Adaptive comanagement endeavors to increase knowledge and responsiveness in the face of uncertainty and complexity. However, when collaboration between agency and nonagency stakeholders is mandated, rigid institutions may hinder participation and ecological outcomes. In this case study we analyzed qualitative data to understand how participants perceive strengths and challenges within an emerging adaptive comanagement in the Agua Fria Watershed in Arizona, USA that utilizes insight and personnel from a long-enduring comanagement project, Las Cienegas. Our work demonstrates that general lessons and approaches from one project may be transferable, but particular institutions, management structures, or projects must be place-specific. As public agencies establish and expand governance networks throughout the western United States, our case study has shed light on how to maintain a shared vision and momentum within an inherently murky and shared decision-making environment.

The Arizona Toad (Bufo [ = Anaxyrus] microscaphus) occupied the entire Agua Fria River drainage in central Arizona until relatively recently. By the 1980s, a close relative, Woodhouse's Toad (Bufo woodhousii), colonized the lower reaches of the Agua Fria and replaced B. microscaphus at some sites. We tested the hypothesis that habitat disturbance drives replacement of B. microscaphus by B. woodhousii, via hybridization, by examining shifts in the distribution of these toads following the expansion of the Waddell Dam on the lower Agua Fria River in the early 1990s. As of 2010, the high elevation headwaters of the Agua Fria River were still occupied by B. microscaphus, the lower reaches near the confluence with the Gila River were occupied by B. woodhousii, and along the middle reaches, hybridization between these two anurans occurred at the same three sites as documented in the early 1990s. Contrary to expectations, evidence of hybridization along middle reaches of the river is largely unchanged: B. microscaphus has not been replaced by B. woodhousii at any additional sites nor is there any evidence of introgression of woodhousii mtDNA into putatively “pure” microscaphus populations upstream of hybrid sites.

The ecological consequences of impoundment construction on riparian systems throughout the U.S. Southwest has profoundly affected a variety of organisms, including many amphibians. To better understand the current extent of hybridization and changes in genetic composition over time in Bufo (Anaxyrus) woodhousii and Bufo microscaphus, we used microsatellite loci to evaluate 260 individuals representing 10 total populations constituting B. woodhousii, B. microscaphus, and putative hybrids along the Agua Fria River in Arizona during two time periods (1992–97 and 2009–10). Consistent with prior work with these two anurans documenting unidirectional replacement or genetic introgression, we predicted that microsatellites would provide evidence of directional introgression of B. woodhousii into B. microscaphus. The putative hybrid populations exhibited the highest number of alleles, and B. microscaphus exhibited the lowest number of alleles. Structure analysis indicated K = 2 as the best-fit population number for both time periods. All pairwise F-statistics were highly significant, corroborating differentiation among populations as inferred by structure analysis. The principal coordinates analysis demonstrated three distinct clusters of individuals that corresponded strongly with prior morphological and mitochondrial assignments within this region over both sampling periods. Our findings indicate that the genetic identity of B. microscaphus remains distinct from B. woodhousii and the hybrids, suggesting that the genetic structure of the corresponding populations has remained intact. Bufo woodhousii has not replaced B. microscaphus along the Agua Fria River beyond those habitats directly associated with impoundment construction.

Water resources in agriculture-dominated basins of the arid western United States are stressed due to long-term impacts from pumping. A review of 88 regional groundwater-flow modeling applications from seven intensively irrigated western states (Arizona, California, Colorado, Idaho, Kansas, Nebraska and Texas) was conducted to provide hydrogeologists, modelers, water managers, and decision makers insight about past modeling studies that will aid future model development. Groundwater models were classified into three types: resource evaluation models (39%), which quantify water budgets and act as preliminary models intended to be updated later, or constitute re-calibrations of older models; management/planning models (55%), used to explore and identify management plans based on the response of the groundwater system to water-development or climate scenarios, sometimes under water-use constraints; and water rights models (7%), used to make water administration decisions based on model output and to quantify water shortages incurred by water users or climate changes. Results for 27 model characteristics are summarized by state and model type, and important comparisons and contrasts are highlighted. Consideration of modeling uncertainty and the management focus toward sustainability, adaptive management and resilience are discussed, and future modeling recommendations, in light of the reviewed models and other published works, are presented.

The processes that affect water chemistry as the water flows from recharge areas through breccia-pipe uranium deposits in the Grand Canyon region of the southwestern United States are not well understood. Pigeon Spring had elevated uranium in 1982 (44 μg/L), compared to other perched springs (2.7–18 μg/L), prior to mining operations at the nearby Pigeon Mine. Perched groundwater springs in an area around the Pigeon Mine were sampled between 2009 and 2015 and compared with material from the Pigeon Mine to better understand the geochemistry and hydrology of the area. Two general groups of perched groundwater springs were identified from this study; one group is characterized by calcium sulfate type water, low uranium activity ratio ²³⁴U/²³⁸U (UAR) values, and a mixture of water with some component of modern water, and the other group by calcium-magnesium sulfate type water, higher UAR values, and radiocarbon ages indicating recharge on the order of several thousand years ago. Multivariate statistical principal components analysis of Pigeon Mine and spring samples indicate Cu, Pb, As, Mn, and Cd concentrations distinguished mining-related leachates from perched groundwater springs. The groundwater potentiometric surface indicates that perched groundwater at Pigeon Mine would likely flow toward the northwest away from Pigeon Spring. The geochemical analysis of the water, sediment and rock samples collected from the Snake Gulch area indicate that the elevated uranium at Pigeon Spring is likely related to a natural source of uranium upgradient from the spring and not likely related to the Pigeon Mine.