Drought 2002 in Colorado: An Unprecedented Drought or a Routine Drought?   总被引：1，自引：0，他引：1  

Roger A. Pielke Sr.  Nolan Doesken  Odilia Bliss  Tara Green  Clara Chaffin  Jose D. Salas  Connie A. Woodhouse  Jeffrey J. Lukas  Klaus Wolter 《Pure and Applied Geophysics》2005,162(8-9):1455-1479

The 2002 drought in Colorado was reported by the media and by public figures, and even by a national drought-monitoring agency, as an exceptionally severe drought. In this paper we examine evidence for this claim. Our study shows that, while the impacts of water shortages were exceptional everywhere, the observed precipitation deficit was less than extreme over a good fraction of the state. A likely explanation of this discrepancy is the imbalance between water supply and water demand over time. For a given level of water supply, water shortages become intensified as water demands increase over time. The sobering conclusion is that Colorado is more vulnerable to drought today than under similar precipitation deficits in the past.  相似文献   

The Relationship Between Monitoring Well and Aquifer Solute Concentrations     

Chen Chiang  Gary Raven  Clint Dawson 《Ground water》1995,33(5):718-726

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A Risk-Based Approach for Managing Hazardous Waste     

C.Y. Chiang  P.D. Petkovsky  P.M. McAllister 《Ground Water Monitoring & Remediation》1995,15(1):79-89

In 1992, the U.S. Environmental Protection Agency (EPA) proposed risk-based management of hazardous waste. A major component of the proposed rule is the determination of non-site- specific screening concentration levels from waste leachate. Ground water at a downgradient exposure point must not exceed those screening levels, or more stringent requirements would apply.
The screening concentration level is determined with verified models and equations that simulate the transport and attenuation of chemicals as they travel from the source area to the exposure point. A consortium of screening levels is determined in this paper by considering varying physical, chemical, and biological conditions. In addition, a method is developed for multi component leaching from contaminated soils in a landfill to determine the time-dependent behavior of a finite source. Finally, this paper discusses infiltration rate through the clay liner.  相似文献   

Hydrocarbon Thickness Fluctuations in Monitoring Wells     

M. W. Kemblowski  C. Y. Chiang 《Ground water》1990,28(2):244-252

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Fuzzy information processing in seismic hazard analysis and decision making     

W. M. Dong  W. L. Chiang  H. C. Shah 《Soil Dynamics and Earthquake Engineering》1987,6(4):220-226

This paper describes a methodology to incorporate vague information, based upon heuristic knowledge and expertise, into the conventional probabilistic approach for the seismic hazard analysis.

The interval analysis method is introduced to process interval information with interpretation from Dempster and Shafer's evidence theory. The Vertex Method is discussed to handle fuzzy information which is a generalization of interval information.

These methods, along with the current approach of seismic hazard analysis, are used to assess the seismic hazard for the San Francisco Bay Area in California and to provide information for deciding strengthening policy of existing buildings.  相似文献   

Multi-Century Tree-Ring Reconstructions of Colorado Streamflow for Water Resource Planning   总被引：3，自引：0，他引：3  

Connie A. Woodhouse  Jeffrey J. Lukas 《Climatic change》2006,78(2-4):293-315

Water resource management requires knowledge of the natural variability in streamflow over multiple time scales. Reconstructions of streamflow derived from moisture-sensitive trees extend, in both time and magnitude, the variability provided by relatively short gage records. In this study, we present a network of 14 annual streamflow reconstructions, 300–600 years long, for gages in the Upper Colorado and South Platte River basins in Colorado generated from new and existing tree-ring chronologies. Gages for the reconstruction were selected on the basis of their importance to two of the largest Colorado Front Range water providers, who provided the natural flow data for the calibration with tree-ring data. The reconstruction models explain 63–76% of the variance in the gage records and capture low flows particularly well. Analyses of the reconstructions indicate that the 20th century gage record does not fully represent the range of streamflow characteristics seen in the prior two to five centuries. Multi-year drought events more severe than the 1950s drought have occurred, notably in the 19th century, and the distribution of extreme low flow years is markedly uneven over the past three centuries. When the 14 reconstructions are grouped into Upper Colorado, northern South Platte, and southern South Platte regional flow reconstructions, the three time series show a high degree of coherence, but also time-varying divergences that may reflect the differential influence of climatic features operating in the western U.S. These reconstructions are currently being used by water managers to assess the reliability of water supply systems under a broader range of conditions than indicated by the gage records alone.  相似文献   

Merging multiple precipitation sources for flash flood forecasting   总被引：3，自引：0，他引：3  

Yen-Ming Chiang  Kuo-Lin Hsu  Fi-John Chang  Yang Hong  Soroosh Sorooshian 《Journal of Hydrology》2007,340(3-4):183-196

We investigated the effectiveness of combining gauge observations and satellite-derived precipitation on flood forecasting. Two data merging processes were proposed: the first one assumes that the individual precipitation measurement is non-bias, while the second process assumes that each precipitation source is biased and both weighting factor and bias parameters are to be calculated. Best weighting factors as well as the bias parameters were calculated by minimizing the error of hourly runoff prediction over Wu-Tu watershed in Taiwan. To simulate the hydrologic response from various sources of rainfall sequences, in our experiment, a recurrent neural network (RNN) model was used.

The results demonstrate that the merged method used in this study can efficiently combine the information from both rainfall sources to improve the accuracy of flood forecasting during typhoon periods. The contribution of satellite-based rainfall, being represented by the weighting factor, to the merging product, however, is highly related to the effectiveness of ground-based rainfall observation provided gauged. As the number of gauge observations in the basin is increased, the effectiveness of satellite-based observation to the merged rainfall is reduced. This is because the gauge measurements provide sufficient information for flood forecasting; as a result the improvements added on satellite-based rainfall are limited. This study provides a potential advantage for extending satellite-derived precipitation to those watersheds where gauge observations are limited.  相似文献   

Note on sediment sorting in a sandy bed under standing water waves     

Blake J. Landry  Matthew J. Hancock  Chiang C. Mei 《Coastal Engineering》2007

We present new quantitative data on the sorting of sediments on a sandy seabed under standing waves. Starting from a flat bed composed of a homogeneous mixture of a coarse and a fine sand with mean diameters 0.11 and 0.21 mm, we observed simultaneous ripple and sand bar formation and sand sorting on the seabed. Over days of wave action, sand bars formed with crests beneath the surface wave nodes and flat plateaus flanked by mounds beneath the antinodes. Bar crests were composed of sand coarser on average than 0.21 mm, while the flat plateaus were covered by sand finer on average than 0.11 mm. Comparison with two experiments involving sand beds of more homogeneous size distributions shows that the mounds are characteristic of the motion of fine suspensions.  相似文献   

Modified Kadomtsev–Petviashvili equation for tsunami over irregular seabed     

Li  Yile  Mei  Chiang C. 《Natural Hazards》2016,84(2):513-528

We derive an asymptotic equation governing the trans-ocean propagation of tsunami from source to the continental shelf. Focus is on disturbances originated from a slender fault of finite length. The variable sea depth is assumed to consist of a slowly varying mean and random fluctuations. The method of multiple scales is used to derive a Kadomtsev–Petviashvili equation with variable coefficients. Modifications by one- and two-dimensional random irregularities are shown to affect the wave speed, dissipation and additional dispersion. The result can be used to facilitate physical insight with modest numerical efforts.  相似文献   

Local economic linkages to community‐based tourism in rural Costa Rica     

Bernardo Trejos  Lan‐Hung Nora Chiang 《Singapore journal of tropical geography》2009,30(3):373-387

This paper reports on the contribution of tourism to the wellbeing of rural residents through the development of economic linkages engaged by community‐based tourism (CBT) in rural Costa Rica. In a qualitative case study of local economic linkages surrounding one such project in Chira Island, economic linkages were assessed at two levels: discourse and practice. The findings indicate that CBT does not involve the collective property of the community, but rather, the collective property of a group of community members organized in a formal association. As a result, a discourse on local economic linkages has been promoted by CBT support organizations in which hopes of wider benefits are placed on small linkages to services and products provided by local community members. However, a field survey suggested that the economic linkages generated by CBT in the community were sporadic and polyvalent and, furthermore, that the linkages with agriculture are negatively affected by scale and seasonality, resulting in leakages out of the community. These findings caution practitioners that CBT may only have small‐scale positive impacts on the local economy.  相似文献