Site Descriptions

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


Data in green indicate monitoring results that meet state standards. 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.



Water Quality Parameters

Dissolved Oxygen

The Cypress Creek standard for dissolved oxygen 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 dissolved oxygen (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)

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 standard for contact recreational use is 126 CFU/100 mL (This is the single sample standard). A water body is considered impaired if the geometric mean is higher than this standard.

E. coli bacteria originate in the digestive tract of endothermic organisms. The Environmental Protection Agency 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. The standard for E. coli impairment is based on the geometric mean (geomean) of the E. coli measurements taken. 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. The standard for contact recreational use of a water body such as Canyon Lake is 126 CFU/100 mL. A water body is considered impaired if the geometric mean is higher than this standard.



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.



Quality Assurance & Quality Control

This section is still under construction. Please check back soon.