Anthropogenic and climatic influences over the past three centuries on characteristics of an Adirondack lake,Eastern North America

Fourth Lake is a drainage lake at 43°N, 74°W, from which a 37‐cm long mud‐water interface core was recovered. ²¹⁰Pb dating indicates the core spans ≈340 years, from the Little Ice Age through modern global warming. Diatom accumulation responds to anthropogenic watershed disturbances, declining slightly up‐core until a peak in the late‐1800s attributable to sediment and nutrient influx from logging and enlargement of the outlet dam. A dramatic decrease occurs ≈1900 as logging and lake filling ceased, and a smaller peak ≈1960 accompanies residential development. Similar changes occur in organic carbon accumulation, which ranges from 0.0038–0.024 mg cm^?2 year^?1, with generally decreasing values up‐core, punctuated by maximum values in the late‐1800s. Expressing diatoms as concentration, however, reveals a doubling up‐core that positively correlates with changes extending beyond the watershed, including Northern Hemisphere temperature, atmospheric CO₂ concentration and solar irradiance (R = 0.627, 0.675 and 0.400, respectively). A >50% increase in % organic carbon, from 3.8% to 5.9%, also positively correlates with these larger‐scale environmental conditions (R = 0.828, 0.830 and 0.832), while negative correlations with the extrabasinal records are exhibited by magnetic susceptibility (R = ?0.654, ?0.496, and ?0.660) and clay (R = ?0.770, ?0.762, and ?0.737). These changes are consistent with decreased sediment influx and reduced dilution of biogenous sedimentary components. In contrast to total diatoms, the accumulation of planktonic genus Asterionella displays a long‐term increase up‐core. Potential explanations include increasing duration of the ice‐free season or a shift in the timing of the spring bloom and a mismatch with abundance of predator(s). Asterionella also increases as a percentage of total diatoms, being positively correlated with extrabasinal conditions (R = 0.827, 0.774 and 0.674). This change occurs at the expense of many benthic genera and, over the past century, at the expense of tychoplanktonic genus, Aulacosiera. Heavily silicified, Aulacosiera requires strong mixing to remain within the epilimnion. Thus, its decline might result from increasing stratification caused by warming.     

GRACE反演近年青藏高原及雅鲁藏布江流域陆地水储量变化

利用2005年至2010年6年的GRACE(Gravity Recovery and Climate Experiment)数据反演,研究了青藏高原地区以及雅鲁藏布江流域的季节及年陆地水储量的变化情况.结果显示:在研究区,伴随着显著地季节性波动,年水储量均有明显的下降趋势.同时,流域GRACE数据反演结果和国际上几种模式的水文模拟结果比较表明,GRACE在两个流域上的反演结果与CPC水文模型模拟结果变化趋势较为一致,但水储量年、季变化幅度偏大,而与GLDAS发布的CLM与VIC模型的结果则相差甚远,主要原因归结为青藏高原地区气候条件复杂导致模型的不确定性及误差较大,而大多水文模型缺乏对地下水变化的模拟能力所致.     

Editorial

Abstract

Defining and measuring sustainability is a major challenge. This article argues these limitations need not stop us from trying to identify and value the possible impacts of what we are doing, or are thinking about doing, over time periods much longer than the lives of our investments, or even of the lives of those of us living today. Sustainability is a relative concept that must be applied in an environment undergoing multiple changes, changes that are occurring over different temporal and spatial scales. We depend on our water resource systems for our survival and welfare. Yet no one expects them to be restored to, or survive in, their most productive pristine states in the face of increasing development pressures for land in their watersheds and for water in their streams, rivers, lakes, and aquifers. A continuing task of water resource planners and managers is to identify the multiple impacts and tradeoffs resulting from what we who are living today may wish to do for ourselves and our immediate children and what we can only guess our yet-to-be-born descendants may wish us to do, or not do, for them in some distant future. This task must involve professionals from other disciplines in a context much broader than just water management. Once these impacts and tradeoffs are identified, it is then up to the political process to make choices when they are in conflict. All of us need to be a part of this decision-making process.     

A SWAT evaluation of the effect of climate change on the hydrology of the Volta River basin

The SWAT (Soil and Water Assessment Tool) was used to evaluate the impacts of a climate scenario based on IPCC A1B emissions on flows in the Volta River basin in West Africa for 2021–2050 and 2071–2100, using 1983–2012 as the reference period. Overall, the simulation indicates increased variability and a decrease of up to 40% in river flow as a consequence of decreasing rainfall and increasing temperature. In particular, the analysis shows smaller absolute but greater relative changes in the hydrology of the northern (upper) part of the basin, particularly at the end of the century.     

Impacts of Global Climate Change Scenarios on Water Supply and Demand in Jordan

Abstract

The potential impact of global climate change is one of the least addressed factors in water resources planning in developing countries. The potential impacts of climate change are examined for Jordan, where a methodology is presented for improved management of water demand under the uncertainties associated with climate change. A temperature/precipitation sensitivity model is constructed and combined with water demand forecasts to project deficits for the year 2020. Deficit reducing options are then evaluated in terms of social and economic viability. The study concludes that only some of the deficits may be alleviated, illustrating the significance of considering climate change in planning for countries that already experience water imbalances.     

Changes of Pan Evaporation in the Recent 40 Years in the Yellow River Basin

Abstract

Based on monitoring data of 123 meteorological stations from 1960 to 2000 near or in the Yellow River Basin, the spatial and temporal distributions and their trends for pan evaporation (PE) are investigated in this study. The results indicate that, despite the annual mean air temperature over the Yellow River Basin has, on average, increased by 0.6° over the past 40 years, the rate of PE has steadily decreased, especially in summer and spring. Compared with the period of 1960s to 1970s, the rate of annual pan evaporation during 1980s to 1990s has decreased by 126mm or 7.0 percent. Spatial distribution of the rate of change show that this kind of trend is general but not universal, PE has significantly decreased over the upper and lower reaches of the Yellow River, but increased to a small degree over the middle reaches. Further analyses show that the decrease of PE is mainly related to reductions in sunshine durations and solar irradiance, owing to more clouds and aerosols.     

Irrigation infrastructure development in the Limarí Basin in Central Chile: implications for adaptation to climate variability and climate change

One option to deal with climate variability in agriculture is to build irrigation infrastructure, although this may lead to the overdevelopment of water resources, leading to ‘basin closure’. The Limarí Basin, in central north Chile, has relied on irrigation infrastructure over the last 30 years to increase water supply reliability and extend irrigated acreage, especially for permanent crops. This situation has reduced adaptation opportunities in the basin, which is currently experiencing a severe drought that, according to climate change projections, is expected to persist in the future, with important consequences for the sustainability of agriculture production.     

尾水重叠变化条件下水电站装机容量选择

董箐水电站的下游与龙滩水库衔接,呈现远景尾水重叠变化的特点。通过分析董箐水电站近远期水头特性、上游光照水库对董箐水电站入库径流的影响、河段综合利用要求、供电范围内负荷特性、电源结构及电力市场需求等,采取近期和远景结合的思路,以梯级发电引用流量匹配为原则,通过多方案技术经济比较,选择董箐水电站装机容量为880 MW。     

武烈河地表水与地下水转化规律研究

分析现状开采条件下武烈河地表水与地下水转化规律河水对地下水的补给量．双峰寺水库建成前后地下水可开采量的变化状况,为承德市区双峰寺水库建成后水源优化调度提供科学依据。     

白洋淀气候变化及对生态系统的影响

根据1955年-2010年白洋淀地区气象数据及生态资料,研究了气候变化对白洋淀湿地生态系统的影响,以期为白洋淀湿地保护和可持续发展提供依据。结果表明:近56年来,白洋淀地区的气温总体呈现上升趋势,且在2007年达到最高值,而降水量、平均风速和日照时数均呈现下降趋势,其中1996年以后的降水量均低于56年的平均降水量。白洋淀地区降水量和年最高水位呈明显的正相关关系,平均气温和水域面积的变化趋势则相反。水位、水域面积的变化以及人类活动等因素影响了白洋淀水质和生物多样性以及不同土地利用类型的分配比例。