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San Antonio River Basin Report Card

2020

Report Card Summary

2020
San Antonio River Basin Report Card Summary
The overall grade for the 2020 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.
66.2
Habitat Quality Index
Habitat Quality Index
How is this being measured?
Explanation of the grade
Key findings

B+Habitat Quality Index

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 including 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 subcategories are rated as exceptional, high, intermediate, limited, or minimal.

The HQI is important for determining the density and health of aquatic and riparian communities. Interpreting the HQI results provides a valuable understanding of the health of aquatic and riparian communities. Therefore, River Authority scientists 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 five years of data for each of the 21 sites in the San Antonio River Basin monitored by the River Authority. The grade is calculated by taking the number of sites meeting the designated use divided by 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 are 16 of 21 sites meeting the designated use:

Grade: B
(16 / 21 * 100 = 76.2%)

Key findings

The HQI grade indicates that the San Antonio River Basin has a relatively high potential for aquatic and riparian 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 an even more richly diverse and healthy aquatic and riparian populations.

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