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521.
Lauren E. Hay Gregory J. McCabe 《Journal of the American Water Resources Association》2002,38(3):847-860
ABSTRACT: A monthly water‐balance (WB) model was tested in 44 river basins from diverse physiographic and climatic regions across the conterminous United States (U.S.). The WB model includes the concepts of climatic water supply and climatic water demand, seasonality in climatic water supply and demand, and soil‐moisture storage. Exhaustive search techniques were employed to determine the optimal set of precipitation and temperature stations, and the optimal set of WB model parameters to use for each basin. It was found that the WB model worked best for basins with: (1) a mean elevation less than 450 meters or greater than 2000 meters, and/or (2) monthly runoff that is greater than 5 millimeters (mm) more than 80 percent of the time. In a separate analysis, a multiple linear regression (MLR) was computed using the adjusted R‐square values obtained by comparing measured and estimated monthly runoff of the original 44 river basins as the dependent variable, and combinations of various independent variables [streamflow gauge latitude, longitude, and elevation; basin area, the long‐term mean and standard deviation of annual precipitation; temperature and runoff; and low‐flow statistics (i.e., the percentage of months with monthly runoff that is less than 5 mm)]. Results from the MLR study showed that the reliability of a WB model for application in a specific region can be estimated from mean basin elevation and the percentage of months with gauged runoff less than 5 mm. The MLR equations were subsequently used to estimate adjusted R‐square values for 1,646 gauging stations across the conterminous U.S. Results of this study indicate that WB models can be used reliably to estimate monthly runoff in the eastern U.S., mountainous areas of the western U.S., and the Pacific Northwest. Applications of monthly WB models in the central U.S. can lead to uncertain estimates of runoff. 相似文献
522.
Jean M. Sogbedji Gregory F. Mclsaac 《Journal of the American Water Resources Association》2002,38(6):1753-1765
ABSTRACT: Evaluation of the applicability and validity of hydrologic simulation models for various cropping systems in different hydrogeologic and soil conditions is needed for a range of spatial scales. We calibrated and tested the ADAPT model for simulating streamflow from 552 to 1,985 km2 watersheds in central Illinois, where more than 79 percent of the land is used for maize‐soybean production and tile drainage is common. Model calibration was performed with a seven year period (1987 through1993) of measured streamflow from one of the watersheds, and model testing was done using independent weather and measured streamflow data from the two neighboring watersheds for the same seven year period. Simulations of annual streamflow were accurate with a coefficient of determination and Willmott's index of agreement of 0.98 and 0.99, respectively. For simulation of monthly streamflow, Willmott's index of agreement ranged from 0.93 to 0.95. For simulation of daily streamflow, Willmott's index of agreement ranged from 0.84 to 0.85. The daily simulations challenged the temporal and spatial resolution of our measured precipitation data. Discrepancies between simulated and measured data may result from the model's inability to effectively address frozen soils and snowmelt runoff processes and in accurately representing evapotranspiration. 相似文献
523.
Zoran S. Petrović Yijin Xu Jelena Milić Gregory Glenn Artur Klamczynski 《Journal of Polymers and the Environment》2010,18(2):94-97
Thermoplastic urethanes based on polyricinoleic acid soft segments and MDI/BD hard segments with varied soft segment concentration
were prepared. Soft segment concentration was varied from, 40 to 70 wt%. Biodegradation was studied by respirometry. Segmented
polyurethanes with soft segments based on polyricinoleic acid degrade relatively slow losing about 11% carbon after 30 days,
but faster than corresponding petrochemical polyesterurethanes. Since biodegradation proceeds mainly through the soft segments,
higher soft segment content polymers displayed slightly higher biodegradation. Polyurethanes with dispersed hard domains in
the soft phase displayed slightly faster biodegradation than those with co-continuous morphology. Polyester diol degrades
slower than castor oil but significantly faster than the polyurethanes with built in soft segments from the same diol. Castor
oil biodegrades slower than soybean oil. 相似文献
524.
Gregory J. Robertson 《Behavioral ecology and sociobiology》1998,43(4-5):289-296
Hypotheses regarding the evolution and maintenance of intraspecific nest parasitism were tested with data collected during
a 3-year study of common eiders (Somateria mollissima) breeding near Churchill, Manitoba. The nest parasitism rate was highest (42.4% of nests) during the year with the highest
nest density and the best environmental conditions, and lowest (20.2% of nests) in the year with the lowest nest density and
the poorest environmental conditions. Over the nesting season, parasitic eggs were laid at the same time as normally laid
eggs. Most parasitic eggs (>75%) were laid before the host female laid her third egg. The majority of the parasitic eggs were
the first or second egg produced by the parasitic female. When a parasitic egg was laid before or on the same day as the host
female initiated her clutch, the probability of her first egg being depredated before incubation was significantly lowered.
First- and second-laid eggs suffered a high rate of predation probably because nesting females do not attend their clutch
until their second or third egg is laid. Hypotheses that some females use intraspecific nest parasitism to parasitize the
parental care of other females were inconsistent with these data. Egg adoption is a likely explanation for the prevalence
of females incubating parasitic eggs in this population.
Received: 30 September 1997 / Accepted after revision: 6 May 1998 相似文献
525.
526.
Gregory A. Norris 《环境质量管理》2001,10(3):59-64
Current life‐cycle assessment (LCA) methodologies rarely include economic analysis—even though this element is almost always crucial to any company's decision making. This article discusses practical tools for integrating economic considerations into LCA. © 2001 John Wiley & Sons, Inc. 相似文献
527.
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529.
The difference in performance of three differently designed circular secondary clarifiers in the same wastewater treatment plant was analyzed in this paper. Data obtained using flocculated suspended solids and disperse suspended solids tests were analyzed using statistical tools. The conventional clarifier showed more variability in the average effluent suspended solids concentration when compared with the flocculator-clarifiers. Furthermore, a difference in performance among the two different flocculator-clarifiers was found. 相似文献
530.
Robb Daniel M. Pieters Roger Lawrence Gregory A. 《Environmental Fluid Mechanics》2021,21(6):1201-1225
Environmental Fluid Mechanics - Turbidity from glacial meltwater limits light penetration with potential ecological consequences. Using profiles of temperature, conductivity, and turbidity, we... 相似文献