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171.
Abstract: Given their physiological requirements, limited dispersal abilities, and hydrologically sensitive habitats, amphibians are likely to be highly sensitive to future climatic changes. We used three approaches to map areas in the western hemisphere where amphibians are particularly likely to be affected by climate change. First, we used bioclimatic models to project potential climate‐driven shifts in the distribution of 413 amphibian species based on 20 climate simulations for 2071–2100. We summarized these projections to produce estimates of species turnover. Second, we mapped the distribution of 1099 species with restricted geographic ranges. Finally, using the 20 future climate‐change simulations, we mapped areas that were consistently projected to receive less seasonal precipitation in the coming century and thus were likely to have altered microclimates and local hydrologies. Species turnover was projected to be highest in the Andes Mountains and parts of Central America and Mexico, where, on average, turnover rates exceeded 60% under the lower of two emissions scenarios. Many of the restricted‐range species not included in our range‐shift analyses were concentrated in parts of the Andes and Central America and in Brazil's Atlantic Forest. Much of Central America, southwestern North America, and parts of South America were consistently projected to experience decreased precipitation by the end of the century. Combining the results of the three analyses highlighted several areas in which amphibians are likely to be significantly affected by climate change for multiple reasons. Portions of southern Central America were simultaneously projected to experience high species turnover, have many additional restricted‐range species, and were consistently projected to receive less precipitation. Together, our three analyses form one potential assessment of the geographic vulnerability of amphibians to climate change and as such provide broad‐scale guidance for directing conservation efforts. 相似文献
172.
ABSTRACT: A climate factor, CT, (T = 2–, 25-, and 100-year recurrence intervals) that delineates regional trends in small-basin flood frequency was derived using data from 71 long-term rainfall record sites. Values of CT at these sites were developed by a regression analysis that related rainfall-runoff model estimates of T-year floods to a sample set of 50 model calibrations. CT was regionalized via kriging to develop maps depicting its geographic variation for a large part of the United States east of the 105th meridian. Kriged estimates of CT and basin-runoff characteristics were used to compute regionalized T-year floods for 200 small drainage basins. Observed T-year flood estimates also were developed for these sites. Regionalized floods are shown to account for a large percentage of the variability in observed flood estimates with coefficients of determination ranging from 0.89 for 2-year floods to 0.82 for 100-year floods. The relative importance of the factors comprising regionalized flood estimates is evaluated in terms of scale (size of drainage area), basin-runoff characteristics (rainfall. runoff model parameters), and climate (CT). 相似文献
173.
Gregory J. McCabe David M. Wolock Lauren E. Hay Mark A. Ayers 《Journal of the American Water Resources Association》1990,26(4):633-643
ABSTRACT: The Thornthwaite moisture index is a useful indicator of the supply of water (precipitation) in an area relative to the demand for water under prevailing climatic conditions (potential evapotranspiration). This study examines the effects of changes in climate (temperature and precipitation) on the Thornthwaite moisture index in the conterminous United States. Estimates of changes in mean annual temperature and precipitation for doubled-atmospheric CO2 conditions derived from three general circulation models (GCMs) are used to study the response of the moisture index under steady-state doubled-CO2 conditions. Results indicate that temperature and precipitation changes under doubled-CO2 conditions generally will cause the Thornthwaite moisture index to decrease, implying a drier climate for most of the United States. The pattern of expected decrease is consistent among the three GCMs, although the amount of decrease depends on which GCM climatic-change scenario is used. Results also suggest that changes in the moisture index are related mainly to changes in the mean annual potential evapotranspiration as a result of changes in the mean annual temperature, rather than to changes in the mean annual precipitation. 相似文献
174.
Gregory J. McCabe Mark A. Ayers 《Journal of the American Water Resources Association》1989,25(6):1231-1242
ABSTRACT: The Thornthwaite water balance and combinations of temperature and precipitation changes representing climate change were used to estimate changes in seasonal soil-moisture and runoff in the Delaware River basin. Winter warming may cause a greater proportion of precipitation in the northern part of the basin to fall as rain, which may increase winter runoff and decrease spring and summer runoff. Estimates of total annual runoff indicate that a 5 percent increase in precipitation would be needed to counteract runoff decreases resulting from a warming of 2°C; a 15 percent increase for a warming of 4°C. A warming of 2° to 4°C, without precipitation increases, may cause a 9 to 25 percent decrease in runoff. The general circulation model derived changes in annual runoff ranged from ?39 to +9 percent. Results generally agree with those obtained in studies elsewhere. The changes in runoff agree in direction but differ in magnitude. In this humid temperate climate, where precipitation is evenly distributed over the year, decreases in snow accumulation in the northern part of the basin and increases in evapotranspiration throughout the basin could change the timing of runoff and significantly reduce total annual water availability unless precipitation were to increase concurrently. 相似文献
175.
ABSTRACT: Drought has been a prevalent feature of the American landscape during the latter part of the 1980s, producing serious socioeconomic and environmental consequences. These recent experiences with drought have renewed concern about the inadequacy of federal and state contingency planning efforts and the lack of coordination for assessment and response efforts between these levels of government. This paper presents the results of research aimed at facilitating the preparation of drought contingency plans by state government in conjunction with a state's overall water management planning activity. The ten-step drought plan development process reported is intended to improve mitigation efforts through more timely, effective, and efficient assessment and response activities. Officials in appropriate state agencies should examine the proposed framework and alter it to best address drought-related concerns, adding or deleting elements as necessary. 相似文献
176.
Lowell F W. Duell 《Journal of the American Water Resources Association》1994,30(5):841-859
ABSTRACT: The sensitivity of streamflow to climate change was investigated in the American, Carson, and Truckee River Basins, California and Nevada. Nine gaging stations were used to represent streamflow in the basins. Annual models were developed by regressing 1961–1991 streamflow data on temperature and precipitation. Climate-change scenarios were used as inputs to the models to determine streamflow sensitivities. Climate-change scenarios were generated from historical time series by modifying mean temperatures by a range of +4°C to—4°C and total precipitation by a range of +25 percent to -25 percent. Results show that streamflow on the warmer, lower west side of the Sierra Nevada generally is more sensitive to temperature and precipitation changes than is streamflow on the colder, higher east side. A 2°C rise in temperature and a 25-percent decrease in precipitation results in stream-flow decreases of 56 percent on the American River and 25 percent on the Carson River. A 2°C decline in temperature and a 25-percent increase in precipitation results in streamflow increases of 102 percent on the American River and 22 percent on the Carson River. 相似文献
177.
During the period of 1972 through 1993, Environmental Concern Inc. (EC) and its recent (1989) affiliate Environmental Construction
Company (ECC) have completed 216 marsh construction projects to control upland bank erosion in tributaries of the Maryland
portion of Chesapeake Bay. Of these projects, 26 have involved marsh construction on unaltered existing shores and 190 have
utilized marsh construction on shores that have been restored to former increased elevations through shoreline filling and
grading. This paper describes the latter restoration technique. Throughout the 21-year period of applying the technique for
long-term upland bank erosion control, refinements to the design standards and criteria for site suitability have been made
so as to optimize its successful application. As a result of this experience, a reliable bioengineering restoration technique
has evolved to control upland bank erosion. This paper describes the details of this successful technique through a review
of: (1) its objectives and benefits, (2) suitability of sites for its application, (3) the design of its shore restoration,
(4) its construction, (5) its maintenance, and (6) comparison of its cost with those of structural techniques for bank erosion
control. Although the technique has only been applied in the Maryland portions of Chesapeake Bay, its applicability should,
with modifications, be broadly applicable to all water bodies. 相似文献
178.
建立城市自然灾害承灾能力指标的思路探讨 总被引:10,自引:0,他引:10
本文论述了城市承灾能力的含义,分析了我国城市主要自然灾害以及承文体的类型和致灾因素,探讨了城市承灾能力指标,为城市承灾能力综合评判提供了依据. 相似文献
179.
Y. Dubuc P. Janneteau R. Labont C. Roy F. Brire 《Journal of the American Water Resources Association》1986,22(2):297-303
ABSTRACT: The use of peatlands as the main form of wastewater treatment in a northern climate was studied for the James Bay Energy Society. The Fontanges campsite (70° 17′ 30″ W; 54° 34′ 00″ N) was chosen as the study site. In less than 1.5 km from the point of discharge BOD5, COD, total hardness, inorganic carbon, orthophosphates, total phosphorus, ammonia and total nitrogen were reduced by at least 90 percent. The peatland treatment system studied is divided into four components, each having a specific function. The first part combines the action of microorganisms and adsorption on peat, thus reducing the organic content while increasing the inorganic constituents. The second part uses peat to adsorb the inorganic elements already present in the wastewater and those produced in the first part of the system. The third component acts as an aerator, increasing the dissolved oxygen and decreasing the BOD5 levels of the water. The fourth part removes most of the remaining nutrients, thus acting like a tertiary treatment. Overall, peatlands seemed to be effective in treating domestic settled wastewater in a cold climate. 相似文献
180.
Alan C. Heyvaert John E. Reuter Charles R. Goldman 《Journal of the American Water Resources Association》2006,42(1):45-54
The Tahoe City Wetland Treatment System (TCWTS) was constructed in 1997 to treat stormwater runoff from 23 ha of commercial, highway, and residential land use in the Lake Tahoe Basin. This subalpine, constructed, surface flow wetland treatment system consists of two cells in series, with a design water surface area of about 0.6 ha. Water quality monitoring from October 2002 through September 2003 was conducted with autosamplers at the inflow and outflow sites during 24 sampling events, with a median duration of 53 hours, representing 42 percent of total inflow to this wetland during the year. Monitoring data indicate an improvement of 49 percent or greater in effluent concentrations of dissolved phosphorus, nitrate, orthophosphorus, and total suspended solids. On average, event mean concentrations of total phosphorus were reduced from a median 279 μg/l at the inflow to 94 μg/l at the outflow. Event mean concentrations of total nitrogen were reduced from a median 1,599 μg/l at the inflow to 810 μg/l at the outflow. Net nutrient retention for the sampling period was estimated at 3 g phosphorus (P)/m2/y and 13 g nitrogen (N)/m2/y. Almost 4,000 kg of suspended sediment was captured by this wetland system during the year. 相似文献