Green Light for Adaptive Policies on the Colorado River

Smerdon

et al. 2022

Nat Rev Earth Environ

The concept of megadroughts came to prominence with research into Common Era (CE; Year 1-present) palaeo climate droughts over western North America 1-5 . This research documented multi decadal periods of extreme aridity (or various hydrological deficits 1-5 ) before 1600 CE, as well as widespread ecological disturbances [6][7][8] and societal disruptions [9][10][11][12] . Although recurrent and persistent droughts are an intrinsic feature of North American hydroclimate variability, these megadroughts were primarily distinguished by their much greater per sistence (for example, multiple decades) than even the most extreme decadal length instrumental era droughts during the 1930s and 1950s 13,14 .Since then, extreme droughts across the globe have been increasingly referred to as megadroughts, despite often large differences in their severity, duration, or spatial extent. These include multi decadal periods of enhanced aridity in Australia 15,16 , South America 17 , Europe 18 , Central Asia 19,20 , and Mesoamerica 21 ; a multi season drought in 1540 CE over Europe 22 ; spatially extensive multi year droughts in India 23 ; the late Ming Dynasty drought in China 24,25 ; and an early twenty first century decadal drought in Chile and Argentina [26][27][28] . As anthropogenic warming is expected to increase drought severity and risk in many regions of the world 29,30 , the term has also been increasingly applied to droughts amplified by climate change, both in observations 26,31 and in model projections 32,33 .The use of the megadrought label has therefore been inconsistent, owing partly to an absence of applicable objective criteria that define when a drought becomes a megadrought, or when a period of moisture deficit

Section: Summary and Future Perspectivesmentioning

confidence: 99%

Megadroughts in the Common Era and the Anthropocene

Smerdon

et al. 2022

Nat Rev Earth Environ

“…River management decisions are rapidly undergoing alteration in response to changing environmental conditions and human use (e.g., Fleck & Castle, 2022). These reevaluations of management needs can be used to reconsider the best ways to manage water distribution across seasons for the benefit of river health, as well as direct human uses.…”

Section: Discussionmentioning

confidence: 99%

The hydroclimate niche: A tool for predicting and managing riparian plant community responses to streamflow seasonality

Butterfield

Palmquist

Yackulic

2022

River Research & Apps

Habitat suitability is a consequence of interacting environmental factors. In riparian ecosystems, suitable plant habitat is influenced by interactions between stream hydrology and climate, hereafter referred to as “hydroclimate”. We tested the hypothesis that hydroclimate variables would improve the fit of ecological niche models for a suite of riparian species using occurrence data from the western United States. We focus on the climate conditions (temperature, precipitation and vapor pressure deficit) during the months of lowest and highest streamflow as integrative hydroclimate metrics of resource and stress levels. We found that the inclusion of hydroclimate variables improved model fit for all species in the western USA dataset. We then tested the utility of the improved habitat suitability models by projecting them onto a regulated segment of the Colorado River to assess potential impacts of streamflow seasonality on vegetation metrics of management concern. Species frequency derived from independent survey data in the Colorado River segment was significantly higher for species with predicted suitable habitat than for species without predicted suitable habitat. Under different simulated hydrographs for the Colorado River, overall species richness was predicted to be greatest with peak streamflows during summer, and native‐to‐non‐native species ratios were predicted to be greatest with lowest streamflows in winter. Summer high flows were particularly associated with higher predicted habitat suitability for species that have increased in cover over recent decades (e.g., Pluchea sericea, Baccharis species). We conclude that hydroclimate covariates can be useful tools for predicting how riparian vegetation communities respond to changes in the seasonal timing of low and high streamflows.

Water Resources Research

“…The uncertain future of Colorado River availability and the response of urban water systems to its basin-wide developments is a salient human-water systems challenge for us to illustrate the general operational and political-economic feedback dynamics in the UWIIM. Multiple scholars (Fleck & Castle, 2022;Schmidt et al, 2023;Wheeler et al, 2022), the Bureau of Reclamation (DOI, 2022), and water users (Goddard & Atkins, 2022), argue that the existing water distribution rules are not enough to address the Colorado River's pressing state, which may require a 2-4 MAFY basin-wide cut in use (DOI, 2022). The Bureau has undergone a Supplemental Environmental Impact Statement process to reform the 2007 guidelines (Bureau of Reclamation, 2022) and published a draft (D-SEIS) in April (Bureau of Reclamation, 2023b) that includes two alternatives to share needed cuts by the traditional priority system or adopt a use-proportional sharing approach.…”

Section: Pma Colorado River Availability Scenariosmentioning

confidence: 99%

Institutional Dynamics Impact the Response of Urban Socio‐Hydrologic Systems to Supply Challenges

Wiechman,

Alonso Vicario,

Anderies

et al. 2024

Designing urban water systems to respond to the accelerating and unpredictable changes of the Anthropocene will require changes not only to built infrastructure and operating rules, but also to the governance arrangements responsible for investing in them. Yet, inclusion of this political‐economic feedback in dynamic models of infrastructure systems and socio‐hydrology has lagged behind operational feedback concerns. We address this gap through a dynamical systems application of the Coupled Infrastructure Systems (CIS) Framework, which provides the conceptual building blocks for analyzing social‐ecological systems through various classes of infrastructure and the flows of material and information among them. In the model, political‐economic feedback involves three decisions—infrastructure investment, rate‐setting, and short‐term demand curtailment—and each decision is constrained by institutional friction, the aggregation of decision and transaction costs associated with taking action. We apply the model to three cities in the Phoenix Metropolitan Area to compare how institutional friction interacts with a city's water resource portfolio and financial position to determine its sensitivity, or the degree to which its performance (e.g., providing sufficient supply to meet demand) changes given reductions in Colorado River water availability. We find that the slowing effect of institutional friction on investment and rate‐setting decisions can increase the sensitivity of a city's supply, but it can also promote objectives that compete with over‐response (e.g., rate burden). The effect is dependent on the initial operating capacity of the CIS and flexibility within the institutions, highlighting the need to consider political‐economic and operational feedback together when evaluating infrastructure systems.