User:ShoreCrab/Arroyo

ShoreCrab (talk) 17:29, 8 February 2009 (UTC)

The Arroyo Colorado is an 89 mi long coastal stream in the Lower Rio Grande Valley of south Texas. It extends from Mission, Texas in Hidalgo County eastward to the Lower Laguna Madre at the  Laguna Atascosa National Wildlife Refuge in  Cameron County.

Course
The source of the Arroyo Colorado is a wastewater treatment plant at Mission, Texas. It proceeds etc. - past Adolph Thomae Jr. County Park and the Laguna Atascosa National Wildlife Refuge, terminated as a branch of the Gulf Intracoastal Waterway.

Natural History
The Lower Rio Grande Valley is the most biologically diverse region in the United States. Characteristics accounting for the diversity of native species are its location in a funnel of the Mississippi Flyway, semitropical climate, peripheral species from adjacent Mexico, and a diversity of habitat types.

The Arroyo Colorado Watershed is in the Matamoran Biotic District of the Tamaulipan Biotic Province. Vegetation becomes less dense from the coast westward. The primary ecological systems along the banks of the arroyo are (1) Lower Rio Grande and Tamaulipan Riparian Woodlands and Forests dominated by sugar hackberry, cedar elm, Rio Grande ash, and honey mesquite and (2) Tamaulipan Mesquite Woodlands, dominated by honey mesquite. Black mangrove and salt flats communities occur near the mouth. Several of the rare plant species of the delta are more common along the arroyo than in other areas of the Rio Grande Valley. Naturally vegetated areas along the arroyo remain as remnant brush tracts separated by urban and agricultural development. The riparian zone is routinely cleared of brush in some areas as a flood control measure.

The dredged portion of the arroyo between its mouth and the Port of Harlingen is estuarine and is termed its "tidal segment." The dominant fish species in this segment are gulf menhaden, spot croaker, Atlantic croaker, pinfish, and white mullet. Marine game fishes (see Sports Fishing) are more abundant in the lower one-half of the tidal segment. Dominant invertebrates are white shrimp, brown shrimp, and grass shrimp. Atlantic bottlenose dolphin are also present. The tidal segment is a nursery for economically important species. A salt water wedge often forms in the tidal segment and some areas experience oxygen depletion and associated fish kills, especially during warmer months. The "non-tidal segment" of the arroyo is between its source and the Port of Harlingen. Dominant fish in the non-tidal segment are gizzard shad, white mullet and Mozambique tilapa; several estuarine species are also present. The invertebrate fauna is primarily benthic, dominated by oligochaetes and chironomids.

One plant (Texas ayenia) and twenty-five animal species associated with the arroyo are listed as endangered or threatened. These include Coues' rice rat, white-nosed coati,  Mexican treefrog,  white-lipped treefrog, South Texas lesser siren,  speckled racer,  Texas hornshell, reddish egret, common black hawk, wood stork, and piping plover.

Nature Enjoyment and Nature Tourism
Combined annual direct travel expenditures in Cameron and Hidalgo Counties is $1.78 billion, and nature-based tourism has an increasingly important roll. The Rio Grande Valley Birding Festival alone generates over $1.5 million in total economic impact each year. The Rio Grande Valley hosts annual nature, birding, butterfly watching, and dragonfly watching festivals. The World Birding Center was developed to support the growth of nature tourim in the Valley; it is comprised of nine parks and nature centers paralleling the Arroyo Colorado and Rio Grande. The Estero Llano Grande State Park and Harlingen-Arroyo Colorado Park components are on the arroyo itself. Other notable nature watching sites on the Arroyo Colorado are Laguna Atascosa National Wildlife Refuge,  Las Palomas Wildlife Management Area – Arroyo Colorado Unit, Adolph Thomae Jr. County Park, the City of Rio Hondo, and the Port of Harlingen.

Birds: The Lower Rio Grande Valley is often considered the number-two birding destination in North America ; it has a bird checklist of over 500 species of birds, including several species found nowhere else in the United States. Some birds of national interest associated with the arroyo are least grebe, neotropic cormorant,Black-bellied whistling-duck, fulvous whistling-duck, mottled duck, ringed kingfisher, green kingfisher, and green jay.

Butterflies: The Lower Rio Grande Valley supports the largest and most diverse butterfly fauna in the United States. Approximately three-fifths of the butterfly species recorded in the United States occur in the region, and seventy of these have been documented nowhere else in the country. Hugh-Ramsey Arroyo Colorado Park and Laguna Atascosa National Wildlife Refuge are Arroyo locations with state-wide significance for butterfly watching.

Dragonflies: Odontate (dragonflies and damselfles) watching has become a popular pastime in recent years. The Rio Grande Valley habitats support 75 dragonfly and 29 damselfly species. Some representatives of neotropical genera not widespread in the United States are narrow-winged damselflies (Acanthagrion & Neoerythromma), skimmers (Brachymesia,  Tholymis & Micrathyria), pinflies (Neoneura), and clubtail drafonflies ( Phyllogomphoides).

Dolphin: Several boating guides in Cameron County offer dolphin watching excursions. Atlantic bottlenose dolphins frequent the Arroyo's tidally influenced portion and are viewed from the shoreline and from boats.

Fishing
Marine sports fishes of the lower arroyo include spotted seatrout, red drum, southern flounder, common snook, and tarpon. Targeted species in lower salinity water include alligator gar, longnose gar, smallmouth buffalo, largemouth bass, and channel catfish. Docking and launching facilities in the eastern portion allow boaters' access to both the arroyo and the Laguna Madre. Alligator gar is the most popular targeted species for bowfishers, but other are the longnose gar, common carp, grass carp, Mozambique tilapa, and white mullet.

Geology and Hydrology
The Lower Rio Grande Valley is part of the Rio Grande delta. The Arroyo was an ancient Rio Grande distributary that captured part of the flow when the Rio Grande's water height rose during floods. It is fed primarily by irrigation return flow and treated municipal wastewater. It probably began headward erosion during the last glaciation and eventually pirated drainage from the northern part of the Holocene-Modern Rio Grande Floodplain.

Post glacial period: During the last glacial period global sea level sea level was about 400 ft below it's current level. About 15,000 to 10,000 years BP glacier melting resulted in global sea level rise. Beginning in the mid to late Holocene, about 10,000 B.P. to  7,000 B.P., the Rio Grande reversed estuarine transgression and began to prograde its delta over earlier Holocene transgressive deposits. Contemporaneous with delta progradation, the upstream Rio Grande slowly filled its subaerial valley by meanderbelt (pointbar) and flood-basin mud deposition. Sediment supply and, consequently, delta progradation began to diminish about the time sea level had risen and reached its approximate present level (4,500 B.P.).

Sea level stabilization: Since about 2,800 B.P. to 2,500 years B. P., when sea level stabilized, the coastal zone has gradually evolved to its present condition by erosion, deposition, compaction, and subsidence-processes still important and operating today. . Padre Island and the Laguna Madre formed. The Rio Grande abandoned the Arroyo Colorado as its primary discharge channel and began to discharge directly into the open Gulf of Mexico.

Modern geological history: When intense hurricanes such as Beulah, Allen, and Dolly are centered over the lower Rio Grande Valley, rainwater floods the abandoned channels and resacas as well as the many depressed flood basins of the relic delta plains. Resacas are filled, and the limited marshes are rejuvenated. For thousands of years the fresh water in the Arroyo was supplemented by Rio Grande flooding and large storm events. It would become an active system, discharging a vast volume of water from the northern floodbasin of the Rio Grande into the Laguna Madre.

Anthropogenic changes: Because of changes to the Rio Grande (Dams) and the Arroyo (levees), now only large storm events provide significant fresh water surges in the Arroyo Colorado. The primary water source for the modern Arroyo Colorado is municipal sewer discharges and irrigation return-flows of water ultimately pumped from the Rio Grande.

Pre-History and History
Pre-History: The Rio Grande Delta was inhabited by Late  Prehistoric hunter-fisher-gatherers designated as the Brownsville Complex (Brownsville-Barril Complex) people (800 AD – 1600 AD). Habitation and burial artifacts indicate an extensive shell industry, including the manufacture of tools and ornaments. Presence of jadeite, obsidian and pottery indicate direct or indirect trade with the Huastec people of the Tamaulipas, Mexico area. The higher landforms of the Arroyo Colorado were important burial and cemetery archeological sites of the Brownsville Complex and are not associated with habitation sites. A burial site at the mouth of the Arroyo is dated as Late Archaic (400 BC – 800 AD).

Mexican-American War: At the onset of the Mexican-American War, General Zachary Taylor's "Army of Occupation" reached the Arroyo Colorado in its march to the Rio Grande on March 19, 1846. The following day, a small contingent of Mexican cavalry, dispatched by General Francisco Mexía, informed Taylor that his crossing the Arroyo would be considered an act of war. Taylor positioned artillery and crossed at a location known as Paso Real. His brief scrimmage with the few Mexicans was the first armed confrontation of the Mexican American War. The importance of the Arroyo to General Mexía was two-fold. He knew it was his only effectual line of resistance because of its difficulty to ford; Taylor assumed the line would be the Rio Grande. Secondly, the port of Brazos Santiago is between the Rio Grande and Arroyo, and it was the only practical funnel through which commerce could pass into northern Mexico. Taylor proceeded to Point Isabel (now Port Isabel) and established a base at the port of Brazos Santiago, negating the strategic importance of the Arroyo.

American Civil War: When  Confederate ports were blockaded during the American Civil War, all Confederate cotton for export was transported across the Arroyo at Paso Real in route to Bagdad, Tamaulipas Mexico for shipment to Europe.

Recent History: A hand-drawn ferry at Paso Real was used by the  Brownsville - Alice Stagecoach line until the arrival of a railroad in 1904. It continued to be used for local travel until 1935. The Arroyo's first railroad bridge was completed in 1904 and the wooden bridge was replaced in 1905 by an iron bridge.

Navigation and Port of Harlingen
The Arroyo Colorado Navigation District of Cameron and Willacy counties was formed in 1927. The 22 mi long tidal portion of the Arroyo was dredged for barge traffic between the Port of Harlingen and the Gulf Intracoastal Waterway from 1938 to 1951. Barge traffic is a crucial link for carrying cargo, especially raw sugar and crude oil to market and for supplying the area with fertilizer, refined petroleum, and building materials, especially sand.


 * of Harlingen website''

Irrigation
The first irrigation network in the delta was constructed in 1895 to support a sugar plantation that ultimately failed due to financial problems. Irrigation projects by land developers prior to 1904 were limited in scope. Land development including irrigation projects rapidly increased after the arrival of the railroad in 1904.

Irrigation water in the Lower Rio Grande Valley is pumped from the Rio Grande and distributed through pipes and irrigation canals to farms. Irrigation return flow is channeled through drainage systems into the Arroyo Colorado except in southeastern Cameron County. (see International Boundary and Water Commission for relevant treaties)

Flood Control
A joint Mexico – United States flood control project for the Rio Grande Delta was initiated in 1932 with levee construction to  guide part of the U.S. allocation of flood diversion into the headwaters of the Arroyo Colorado. An expansion in 1960 included construction of Anzalduas Diversion Dam on the Rio Grande near the city of Mission, Texas and expansion of the interior levee system. The diverted water reaches the Arroyo through a short levee system known as the "Banker Floodway." The first 29 mi of levees constitute the "Main Floodway," with the Arroyo acting as its pilot channel. The Main Floodway drains into the shallow Llano Grande Lake near the city of Mercedes, Texas. There, flood waters are proportioned between the Arroyo and a levee system known as the "North Floodway." The North Floodway is 46 mi long and drains to the Laguna Madre north of the mouth of the Arroyo. Most of the North Floodway is floored by agricultural land. Designed elevation differences prevent water from entering the North Floodway until the flow in the Arroyo exceeds 40 cuft/s. Designed flows are: Main Floodway = 105,000 cfs (2,970 cms); North Floodway = 84,000 cfs (2,380 cms); Arroyo Colorado east of Llano Grande Lake= 21,000 cfs (590 cms)

Water Quality
Use of the water in the Arroyo Colorado for municipal, industrial or irrigation purposes is severely limited because of poor water quality conditions. Salinity concentrations in the Arroyo typically exceed the limits considered desirable for human consumption as well as those acceptable for irrigation of crops. None of the Arroyo meets the state’s water quality standards designed to protect aquatic life use. It exceeds state standards for waterborne bacteria levels and fish tissue mercury and PCB levels in smallmouth buffalo and longnose gar. A portion of the tidal segment near Rio Hondo also fails to meet state water quality standards because of depressed dissolved oxygen.

The Arroyo is highly eutrophied due to chemical nutrient inputs from municipal wastewater treatment plants and from excess fertilizer carried into the stream by irrigation water and rain water runoff and leaching. High nutrient loading promotes a dense growth of suspended microalgae. Oxygen consumption, especially by bacteria and nighttime respiration of microalgae, results in hypoxic conditions unhealthy for aquatic life. The salt water wedge and high banks near the City of Rio Hondo contribute to persistently low dissolved oxygen concentrations in that area. Resource managers have expressed concern that the Laguna Madre seagrass ecosystem may be degraded by the Arroyo’s nutrient input.

In 1998, the Texas Commission on Environmental Quality initiated an effort to develop a Total Maximum Daily Load (TMDL) for pollutants contributing to low dissolved oxygen in the stream’s tidal portion. It was completed in 2002, but was not adopted. Rather, the commission began development of a watershed protection plan to address the problem. This led to the establishment of the Arroyo Colorado Watershed Partnership in July 2003. The partnership is organized with a steering committee and five work groups (habitat restoration, wastewater infrastructure, refinement of the TMDL, agricultural issues, and outreach and education).


 * Arroyo Colorado Watershed Partnership website

Folklore
Many years ago a rancher traveling from Veleño to Matamoros Mexico buried his gold under a mesquite tree on the bank of the Arroyo Colorado and took a swim. The water made him go blind, and he was unable to find his gold which has never been recovered. Many of the area’s inhabitants refused to bathe in the arroyo afterwards.