关键词：农药；水污染监测；水质
摘 要：The Arroyo Colorado is an ancient channel of the Rio Grande River that extends eastward for about 90 miles from near the city of Mission, Texas through southern Hidalgo County to the city of Harlingen in Cameron County, eventually discharging into the Laguna Madre near the Cameron- Willacy County line. The tidal segment of the Arroyo Colorado, as classified by the Texas Commission on Environmental Quality (TCEQ), is between the confluence with Laguna Madre in Cameron/Willacy County to a point 100 meters (110 yards) downstream of Cemetery Road, south of Port Harlingen in Cameron County. This part of the river is also defined as a coastal natural resource area (CNRA) and a coastal wetland in the Coastal Coordination Act. Water quality monitoring over the past decade has confirmed low oxygen levels and escalated ammonia and nitrate concentrations that have contributed to multiple fish kills in the tidal segment. These sub-optimal aquatic conditions resulted in this portion of the Arroyo Colorado being placed on the Texas Water Quality Inventory and 303(d) List for high aquatic life use impairment in 2002. Numerous urban sources, such as point source wastewater discharges, have contributed to this impairment; however, according to the Arroyo Colorado Watershed Protection Plan (ACWPP), nonpoint source agricultural runoff accounts for much of the water quality issues in the tidal segment.