Texas Stream Team citizen scientist water quality monitoring data collected for the Medina River was compiled, analyzed and summarized in a report titled the Medina River Watershed Data Report (October 2019) . The purpose of the report was to analyze the data collected by citizen scientists to inform partners and the public regarding the status of water quality at selected monitoring sites within the Medina River watershed.

Citizen scientists monitored Standard Core and Advanced water quality parameters from six different sites in the Medina River above Medina Lake (Segment 1905) from 2010 to 2019 including air and water temperature, TDS, DO, pH, and E. coli (Fig. 1). All data were collected under an approved quality assurance project plan using the methods described in the Texas Stream Core and Advanced Citizen Scientist Water Quality Monitoring Manuals. Data from the six monitoring sites were analyzed to provide an overview of findings during the period of record.

Highlights of the results include:

  • An upstream to downstream water temperature gradient from colder to warmer was apparent, likely a result of the proximity of the spring water source at the upstream sites. The temperature water quality standard (31.0 °C) was exceeded at the downstream sites where more urbanization is prominent than at the upstream sites.
  • Total dissolved solid (TDS) measurements had a bimodal spatial distribution, with the two upper sites (80690 and 80691) revealing lower TDS values than the lower four sites within the watershed. This was likely a result of the proximity to the spring water source which typically exhibits lower TDS values.
  • Dissolved oxygen was consistently above the water quality standard at most sites with higher overall values at the two upper (80690 and 80691) and two lower (80575 and 80576) sites (>7.1 mg/L) within the watershed. The lower DO values (<6.8 mg/L) appeared at the two middle sites (80657 and 80658) along the continuum from upstream to downstream, which are also the sites located either in the city or just downstream of the city of Medina. Some values fell below the minimum water quality standard (4.0 mg/L) at the most upstream site (80690) and the site downstream of the city of Medina (80658).
  • The pH values were all within the range of values associated with the water quality standard (6.5-9.0). No values dropped below or above that range.
  • E. coli values exceeded both the geomean and single sample standard on several occasions at most sites, except the most downstream site (80576), but it had a very limited data set (2 data points). The highest geomean with the greatest standard deviation (123+169 CFU/100mL) was observed at site 80575 in the lower portion of the segment with 20 of the 38 samples exceeding the geometric mean water quality criterion.

The Texas Stream Team citizen scientist monitoring group, Bandera Stream Team, will continue to monitor the water quality of the Medina River watershed. Texas Stream Team will continue to support citizen scientists in the collection and testing of water quality. If you are interested in becoming a Texas Stream Citizen Scientist, contact us at txstreamteam@txstate.edu.

Sandra Arismendez

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