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Phoenix, AZ, United States

Eakin H.,Arizona State University | York A.,Arizona State University | Aggarwal R.,Arizona State University | Waters S.,Sonoran Institute | And 5 more authors.
Regional Environmental Change | Year: 2015

The prospect of unprecedented environmental change, combined with increasing demand on limited resources, demands adaptive responses at multiple levels. In this article, we analyze different attributes of farm-level capacity in central Arizona, USA, in relation to farmers’ responses to recent dynamism in commodity and land markets, and the institutional and social contexts of farmers’ water and production portfolios. Irrigated agriculture is at the heart of the history and identity of the American Southwest, although the future of agriculture is now threatened by the prospect of “mega-droughts,” urbanization and associated inter-sector and inter-state competition over water in an era of climatic change. We use farm-level survey data, supplemented by in-depth interviews, to explore the cross-level dimensions of capacity in the agriculture–urban nexus of central Arizona. The surveyed farmers demonstrate an interest in learning, capacity for adaptive management and risk-taking attitudes consistent with emerging theory of capacity for land use and livelihood transformation. However, many respondents perceive their self-efficacy in the face of future climatic and hydrological change as uncertain. Our study suggests that the components of transformational capacity will necessarily need to go beyond the objective resources and cognitive capacities of individuals to incorporate “linking” capacities: the political and social attributes necessary for collective strategy formation to shape choice and opportunity in the future. © 2015 Springer-Verlag Berlin Heidelberg

Nelson S.M.,6101 NE 102nd Avenue Apt. 5 | Fielding E.J.,Jet Propulsion Laboratory | Zamora-Arroyo F.,Sonoran Institute | Flessa K.,University of Arizona
Ecological Engineering | Year: 2013

The intertidal portion of Mexico's Colorado River Delta is a dynamic environment subject to complex interactions of tectonic, fluvial, and tidal forces at the head of the Gulf of California. We review the historical interactions of these forces, use sequential satellite images, overflights, ground observations, and interferometric synthetic aperture radar (InSAR) data to study the effects of the 2010 Mw 7.2 El Mayor-Cucapah Earthquake on changing patterns of tidal inundation within the Delta, and assess effects of these changes to the fluvial/hydrological regime of the Colorado River estuary and nearby Ciénega de Santa Clara wetland. The objectives of this study are to highlight for environmental scientists, land managers, and ecological engineers the contribution of tectonic forces in shaping the intertidal Delta environment and to provide information on the effects of the 2010 earthquake which will be of practical value in planning and designing management measures and restoration projects for the estuary and Ciénega.The Colorado River estuary is at present blocked by a tidal sand bar which restricts access by marine species to the upper estuary and obstructs the flow of fresh water into the lower estuary. Located 13. km east of the estuary, the Ciénega is a 6000. ha wetland supported by agricultural drain water from Arizona and Mexico. South of the Ciénega is the Santa Clara Slough, an unvegetated 26,000. ha basin subject to periodic inundation from the northern Gulf's high amplitude tides, which have historically reached the margins of the Ciénega several times each year.The El Mayor-Cucapah earthquake ruptured the previously unknown Indiviso Fault which extends into the intertidal zone just west of the Ciénega. The Ciénega experienced only minor surface deformation having no direct effects to the wetland. Most of the significant ground movement and surface deformation occurred west of the Indiviso Fault adjacent to the estuary, where portions of the intertidal flats underwent extensive liquefaction, northward coseismic displacement and post-seismic subsidence. These surface deformations changed the pattern of tidal inundation, triggering development of a new system of natural tidal channels and creating conditions favorable for installation of projects to restore connectivity between the upper and lower estuary. The changed pattern of tidal inundation may also have contributed to an observed reduction in the occurrence of tidal flooding along the southwestern margin of the Ciénega following the earthquake. © 2012 Elsevier B.V.

Mexicano L.,University of Arizona | Nagler P.L.,U.S. Geological Survey | Zamora-Arrroyo F.,Sonoran Institute | Zamora-Arrroyo F.,University of Arizona | Glenn E.P.,University of Arizona
Ecological Engineering | Year: 2013

The Cienega de Santa Clara is a 5600. ha, anthropogenic wetland in the delta of the Colorado River in Mexico. It is the inadvertent creation of the disposal of brackish agricultural waste water from the U.S. into the intertidal zone of the river delta in Mexico, but has become an internationally important wetland for resident and migratory water birds. We used high resolution Quickbird and WorldView-2 images to produce seasonal vegetation maps of the Cienega before, during and after a test run of the Yuma Desalting Plant, which will remove water from the inflow stream and replace it with brine. We also used moderate resolution, 16-day composite NDVI imagery from the Moderate Resolution Imaging Spectrometer (MODIS) sensors on the Terra satellite to determine the main factors controlling green vegetation density over the years 2000-2011. The marsh is dominated by Typha domingensis Pers. with Phragmites australis (Cav.) Trin. Ex Steud. as a sub-dominant species in shallower marsh areas. The most important factor controlling vegetation density was fire. Spring fires in 2006 and 2011 were followed by much more rapid green-up of T. domingensis in late spring and 30% higher peak summer NDVI values compared to non-fire years (P<. 0.001). Fires removed thatch and returned nutrients to the water, resulting in more vigorous vegetation growth compared to non-fire years. The second significant (P<. 0.01) factor controlling NDVI was flow rate of agricultural drain water from the U.S. into the marsh. Reduced summer flows in 2001 due to canal repairs, and in 2010 during the YDP test run, produced the two lowest NDVI values of the time series from 2000 to 2011 (P<. 0.05). Salinity is a further determinant of vegetation dynamics as determined by greenhouse experiments, but was nearly constant over the period 2000-2011, so it was not a significant variable in regression analyses. It is concluded that any reduction in inflow volumes will result in a linear decrease in green foliage density in the marsh. © 2012 Elsevier B.V.

Glenn E.P.,University of Arizona | Mexicano L.,University of Arizona | Garcia-Hernandez J.,Research Center En Alimentacion sarrollo Ac | Nagler P.L.,U.S. Geological Survey | And 5 more authors.
Ecological Engineering | Year: 2013

Evapotranspiration (ET) and other water balance components were estimated for Cienega de Santa Clara, an anthropogenic brackish wetland in the delta of the Colorado River in Mexico. The marsh is in the Biosphere Reserve of the Upper Gulf of California and Delta of the Colorado River, and supports a high abundance and diversity of wildlife. Over 95% of its water supply originates as agricultural drain water from the USA, sent for disposal in Mexico. This study was conducted from 2009 to 2011, before, during and after a trial run of the Yuma Desalting Plant in the USA, which will divert water from the wetland and replace it with brine from the desalting operation. The goal was to estimate the main components in the water budget to be used in creating management scenarios for this marsh. We used a remote sensing algorithm to estimate ET from meteorological data and Enhanced Vegetation Index values from the Moderate Resolution Imaging Spectrometer (MODIS) sensors on the Terra satellite. ET estimates from the MODIS method were then compared to results from a mass balance of water and salt inflows and outflows over the study period. By both methods, mean annual ET estimates ranged from 2.6 to 3.0mmd-1, or 50 to 60% of reference ET (ETo). Water entered at a mean salinity of 2.6gL-1 TDS and mean salinity in the wetland was 3.73gL-1 TDS over the 33 month study period. Over an annual cycle, 54% of inflows supported ET while the rest exited the marsh as outflows; however, in winter when ET was low, up to 90% of the inflows exited the marsh. An analysis of ET estimates over the years 2000-2011 showed that annual ET was proportional to the volume of inflows, but was also markedly stimulated by fires. Spring fires in 2006 and 2011 burned off accumulated thatch, resulting in vigorous growth of new leaves and a 30% increase in peak summer ET compared to non-fire years. Following fires, peak summer ET estimates were equal to ETo, while in non-fire years peak ET was equal to only one-half to two-thirds of ETo. Over annual cycles, estimated ET was always lower than ETo, because T. domingensis is dormant in winter and shades the water surface, reducing direct evaporation. Thus, ET of a Typha marsh is likely to be less than an open water surface under most conditions. © 2012 Elsevier B.V.

Nelson S.M.,Apt Therapeutics, Inc. | Zamora-Arroyo F.,Sonoran Institute | Ramirez-Hernandez J.,Autonomous University of Baja California | Santiago-Serrano E.,Sonoran Institute
Ecological Engineering | Year: 2013

An obstructive tidal sandbar forms in the estuary of the Colorado River, Mexico, during periods of low fluvial discharge. The sandbar typically develops at a bedload convergence zone centered approximately 30. km landward from Montague Island near the river's mouth. The estuary provides important spawning habitat for the endangered totoaba (Totoaba macdonaldi) and commercially exploited Gulf corvina (Cynoscion othonopterus), as well as habitat for larval shrimp, all of which are impacted by reduced freshwater/sea water mixing when the sandbar is present.Sequential satellite images, aerial photographs, overflights, and ground observations were used to document the geomorphology of the tidal sandbar and its formation, removal, and subsequent reappearance in response to long-term variations in fluvial flow following completion of Glen Canyon Dam in 1964. Evidence for the formation of the sandbar during low-discharge periods prior to anthropogenic manipulation of the river's flow was also examined.Water data sensors were installed upstream from the current sandbar to monitor the frequency of tidal overflow and document the effect of tides on salinity. Topographic surveys of the sandbar were completed both before and after the 2010 Mw 7.2 El Mayor-Cucapah Earthquake which caused subsidence of lands immediately east of the sandbar's crest.Utilizing topographic data and knowledge of the sandbar's geomorphologic and sedimentary history, we designed and installed a system of dredged pilot channels to improve connectivity between the upper and lower estuary by facilitating tidal and fluvial flow across the barrier. The effectiveness of the pilot channels is currently under evaluation. If the pilot channels fail to establish the desired level of connectivity, installation and maintenance of a more substantial dredged channel may be necessary to meet restoration objectives. © 2013 Elsevier B.V.

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