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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
Index of Biotic Integrity
Index of Biotic Integrity
How is this being measured?
Explanation of the grade
Key findings

CIndex of Biotic Integrity

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 Index of Biotic Integrity grade is primarily related to the clean aspect.

Index of Biotic Integrity

The Index of Biotic Integrity (IBI) is designed as a way for River Authority Environmental Sciences Department (ESD) staff to sample, evaluate, and describe the condition of warm water creeks and rivers throughout the basin. These metrics reflect fish species richness, trophic level composition (e.g. predators and omnivores), number and abundance of species, and condition of individual fish among other aspects of the overall fish community. These are considered Designated Aquatic Life Uses (ALU) by the Texas Commission on Environmental Quality (TCEQ) and Environmental Protection Agency (EPA), and are rated as being Minimal, Limited, Intermediate, High, and Exceptional. Theoretically, the less disturbed a stream is, the higher the IBI rating will be. River Authority biologists are constantly monitoring the San Antonio River Basin at numerous sites throughout the entire watershed to determine IBI.

How is this being measured?

To determine the IBI grade for the 2020 San Antonio River Basin Report Card, we will use last five years of data for each of the 21 sites monitored throughout the basin by the River Authority. The grade will be determined by the number of sites meeting designated ALU divided by total number of sites monitored, multiple 100. Therefore, the grade for this metric is based on the percentage of monitored sites that meet the ALU designation.

Explanation of the grade

There are 11 of 21 sites achieving the associated ALU designation:

Grade: C
(11 / 21 * 100 = 52.4%)

 

Key findings

This grade indicates that some of the creeks and rivers of the San Antonio River Basin have healthy fish communities. However, the score does indicate that further improvements can be made to enhance the diversity and abundance of these communities throughout the basin. Reducing disturbances to area creeks and rivers can help protect and enhance the health of their biotic communities. Healthy ecosystems are more resilient to existing disturbances and are characterized by high species diversity. A healthy San Antonio River Basin is a benefit not only for the aquatic communities that inhabit its waters, it is a valuable amenity for all residents of the basin.

Index of Biotic Integrity
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