Surface evaporation in arid regions determines the fraction of rainfall that remains to support vegetation and recharge. The surface evaporation capacitor approach was used to estimate rainfall ...partitioning to surface evaporation and leakage into deeper layers. The surface evaporation capacitor estimates a soil‐specific surface evaporation depth and critical storage capacitance that defines rainfall events that exceed local capacitance and result in leakage into deeper layers protected from surface evaporation. A decade‐long record of hydrologic observations in deep and barren lysimeters near Las Vegas revealed the dominance of a few large rainfall events in generating leakage and increasing interannual soil water storage. The surface evaporation capacitor was used to estimate mean annual surface evaporation and leakage protected from surface evaporation in all arid regions globally. About 13% of arid region rainfall contributes to soil water storage (in the absence of vegetation), similar to 11% found in the lysimeter study.
Key Points
The surface capacitor model was applied for global arid regions and estimated that 13% of rainfall amount is protected from soil evaporation
A soil‐dependent characteristic depth and critical water content determine the rainfall amounts required for redistribution to deeper layers
Only three rainfall events during one decade contributed to water storage beneath surface of a desert soil lysimeter in Nevada
Increased requirements for public involvement in water resources management (WRM) over the past century have stimulated the development of more collaborative decision‐making methods. Participatory ...modeling (PM) uses computer models to inform and engage stakeholders in the planning process in order to influence collaborative decisions in WRM. Past evaluations of participatory models focused on process and final outcomes, yet, were hindered by diversity of purpose and inconsistent documentation. This paper presents a two‐stage framework for evaluating PM based on mechanisms for improving model effectiveness as participatory tools. The five dimensions characterize the “who, when, how, and why” of each participatory effort (stage 1). Models are evaluated as “boundary objects,” a concept used to describe tools that bridge understanding and translate different bodies of knowledge to improve credibility, salience, and legitimacy (stage 2). This evaluation framework is applied to five existing case studies from the literature. Though the goals of participation can be diverse, the novel contribution of the two‐stage proposed framework is the flexibility it has to evaluate a wide range of cases that differ in scope, modeling approach, and participatory context. Also, the evaluation criteria provide a structured vocabulary based on clear mechanisms that extend beyond previous process‐based and outcome‐based evaluations. Effective models are those that take advantage of mechanisms that facilitate dialogue and resolution and improve the accessibility and applicability of technical knowledge. Furthermore, the framework can help build more complete records and systematic documentation of evidence to help standardize the field of PM.
Key Points
Paper presents a two‐stage framework that captures the interdisciplinary nature of participatory models
The two‐stage framework is applied to five case studies to evaluate mechanisms that improve model effectiveness as participatory tools
Effective models are those which improve mechanisms for increasing credibility, salience, and legitimacy of technical knowledge
•Sentinel-1 land subsidence map across Southwest US during 11/2014-11/2017.•Groundwater levels recovered at major aquifers following the 2012–2015 drought.•Post-drought land subsidence indicates ...residual compaction of some aquifer-systems.
During the drought period 2012–2015, some of the major metropolitans and agricultural hubs within the Southwest US, including Phoenix and Tucson in Arizona, San Joaquin Valley in California, Colorado Springs in Colorado, Las Vegas in Nevada, and Albuquerque in New Mexico, experienced significant groundwater overdraft. At the end of the drought, GRACE-based estimates of total water storage show a rising trend. Also, the precipitation anomalies, considering monthly averages over 2002–2017, are positive. But, it is unclear if a pressure equilibrium is achieved within the aquifer systems, which is a requirement for residual compaction to halt. To this end, we perform a multidisciplinary multi-resolution analysis of space-borne and ground-based observations. We find that following the drought period and during wetter years, due to reduced pumping, owing to significant precipitation and the supply of surface water, groundwater levels begin to rise at all sites while compaction of aquifer-systems continues. A multi-temporal interferometric analysis of Sentinel-1A/B SAR datasets during Nov. 2014–Nov. 2017 shows subsidence rates of ~6 mm/yr, ~3 mm/yr, ~200–300 mm/yr, ~3–4 mm/yr, ~4–6 mm/yr, ~2 mm/yr affecting parts of Phoenix, Tucson, San Joaquin Valley, Colorado Springs, Las Vegas, Albuquerque, respectively, which are attributed to delayed compaction of fine-grain aquitard layer. We conclude that the aquifer-systems did not reach pressure equilibrium at least within ~2.5 years following the drought. The data provided here can assist policymakers and urban planners to improve groundwater management plans in the southwest and elsewhere.
Growing evidence supports the notion that plutons are constructed incrementally, commonly over long periods of time, yet field evidence for the multiple injections that seem to be required is ...commonly sparse or absent. Timescales of up to several million years, among other arguments, indicate that the dominant volume does not remain largely molten, yet if growing plutons are constructed from rapidly solidifying increments it is unlikely that intrusive contacts would escape notice. A model wherein magma increments are emplaced into melt-bearing but crystal-rich host, rather than either solid or crystal-poor material, provides a plausible explanation for this apparent conundrum. A partially solidified intrusion undoubtedly comprises zones with contrasting melt fraction and therefore strength. Depending on whether these zones behave elastically or ductilely in response to dike emplacement, intruding magma may spread to form sheets by either of two mechanisms. If the melt-bearing host is elastic on the relevant timescale, magma spreads rather than continuing to propagate upward, where it encounters a zone of higher rigidity (higher crystal fraction). Similarly, if the dike at first ascends through rigid, melt-poor material and then encounters a zone that is weak enough (poor enough in crystals) to respond ductilely, the ascending material will also spread because the dike tip ceases to propagate as in rigid material. We propose that ascending magma is thus in essence trapped, by either mechanism, within relatively crystal-poor zones. Contacts will commonly be obscure from the start because the contrast between intruding material (crystal-poorer magma) and host (crystal-richer material) is subtle, and they may be obscured even further by subsequent destabilization of the crystal-melt framework.
Field evidence and zircon zoning stratigraphy in plutons of the Colorado River region of southern Nevada support the hypothesis that emplacement of magma replenishments into a crystal-laden host is important in pluton construction. The dominant granite unit of the Spirit Mountain batholith displays only subtle internal contacts. However, ages and elemental zoning in zircons demonstrate a protracted history of almost 2 million years, major fluctuations in T and host melt chemistry, and mixing of strongly contrasting populations of magmatic zircon in single samples. We interpret this to reflect reactivation of rigid sponge and mush and entrainment of earlier-formed crystals, and we infer that this was in response to granitic replenishment.
Much of the smaller Aztec Wash pluton comprises interlayered cumulate-textured quartz monzonite and mafic sheets. The latest phase of pluton emplacement is marked by numerous thick, fine-grained granite “sills” that intruded the subhorizontal quartz monzonite sheets. Contacts between granite and quartz monzonite are “soft,” highly irregular on cm–dm scale with coarse xenocrysts from the quartz monzonite entrained in the fine-grained granite. We interpret the granite replenishments to have spread laterally within crystal-rich, melt-bearing quartz monzonite beneath rigid mafic sheets. In this case, clear evidence for the emplacement process is fortuitously preserved because the granite was emplaced in the waning stage of the thermal lifetime of the pluton, and because the mafic sheets enhance the strength contrast and make the geometry more visible. Similar “sills” of fine-grained granite were also preserved during the late stages of the history of the Spirit Mountain batholith.
This study examines the impact of spatial landscape configuration (e.g., clustered, dispersed) on land-surface temperatures (LST) over Phoenix, Arizona, and Las Vegas, Nevada, USA. We classified ...detailed land-cover types via object-based image analysis (OBIA) using Geoeye-1 at 3-m resolution (Las Vegas) and QuickBird at 2.4-m resolution (Phoenix). Spatial autocorrelation (local Moran's
I
) was then used to test for spatial dependence and to determine how clustered or dispersed points were arranged. Next, we used Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data acquired over Phoenix (daytime on 10 June and nighttime on 17 October 2011) and Las Vegas (daytime on 6 July and nighttime on 27 August 2005) to examine day- and nighttime LST with regard to the spatial arrangement of anthropogenic and vegetation features. Local Moran's
I
values of each land-cover type were spatially correlated to surface temperature. The spatial configuration of grass and trees shows strong negative correlations with LST, implying that clustered vegetation lowers surface temperatures more effectively. In contrast, clustered spatial arrangements of anthropogenic land-cover types, especially impervious surfaces and open soil, elevate LST. These findings suggest that city planners and managers should, where possible, incorporate clustered grass and trees to disperse unmanaged soil and paved surfaces, and fill open unmanaged soil with vegetation. Our findings are in line with national efforts to augment and strengthen green infrastructure, complete streets, parking management, and transit-oriented development practices, and reduce sprawling, unwalkable housing development.
Researchers for the electricity industry, national laboratories, and state and federal agencies have begun to argue that the country could face water shortages resulting from the addition of ...thermoelectric power plants, but have not attempted to depict more precisely
where or how
severe those shortages will be. Using county-level data on rates of population growth collected from the US Census Bureau, utility estimates of future planned capacity additions in the contiguous United States reported to the US Energy Information Administration, and scientific estimates of anticipated water shortages provided from the US Geologic Survey and National Oceanic and Atmospheric Administration, this paper highlights the most likely locations of severe shortages in 22 counties brought about by thermoelectric capacity additions. Within these areas are some 20 major metropolitan regions where millions of people live. After exploring the electricity–water nexus and explaining the study's methodology, the article then focuses on four of these metropolitan areas – Houston, Texas; Atlanta, Georgia; Las Vegas, Nevada; New York, New York – to deepen an understanding of the water and electricity challenges they may soon be facing. It concludes by identifying an assortment of technologies and policies that could respond to these electricity–water tradeoffs.
U.S. Urban Water Prices: Cheaper When Drier Luby, Ian H.; Polasky, Stephen; Swackhamer, Deborah L.
Water resources research,
September 2018, 2018-09-00, 20180901, Volume:
54, Issue:
9
Journal Article
Peer reviewed
Open access
Public water utilities are called upon to address multiple and often partially conflicting objectives, allocating potentially scarce water in an efficient and equitable manner while covering the ...costs of water supply. Economists typically advocate using prices to balance supply and demand of a scarce resource. But high prices necessary to balance supply and demand for scarce water may unduly burden poor households. We analyze the pricing policy of public water utilities in the major city of the 35 largest metropolitan areas in the United States. We would expect water prices to be higher in water‐stressed regions. However, we find the opposite pattern in the data: cities facing greater water scarcity tend to have lower water prices. Sacramento, Las Vegas, and Phoenix, have the lowest water prices. To address equity and ensure that all households have access to water, we would expect low prices on essential water use with higher prices for additional water beyond essential use. However, we find that the majority of cities have higher per unit water prices (average price) for low use than for high use. Such pricing may leave major urban areas in the United States ill‐prepared to meet future water shortages in an equitable manner.
Key Points
Water utilities face conflicting objectives when allocating scarce water efficiently and equitably while covering the costs of water supply
We find that cities in areas with greater water scarcity tend to have lower water prices using data from large U.S. cities
We find that the majority of cities have higher per unit water prices (average price) for low use than for high use
► We tested the ability of GCMs/RCMs to represent multi-scale temporal precipitation variability. ► We investigated storm properties and precipitation variabilities in GCMs/RCMs outputs. ► Current ...GCMs/RCMs tend to simulate longer storm duration and lower storm intensity. ► Most GCMs/RCMs fail to produce the high-intensity summer storms. ► Studied GCMs/RCMs capture long-term monthly mean but not precipitation variability.
Multi-scale temporal variability of precipitation has an established relationship with floods and droughts. In this paper, we present the diagnostics on the ability of 16 General Circulation Models (GCMs) from Bias Corrected and Downscaled (BCSD) World Climate Research Program’s (WCRP’s) Coupled Model Inter-comparison Project Phase 3 (CMIP3) projections and 10 Regional Climate Models (RCMs) that participated in the North American Regional Climate Change Assessment Program (NARCCAP) to represent multi-scale temporal variability determined from the observed station data. Four regions (Los Angeles, Las Vegas, Tucson, and Cimarron) in the Southwest United States are selected as they represent four different precipitation regions classified by clustering method. We investigate how storm properties and seasonal, inter-annual, and decadal precipitation variabilities differed between GCMs/RCMs and observed records in these regions. We find that current GCMs/RCMs tend to simulate longer storm duration and lower storm intensity compared to those from observed records. Most GCMs/RCMs fail to produce the high-intensity summer storms caused by local convective heat transport associated with the summer monsoon. Both inter-annual and decadal bands are present in the GCM/RCM-simulated precipitation time series; however, these do not line up to the patterns of large-scale ocean oscillations such as El Nino/La Nina Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO). Our results show that the studied GCMs/RCMs can capture long-term monthly mean as the examined data is bias-corrected and downscaled, but fail to simulate the multi-scale precipitation variability including flood generating extreme events, which suggests their inadequacy for studies on floods and droughts that are strongly associated with multi-scale temporal precipitation variability.
Monitoring neighbourhood change associated with a redevelopment is important for policy-makers, business leaders and residents. It helps evaluate public policy and changes in the needs of residents ...and businesses. However, using raw data (e.g. census data) to track such changes can be problematic. It does not allow one to distinguish between trends attributable to macro- and micro-scale processes. This paper demonstrates how a novel neighbourhood-level, GIS-based spatial approach using shift-share analysis can help resolve this issue. To illustrate its utility, this technique is used to examine the local socio-economic impact of destination redevelopments in Las Vegas between 1990 and 2010.
A middle to late Pleistocene sedimentary sequence in the upper Las Vegas Wash, north of Las Vegas, Nevada, has yielded the largest open-site Rancholabrean vertebrate fossil assemblage in the southern ...Great Basin and Mojave Deserts. Recent paleontologic field studies have led to the discovery of hundreds of fossil localities and specimens, greatly extending the geographic and temporal footprint of original investigations in the early 1960s. The significance of the deposits and their entombed fossils led to the preservation of 22,650 acres of the upper Las Vegas Wash as Tule Springs Fossil Beds National Monument. These discoveries also warrant designation of the assemblage as a local fauna, named for the site of the original paleontologic studies at Tule Springs.
The large mammal component of the Tule Springs local fauna is dominated by remains of Mammuthus columbi as well as Camelops hesternus, along with less common remains of Equus (including E. scotti) and Bison. Large carnivorans including Canis dirus, Smilodon fatalis, and Panthera atrox are also recorded. Micromammals, amphibians, lizards, snakes, birds, invertebrates, plant macrofossils, and pollen also occur in the deposits and provide important and complementary paleoenvironmental information. The fauna occurs within the Las Vegas Formation, an extensive and stratigraphically complex sequence of groundwater discharge deposits that represent a mosaic of desert wetland environments. Radiometric and luminescence dating indicates the sequence spans the last ∼570 ka, and records hydrologic changes in a dynamic and temporally congruent response to northern hemispheric abrupt climatic oscillations. The vertebrate fauna occurs in multiple stratigraphic horizons in this sequence, with ages of the fossils spanning from ∼100 to ∼12.5 ka.
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