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11.
Kristina Cydzik Terri S. Hogue 《Journal of the American Water Resources Association》2009,45(3):702-714
Abstract: This paper investigates application of the Army Corps of Engineers’ Hydrologic Engineering Center Hydrologic Modeling System (HEC‐HMS) to a burned watershed in San Bernardino County, California. We evaluate the HEC‐HMS’ ability to simulate discharge in prefire and postfire conditions in a semi arid watershed and the necessary parameterizations for modeling hydrologic response during the immediate, and subsequent recovery, period after a wildfire. The model is applied to City Creek watershed, which was 90% burned during the Old Fire of October 2003. An optimal spatial resolution for the HEC‐HMS model was chosen based on an initial sensitivity analysis of subbasin configurations and related model performance. Five prefire storms were calibrated for the selected model resolution, defining a set of parameters that reasonably simulate prefire conditions. Six postfire storms, two from each of the following rainy (winter) seasons were then selected to simulate postfire response and evaluate relative changes in parameter values and model behavior. There were clear trends in the postfire parameters [initial abstractions (Ia), curve number (CN), and lag time] that reveal significant (and expected) changes in watershed behavior. CN returns to prefire (baseline) values by the end of Year 2, while Ia approaches baseline by the end of the third rainy season. However, lag time remains significantly lower than prefire values throughout the three‐year study period. Our results indicate that recovery of soil conditions and related runoff response is not entirely evidenced by the end of the study period (three rainy seasons postfire). Understanding the evolution of the land surface and related hydrologic properties during the highly dynamic postfire period, and accounting for these changes in model parameterizations, will allow for more accurate and reliable discharge simulations in both the immediate, and subsequent, rainy seasons following fire. 相似文献
12.
Qing Zhou Christine W. Chan Paitoon Tontiwachiwuthikul Raphael Idem Don Gelowitz 《International Journal of Greenhouse Gas Control》2009,3(5):535-544
Post combustion carbon dioxide (CO2) capture is one of the most commonly adopted technologies for reducing industrial CO2 emissions, which is now an important goal given the widespread concern over global warming. Research on amine-based CO2 capture has mainly focused on improving effectiveness and efficiency of the CO2 capture process. Our research work focuses on studying the relationships among the significant parameters influencing CO2 production because an enhanced understanding of the intricate relationships among the parameters involved in the process is critical for improving efficiency of the CO2 capture process. This paper presents a statistical study that explores the relationships among parameters involved in the amine-based post combustion CO2 capture process at the International Centre for CO2 Capture (ITC) located in Regina, Saskatchewan of Canada. A multiple regression technique has been applied for analysis of data collected at the CO2 capture pilot plant at ITC. The parameters have been carefully selected to avoid issues of multicollinearity, and four mathematical models among the key parameters identified have been developed. The models have been tested, and accuracy of the models is found to be satisfactory. The models developed in this study describe part of the CO2 capture process and can help to predict performance of the CO2 capture process at ITC under different conditions. Some results from a preliminary validation process will also be presented. 相似文献
13.
Managing the integrity of tailings infrastructure is an important aspect of handling mine tailings. Unfortunately, little
research is directed towards its efficient modeling. This paper presents salient aspects of tailings management. It proposes
an integrated geographic information systems (GIS)-based conceptual model for efficient handling of these aspects. The paper
also discusses the various integrated modules and comments on the systematic implementation of the model to achieve desired
results. The modules include: structural integrity management (SIM), release impact assessment (RIA), and hazardous risk assessment
and control (HRAC). 相似文献
14.
Long-term (1860–2010) catchment mass balance calculations rely on models and assumptions which are sources of uncertainty
in acidification assessments. In this article, we report on an application of MAGIC to model acidification at the four Swedish
IM forested catchments that have been subject to differing degrees of acidification stress. Uncertainties in the modeled mass
balances were mainly associated with the deposition scenario and assumptions about sulfate adsorption and soil mass. Estimated
base cation (BC) release rates (weathering) varied in a relatively narrow range of 47–62 or 42–47 meq m−2 year−1, depending on assumptions made about soil cation exchange capacity and base saturation. By varying aluminum solubility or
introducing a dynamic weathering feedback that allowed BC release to increase at more acidic pHs, a systematic effect on predicted
changes in acid neutralizing capacity (ΔANC ca. 10–41 μeq l−1) and pH (ca. ΔpH = 0.1–0.6) at all sites was observed. More robust projections of future changes in pH and ANC are dependent
on reducing uncertainties in BC release rates, the timing, and extent of natural acidification through BC uptake by plants,
temporal changes in soil element pools, and fluxes of Al between compartments. 相似文献
15.
The fate and transport processes of a toxic chemical such as atrazine, an herbicide, in a reservoir are significantly influenced
by hydrodynamic regimes of the reservoir. The two-dimensional (2D) laterally-integrated hydrodynamics and mass transport model,
CE-QUAL-W2, was enhanced by incorporating a submodel for toxic contaminants and applied to Saylorville Reservoir, Iowa. The
submodel describes the physical, chemical, and biological processes and predicts unsteady vertical and longitudinal distributions
of a toxic chemical. The simulation results from the enhanced 2D reservoir model were validated by measured temperatures and
atrazine concentrations in the reservoir. Although a strong thermal stratification was not identified from both observed and
predicted water temperatures, the spatial variation of atrazine concentrations was largely affected by seasonal flow circulation
patterns in the reservoir. In particular, the results showed the effect of flow circulation on spatial distribution of atrazine
during summer months as the river flow formed an underflow within the reservoir and resulted in greater concentrations near
the surface of the reservoir. Atrazine concentrations in the reservoir peaked around the end of May and early June. A good
agreement between predicted and observed times and magnitudes of peak concentrations was obtained. The use of time-variable
decay rates of atrazine led to more accurate prediction of atrazine concentrations, while the use of a constant half-life
(60 days) over the entire period resulted in a 40% overestimation of peak concentrations. The results provide a better understanding
of the fate and transport of atrazine in the reservoir and information useful in the development of reservoir operation strategies
with respect to timing, amount, and depth of withdrawal. 相似文献
16.
Kaivosoja T Virén A Tissari J Ruuskanen J Tarhanen J Sippula O Jokiniemi J 《Chemosphere》2012,86(3):278-285
Temporal variations in concentrations of perfluorinated carboxylic acids (PFCAs) and sulfonic acids (PFSAs), including perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) structural isomers, were examined in livers of pilot whale (Globicephala melas), ringed seal (Phoca hisida), minke whale (Balaenoptera acutorostrata), harbor porpoise (Phocoena phocoena), hooded seal (Cystophora cristata), Atlantic white-sided dolphin (Lagenorhynchus acutus) and in muscle tissue of fin whales (Balaenoptera physalus). The sampling spanned over 20 years (1984-2009) and covered a large geographical area of the North Atlantic and West Greenland. Liver and muscle samples were homogenized, extracted with acetonitrile, cleaned up using hexane and solid phase extraction (SPE), and analyzed by liquid chromatography with negative electrospray tandem mass spectrometry (LC-MS/MS). In general, the levels of the long-chained PFCAs (C9-C12) increased whereas the levels of PFOS remained steady over the studied period. The PFOS isomer pattern in pilot whale liver was relatively constant over the sampling years. However, in ringed seals there seemed to be a decrease in linear PFOS (L-PFOS) with time, going from 91% in 1984 to 83% in 2006. 相似文献
17.
Modeling the spatial dynamics of regional land use: the CLUE-S model 总被引:95,自引:3,他引:92
Verburg PH Soepboer W Veldkamp A Limpiada R Espaldon V Mastura SS 《Environmental management》2002,30(3):391-405
Land-use change models are important tools for integrated environmental management. Through scenario analysis they can help
to identify near-future critical locations in the face of environmental change. A dynamic, spatially explicit, land-use change
model is presented for the regional scale: CLUE-S. The model is specifically developed for the analysis of land use in small
regions (e.g., a watershed or province) at a fine spatial resolution. The model structure is based on systems theory to allow
the integrated analysis of land-use change in relation to socio-economic and biophysical driving factors. The model explicitly
addresses the hierarchical organization of land use systems, spatial connectivity between locations and stability. Stability
is incorporated by a set of variables that define the relative elasticity of the actual land-use type to conversion. The user
can specify these settings based on expert knowledge or survey data. Two applications of the model in the Philippines and
Malaysia are used to illustrate the functioning of the model and its validation. 相似文献
18.
Regional Representativeness of Swedish Reference Lakes 总被引:1,自引:1,他引:0
Richard K. Johnson 《Environmental management》1999,23(1):115-124
/ Recent focus has been placed on ecoregion delineations for providing an appropriate framework for monitoring and assessment of region-specific attainable water/habitat quality. Using an ecoregion approach to stratify variance, this study was conducted to determine whether earlier (subjectively) selected Swedish reference lakes may be considered as regionally representative reference sites when compared with a randomly selected lake population. Predictive modeling by discriminant function analysis with lakes classified by ecoregion and lake surface area and six physicochemical variables showed that the greater majority of reference lakes may be considered as regionally representative. The highest proportion of lake "misclassifications" occurred in the boreonemoral ecoregion, a relatively diverse ecoregion of southern Sweden. This apparent bias may be in part be due to the criteria used in selecting regional reference lakes. In the earlier selection of reference lakes emphasis was placed on lakes not being adversely affected by land usage or pollutant discharges, consequently forest lakes were often overrepresented and sites in agricultural areas underrepresented in the selected reference sites. As a complement to predictive modeling, PCA ordination showed the placement of reference lakes within the random lake population and indicated where reference sites might be missing along potentially important ecological gradients. KEY WORDS: Regionalization; Ecoregion; Representativeness; Reference; Ordination; Modeling; Temperate lakes 相似文献
19.
Pruess K 《Journal of contaminant hydrology》2004,70(3-4):225-247
Saturated-unsaturated flow in strictly layered sediments proceeds via conductors in parallel in the direction parallel to bedding, and via resistors in series in the direction perpendicular to bedding. On sufficiently small scales of space and time, flow in such media will be subject to approximate capillary equilibrium locally, which provides a basis for approximating the effective hydraulic conductivity of a composite multi-layer medium in terms of the conductivities of the individual layers. Equations for the hydraulic conductivity tensor in "composite medium approximation" (COMA) are given in a coordinate system aligned with bedding. Hydraulic conductivity parallel to bedding is generally larger than in the perpendicular direction. The anisotropy depends on the spread of the conductivity distribution, and tends to increase for dryer conditions. The COMA model was implemented in a multi-phase flow simulator and tested by comparison with high-resolution simulations in which all layering heterogeneity is resolved explicitly. Under favorable conditions, COMA is found to accurately represent sub-grid scale flow and transport processes, providing a practical method for simulating field-scale flow and transport in layered media. The approximation improves when layers are thinner, and when flow rates are smaller. 相似文献
20.
Monitoring Forest Carbon Sequestration with Remote Sensing and Carbon Cycle Modeling 总被引:1,自引:0,他引:1
Sources and sinks of carbon associated with forests depend strongly on the management regime and spatial patterns in potential productivity. Satellite remote sensing can provide spatially explicit information on land cover, stand-age class, and harvesting. Carbon-cycle process models coupled to regional climate databases can provide information on potential rates of production and related rates of decomposition. The integration of remote sensing and modeling thus produces spatially explicit information on carbon storage and flux. This integrated approach was employed to compare carbon flux for the period 1992–1997 over two 165-km2 areas in western Oregon. The Coast Range study area was predominately private land managed for timber production, whereas the West Cascades study area was predominantly public land that was less productive but experienced little harvesting in the 1990s. In the Coast Range area, 17% of the land base was harvested between 1991 and 2000. Much of the area was in relatively young, productive-age classes that simulations indicate are a carbon sink. Mean annual harvest removals from the Coast Range were greater than mean annual net ecosystem production. On the West Cascades study area, a relatively small proportion (< 1%) of the land was harvested and the area as a whole was accumulating carbon. The spatially and temporally explicit nature of this approach permits identification of mechanisms underlying land base carbon flux.
Published online 相似文献