General Water Quality Information

The water quality of streams directly affects the water quality of the aquifer due to rapid recharge through karst formations such as fractures and sinkholes. The reverse is also true where groundwater contained within aquifers contribute to river flows. The health of the creek is highly dependent on maintaining adequate spring flows, making recharge and groundwater management in the larger region critical to maintaining a healthy system in The Cypress Creek watershed. A watershed is an area of land that collects the water within a specific area and drains into the same location or body of water. Watersheds are defined by high-points in topography and capture all areas of land sloping downward until a creek or stream is reached.

The Cypress Creek Watershed is not currently listed for surface water quality impairments. However, the creek often experiences elevated levels of bacteria and reduced levels of Dissolved Oxygen (DO). Changes in water quality are likely due to seasonal and annual climate variability, nonpoint source pollution, and changes in land use and/or management in the watershed. Issues of concern include excess sediment in the creek, high bacteria concentrations and occasionally very high nutrient levels, which indicate potential nonpoint sources of pollution including pet and animal waste, excess fertilizer application, and poorly performing septic systems.

About the Water Monitoring Groups

Clean Rivers Program (CRP)

The Clean Rivers Program conducts water quality monitoring, assessment, and stakeholder participation to improve the quality of surface water within each river basin in Texas. Managed by the Texas Commissions on Environmental Quality (TCEQ) and partnered with the Guadalupe-Blanco River Authority (GBRA), the CRP is funded by fees assessed to wastewater discharge and water rights permit holders. The Wimberley Valley Watershed Association with assistance from the  Meadows Center for Water and the Environment performs quarterly water quality monitoring under the Guadalupe Basin CRP quality assurance project plan from the Blanco River and Cypress Creek watersheds.

Texas Stream Team (TST)

The Texas Stream Team at The Meadows Center is a group of citizen scientists who dedicate their time to understanding and protecting the 191,000 miles of Texas waterways. Several sites along Cypress Creek are monitored by volunteer citizen scientists under a state and federally approved quality assurance project plan. Data is also quality assured by TST staff and can be seen at the TST Dataviewer. These sites are usually tested once a month and submitted to the TST Dataviewer, which is accessible to the public.

Wimberley Water Advisory Group (WWAG)

The Wimberley Water Advisory Group regularly tests for E. coli at several sites This routine monitoring is led by Pete Anderson. Please click here to see a map and data of these sites.

Watershed Protection Plan (WPP)

Starting in 2019, the Watershed Protection Plan staff will conduct both regular surface water and groundwater (wells) monitoring under a state and federal quality assurance protection plan. 

Cypress Creek Watershed Segments

Segment 1813 (Upper Blanco River:

Flowing 71 miles from northern Kendall County until Lime Kiln Road in Hays County, the upper Blanco is a spring-fed stream. Cypress Creek joins the river in the Village of Wimberley. The steep-sloped, intermittent, meandering stream is lined with bald cypress, oak and ashe juniper.

Segment 1815 (Cypress Creek):

The spring-fed creek flows 14 miles into the Village of Wimberley where it merges with the Blanco River in Hays County. A picturesque creek, lined with bald cypress trees, with good water quality

Color Meaning

The data set tables on the Water Quality Data Summaries page are color coded with designated colors described below.
Data in green indicate monitoring results that meet state standards.
Data in orange indicate reduced water quality.
Data in red means that bacteria counts are higher than the allowable limits and dissolved oxygen concentrations are below minimum requirements.
Continue reading below to understand more about these water quality parameters in detail.

Texas Surface Water Quality Standards


The Texas Surface Water Quality Standards establish explicit goals for the quality of streams, rivers, lakes, and bays throughout the state. The standards are developed to maintain the quality of surface waters in Texas so that it supports public health and protects aquatic life, consistent with the sustainable economic development of the state.

Water quality standards identify appropriate uses for the state’s surface waters, including aquatic life, recreation, and sources of public water supply (or drinking water). The criteria for evaluating support of those uses include DO, temperature, pH, TDS, toxic substances, and bacteria.

The Texas Surface Water Quality Standards also contain narrative criteria (verbal descriptions) that apply to all waters of the state and are used to evaluate support of applicable uses. Narrative criteria include general descriptions, such as the existence of excessive aquatic plant growth, foaming of surface waters, taste- and odor producing substances, sediment build-up, and toxic materials. Narrative criteria are evaluated by using screening levels, if they are available, as well as other information, including water quality studies, existence of fish kills or contaminant spills, photographic evidence, and local knowledge. Screening levels serve as a reference point to indicate when water quality parameters may be approaching levels of concern.

Water Quality Parameters

Dissolved Oxygen

The Cypress Creek standard for dissolved oxygen (DO) is 6 mg/L. Oxygen is necessary for the survival of organisms like fish and aquatic insects. The amount of oxygen needed for survival and reproduction of aquatic communities varies according to species composition and adaptations to watershed characteristics like stream gradient, habitat, and available stream flow. The TCEQ Water Quality Standards document lists daily minimum DO criteria for specific water bodies and presumes criteria according to flow status (perennial, intermittent with perennial pools, and intermittent), aquatic life attributes, and habitat. These criteria are protective of aquatic life and may be used for general comparison purposes.

Aquatic Life- Sub CategoryDaily Minimum Dissovled Oxygen (mg/L)

DO is of concern because the creek was briefly listed on the 303(d) list for inadequate DO levels in 2000. In addition, new data provided by GBRA in the 2013 CRP report (pg. 51) indicates a downward trend in DO in Cypress Creek.

The DO concentrations may be influenced by other water quality parameters such as nutrients and temperature. High concentrations of nutrients can lead to excessive surface vegetation growth and algae, which may starve subsurface vegetation of sunlight, and therefore limit the amount of DO in a water body due to reduced photosynthesis. This process, known as eutrophication, is enhanced when the subsurface vegetation and algae die and oxygen is consumed by bacteria during decomposition. Low DO levels may also result from high groundwater inflows due to minimal groundwater aeration, high temperatures that reduce oxygen solubility, or water releases from deeper portions of dams where DO stratification occurs. Supersaturation typically only occurs underneath waterfalls or dams with water flowing over the top.

E. Coli Bacteria

The Environmental Protection Agency (EPA) has determined E. coli to be the best indicator of the degree of pathogens in a water body, which are far too numerous to be tested for directly, considering the amount of water bodies tested. A pathogen is a biological agent that causes disease. 

A geometric mean is a type of average that incorporates the high variability found in parameters such as E. coli which can vary from zero to tens of thousands of CFU/100 mL. According to Texas Surface Water Quality Standards (Title 30, Chapter 307 of the Texas Administrative Code), the standard for contact recreational use in fresh water is  geometric mean 126 colonies per 100 mL.  A water body is considered impaired if the geometric mean is higher than this standard. The single sample max standard is 394 colonies per 100 mL.

What is E.coli bacteria?

Escherichia coli, or E. coli, bacteria originate in the digestive tract of endothermic organisms. It is a type of fecal coliform bacteria that comes from human and animal waste. Since disease-causing bacteria, viruses and protozoans may be present in water that has elevated levels of E. coli, it serves as an indicator of bacterial pollution which is often present when contamination exists from untreated sewage, manure, wildlife or pet waste and therefore serves to identify times when it is unsafe for contact recreation. 

Fecal coliform bacteria like E. coli indicate contamination due to untreated sewage, manure, or pet waste in contributing areas. High E. coli values during high and median flows may be associated with elevated sediment and nitrogen levels. BMPs that help to retain sediment and organic matter in upland areas will help to reduce bacteria entering the creek during these times. High E. coli levels at ambient condition and very low flows, however, tend to indicate a problem with malfunctioning septic systems near the creek or animal waste (pets, birds, bats and other wildlife) deposited directly into the stream.