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221.
F Jay Breidt Duane C. Boes Joel I. Wagner Mark D. Flora 《Journal of the American Water Resources Association》1991,27(5):849-858
ABSTRACT: Existing water quality for the Middle Delaware Scenic and Recreational River is significantly better than is required by current standards, leaving a potential for degradation. A method is presented for deriving candidate antidegradation water quality criteria for this segment of the Delaware River using statistical analysis of historic (ambient) water quality data. Data for 34 water quality parameters are first evaluated for data density, serial correlation, trend, seasonality, and other factors. These preliminary analyses are based on observation of data plots and application of distribution-free statistical techniques that are insensitive to outliers and are robust to relatively mild violations of basic assumptions. Data for 12 of the parameters have sufficient density for further analysis and can reasonably be modeled as independent and identically distributed over time (either seasonally or for the entire data sets). For these 12 parameters, distribution-free statistical methods are developed and used to derive intervals within which there is high confidence (usually greater than 95 percent) that the quantiles with potential use as anti-degradation criteria (the 0.85th, 0.90th, and 0.95th quantiles in this study) for a particular parameter lie. 相似文献
222.
Integrating ecology into natural resource management policy 总被引:1,自引:0,他引:1
223.
Muhammad Akram Kahlown Joel R. Hamilton 《Journal of the American Water Resources Association》1994,30(1):125-134
ABSTRACT: The karez is a traditional irrigation water source, consisting of hand-dug horizontal wells, that is still used in parts of South Asia, the Middle East, and North Africa. This paper describes the construction, management, and current problems of karez irrigation systems based on investigations conducted in Baluchistan Province, Pakistan. While karezes have served irrigation needs well in the past, they are now threatened by high costs of labor for construction and maintenance, and by the encroachment of tubewells which lower the water tables on which the karez systems depend. Possible methods for improving karez performance and needs for research are discussed. 相似文献
224.
225.
A note on permits, standards, and technological innovation 总被引:1,自引:0,他引:1
Montero (J. Environ. Econom. Manage. 44 (2002) 23) contrasts the incentives to invest in new abatement technologies under different regulatory instruments and argues that one needs to consider the induced output effects that derive from lower abatement costs. Montero shows that, once one takes into account these effects on output, command-and-control instruments can generate stronger incentives to innovate than market-based instruments. This result rests on strategic output effects under command-and-control. However, he maintains that, under perfectly competitive conditions, market-based instruments will continue to weakly dominate command-and-control regulation. This note clarifies two issues raised by Montero. First, I use Montero's approach to show that in fact performance (concentration) standards will generate greater incentives to innovate than market-based instruments in perfectly competitive markets. One does not require strategic effects to get this result. Second, Montero abstracts from production costs and concentrates solely on abatement costs. He implicitly assumes that marginal production costs are constant. I show that some of Montero's results change once increasing marginal production costs are considered. When marginal costs are increasing, the benefit of additional output is tempered and market-based instruments again look more favorable. 相似文献
226.
Is It Acceptable to Let a Species Go Extinct in a National Park? 总被引:1,自引:0,他引:1
Joel Berger 《Conservation biology》2003,17(5):1451-1454
227.
228.
Streamflow,Sediment Transport,and Geomorphic Change during the 2011 Flood on the Missouri River Near Bismarck–Mandan,ND
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Rochelle A. Nustad Adam J. Benthem Katherine J. Skalak Richard R. McDonald Edward R. Schenk Joel M. Galloway 《Journal of the American Water Resources Association》2018,54(5):1151-1167
Geomorphic change from extreme events in large managed rivers has implications for river management. A steady‐state, quasi‐three‐dimensional hydrodynamic model was applied to a 29‐km reach of the Missouri River using 2011 flood data. Model results for an extreme flow (500‐year recurrence interval [RI]) and an elevated managed flow (75‐year RI) were used to assess sediment mobility through examination of the spatial distribution of boundary or bed shear stress (τb) and longitudinal patterns of average τb, velocity, and kurtosis of τb. Kurtosis of τb was used as an indicator of planform channel complexity and can be applied to other river systems. From differences in longitudinal patterns of sediment mobility for the two flows we can infer: (1) under extreme flow, the channel behaves as a single‐thread channel controlled primarily by flow, which enhances the meander pattern; (2) under elevated managed flows, the channel behaves as multithread channel controlled by the interaction of flow with bed and channel topography, resulting in a more complex channel; and (3) for both flows, the model reach lacks a consistent pattern of deposition or erosion, which indicates migration of areas of erosion and deposition within the reach. Despite caveats and limitations, the analysis provides useful information about geomorphic change under extreme flow and potential implications for river management. Although a 500‐year RI is rare, extreme hydrologic events such as this are predicted to increase in frequency. 相似文献
229.
Ashley A. Weaver Kristen M. Beavers R. Caresse Hightower Sarah K. Lynch Anna N. Miller Joel D. Stitzel 《Traffic injury prevention》2015,16(7):S153-S160
Objective: Low bone quality is a contributing factor to motor vehicle crash (MVC) injury. Quantification of occupant bone mineral density (BMD) is important from an injury causation standpoint. The first aim of this study was to validate a technique for measuring lumbar volumetric BMD (vBMD) from phantomless computed tomography (CT) scans. The second aim was to apply the validated phantomless technique to quantify lumbar vBMD in Crash Injury Research and Engineering Network (CIREN) occupants for correlation with age, fracture incidence, and osteopenia/osteoporosis diagnoses.Methods: Quantitative CT (qCT) and dual-energy X-ray absorptiometry (DXA) were collected prospectively for 50 subjects and used to validate a technique to measure vBMD from 281 phantomless CT scans of CIREN occupants. Hounsfield unit (HU) measurements were collected from the L1–L5 vertebrae, right psoas major muscle, and anterior subcutaneous fat for all subjects and from 3 phantom ports with known mg/cc calcium hydroxyapatite values for the validation group. qCT calibration was accomplished using regressions between the phantom HU and mg/cc values to convert L1–L5 HU values to mg/cc. A phantomless calibration technique was developed where the fat and muscle HU values were linearly regressed against fat (?69 mg/cc) and muscle (77 mg/cc) to establish a conversion for L1–L5 HU measurements to mg/cc. vBMD calculated from qCT versus the phantomless method was compared for the 50 subjects to assess agreement and a mg/cc osteopenia threshold was established using DXA T-scores. CIREN HU measurements were converted to mg/cc using the phantomless technique and the mg/cc osteopenia threshold was used to compare vBMD to age, fracture incidence, and osteopenia comorbidity classifications in CIREN.Results: Linear regression of lumbar vBMD derived from the qCT versus phantomless calibrations showed excellent agreement (R2 = 0.87, P <.0001). A 145 mg/cc threshold for osteopenia was established (sensitivity = 1, specificity = 0.57) and 44 CIREN occupants had vBMD below this threshold. Of these 44 occupants, 64% were not classified as osteopenic in CIREN, but vBMD suggested undiagnosed osteopenia. Age was negatively correlated with vBMD in both sexes (P <.0001) and CIREN occupants with less than 145 mg/cc vBMD sustained an average 1.7 additional rib/sternum fractures (P =.036).Conclusions: Because lumbar vBMD was estimated from phantomless CT scans with accuracy similar to qCT, the phantomless technique can be broadly applied to both prospectively and retrospectively assess patient bone quality for research and clinical studies related to MVCs, falls, and aging. 相似文献
230.
A stakeholder driven process to reduce vulnerability to climate change in Hermosillo,Sonora, Mexico 总被引:1,自引:0,他引:1
Hallie Eakin Victor Magaña Joel Smith José Luis Moreno José Maria Martínez Osvaldo Landavazo 《Mitigation and Adaptation Strategies for Global Change》2007,12(5):935-955
While there is a growing body of knowledge on potential impacts of climate change on water availability, there has been much
less empirical research on exploring the viability of particular adaptation options. The participation of stakeholders in
defining appropriate adaptation strategies is increasingly recognized as a critical element in the translation of climate
change impact research into effective actions to reduce future vulnerability, yet the process by which stakeholders are included
in such initiatives is not well-defined. This article presents the results of a pilot project in which a participatory approach
was employed to identify and evaluate adaptation options to climate change scenarios for Sonora’s capital city, Hermosillo.
In an iterative process, stakeholders representing different water users and managers in the city met to discuss climate change
scenarios, identify specific adaptation options, and evaluate a subset of options for possible future implementation. This
process enabled the focus of the investigation on those adaptations that addressed not only concerns with the potential future
impacts of climate change but also the immediate and pressing concerns about development patterns and water use in the city.
Two of the adaptations to climate change identified by stakeholders would also reduce energy demand. The simplicity of the
approach makes it a feasible model for adaptation initiatives in other regions of Mexico and in other countries in Latin America.
相似文献
Osvaldo LandavazoEmail: |