By Mary Waters, Texas Stream Team

Outline  About the Arroyo Colorado  Basic information (geography)  History  Major uses  Water quality summary  Segment 2202  Professionally collected data  Volunteer collected data  Segment 2201  Professionally collected data  Volunteer collected data  Watershed protection and TMDL

About the Arroyo Colorado  90 mile long water body with a watershed of 700 square-miles  Starts Southwest of Mission, TX and ends at the Laguna Madre  Upstream segment to Port Harlingen is freshwater, and downstream segment is tidal  Its source water is effluent from municipal wastewater- treatment plants, irrigation return flow, and storm water runoff, and base flows from shallow groundwater. During flooding, Rio Grande water can supply flows to the Arroyo Colorado

Arroyo Colorado Watershed and Major Stream Segments

History  Before the turn of the century, the natural stream meandered from the Rio Grande to the coast in a delta of thick semi-tropical forests and ending in a series of brackish wetlands  Land was cleared in the 1920’s and ‘30’s to make way for agriculture  Irrigation canals were built between 1900 and the early 1930’s.  The late 1940’s brought a large- scale flood control project to the entire Lower Rio Grande Valley

Major Uses  A floodway  A conduit for wastewater conveyance  Irrigation source  Recreational fishing and boating  Fish Consumption  Commercial barge traffic  Nursery for fish, shrimp and crab  Major source of freshwater to the Laguna Madre  Habitat

Biodiversity  Neotropical migratory songbirds, snakes, lizards, fish and invertebrates  Mammals  Ocelot  Jagaurundi  Salamanders  Black-spotted newt  Lesser Rio Grande siren

Water Quality  Water quality summary  Segment 2202  Volunteer collected data  Professionally collected data

Causes of Water Quality Degredation  Pollutant loading  Degradation and loss of aquatic and riparian habitat  More than 95% of the native brush land in the Lower Rio Grande Valley has been cleared for agriculture and urban development  Dredging for Barge Traffic

Professional Data  TCEQ’s Surface Water Quality Monitoring (SWQM) program.  The Nueces River Authority (NRA)  48 monitoring stations: 35 in Segment 2202 (non-tidal) 13 in Segment 2201 (tidal)

Volunteer Data

Professional Data Monitoring Sites

Segment 2202 (Headwaters to Port of Harlingen)  Professional Data - Impairments

2202 Dissolved Oxygen and Water Temperature

Above Criteria Data (Professional)  Dissolved Oxygen: 1 of 35 below criteria

Fecal Bacteria – 2202  E.Coli and Enterococcus  Exceed the criteria

Segment 2201 (Port of Harlingen to Laguna Madre)  Professional Data - Impairments

Dissolved Oxygen  High Aquatic Life use designation  Associated 24- hour DO criterion:  Average 4.0 mg/l  minimum 3.0 mg/l.  Diurnal Variability: Low in the night and High in the afternoon  6 of 13 stations showed values below the criteria

Causes of Low Dissolved Oxygen in Segment 2201  nutrient loading from the watershed  hydraulic effects in the dredged navigational channel

Nutrient Enrichment Problems Entire Arroyo Colorado  Nitrogen exceed the screening criteria from 1990 – 2006, increasing over time  Phosphorus concentrations exceed the screening criteria from , remaining the same over time  Chlorophyll-a, an indicator of excessive algal growth, exceed the screening criteria, reaching very high levels from (a similar trend to Nitrogen)

Fecal Bacteria  Figure 21. shows E. coli and Enterococcus  concentrations at water quality stations located  upstream (13074) and downstream (13072) of the  Tidal Segment boundary of the Arroyo Colorado from  2001 to E. coli concentrations in the Above Tidal  Segment of the Arroyo Colorado exceed the criteria  more frequently than in the Tidal Segment. The Above  Tidal Segment of the Arroyo Colorado is currently listed  on the 2004 Texas 303(d) list for elevated levels of E.  coli.

42 Fish Kills Documented  Agriculture (7),  Aquaculture (1)  Industry (12)  Municipal (5)  Natural processes (8)  Unknown (4)  Weather (5)  In 34 of the 42 events, the direct cause of the fish kills was low dissolved oxygen in the water column  Most occurred in the tidal segment

Data Comparisons Does the volunteer data show improvements or continued impairments?  Professional  Volunteer  graph  Table  Conclusions

Sources  QualityWater-Quality and Ancillary Data Collected From the Arroyo Colorado Near Rio Hondo, Texas, 2006  By Meghan C. Roussel, Michael G. Canova, William H. Asquith, and Richard L. Kiesling USGS  Handbook of Texas Online, Texas State Historical Association  A Watershed Protection Plan for the Arroyo Colorado – Phase I, 2007 (A Report of the Arroyo Colorado Watershed Partnership and Texas Sea Grant Pursuant to a 2003 USEPA Clean Water Act Section 319(h) Grant Awarded through Texas Commission on Environmental Quality Contract Agreement )  Ocelot Image courtesy of tpwd.state.tx.us  Spoonbill image courtesy of lagunamadre.net