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TR-429

Arroyo Colorado Agricultural Nonpoint Source Assessment Final Report

A. Berthold

As a result of low dissolved oxygen levels, the tidal segment of the Arroyo Colorado (Segment 2201), does not currently meet the aquatic life use designated by the State of Texas and described in the Texas Water Quality Standards. This has been the case for every 303(d) list prepared by the State since 1986. There have also been concerns for high nutrient levels in this water body as documented on every 305(b) assessment prepared by the State since 1988. To meet the dissolved oxygen criteria (24-hour average of 4.0 mg/L and minimum of 3.0 mg/L) at least 90% of the time between the critical period of March through October, Texas Commission on Environmental Quality (TCEQ) (2003) estimates a 90% reduction in nitrogen, phosphorous, oxygen-demanding substances and sediment will be necessary.

In response to this impairment, a local effort was initiated to develop a watershed protection plant (WPP) to improve conditions in the Arroyo Colorado. Working with the TCEQ, the Texas State Soil and Water Conservation Board (TSSWCB) and other agencies, a local steering committee has and will continue devise and implement strategies to increase dissolved oxygen in the Arroyo Colorado and improve its environmental conditions.

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