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San Antonio River Basin Report Card 2022

San Antonio River Basin Report Card Summary
The overall grade for the 2022 San Antonio River Basin Report Card is B. This grade is the average of twelve individual indicator grades, which are explained in greater detail below.
Habitat Quality Index
Habitat Quality Index
How is this being measured?
Explanation of the grade
Key findings

B-Habitat Quality Index

Why is this important?

While all the metrics in the San Antonio River Basin Report Card have overlapping correlation to the safe, clean, enjoyable creeks and rivers aspects of the River Authority’s mission, the Habitat Quality Index grade is primarily related to the clean aspect.

Habitat Quality Index


One of the main functions of a habitat assessment is to characterize the aquatic- and riparian-life potential of a creek or river. The Habitat Quality Index (HQI) is a requirement of all bioassessment activities in Texas per the Texas Commission on Environmental Quality’s (TCEQ) Surface Water Quality Monitoring (SWQM) Procedures, Volume 2. The HQI provides quantifiable, reproducible data reported to the TCEQ.

The HQI has primary, secondary, and tertiary attributes. Primary attributes include bottom substrate stability, dimensions of largest pool, and available instream cover. Secondary attributes include number of riffles, channel flow status, and channel sinuosity. Tertiary attributes include bank stability, riparian buffer vegetation, and aesthetics of reach. Scores for each of the HQI attributes are scored and added up. That total value is then rated as exceptional, high, intermediate, or limited based on ranges established by TCEQ.

The HQI is important for assessing the health of riparian communities and a waterbody’s capacity to support a robust instream community. It is important to note, that while a healthy and robust habitat may be present, it does not necessarily mean that robust instream populations are present. For more information on instream communities, see the Index of Biotic Integrity page in the Basin Report Card. Therefore, River Authority biologists are constantly monitoring the habitats of the San Antonio River Basin to determine current HQI.

How is this being measured?

To determine the Habitat Quality Index (HQI), we examined the last three years of data for each of the 17 sites in the San Antonio River Basin monitored by the River Authority. Last year these metrics were calculated based on 20 sites. These measurements are done on a 3-year rolling average, and three sites that were assessed last year did not have data for the updated 3-year time frame. The River Authority adds or drops monitoring stations for a myriad reasons including special studies based on watershed conditions starting or stopping, a more representative site is found within a waterbody, or site accessibility issues.

The grade is calculated by taking the number of sites meeting the designated use divided by the total number of sites monitored, multiplied by 100. Therefore, the grade for this metric is based on the percentage of monitored sites that meet the designated use.

Explanation of the grade

There were 11 of 17 sites meeting the designated use:

11 / 17 * 100 = 64.7%

Grade: B-

Key findings

The HQI grade indicates that the San Antonio River Basin has a relatively high potential for aquatic life, and thus, a relatively high potential for maintaining biodiversity and species richness. The HQI score does indicate that improvements can still be made to further enhance the potential of the basin to support even more richly diverse and healthy aquatic and riparian populations.

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