Section 303(d) of the Federal Clean Water Act requires states to identify waterbodies that are not meeting water quality standards and to develop total maximum daily pollutant loads for those waterbodies. A total maximum daily load (TMDL) is the amount of a pollutant that a waterbody can assimilate without exceeding the established water quality standard for that pollutant. Through a TMDL, pollutant loads can be allocated to point sources and nonpoint sources discharging to the waterbody. This report presents a TMDL for nitrate for Days Creek (reach 11140302-003) in southwestern Arkansas. Days Creek starts in Texas, drains most of the Texarkana metropolitan area, and flows into Arkansas before emptying into the Sulphur River. Days Creek is located within the Gulf Coastal Plain ecoregion and has a drainage area of approximately 144 mi2 at its mouth. There are a total of six point source discharges in the Days Creek watershed, including two City of Texarkana wastewater treatment facilities with design flows of 2 MGD and 18 MGD, respectively. Reach 11140302-003 includes the entire portion of Days Creek in Arkansas, which is approximately 11 miles. This stream reach was included on the 2002 Arkansas 303(d) list as not supporting its designated use of domestic, industrial, and agricultural water supply. Based on the 303(d) listing, the primary cause of impairment is nitrate nitrogen and the primary source of contamination is municipal point source. The Arkansas Department of Environmental Quality (ADEQ) has no numeric water quality standard for nitrate but uses the Safe Drinking Water Act maximum contaminant level (MCL) for nitrate of 10 mg/L as a criterion for streams with a designated use of drinking water supply. Therefore, this TMDL used a nitrate nitrogen concentration of 10 mg/L as the target concentration (endpoint). Days Creek was not included on the 2002 Texas 303(d) list because domestic water supply is not a designated use for the portion of Days Creek in Texas. Historical monitoring data for nitrate have been collected in Days Creek at the Texas/Arkansas state line by TCEQ (Texas Commission on Environmental Quality) and several miles downstream of the state line by ADEQ. These data were analyzed for long term trends.