Watershed Protection Plan - Lower Rio Grande Valley Development ...

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THE ARROYO COLORADO WATERSHED the Donna Wastewater Treatment Plant ditch (unnamed), and an unnamed ditch at IBWC Gate No. 23-L (Figure 6). Natural overland drainage to the Arroyo Colorado is restricted due to the absence of signifi cant topographic relief and intense land development. Subsurface drainage, similarly, is limited because soils are generally saturated due to shallow groundwater levels. The shallow water table tends to intersect even shallow channels, which, when combined with the high permeability of host sediments, result in a high degree of communication between groundwater and surface water (TWC, 1990). Measuring fl ow above tidal infl uence levees. This freshwater segment of the Arroyo Colorado averages less than 40 feet wide and is approximately two to three feet deep. The channel bottom is composed mainly of loosely consolidated silty-clay sediments and the sparsely vegetated banks are in a continual state of sloughing. The Arroyo Colorado Tidal (Segment 2201) is dredged to accommodate barge traffi c to the Port of Harlingen and is characterized by steep eroding slopes with bank heights up to 50 feet. The steep banks are partly the result of the placement of dredge spoil material on the banks of the stream. In the upper portions of the tidal segment, the steep banks are thought to occasionally impede the fl ow of air across the surface of the stream, which can reduce aeration and vertical mixing, factors that contribute to the low levels of dissolved oxygen observed in this portion of the stream. The average width of the tidal segment of the Arroyo Colorado is about 200 feet and the average depth is 13 feet. Being tidally infl uenced, it is brackish to saline (slightly salty to very salty) and usually stratifi es under warm weather conditions, forming layers of warmer, fresher water on the surface and cooler, more saline water near the bottom. For most of its course, the tidal segment of the Arroyo Colorado has a signifi cant degree of natural sinuosity. However, sinuosity in the tidal segment of the Arroyo Colorado is severely diminished in the fi nal four miles of the stream as the Arroyo Colorado fl ows into a man-made channel that leads to the Intracoastal Waterway and the Lower Laguna Madre. Tributary infl ows to the Arroyo Colorado occur through an extensive network of drainage ditches. The four major tributary ditches that fl ow into the Arroyo Colorado are the Banker Floodway, Arroyo Anacuitas, Topography Generally, water fl ows on gentle slopes from west to east through the heart of the Lower Rio Grande Valley. The region is a fl at coastal plain with an average slope of less than 1.5 feet per mile. The highest elevation in the Arroyo Colorado watershed is about 120 feet above mean sea level. Some common natural landscape features in the Lower Rio Grande Valley are depressions, resacas (oxbow lakes), salt lagoons, coastal marshes, tidal fl ats, point-bars and barrier islands. Man-made landscape features include levees, drainage ditches and raised irrigation canals. Geology and Soils The upper two-thirds of the Arroyo Colorado are underlain by alluvium consisting mostly of muds and silts deposited by the Rio Grande, while the lower onethird is underlain by barrier island deposits of mostly sand with some silt and clay. Almost all of the deposits underlying the Arroyo Colorado are of Holocene origin except for a short distance in the lower one-third of its course where the Beaumont Formation, of Pleistocene Channelized portion of the Arroyo Colorado Tidal near the confluence with the Lower Laguna Madre. Arroyo Colorado Watershed Protection Plan 24 January 2007
THE ARROYO COLORADO WATERSHED origin, abuts the northern and western banks of the Arroyo Colorado (Brown et. al., 1980). The geologic age of the sediments in the region increase in age from east to west. The Pleistocene sediments, otherwise called the Beaumont Formation, were deposited after the last interglacial period about 70,000 years ago. This formation is composed mostly of clay with some fi ne sand and silt. The Holocene sediments (approximately 10,000 years old) consist of sands and silts and are both open marine and meandering fl uvial (Figure 7). The Lower Rio Grande Valley region is characterized by its unconsolidated soil substrate. The soils in the Arroyo Colorado watershed are clays, clay loams and sandy loams (Figure 8). Most soil depths range from about 63-78 inches. The Harlingen, Mercedes and Raymondville soil series consist predominantly of clay soils with low permeability. A representative soil profi le consists of about 71-78 inches of clay. The Hidalgo, Rio Grande and Willacy soil series consist predominantly of sandy loam and sandy clay loam soils with moderate permeability. A representative soil profi le consists of about 14-15 inches of sandy loam overlying 48-60 inches of sandy clay loam. The Arroyo Colorado fl ows over the fl uvio-deltaic plain of the Rio Grande. Fluvio-deltaic plains are large geographic features that form in coastal areas near the outlet of large rivers. Fluvio-deltaic sediments are typically composed of interwoven lenses of sands, silts and clays deposited by rivers as they reach the coast and distribute their load of fi ne, organic-rich sediment Areal view of the Arroyo Colorado above the Laguna Atascosa over a triangular coastal region known as the delta plain. The entire delta plain of the Rio Grande slowly subsides or sinks, as does the entire Gulf Coast. However, subsidence rates in the Rio Grande Valley (~6 mm/yr) are some of the lowest in the Gulf Coast. Delta plains are typically fertile and make ideal environments for agricultural development. Natural sedimentation in a delta plain occurs as the result of overbank deposition during natural cycles of fl ooding. Much of the natural sedimentation that formed the fl uvio-deltaic plain of the Rio Grande is, today, largely inhibited by fl ood control and conveyance structures that protect urban areas from catastrophic fl ooding and divert water for human use. Groundwater in the Rio Grande Valley is typically Figure 7. Surface Geology in the Arroyo Colorado Watershed Legend Hfs - fill and spoil Qac - Alluvium in Rio Grande, subdivided into areas predominantly of c Qal - alluvium Qas - Alluvium in Rio Grande, subdivided into areas predominantly of s Qbc - Beaumont Formation, areas predominantly clay Qbr - barrier ridge and barrier flat deposts Qbs - Beaumont Formation, areas predominantly sand Qbv - in Rio Grande delta area, clay veneer over meanderbelt sand Qcd - clay dune Qds - dune sand sheet deposits Ql - Lissie Formation water - water Data Source: United States Geogological Survey Texas Bureau of Economic Geology Barnes 1992 Geologic Map of Texas Map Source: Texas Coastal Watershed Program www.Urban-Nature.org ¯ 0 2.5 5 10 Miles Laguna Madre Arroyo Colorado January 2007 25 Arroyo Colorado Watershed Protection Plan
Page 2 and 3: Photos courtesy of Brand Cowan, Cam
Page 5 and 6: CONTENTS ACKNOWLEDGEMENTS .........
Page 7 and 8: CONTENTS - FIGURES Habitat Restorat
Page 9: TABLES LIST OF TABLES Table 1. Tabl
Page 13 and 14: EXECUTIVE SUMMARY The Arroyo Colora
Page 15 and 16: EXECUTIVE SUMMARY Habitat Approxima
Page 17 and 18: EXECUTIVE SUMMARY management practi
Page 19 and 20: EXECUTIVE SUMMARY Elements of the W
Page 22 and 23: INTRODUCTION In its most pristine c
Page 24 and 25: INTRODUCTION Colorado, where physic
Page 27 and 28: THE ARROYO COLORADO WATERSHED PARTN
Page 34 and 35: THE ARROYO COLORADO WATERSHED The A
Page 38 and 39: THE ARROYO COLORADO WATERSHED Figur
Page 40 and 41: THE ARROYO COLORADO WATERSHED Table
Page 42 and 43: THE ARROYO COLORADO WATERSHED Resac
Page 45 and 46: STATE OF THE WATERSHED From a natur
Page 47 and 48: STATE OF THE WATERSHED resacas loca
Page 49 and 50: STATE OF THE WATERSHED Water Qualit
Page 51 and 52: STATE OF THE WATERSHED Table 8. Des
Page 53 and 54: STATE OF THE WATERSHED Figure 12. L
Page 55 and 56: STATE OF THE WATERSHED Figure 14. 1
Page 57 and 58: STATE OF THE WATERSHED Figure 18. T
Page 59 and 60: STATE OF THE WATERSHED Figure 20. T
Page 61 and 62: STATE OF THE WATERSHED facilities a
Page 63 and 64: STATE OF THE WATERSHED controlled.
Page 65 and 66: STATE OF THE WATERSHED Tree plantin
Page 67 and 68: XXX Arroyo Colorado Watershed Prote
Page 69 and 70: POLLUTION IN THE ARROYO COLORADO
Page 71 and 72: POLLUTION IN THE ARROYO COLORADO 1)
Page 73 and 74: POLLUTION IN THE ARROYO COLORADO St
Page 76 and 77: INSTITUTIONAL FRAMEWORK Successful
Page 78 and 79: INSTITUTIONAL FRAMEWORK the water r
Page 80 and 81: INSTITUTIONAL FRAMEWORK managing pr
Page 82 and 83: INSTITUTIONAL FRAMEWORK criteria fo
Page 84 and 85: INSTITUTIONAL FRAMEWORK pertaining
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ELEMENTS OF THE ARROYO COLORADO WAT
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EDUCATION AND OUTREACH Fostering lo
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EDUCATION AND OUTREACH • Distribu
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EDUCATION AND OUTREACH quality prob
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EDUCATION AND OUTREACH • Develop
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EDUCATION AND OUTREACH take to do t
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EDUCATION AND OUTREACH industry, de
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EDUCATION AND OUTREACH To support m
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EDUCATION AND OUTREACH members of t
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ESTIMATED WATERSHED LOADINGS AND LO
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WATER QUALITY MONITORING PLAN Figur
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WATER QUALITY MONITORING PLAN Figur
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WATER QUALITY MONITORING PLAN Autom
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TECHNICAL AND FINANCIAL ASSISTANCE
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SOURCES OF TECHNICAL AND FINANCIAL
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IMPLEMENTATION SCHEDULE Federal CWA
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IMPLEMENTATION SCHEDULE Table 24. T
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IMPLEMENTATION SCHEDULE TMDL Monito
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MEASURING PROGRESS The ultimate mea
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MEASURING PROGRESS Table 25. Criter
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MEASURING PROGRESS Table 27. Milest
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APPENDICES HUC HWWS IBWC IMAS km LL
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APPENDICES APPENDIX B Arroyo Colora
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APPENDICES arise necessitating the
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APPENDICES c. Committee Members: Co
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APPENDICES APPENDIX C Arroyo Colora
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APPENDICES FRANK MARTINEZ IBWC JAME
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APPENDICES WESLEY ROSENTHAL TAMU JE
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APPENDICES APPENDIX E Rare Plants a
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APPENDICES Common Name Scientific N
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APPENDICES APPENDIX F Locally Activ
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APPENDICES Gorgas Science Foundatio
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APPENDICES Endangered Species Act T
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APPENDICES APPENDIX H List of Feder
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APPENDICES Common Name Scientific N
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APPENDICES APPENDIX I Selected Mars
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APPENDICES Mid-Depths - 15 to 50 cm
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REFERENCES Arnold, J.G., P.M. Allen
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REFERENCES IBWC, 2003. Hydraulic Mo
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REFERENCES TAES (Texas Agricultural
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REFERENCES USEPA, 1999. Draft Guida
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