共查询到20条相似文献，搜索用时 0 毫秒
1.
Globally, dams fragment river networks, threatening migratory fishes which require access to distinct habitats to complete their life cycles. Efforts to understand how cumulative effects of multiple dams affect migratory fishes across large regions, such as a country or continent, could help to identify locations for connectivity-enhancing actions to conserve migratory fishes. To address this, we evaluated cumulative effects of dams on migratory fishes in rivers across nine ecoregions of the conterminous USA. First, using fish data from thousands of sites (N = 45,989), we summarized ecoregional patterns in assemblages, quantifying the number of migratory species comprising assemblages, showing the prominence of potamodromous species across the large region as well as differences in migratory life history traits among ecoregions. Next, we compared the importance of a set of river network fragmentation metrics that captured influences of multiple dams in networks versus other anthropogenic landscape stressors and natural landscape factors that impact migratory fishes by ecoregion. We found that migratory fishes were more sensitive to cumulative dam effects than other stressors including urbanization and agriculture in the eastern USA. To further identify specific effects of environmental variables on potamodromous fishes, we conducted Boosted Regression Trees analysis in the eastern ecoregions. Our results suggested that the key natural influences on river fishes included catchment area as well as river baseflow and air temperature, suggesting that migratory fishes may be affected by changing climate. Additionally, we found that downstream dams were more influential than other human stressors to potamodromous fishes, underscoring the importance of enhancing connectivity within river networks to conserve migratory fishes. Collectively, our results provide new insights in identifying threats to migratory fish species across the USA, providing information that can aid in conserving this vulnerable but ecologically and socioeconomically important group of fishes. 相似文献
2.
C. A. M. van Turnhout R. S. E. W. Leuven A. J. Hendriks G. Kurstjens A. van Strien R. P. B. Foppen H. Siepel 《河流研究与利用》2012,28(3):269-282
To improve the ecological functioning of riverine ecosystems, large‐scale floodplain rehabilitation has been carried out in the Rhine–Meuse Delta since the 1990s. This paper evaluates changes in abundance of 93 breeding bird species over a period of 10 years in response to rehabilitation, by comparing population changes in 75 rehabilitated sites with 124 non‐rehabilitated reference sites. Such quantitative, multi‐species, large‐scale and long‐term evaluations of floodplain rehabilitation on biodiversity are still scarce, particularly studies that focus on the terrestrial component. We try to understand the effects by relating population trends to ecological and life‐history traits and strategies of breeding birds. More specifically, we try to answer the question whether rehabilitation of vegetation succession or hydro‐geomorphological river processes is the key driver behind recent population changes in rehabilitated sites. Populations of 35 species have significantly performed better in rehabilitated sites compared to non‐rehabilitated floodplains, whereas only 8 have responded negatively to rehabilitation. Differences in effects between species are best explained by the trait selection of nest location. Reproductive investment and migratory behaviour were less strong predictors. Based on these three traits we defined eight life‐history strategies that successfully captured a substantial amount of variation in rehabilitation effects. We conclude that spontaneous vegetation succession and initial excavations are currently more important drivers of population changes than rehabilitation of hydrodynamics. The latter are strongly constrained by river regulation. If rehabilitation of hydro‐geomorphological processes remains incomplete in future, artificial cyclic floodplain rejuvenation will be necessary for sustainable conservation of characteristic river birds. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
3.
不同气候条件的抚河流域SWAT径流模拟与验证 总被引：1，自引：0，他引：1
以鄱阳湖水系的抚河流域为研究对象,构建了抚河流域的SWAT模型,并对李家渡水文站的径流数据进行了模拟。模拟结果表明该模型适用于抚河流域的径流模拟。为了进一步验证模型在极端气候条件下的稳定性,分别选取连续丰水年(1975—1977年)和枯水年(1963—1965年)、连续高温年(1963—1965年)和低温年(1969—1971年)对模型进行验证。通过对气候变化条件下流域径流的模拟,率定期的决定系数R2与效率系数ENS均在0.85以上,验证期(1991—1998年)的R2与ENS均在0.80以上,说明构建的模型在极端气候年份具有一定的稳定性。 相似文献
4.
5.
干旱监测指标作为干旱研究的基础与关键,仍存在缺乏有效的分类与使用等问题,为进一步明晰旱情监测指标分类及旱情监测指标分析的不足,通过对旱情监测指标的科学梳理与总结,系统的对旱情监测指标体系进行了归类工作,将旱情监测指标分为气象干旱指标、水文干旱指标、农业干旱指标、社会经济干旱指标、生态干旱指标及综合干旱指标,总结和对比了现有旱情监测指标分类和指标本身的不足。在此基础上,基于干旱研究的未来发展诉求,提出了探索指标深度广度、完善指标动态监测功能、强化指标时空耦合性、耦合多模型多模式干旱体系、耦合多变量干旱监测体系、推进遥感旱情指标监测和提升大数据旱情监测平台构建能力等未来可能发展趋势,为当前进一步开展旱情监测、预测、预警和评估工作奠定基础。 相似文献
6.
Valerie L. Thayer Thomas C. Johnson Hans J. Schrader 《Journal of Great Lakes research》1983,9(4):508-516
Nine fossil planktonic diatom species were used for quantitative stratigraphic analysis of four cores from Lake Superior. Few changes in relative abundances of diatom species can be correlated among the cores. However, a consistent increase in Melosira islandica within the upper 20 cm of sediment is evident in all four cores. This increase occurs before an increase in Ambrosia (ragweed) pollen that marks the postsettlement horizon. Therefore, the Melosira islandica increase cannot be attributed to nutrient enrichment by man but may be a response to gradual climatic cooling over the last few thousand years, to differential dissolution, or to some other unknown cause. 相似文献
7.
若尔盖湿地流域径流变化及其对气候变化的响应 总被引：1，自引：0，他引：1
为探索未来气候变化情景下若尔盖高寒湿地水文过程和水循环演变规律,利用分布式水文模型,研究2020—2050年不同气候变化情景下若尔盖湿地流域径流变化趋势以及气候变化对湿地径流的影响。结果表明:在未来气候变化情景下,若尔盖湿地流域径流呈减少趋势,玛曲站径流减少比率最大,其次为若尔盖站,最后为唐克站;非汛期径流量减少幅度明显高于汛期,若尔盖湿地2020—2050年非汛期径流在未来气候变化情景下径流减少比率大部分在25%以上。非汛期径流的锐减可能会进一步加剧若尔盖湿地的退化和萎缩,导致黄河中下游区域的可利用水资源量减少。 相似文献
8.
基于14个CMIP6全球气候模式降尺度模拟结果,预测了未来SSP1-2.6、SSP2-4.5和SSP5-8.5情景下中国洪水-热浪复合极端(SFHE)事件及人口暴露度的时空变化特征,量化了气候效应、人口效应以及两者共同作用效应对人口暴露度的相对影响。结果表明：气候变暖加剧了未来华东和华南地区SFHE事件发生的风险,并导致SFHE事件历时及土地暴露度增长;SSP1-2.6、SSP2-4.5和SSP5-8.5情景下21世纪末中国SFHE事件年均频次与历史基准期(1961—2014年)相比,预计分别增加0.13、0.28、0.44次,SFHE事件平均历时分别增长1.4、3.9、8.1 d,年土地暴露度分别增加6.0%、13.8%、18.3%,而洪水、热浪平均间隔分别缩短0.16、0.37、0.75 d, SFHE事件突发性更强;未来SFHE事件人口暴露度增加的区域主要集中在中国东部和南部地区,由气候变化导致人口暴露度增加的效应逐渐增强。 相似文献
9.
10.
为了增强水资源系统的适应能力,减少气候变化造成的不利影响,通过实施＂黄河流域气候变化情景研究-快速评估＂项目,总结分析了1961年以来气候、水文等相关历史数据和2050年前的预测数据,进而阐述了因水资源短缺将会造成的影响及应采取的相应对策,为快速评估黄河流域气候变化情景提供了科学依据。 相似文献
11.
Justin T. Schoof 《Journal of Contemporary Water Research & Education》2012,147(1):8-16
Many of the processes that govern precipitation occurrence and intensity occur at spatial and temporal scales that remain unresolved by the current generation of climate models. The resulting mismatch between the information reliably provided by such models and the needs of researchers assessing impacts associated with changes in precipitation has led to the development of downscaling techniques. In this paper, the need for downscaling is demonstrated by describing (1) the difference between real‐world precipitation‐governing processes and their representation in climate models and (2) the differences between theoretical expectations of precipitation changes at large and small scales in a warmer world. With a primary focus on empirical‐statistical downscaling, the general strategy for developing regional scenarios is described along with outstanding issues that are likely to shape the next decade of downscaling research. 相似文献
12.
Switzerland is prone to many natural hazards causing high yearly damage to infrastructure and settlements. In this study questions about trends in data on damage from floods, debris flows and landslides are addressed and a potential connection to climate change is discussed. The data set of the Swiss flood and landslide damage database was normalised with three different approaches and trend tests were applied to yearly damage data from the period 1972–2016. Socio‐economic developments including those related to population and wealth were accounted for. The normalisation of the nominal damage data resulted in much higher values in the earlier years of the study period, especially for high damage years. Total and mean damage were both around twice as high with normalisation. Around 71–75% of the total (nominal and normalised) damage was found to occur from June through August, and spatial analysis showed the highest damage in central Switzerland and along river reaches in the main Alpine valleys. The results indicated no statistically significant increase over time in yearly nominal damage data or in data normalised with any of the three approaches. Potential effects of climate change on damage data therefore were not detected. 相似文献
13.
中国水资源响应全球气候变化的对策建议 总被引：18，自引：0，他引：18
根据全球气候变化对我国水资源影响的分析,应在无悔策略的指导下,运用科技、经济手段,加强基础设施建设,建立现代化的水利管理体系,以提高我国水资源系统对气候变化的适应能力。 相似文献
14.
15.
《Journal of Contemporary Water Research & Education》2017,162(1):18-30
Kansas extends 660 km from the moderate elevations and semi‐humid conditions of the Lower Missouri Basin to the High Plains lying above the Ogallala Aquifer and along the Rockies’ eastern slope. Such characteristics result in significant climate variability across the state, making timely and accurate climate trend and change information valuable for water resources management and crop production. Here we used high‐quality daily and monthly climate observations spanning a long‐term period of 121 years (1895–2015) to assess trends and changes in air temperature, precipitation, drought, and frost‐free days across Kansas. We show that a statewide average warming rate of 0.06°C (0.11°F) per decade was mainly driven by trends in daily minimum temperatures. However, there were no statistically significant trends in precipitation in either western, central, or eastern Kansas. Western Kansas tended toward increasing dryness, but central and eastern Kansas trended wetter as indicated by changes in the Palmer Drought Severity Index (PDSI), a trend that was consistent with a weak wetting signal in eastern Kansas. The length of frost‐free season increased by 5.2 days in western, 7.2 days in central, and 12.6 days in eastern Kansas, which reflected more warming in the east and less in the west, especially for changing magnitudes of nighttime temperatures. Such increases of frost‐free days, especially in moisture‐limited areas (e.g., western Kansas), might increase seasonal evapotranspiration loss, thus exacerbating soil moisture stress and associated management challenges. 相似文献
16.
17.
《Journal of Great Lakes research》2020,46(2):255-266
The Great Lakes Basin plays an important role in the economy and society of the United States and Canada, and climate change in this region may affect many sectors. In this study, six GCM simulations were downscaled to resolve the Great Lakes using a regional climate model (RCM) with 25 km × 25 km resolution. This model was used to project changes in temperature and precipitation during the mid-century (2040–2069) and late-century (2070–2099) over the Great Lakes basin region with reference to a baseline of 1980–2009. The whole-basin annual mean temperature is projected to increase 2.1 °C to 4.0 °C above the baseline during the mid-century, and 3.3 °C to 6.0 °C during the late-century. Summer temperatures in the southern portion of the basin are projected to increase more than the temperatures in the northern portion of the basin; whereas winter temperatures are projected to increase more in the north than in the south. Estimates of the whole-basin annual precipitation with respect to the baseline vary from −3.0% to 16.5% during the mid-century and −2.9% to 21.6% during the late-century, respectively. Future summer precipitation in southwestern areas of this region is expected to decrease by 20%–30% compared to the baseline, but winter precipitation (mostly snow) is expected to increase by 11.6% and 15.4% during the mid-century and late-century. This study highlights the effects of the large expanses of water (such as the Great Lakes) on regional climate projections and the associated uncertainties of climate change. 相似文献
18.
The present study aims to develop river ecosystem indicators, in particular for the River Rhine, on the basis of theoretical concepts describing natural rivers. The study includes river ecology concepts on zonation, stream hydraulics, river continuum, nutrient spiralling, serial discontinuity, flood pulse, riverine productivity and catchment hierarchy. The abiotic steering variables describing the hydrology, geomorphology and water quality, act as a template for ecosystem functioning. Functional processes are characterized by the flux of matter, which is affected by input, processing and retention of organic matter and nutrients. Spatial and temporal variation of input and retention of matter and the flow along the length of the river cause shifts in species distribution. These are reflected in gradients of macroinvertebrates and zonation of fish and benthic fauna, which form a dominant structural characteristic of the river ecosystem. Indicators proposed are retention of matter as an indicator for the functional characteristics and zonation of species as an indicator for the structural characteristics of the river ecosystem. Present river ecosystems are far from undisturbed. To allow efficient management of the river ecosystem, indicators and variables are required that reflect the cause–effect chain of human disturbance. River ecologists have developed a more spatially integrated and interdisciplinary view on rivers. Accordingly, the design, implementation and ecological assessment of monitoring programmes should reflect such an integrated spatial view. This means that a set of water quality, hydrological, geomorphological and ecological variables should be measured on a catchment scale, and that resulting data should be related to each other. Finally, this study presents some recommendations for monitoring, in particular for the Rhine monitoring programme. © 1997 John Wiley & Sons, Ltd. 相似文献
19.
C. H. D. Magadza 《Lakes & Reservoirs: Research and Management》2011,16(1):15-22
The pelagic fishery of Lake Kariba comprises the introduced clupeid, Limnothrissa miodon, from Lake Tanganyika. The annual fishery catches grew logistically from 1974, when commercial fishing began. It peaked at 37 000 tonnes (estimated mean sustainable yield = 40 000 tonnes) around 1990 and declined steadily thereafter. A piecewise regression of Limnothrissa catches against time gives a breakpoint around 1987–1988. Regressions of Limnothrissa against air temperature and lake temperature gave breakpoints of 34.8 and 28.7 °C, respectively. Other studies indicate that Lake Kariba has warmed by close to 2 °C, with accompanying changes in thermal stratification. The lake phytoplankton is now dominated by Cyanophyceae, particularly Cylindrospermum raciborskii. The lake zooplankton population has greatly diminished. These data are similar to the results obtained for Lake Tanganyika (Nature 2003; 424 , 766–8). In the Lake Tanganyika study, the declining pelagic fishery has been attributed to reduced food availability resulting from a reduced phototrophic zone depth, as well as epilimnion nutrient recharge from reduced mixing. The warming observed in Lake Kariba and its environs is consistent with the IPCC Fourth Assessment Report (AR4). While the effects of global warming have been observed in large natural lakes, this is the first study in which global warming has affected the ecosystem of a large impoundment. 相似文献
20.
基于不同大气环流模型评估气候变迁对高屏溪流域河川流量的影响 总被引：1，自引：0，他引：1
以五种大气环流模型(GCM)统计的雨量资料进行降雨比值分析,再由降雨资料用GWLF水文模型进行水文模拟,从而分析了气候变化对高屏溪流域河川径流的影响。分析结果表明未来丰水期水量上升,而枯水期流量呈现小幅减少趋势。各模型的变化范围随未来时间发生变化,即时间愈长其变化愈大。枯水期各模型的变化范围为-26%～+15%,而丰水期的变化范围为-10%～+82%。其中在区域经济发展极不均衡的(A2)情景下,枯水期各模型的变化范围为-26%～+13%,而丰水期的变化范围为-10%～+66%;而在区域经济可持续发展的(B2)情景下,枯水期各模型的变化范围为-18%～+15%,而丰水期的变化范围为-3%～+82%。 相似文献