c/ ' » ; ' .-/ ¿¡feTT^/S'/'73 ;:i C^*i' 1 M ENVIRONMENTAL STUDY ■ -4 FOR THE M GILA RIVER M BELOW PAINTED ROCK DAM M ■ :s •J By '4 ■4 University of Arizona ■ it School of Earth Sciences Office of Arid Lands Studies TD 194.56 .A6 P356 1970 |ii,t i,Bjp j i i | M I .....-rr/M m i1 r . w 1 1 IMI "" t I -"ai ion vtKv A d V \ ENVIRONMENTAL STUDY FOR THE GILA RIVER BELOW PAINTED ROCK DAM Under Contract with Department of the Army Los Angeles District Corps of Engineers Contract Number DACW09-70-C-0079 by University of Arizona School of Earth Sciences Office of Arid Lands Studies Y ¡11 October 1970 Bureau 01 Ru:!s; nc it! on Derwui, Uolorao10 The Gila River at the Dome Gaging Station. Photograph taken December 23, 1930 by U.S.G.S. Matched photograph taken June 23, 1970 by Office of Arid Lands Studies. Significant changes include considerably more sur­ face water and heavy salt cedar growth, apparently a result of heavy irrigation runoff and perhaps the close proximity of bed­ rock to the surface. The line of young cottonwoods (center) has disappeared. CONTENTS «»•«»»••»»•••si« -«-wit* ilij ■_ j o*> ' r ■ .. \ t > . ' P FRONTISPIECE............... iSi FIGURES .... ... .................. • * i* TABLES ...................... ............ xi ABSTRACT ........................................... • • • xiii INTRODUCTION............................... 1 Location and Extent . .......... ............ 1 Authority ........ .................... 1 Object and Scope of Study ....•••••«••••»••» 1 General Organization and Procedures ............ ..... 2 SURVEY AND INVENTORY .......................... 2 Geology, Landforms, and Surficial Deposits ....... .... 2 Structure, Earthquakes, and Economic Geology ....... 4 Channel Characteristics of the Lower Gila River ....... 4 Characteristics of the Major Tributary Washes............ 5 CLIMATE .................................... 8 WATER FEATURES................................. 9 Surface Water ........................... 9 Irrigation....................... »,« 10 Groundwater ............ ....... .............. 11 Hydrology............... 12 VEGETATION.............................. 13 Important Species .. ............. ........... 13 v Page Subunits .................... 16 Plant Communities ....... ...................... ... 17 / ' Floodplain Plant C o m m u n i t i e s ............ ................. 17 Plant Communities of the Floodplain as ;7- .Designated for Impact Studies .......... ......... 18 Description of Communities ..................... ............ 22 Successional Changes .... .......... .......... 22 Upland Plant Communities ..... ........ ........ 23 Intermont Plains and Bajadas ........ ........... 25 Sandy Plains and Dunes ................................. 25 Malpais Fields and Volcanic Hills .......... .......... 26 Older Volcanics.............. 26 Granitic Mountains and Hills ............................... 26 Successional Changes . ........ ............ 27 ANIMAL LIFE ................ 27 B i r d s .............. 27 Other Animals.................. 29 Rare and Endangered Species ............................... 30 Insect Population........................ 31 ESTHETIC VALUES ........... ........ 31 Contemporary Recreational Use ........... ........ 31 Archaeologic and Historic Sites 32 LAND U S E ........................ 33 Land Status .......... .......... ................ 33 Farmlands . ................... 34 vi c INTERRELATIONSHIPS .............. ............ 36 EVALUATION OF ALTERNATE PROPOSALS .............. 38 CONCLUSIONS ..... ........................ 45 Impacts of No Program ..... ............ 45 Impacts of Proposed Program ......... 47 Adverse Environmental Effects ............ 49 Alternatives to the Proposed Action ........ 50 Relationships between Long and Short-Term Uses 52 Irreversible and Irretrievable Commitments 53 APPENDICES A. Individuals and Organizations Contacted * . 55 B. Scientific and Common Names of Plants .... 57 C. Birds . ..................... .. ............. 63 D. Other Animals ............ .................. 67 E. Flood Control Plans ........................ 69 F. Alternative Plans, 23 June 1970 ............ 77 6. Selected References ............ .......... 81 H. Project Personnel . ...................... 89 I. General Organization and Procedures ........ 91 vii LIST OF FIGURES Page Frontispiece - Matched photographs of the Gila River at the Dome Gaging Station 1930 and 1970 iii 1. Drainage Àrea for the Gila River below Painted Rock D a m ........ ...................... .. following 2 2. Generalized Geologic Map .......... .. following 3 3. Histograms of Sediment Sample Size . following 4 4. Historic and Prehistoric sites .................. following 32 5. Interrelations in the Ecosystem ........ .. following 36 6. Map below 5th Street . ............. .............. following 41 7. Ponded Area 30th Avenue .................. .. following 41 8. Ponded Area 39th Avenue .............. .. following 41 9. Ponded Area 42nd Avenue ......................... .. following 41 lx LIST OF TABLES Page 1. Summary of Stratigraphy of the Lower Gila River Watershed............ ............................ 3 2. Analysis of Soil Samples taken from Watersheds below Painted Rock Dam .......................... 6 3. Location of Soil Samples taken from Watersheds below Painted Rock Dam July 24, 1970 .................... .......................... 7 4. A Summary of the Soil Conditions as Indicated by the Principal Plant • Communities of the Southwestern Desert (After Shantz and Piemeisel, 1924) .......................... 19 5. Acreage of Ecological Types and Communities ........ 20 6. Acreage of Ecological Types by L o c a t i o n .................. .. 21 7. Historic and Prehistoric Sites .................... ..... 32a 8. Land Ownership Pattern, Yuma C o u n t y ................ .. 33 9. Farm Size Distribution Based on Irrigable Acres per Water Contract in 1960 ........ .......... 35 10. Acreage of Vegetation under Various Alternatives ............. 40 i xl ENVIRONMENTAL IMPACT STUDY ON THE GILA RIVER BELOW PAINTED ROCK DAM c ABSTRACT An environmental impact study of the proposed U. S. Army Corps of Engineers flood control project, on the Gila River in Arizona down­ stream from Painted Rock Reservoir, was conducted by the University of Arizona School of Earth Sciences. Utilizing consultants from several university departments, a survey and inventory of the following elements were made: geology, landforms, climate, water features including sur­ face water, irrigation and groundwater; vegetation, animal life, land use and esthetics, including recreation and archaeology. For the purpose of this study three ecological subregions were recognized. These were: (1) farmland, (2) non-cultivated floodplain, and (3) upland. The geology of the watershed is typically characteristic of the Basin and Range Physiographic Province. Sandy soils are characteristic of several contributing watersheds, resulting in a lack of heavy runoff in the last several decades. Other watersheds contributing considerably less area, have fairly high runoff characteristics. There has been little use of the area for recreation other than hunting and significant archaeological sites have already been destroyed. Seven floodplain and 5 upland plant communities were recognized. The most valuable wildlife habitat includes salt cedar/mesquite which provides for excellent dove nesting and cattail marsh which is particu­ larly rare in southern Arizona and provides nesting and food for a dozen or so species of birds and other animals. The bird survey and inventory of 142 species includes 53 species which were not previously listed for the area. The impact of the authorized plan and several alternatives was evaluated. Although all flood control alternatives provide adequate flood protection, they vary in their detrimental effects on wildlife hab­ itat. If phreatophyte and cattail marsh habitats were maintained outside the proposed levees, the difference between alternatives is of somewhat less concern since almost two thirds of salt cedar/mesquite and over one half of cattail marsh habitat is outside the right-of-way; however, the wildlife habitats are not now preserved by any appropriate federal or state agency. The sale and clearing of several thousand acres of habitat, classified as irrigable lands and withdrawn for the original irrigation project, are planned in the near future. xiii ENVIRONMENTAL IMPACT STUDY ON THE GILA RIVER BELOW PAINTED ROCK DAM INTRODUCTION Location and Extent The project area under study lies between Texas Hill (river mile 68.5) and the Gila Siphon (river mile 8.4) in the Gila River Basin which in­ cludes most of the southern part of Arizona and a part of southwestern New Mexico. The drainage basin comprises about 58,200 square miles, 5,600 of which are in New Mexico; 51,500 in Arizona and 1,100 in Sonora, Mexico. The Gila River Basin downstream from Painted Rock Dam comprises about 7,300 square miles of which 2,700 square miles are between the dam and Texas Hill. Painted Rock Reservoir is an integral part of the flood control program, but at the time'this report was written, no flood con­ trol was contemplated between Painted Rock Dam and Texas Hill and hence, this evaluation is on alternative flood control proposals for the chan­ nel between Texas Hill and the Gila Siphon but recognizing that upstream flood control by Painted Rock Dam is an essential part of the program. Authority This ecological impact evaluation was initiated in compliance with Title I of Public Law 91-190 entitled National Environmental