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Aquilla Reservoir: Drinking Water Sources

This is a completed TMDL project to reduce atrazine in Aquilla Reservoir, which is a source of drinking water for several communities. The adopted total maximum daily loads (TMDLs) and the approved implementation plan (I-Plan) are the road map for improving water quality in the lake.

photo of filter strip at edge of cornfield in Aquilla Reservoir watershed
Filter Strip at edge of on a farm in the
watershed of Aquilla Reservoir
map of the Aquilla Reservoir TMDL watershed

County: Hill
Parameter: Atrazine
Basin: Brazos River
Segment: 1254

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Background and Goal

Aquilla Reservoir is a 3,280-acre lake located in Hill County. It was constructed in 1983 for use as flood control, recreation, and as a supply for drinking water treatment facilities. Testing of treated drinking water at a regional treatment facility found high levels of the herbicide atrazine, which pointed to contamination in the lake.

Agricultural sources were the primary contributors to pollution in the reservoir. The goal of the project was to reduce atrazine concentrations in the reservoir to safe levels.

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Watershed Description

Aquilla Reservoir is a 3,280-acre reservoir on Aquilla and Hackberry Creeks in the Brazos River Basin, southwest of Hillsboro. The reservoir was constructed in 1983 and is owned by the U.S. Army Corps of Engineers. The reservoir's watershed is 255 square miles.

Aquilla Reservoir is an important resource to nearby communities. In 2000, it was the source of drinking water to about 8,000 people—including the communities of Hillsboro (population: 7,072), Milford (population: 711), and Bynum (population: 192), along with several water supply companies (Chatt, Files Valley, Hill County, Parker, Branden-Irene). The Corps of Engineers operates three parks by the lake—Dairy Hill Ramp (12,700 visitors annually), Old School Ramp (14,300 visitors annually), and Outlet Area (6,900 visitors annually). 


Atrazine concentrations in Aquilla Reservoir have been reduced to safe levels. Water from the reservoir is sampled at regular intervals to ensure that atrazine concentrations remain within an acceptable range. Routine tests of treated drinking water also continue and indicate that atrazine is below the criteria used determine its safety for human consumption. For more information about how the goal was achieved, read:

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Public Participation

In all its projects, TCEQ gathers opinions and information from people who represent government, permitted facilities, agriculture, business, environmental groups, and community and private interests in the watershed. Stakeholder participation is vital to the success of TMDL projects. Two forums worked with TCEQ on the Aquilla Reservoir TMDL and I-Plan.

The Surface Water Protection Committee included representatives from the Texas State Soil and Water Conservation Board, the Texas Department of Agriculture, Texas A&M University, Novartis, USDA-Natural Resources Conservation Service, USDA-Agricultural Research Service, the Texas Farm Bureau, the Brazos River Authority, and municipal representatives.

A second stakeholder group included representatives of affected agricultural operations, water supply companies, and cities.

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Adopted TMDLs and Approved I-Plan

The commission adopted this TMDL on March 23, 2001; it adopted revisions to the TMDL on June 14, 2002. The EPA approved the TMDL on October 30, 2002, at which time it became part of the state's Water Quality Management Plan.

The commission approved the I-Plan on January 18, 2002.

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Contact the TMDL Program

Please e-mail and mention Aquilla Reservoir in the subject line. Or call us at 512-239-6682.

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Communities Working Together