Analysis of Water Quality Data for East Elm, West Elm and Lorence Creeks

Author Water Resources Associates, Inc and James Miertschin and Associates
Year 1986
Description Water quality in three small watersheds in the Edwards Aquifer Recharge Zone in relation to storm water runoff and urbanization, 1976 - 1980
Publisher Edwards Underground Water District
Location Edwards Aquifer, Balcones Fault Zone, San Antonio Segment, Recharge Zone
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Water quality data collected on East Elm, West Elm and Lorence Creeks were compiled and analyzed. The watersheds of the three streams are characterized by different levels of urbanization. The East Elm watershed is largely undeveloped, while the Lorence Creek basin is almost completely urbanized as a residential area. The West Elm watershed represents an intermediate level of development.

Statistical analysis of the water quality data indicated that mean concentration values of most of the constituents were higher at the Lorence Creek station than at either the East Elm or West Elm sites. Further, mean concentration values at the West Elm station were higher than corresponding values at the East Elm station.

The most apparent factor which may contribute to the observed differences in constituent concentrations is the level of urbanization in the test watersheds. However, additional factors could also contribute, such as physiographic variables and differences in the frequency and duration of stormwater runoff events. On the basis of flow-weighted average concentrations, West Elm Creek displayed the highest values, with no consistent difference evident between Lorence Creek and East Elm Creek.

Several mathematical relationships were examined to investigate correlations between constituent concentration and discharge rate for the three sampling stations. Only poor correlations were evident, indicating that concentrations are not a function of flow rate.