About the Watershed
- Where is the Arroyo Colorado?
- Located in the Lower Rio Grande Valley of South Texas.
- Its headwaters are southwest of the city of Mission and it
drains into the Lower Laguna Madre.
- It is a sub-watershed of the Nueces-Rio Grande Coastal Basin,
also known as the South (Lower) Laguna Madre Watershed (Hydrologic
Unit Code 12110208).
- How big is the Arroyo Colorado?
- It is approximately 706 square miles (1,828 square kilometers)
or 451,840 acres (182,853 hectares).
- It is approximately 90 miles long.
- Average range of width is 40 to 200 feet.
- Average depth range can be as shallow as 2 feet or as deep as
- How do we use the Arroyo Colorado?
- Primarily as a floodway and a conduit for wastewater
- For commercial barge traffic and as a recreational area for
boating and fishing.
- An important nursery and foraging area for numerous marine
- Predominate land use within the watershed is agriculture
(~330,000 acres) with a rapidly growing urban populations.
- What feeds the Arroyo Colorado?
- It has a freshwater segment (Segment 2202) and a tidally
influenced marine segment (Segment 2201).
- Perennial (year-round) flow is sustained mainly by flows from
municipal wastewater treatment facilities.
- Irrigation return flows and urban runoff supplement the flow on
a seasonal basis.
- What are impairments in the Arroyo Colorado?
- Segments 2201 and 2202 are listed as impaired for high bacteria
- Segment 2201 is also listed as impaired for low dissolved
- Nutrient concentrations (nitrogen and phosphorus compounds) are
high in both segments.
imagery and census data are also available.