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701.
唐燕娟 《防灾减灾工程学报》1998,(4)
利用多方面收集的资料,对震级问题作了较为全面的阐述,以期对地震工作者尤其是新参加工作的同行进一步了解震级定性定量的由来、发展和现状作引荐。 相似文献
702.
Brian G. Katz Rodney S. DeHan Joshua J. Hirten John S. Catches 《Journal of the American Water Resources Association》1997,33(6):1237-1254
ABSTRACT: Ground water and surface water constitute a single dynamic system in most parts of the Suwannee River basin due to the presence of karst features that facilitate the interaction between the surface and subsurface. Low radon-222 concentrations (below background levels) and enriched amounts of oxygen-18 and deuterium in ground water indicate mixing with surface water in parts of the basin. Comparison of surface water and regional ground water flow patterns indicate that boundaries for ground water basins typically do not coincide with surface water drainage subbasins. There are several areas in the basin where ground water flow that originates outside of the Suwannee River basin crosses surface water basin boundaries during both low-flow and high-flow conditions. In a study area adjacent to the Suwannee River that consists predominantly of agricultural land use, 18 wells tapping the Upper Floridan aquifer and 7 springs were sampled three times during 1990 through 1994 for major dissolved inorganic constituents, trace elements, and nutrients. During a period of above normal rainfall that resulted in high river stage and high ground water levels in 1991, the combination of increased amounts of dissolved organic carbon and decreased levels of dissolved oxygen in ground water created conditions favorable for the natural reduction of nitrate by denitrification reactions in the aquifer. As a result, less nitrate was discharged by ground water to the Suwannee River. 相似文献
703.
Deborah H. Lee Thomas E. Croley Frank H. Quinn 《Journal of the American Water Resources Association》1997,33(1):55-69
ABSTRACT: The implications of Lake Ontario regulation under transposed climates with changed means and variability are presented for seasonal and annual time scales. The current regulation plan is evaluated with climates other than the climate for which it was developed and tested. This provides insight into potential conflicts and management issues, development of regulation criteria for extreme conditions, and potential modification of the regulation plan. Transposed climates from the southeastern and south central continental United States are applied to thermodynamic models of the Great Lakes and hydrologic models of their watersheds; these climates provide four alternative scenarios of water supplies to Lake Ontario. The scenarios are analyzed with reference to the present Great Lakes climate. The responses of the Lake Ontario regulation plan to the transposed climate scenarios illustrate several key issues: (1) historical water supplies should no longer be the sole basis for testing and developing lake regulation plans; (2) during extreme supply conditions, none of the regulation criteria can be met simultaneously, priority of interests may change, and new interests may need to be considered, potentially requiring substantial revision to the Boundary Waters Treaty of 1909; (3) revised regulation criteria should be based on ecosystem health and socio-economic benefits for a wider spectrum of interests and not on frequencies and ranges of levels and flows of the historical climate; and (4) operational management of the lake should be improved under the present climate, and under any future climate with more variability, through the use of improved water supply forecasts and monitoring of current hydrologic conditions. 相似文献
704.
David C. Froehlich 《Journal of the American Water Resources Association》1994,30(6):1055-1062
ABSTRACT: Design of a stormwater pump station is a complicated procedure because of the large number of parameters that are involved. Even the most basic pump station serving a small catchment requires a computationally intensive iterative evaluation. However, the design problem consists primarily of finding the combination of temporary storage and pump capacity that accommodates runoff of the selected recurrence interval for the least cost. A procedure is developed for rapidly obtaining the needed relation between storage volume and discharge for small pump stations where a constant outflow can be assumed and the inflow hydro-graph can be represented using the modified rational method with rainfall given by a widely-used intensity-duration equation. Accepting the limitations of the modified rational method and the simplifications applied to pump station operation, the procedure provides an uncomplicated way of rapidly finding the stormwater runoff volume that needs to be temporarily stored for given values of pump discharge and activation water level (or, equivalently, activation storage volume). Ultimate determination of temporary runoff storage will depend on an economic analysis of the trade-off between storage volume and pump capacity. 相似文献
705.
G. D. Naslas W W. Miller R. R. Blank G. F. Gifford 《Journal of the American Water Resources Association》1994,30(3):409-417
ABSTRACT: Few studies have addressed the natural pollution potential of pristine subalpine forested watersheds on a site-specific basis. Consequently, specific source and amounts of nutrient discharge to tributaries of the Tahoe Basin are difficult to identify. The sediment content and nitrate and ammonium levels in surface runoff from two soil types (Meeks and Umpa), four plot conditions (wooded natural and disturbed, open natural and disturbed), and three slopes (gentle, moderate, and steep) were studied using rainfall simulation that applied a 9 cm h1, 1-h event. A significant (P ≤ 0.005) two-way interaction between soil type and plot condition affected runoff nitrate concentration. Runoff from natural or disturbed open plots contained significantly (P = 0.05) greater nitrate than wooded plots. Peak concentrations of nitrate commonly occurred during early runoff, suggesting that peak nitrate discharge to Lake Tahoe tributaries can be expected during early runoff from snowmelt and summer precipitation events. The highest nitrate runoff concentration and 1-h cumulative loading from the 0.46 m2 plots were 6.7 mg L-1 (Umpa, open natural, 15–30 percent slope), and 0.7 mg (Umpa, open natural, ≥ 30 percent slope), respectively. Ammonium in surface runoff was generally below detection limits (≤ 0.05 μg L?1). No statistical relationship between runoff nitrate and sediment discharge was detected. 相似文献
706.
ABSTRACT: This paper examines the performance of snowmelt-runoff models in conditions approximating real-time forecast situations. These tests are one part of an intercomparison of models recently conducted by the World Meteorological Organization (WMO). Daily runoff from the Canadian snowmelt basin Illecille. waet (1155 km2, 509–3150 m a.s.l.) was forecast for 1 to 20 days ahead. The performance of models was better than in a previous WMO project, which dealt with runoff simulations from historical data, for the following reasons: (1) conditions for models were more favorable than a real-time forecast situation because measured input data and not meteorological forecast inputs were distributed to the modelers; (2) the selected test basin was relatively easy to handle and familiar from the previous WMO project; and (3) all kinds of updating were allowed so that some models even improved their accuracy towards longer forecast times. Based on this experience, a more realistic follow-up project can be imagined which would include temperature forecasts and quantitative precipitation forecasts instead of measured data. 相似文献
707.
Michael A. Huston Thomas A. Fontaine 《Journal of the American Water Resources Association》1994,30(4):651-661
ABSTRACT: A large storm in December 1990 allowed the evaluation of flood predictions from a hydrologic model (TOPMODEL) that had been previously calibrated on the West Fork of Walker Branch Watershed, a gauged 37.5 ha catchment near Oak Ridge, Tennessee. The model predicts both hydrograph dynamics and the spatial distribution of overland flow using an index based on topography. Maximum extent of overland flow during the storm was determined from patterns of leaf litter removal from valley bottoms. Both the flood hydrograph and the extent of overland flow were accurately predicted using model parameters obtained from a three-month period of normal flow conditions during 1983. 相似文献
708.
David S. Leigh 《Journal of the American Water Resources Association》1994,30(4):739-748
ABSTRACT: Gold was discovered in Georgia in 1829 and mined until about 1940 in the Dahionega Gold Belt of the north Goorgia Piedmont. Streams there are characterized by gravel beds and fine sandy to silty banks. Historical mining-related alluvium is clearly distinguished from prehistoric alluvium because it is contaminated with mercury (Hg), which was used by miners to amalgamate gold. Mercury concentrations in historical floodplain sediments range from 0.04 to 4.0 mg kg?1, exceeding background (0.04 mg kg1) by as much as two orders of magnitude near the core of the mining district and decreasing in the downstream direction. Low levels (≤ 0.1 mg kg1) of Hg are established within about 10–15 km from the source mines. The mercury-contaminated sediment exceeds sediment quality guidelines set by many agencies, and is a significant nonpoint source for mercury pollution. Hydraulic mining of saprolite, which began in 1868, and cutting of forests associated with mining and settlement caused unusually rapid sedimentation (1–3 cm yr?l) and floodplain aggradation in the region. After mining ceased, streams adjusted by downcutting and forming an historical-age terrace. A new floodplain is currently being formed as streams migrate lateraily and erode the mining-related sediment of the historical terrace. High magnitude floods are contained within the confines of the historical terrace, thus limiting quantities of over-bank sedimentation, causing channel bank erosion, and transmitting high sediment yields to reservoirs in the region. 相似文献
709.
710.
译文叙述了地面和地下储油罐对环境影响的差异、美国环保局(EPA)对此的有关规定、石油污染法、全国污染物排除控制系统(NPDES)等。最后介绍地面油罐法规具体内容。 相似文献