General Water Quality Information

Although water quality in the Cypress Creek Watershed meets water quality standards, data suggests both spatial and temporal trends that may be due to climate variability, nonpoint source pollution, or changes in land use and/or management in the watershed. Moreover, water quality parameters vary from site to site throughout the perennial part of the stream. Furthermore, the inflow of groundwater highly influences the upper three sites (Jacob’s Well, RR12 North, and Blue Hole) in terms of water chemistry, while the lower two sites (RR12 downtown and the Blanco confluence) tend to cluster closer together, showing more of an influence of local stream conditions and runoff from contributing watersheds. 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.



More on 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


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)

Dissolved oxygen 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

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. The single sample max standard is 394 colonies per 100 mL. A water body is considered impaired if the geometric mean is higher than this standard. The Stakeholder Committee determined to set target E. coli levels below state standards to maintain the creek’s contact recreation designated use. 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.

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. Bacteria strongly impacts contact recreation in the creek and we have seen very high bacteria levels recorded at all sites during medium to high flows. There is a cluster of very high values under the highest flow conditions, indicating a nonpoint source that washes E. coli in with higher surface or shallow sub-surface flows. These tend to be in the summer and fall when high temperatures favor the growth of bacteria and large flow events wash these bacteria into the creek. At median flow levels, all sites show exceedances at various times, including Jacob’s Well. These median flows tend to occur in the spring and fall, and exceedances here occur in association with elevated sediment and nitrogen levels entering the creek. At lower flows, E. coli exceedances occur primarily at RR12 downtown.

The contribution of E. coli must originate by shallow subsurface flow from septic systems in the local area or pet/animal waste placed directly in the stream and riparian area as there would be very little surface flow during these dry periods. Associated with higher E. coli values are elevated TSS levels at all sites except at Jacob’s Well, which tends to have the lowest bacteria concentrations due to the influence of spring flow, but also has the greatest variability of observed concentrations. Stormflow monitoring recorded E. coli levels as high as 3,110 mpn/100mL at the confluence and 680 mpn/100mL above Jacob’s Well. These high values occurred during a time of periodic rain events with no more than 4 days between storm events. Smaller events that followed nearly two weeks of no rainfall had lower E. coli levels, between 160 and 280 mpn/100mL at the peak.

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, and their association with elevated sediment and nitrogen levels, mean that BMPs that help to retain sediment and organic matter on the upland areas will help to reduce bacteria entering the creek during these times. High E. coli levels at very low flows, however, tend to indicate a problem with malfunctioning septic systems near the creek or animal waste deposited directly into the stream. For that reason, the Stakeholder Committee determined to set target E. coli levels below state standards to maintain the creek’s contact recreation designated use. The Stakeholder Committee identified BMPs and a monitoring strategy that will comprehensively address this concern. BMPs including proper septic maintenance and education regarding picking up pet waste and limiting animal access to the creek will help to mitigate these low-flow problems. For more detailed information on E. coli loading refer to Section 6.3 of the Cypress Creek Watershed Characterization Report.



Routine Monitoring

Routine monitoring of climate, hydrology, and water quality in Cypress Creek aids our understanding of the physical context of the creek and its response to activities within the watershed area. The Clean Rivers Program (CRP) conducts routine water quality monitoring at five sites along the creek, from Jacob’s Well to its confluence with the Blanco River. However, neither routine monitoring or flow data collection occurs above the headwaters at Jacob’s Well. Sampling at TCEQ Site 12674 (RR 12, Downtown Wimberley) occurs monthly or quarterly since 1973 by the TCEQ and GBRA.

The CRP has conducted monthly sampling at the Jacob’s Well CRP Site 12677 since 2002, and continuously at the USGS site #08170990 since 2005. Additional sites on Cypress Creek include: Ranch Road 12 approx. 4.5 river km downstream of Jacob’s Well (Site 12676), sampled since 2003; Blue Hole spring (Site 12675) approx. 6.7 river km from Jacob’s Well, sampled since 2005; and at the Blanco confluence (Site 12673), sampled since 2002. 

TCEQ and CRP monitoring sites include instantaneous flow data and the following water quality parameters: temperature (°C), dissolved oxygen (mg/L), specific conductance (umhos/cm), pH (SU), nitrate-nitrogen (mg/L), total phosphorus (mg/L), total suspended solids (mg/L), ammonia (mg/L), and E. coli (colonies/100mL). Infrequent sampling for Ortho phosphorus (mg/L), total dissolved solids (mg/L), and fecal coliform occur at various sites. Furthermore, we analyze concentrations of various pollutants in relation to one another and to available data on precipitation, temperature, and streamflow, to better understand both the physical nature of the watershed and the potential sources and distributions of nonpoint source pollution throughout the contributing area. We constructed load duration curves using daily mean flow estimated at the Blanco confluence and available water quality data. We compare data from 1973 to 1999 to data from 2000 to 2009 for Site 12674 to evaluate any long-term changes in water quality.

Primarily, we collected ambient monitoring data under baseflow conditions and occasionally following storm events during elevated flows. Though, we were sure not to collect during elevated flows that could compromise the safety of monitoring teams, nor were daily streamflow measurements routinely collected. Yet, proper characterization of the hydrology and water quality of the creek requires reliable data on streamflow, and is also necessary to calculate average pollutant loads using ambient data. Furthermore, data on both streamflow and water quality should characterize the range and temporal variability of water quantity and quality under the full range of natural conditions. Since flow rate highly influences water quality parameters, it’s important to understand the hydrologic response of the watershed to identify causes and sources of nonpoint source pollution, in addition to identifying and developing appropriate best management practices (BMPs) to address pollution issues of concern.

Modeling efforts of the Cypress Creek Project are also dependent on accurate flow estimates to ensure the highest accuracy when evaluating potential impacts of future development. As a result, the Cypress Creek Project installed two automatic stormflow monitoring devices along the main creek channel to record stage, sediment, nutrient, and bacteria concentrations during runoff events to help address data gaps (Figure 3.1).

Figure 3.1 Map of Cypress Creek Project Phase I water quality monitoring sites.



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

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