than I want to know. How can I just get basics on water quality in my area?

If you live along the upper portions of the Colorado, check the Upper Colorado River Authority or the Colorado River Municipal Water District. You can get data on most all Texas water bodies at TCEQ's water quality viewer.

Where else can I learn about water quality?
See these Web sites:

• Texas Commission on Environmental Quality
• The Environmental Protection Agency: Monitoring and Assessing Water Quality
• The Water Quality Association