Actual state of European wetlands and their possible future in the context of global climate change

The present area of European wetlands is only a fraction of their area before the start of large-scale human colonization of Europe. Many European wetlands have been exploited and managed for various purposes. Large wetland areas have been drained and reclaimed mainly for agriculture and establishment of human settlements. These threats to European wetlands persist. The main responses of European wetlands to ongoing climate change will vary according to wetland type and geographical location. Sea level rise will probably be the decisive factor affecting coastal wetlands, especially along the Atlantic coast. In the boreal part of Europe, increased temperatures will probably lead to increased annual evapotranspiration and lower organic matter accumulation in soil. The role of vast boreal wetlands as carbon sinks may thus be suppressed. In central and western Europe, the risk of floods may support the political will for ecosystem-unfriendly flood defence measures, which may threaten the hydrology of existing wetlands. Southern Europe will probably suffer most from water shortage, which may strengthen the competition for water resources between agriculture, industry and settlements on the one hand and nature conservancy, including wetland conservation, on the other.     

The effects of possible future climate change on evaporation losses from four contrasting UK water catchment areas

Evaporation losses from four water catchment areas under different land uses and climatic conditions were calculated using formulations developed from small plot studies. These formulations, dependent on rainfall inputs, potential evaporation and air temperature, were extrapolated to the catchment scale using land classifications based on analysing remotely sensed imagery. The approach adopted was verified by comparing the estimated annual evaporation losses with catchment water use, given by the difference between rainfall inputs and stream flow outputs, allowing for changes in soil moisture. This procedure was repeated using modified values of rainfall, potential evaporation and air temperature, as given by a climate change scenario. The computed evaporation losses were used in annual water balances to calculate stream flow losses under the climate change scenario. It was found that, in general, stream flow from areas receiving high rainfall would increase as a result of climate change. For low rainfall areas, a decrease in stream flow was predicted. The largest actual changes in stream flow were predicted to occur during the winter months, although the largest percentage changes will occur during the summer months. The implications of these changes on potable water supply are discussed. © 1998 John Wiley & Sons, Ltd.     

GIS技术在洪湖环境演变研究中的应用

本文运用GIS技术,探索了洪湖环境的近期变化及其机理,以空间的、定量的形式,展示了与修建隔堤、分割湖区、围湖垦殖及水位控制等人为活动因素相联系的湖泊环境变化效应和过程,分析了湖中挺水植物分布的动态变化与趋协。这项工作进一步表明了地理信息系统方法在湖泊环境变化的监测、评价和研究中具有独特的功效和实用价值。     

Several characteristics of contemporary climate change in the Tibetan Plateau

Characteristics of contemporary climate change in the Tibetan Plateau have been investigated based on the observational data of monthly mean air temperature, monthly mean maximum and minimum air temperatures, and precipitation amount at 217 stations in the Plateau and its adjacent areas in 1951–1998, in which the temperature data at Lhasa, Lanzhou, Kunming and Chengdu were extended to a period of 1935–1950. The following conclusions can be drawn. (1) The air temperature in the Tibetan Plateau decreased from the 1950s to the 1960s, afterwards it began warming up to the 1990s. The data at the Lhasa Station beginning from 1935 have indicated that the air temperature at the station was the highest in the 1940s, then it became cooling until the 1960s. After the 1960s, it began warming until the 1990s. However, the air temperature at Lhasa in the 1990s still did not reach as high as in the 1940s. (2) Since the 1960s, there has existed a cooling belt below 3000 m altitude above sea level, which is located in eastern and southeastern Tibetan Plateau, and there has existed a strong warming belt from south to north in 85–95° E. Because there are very nonhomogeneous and positive-negative alternating changes between cooling and warming belts, the air temperature is not linearly increased with increasing height. (3) Since the 1960s, there has existed a precipitation decreasing belt distributed over southwestern to northeastern Plateau as well as over a below 3000 m a.s.l. area in southeastern Plateau. The warming with decreasing precipitation occurs in the central area of the Plateau and the above 3000 m western Plateau; the warming with increasing precipitation occurs in the northern and southern Plateau; and the cooling with decreasing precipitation occurs in the below 3000 m southeastern Plateau.     

A nonstationary runoff frequency analysis for future climate change and its uncertainties

With the intensification of climate change, its impact on runoff variations cannot be ignored. The main purpose of this study is to analyse the nonstationarity of runoff frequency adjusted for future climate change in the Luanhe River basin, China, and quantify the different sources of uncertainties in nonstationary runoff frequency analysis. The advantage of our method is the combination of generalized additive models in location, scale, and shape (GAMLSS) and downscaling models. The nonstationary GAMLSS models were established for the nonstationary frequency analysis of runoff (1961–2010) by using the observed precipitation as a covariate, which is closely related to runoff and contributes significantly to its nonstationarity. To consider the nonstationary effects of future climate change on future runoff variations, the downscaled precipitation series in the future (2011–2080) from the general circulation models (GCMs) were substituted into the selected nonstationary model to calculate the statistical parameters and runoff frequency in the future. A variance decomposition method was applied to quantify the impacts of different sources of uncertainty on the nonstationary runoff frequency analysis. The results show that the impacts of uncertainty in the GCMs, scenarios, and statistical parameters of the GAMLSS model increase with increasing runoff magnitude. In addition, GCMs and GAMLSS model parameters have the main impacts on runoff uncertainty, accounting for 14% and 83% of the total uncertainty sources, respectively. Conversely, the interactions and scenarios make limited contributions, accounting for 2% and 1%, respectively. Further analysis shows that the sources of uncertainty in the statistical parameters of the nonstationary model mainly result from the fluctuations in the precipitation sequence. This result indicates the necessity of considering the precipitation sequence as a covariate for runoff frequency analysis in the future.     

Hydrological response to future land-use change and climate change in a tropical catchment

Hydrological response to expected future changes in land use and climate in the Samin catchment (278 km²) in Java, Indonesia, was simulated using the Soil and Water Assessment Tool model. We analysed changes between the baseline period 1983–2005 and the future period 2030–2050 under both land-use change and climate change. We used the outputs of a bias-corrected regional climate model and six global climate models to include climate model uncertainty. The results show that land-use change and climate change individually will cause changes in the water balance components, but that more pronounced changes are expected if the drivers are combined, in particular for changes in annual streamflow and surface runoff. The findings of this study will be useful for water resource managers to mitigate future risks associated with land-use and climate changes in the study catchment.     

湖泊生态服务生产函数构建研究——以博斯腾湖为例

湖泊生态系统服务（LES）在维持区域乃至全球生态安全格局中发挥重要作用,是目前生态系统服务研究的热点之一。由于湖泊面广量大、类型丰富、区域差异大及基础数据较为缺乏等原因,适用于LES定量评估且较为便捷、可行的模型方法较少。本文以博斯腾湖为例,基于生态系统最终服务与关键特征指标构建湖泊生态服务生产函数（LEPF）,用于定量评估湖泊生态系统服务价值（LESV）并甄别关键特征指标的贡献度。结果表明：（1）博斯腾湖1990 2019年生态系统最终服务年均价值量为2226.84亿元,总体呈“上升下降上升”的变化趋势,气候调节、防洪蓄水为主导生态系统服务;（2）LEPF拟合结果较好地反映了5类关键特征指标对LESV的贡献度,从高到低依次为：湖泊水位>蒸发量>面积>水生植被面积>综合营养状态指数;（3）5类关键特征指标中水位的产出弹性较高,表明水位波动与生态系统最终服务价值变化密切相关。     

基于Copula函数的连河通江湖泊防洪安全设计:以洪泽湖为例

湖泊作为一种蓄水单元,尤其是大型过水性湖泊,是一种典型的平原型水库,在功能上与山谷型水库具有许多相似之处,但由于其特殊的地理地形构造,使得入湖洪水过程与入库洪水过程存在着较大的差异.在防洪安全设计研究中,山谷型水库关注的多是坝址洪水,即总的入库洪水过程,而对于湖泊来说,还需要关注各个分区的入湖洪水过程对湖区洪水演进的影...     

Seasonality and magnitude of floods in Switzerland under future climate change

The flood seasonality of catchments in Switzerland is likely to change under climate change because of anticipated alterations of precipitation as well as snow accumulation and melt. Information on this change is crucial for flood protection policies, for example, or regional flood frequency analysis. We analysed projected changes in mean annual and maximum floods of a 22‐year period for 189 catchments in Switzerland and two scenario periods in the 21st century based on an ensemble of climate scenarios. The flood seasonality was analysed with directional statistics that allow assessing both changes in the mean date a flood occurs as well as changes in the strength of the seasonality. We found that the simulated change in flood seasonality is a function of the change in flow regime type. If snow accumulation and melt is important in a catchment during the control period, then the anticipated change in flood seasonality is most pronounced. Decreasing summer precipitation in the scenarios additionally affects the flood seasonality (mean date of flood occurrence) and leads to a decreasing strength of seasonality, that is a higher temporal variability in most cases. The magnitudes of mean annual floods and more clearly of maximum floods (in a 22‐year period) are expected to increase in the future because of changes in flood‐generating processes and scaled extreme precipitation. Southern alpine catchments show a different signal, though: the simulated mean annual floods decrease in the far future, that is at the end of the 21st century. Copyright © 2013 John Wiley & Sons, Ltd.     

Effects of future land use change on the regional climate in China

Land use and land cover change(LUCC)is one of the important human forcing on climate.However,it is difficult to infer how LUCC will affect climate in the future from the effects of previous LUCC on regional climates in the past.Thus,based on the land cover data recommended by the Coupled Model Intercomparison Project Phase 5(CMIP5),a regional climate model(Reg CM4)was used to investigate the climate effects of future land use change over China.Two 15-year simulations(2036–2050),one with the current land use data and the other with future land cover scenario(2050)were conducted.It is noted that future LUCC in China is mainly characterized by the transition from the grassland to the forest.Results suggest that the magnitudes and ranges of the changes in temperature and precipitation caused by future LUCC show evident seasonality,which are more prominent in summer and autumn.Significant response of climate to future LUCC mainly happens in Northeast China,North China,the Hetao Area,Eastern Qinghai-Tibetan Plateau and South China.Further investigation shows that future LUCC can also produce significant impacts on the atmospheric circulation.LUCC results in abnormal southwesterly wind over extensive areas from the Indian peninsula to the coasts of the South China Sea and South China through the Bay of Bengal.Furthermore,Indian tropical southwest monsoons and South Sea southwest monsoons will both be strong,and the abnormal water vapor convergence from the South China Sea and the Indian Ocean will result in more precipitation in South China.     

Effect of climate change on overland flow generation: a case study in central Germany

The impact of global climate change on runoff components, especially on the type of overland flow, is of utmost significance. High‐resolution temporal rainfall plays an important role in determining the hydrological response of quick runoff components. However, hydrological climate change scenario analyses with high temporal resolution are rare. This study investigates the impact of climate change on discharge peak events generated by rainfall, snowmelt, and soil‐frost induced runoff using high‐resolution hydrological modelling. The study area is Schäfertal catchment (1.44 km²) in the lower Harz Mountains in central Germany. The WaSiM‐ETH hydrological model is used to investigate the rainfall response of runoff components under near future (2021–2050) and far‐distant future (2071–2100) climatic conditions. Disaggregated daily climate variables of WETTREG2010 SRES scenario A1B are used on a temporal resolution of 10 min. Hydrological model parameter optimization and uncertainty analysis was conducted using the Differential Evolution Adaptive Metropolis (DREAM_(ZS)) uncertainty tool. The scenario results show that total runoff and interflow will increase by 3.8% and 3.5% in the near future and decrease by 32.85% and 31% in the far‐distant future compared to the baseline scenario. In contrast, overland flow and the number and size of peak runoff will decrease moderately for the near future and drastically for the far‐distant future compared to the baseline scenario. We found the strongest decrease for soil‐frost induced discharge peaks at 79.6% in the near future and at 98.2% in the far‐distant future scenario. It can be concluded that high‐resolution hydrological modelling can provide detailed predictions of future hydrological regimes and discharge peak events of the catchment. Copyright © 2014 John Wiley & Sons, Ltd.     

Analysis on urban lake change during rapid urbanization using a synergistic approach: A case study of Wuhan,China

To grasp the evolution of urban lakes accurately is quite necessary for studying on the mechanism of city ecological development. The study about extraction with different types of water by remote sensing technology has developed for decades. Many water indexes as the main methods are used to extract water information. Each method has advantage and disadvantage in different situation. A synergistic approach in this study can reduce the uncertainty of urban lake extraction by using four methods: NDWI, MNDWI, RNDWI and SPM. The basic idea behind the synergistic approach is to give each pixel a score based upon the agreement among the different products of four water extraction methods. According to the score of each pixel, the synergy map, which has been created by the products of four methods, is decomposed into sixteen sub-synergy maps. We use Bayesian Decision Theory to screen out the sub-synergy maps with low confidence level. The remaining ones are recombined a refined map. The overall accuracy of refined map reaches 96.44%, higher than any one of the four methods. Wuhan, known as the City of Hundred Lakes, is selected as the study area. We use the synergistic method to keep track of twenty lakes in Wuhan City changing from 1990 to 2013. The total area of twenty lakes has reduced from 130.2478 km² to 102.2971 km² during twenty-three years. The area of Shaihu Lake, which is the most serious of all observed lakes, has shrunk by 77.27%. And Nanhu Lake has lost 8.5 km² of its area that is the most among all lakes. We also find 1990–2000 is the high tide of urban lake shrinking. After the year of 2000, the situation of lake shrinking has been controlled gradually.     

Modelling climate change impacts on hydropower lake inflows and braided rivers in a mountain basin

This study models climate change impacts on the natural flow regime of braided rivers and inflows to hydropower lakes in a New Zealand mountain basin. Flow metrics include the magnitude, frequency, timing and duration of unaltered flows. The TopNet hydrological model was used to simulate impacts in the Upper Waitaki Basin of the South Island for the 1990s, 2040s and 2090s. An average emissions scenario and results from 12 global circulation models were used as input. Indicators of hydrological alteration and Kruskal-Wallis tests were used to evaluate flow differences. Modelled total inflows increase over time for all lakes, with most increases in winter/early spring and small decreases in summer/autumn. High flows generally increase, while low flows decrease. Although these changes may benefit hydropower and floodplain ecology, they may increase flood risk in winter and spring and drought risk in summer and autumn, causing additional challenges managing hydropower operations.

EDITOR M.C. Acreman

ASSOCIATE EDITOR S. Kanae     

Effects of climate change on thermal properties of lakes and reservoirs, and possible implications

Meteorologic-driven processes exert large and diverse impacts on lakes’ internal heating, cooling, and mixing. Thus, continued global warming and climate change will affect lakes’ thermal properties, dynamics, and ecosystem. The impact of climate change on Lake Tahoe (in the states of California and Nevada in the United States) is investigated here, as a case study of climate change effects on the physical processes occurring within a lake. In the Tahoe basin, air temperature data show upward trends and streamflow trends indicate earlier snowmelt. Precipitation in the basin is shifting from snow to rain, and the frequency of intense rainfall events is increasing. In-lake water temperature records of the past 38 years (1970–2007) show that Lake Tahoe is warming at an average rate of 0.013°C/year. The future trends of weather variables, such as air temperature, precipitation, longwave radiation, downward shortwave radiation, and wind speed are estimated from predictions of three General Circulation Models (GCMs) for the period 2001–2100. Future trends of weather variables of each GCM are found to be different to those of the other GCMs. A series of simulation years into the future (2000–2040) is established using streamflows and associated loadings, and meteorologic data sets for the period 1994–2004. Future simulation years and trends of weather variables are selected so that: (1) future simulated warming trend would be consistent with the observed warming trend (0.013°C/year); and (2) future mixing pattern frequency would closely match with the historical mixing pattern frequency. Results of 40-year simulations show that the lake continues to become warmer and more stable, and mixing is reduced. Continued warming in the Tahoe has important implications for efforts towards managing biodiversity and maintaining clarity of the lake.     

Hydrologic response of a Hawaiian watershed to future climate change scenarios

The impact of potential future climate change scenarios on streamflow and evapotranspiration (ET) in a mountainous Hawaii watershed was studied using the distributed hydrology soil vegetation model (DHSVM). The hydrologic response of the watershed was simulated for 43 years for different levels of atmospheric CO₂ (330, 550, 710 and 970 ppm), temperature (+1.1 and + 6.4 °C) and precipitation (±5%, ±10% and ±20%) on the basis of the Intergovernmental Panel on Climate Change (IPCC) AR4 projections under current, B1, A1B1 and A1F1 emission scenarios. Vegetation leaf conductance and leaf area index were modified to reflect the increase in CO₂ concentration. The relative departure of streamflow and ET from their levels during the reference scenarios was calculated on a monthly and annual basis. Results of this study indicate that the streamflow and ET are less sensitive to changes in temperature compared with changes in precipitation. However, temperature increase coupled with precipitation showed significant effect on ET and streamflow. Changes in leaf conductance and leaf area index with increasing CO₂ concentration under A1F1 scenario had a significant effect on ET and subsequently on streamflow. Evapotranspiration is less sensitive than streamflow for a similar level of change in precipitation. On the basis of a range of climate change scenarios, DHSVM predicted a change in ET by ±10% and streamflow between ?51% and 90%. From the six ensemble mean scenarios for AR4 A1B, simulations suggest reduction in streamflow by 6.7% to 17.2%. These reductions would produce severe impact on water availability in the region. Copyright © 2011 John Wiley & Sons, Ltd.     

The effects of climate change on historical and future extreme rainfall in Antalya,Turkey

Abstract

There is increasing concern that flood risk will be exacerbated in Antalya, Turkey as a result of global-warming-induced, more frequent and intensive, heavy rainfalls. In this paper, first, trends in extreme rainfall indices in the Antalya region were analysed using daily rainfall data. All stations in the study area showed statistically significant increasing trends for at least one extreme rainfall index. Extreme rainfall datasets for current (1970–1989) and future periods (2080–2099) were then constructed for frequency analysis using the peaks-over-threshold method. Frequency analysis of extreme rainfall data was performed using generalized Pareto distribution for current and future periods in order to estimate rainfall intensities for various return periods. Rainfall intensities for the future period were found to increase by up to 23% more than the current period. This study contributed to better understanding of climate change effects on extreme rainfalls in Antalya, Turkey.     

Impacts of future land cover and climate change on the water balance in northern Iran

We evaluated the potential impacts of future land cover change and climate variability on hydrological processes in the Neka River basin, northern Iran. This catchment is the main source of water for the intensively cultivated area of Neka County. Hydrological simulations were conducted using the Soil and Water Assessment Tool. An ensemble of 17 CMIP5 climate models was applied to assess changes in temperature and precipitation under the moderate and high emissions scenarios. To generate the business-as-usual scenario map for year 2050 we used the Land Change Modeler. With a combined change in land cover and climate, discharge is expected to decline in all seasons except the end of autumn and winter, based on the inter-model average and various climate models, which illustrated a high degree of uncertainty in discharge projections. Land cover change had a minor influence on discharge relative to that resulting from climate change.     

A comparative study of geothermal and meteorological records of climate change in Kamchatka

To reconstruct the recent climate history in Kamchatka, a series of repeated precise temperature logs were performed in a number of boreholes located in a broad east-west strip (between 52 and 54°N) in the central part of Kamchatka west of Petropavlovsk-Kamchatski. Within three years more than 30 temperature logs were performed in 10 holes (one up to six logs per hole) to the depth of up to 400 metres. Measured temperature gradients varied in a broad interval 0 to 60 mK/m and in some holes a sizeable variation in the subsurface temperatures due to advective heat transport by underground water was observed. Measured data were compared with older temperature profiles obtained in the early eighties by Sugrobov and Yanovsky (1993). Even when older data are of poorer precision (accuracy of about 0.1 K), they presented valuable information of the subsurface temperature conditions existing 20–25 years ago. Borehole observations and the inverted ground surface temperature histories (GSTHs) used for the paleoclimate reconstruction were complemented with a detailed survey of meteorological data. Namely, the long-term surface air temperature (SAT) and precipitation records from Petropavlovsk station (in operation since 1890) were used together with similar data from a number of local subsidiary meteo-stations operating in Central Kamchatka since 1950. Regardless of extreme complexity of the local meteorological/climate conditions, diversity of borehole sites and calibration of measuring devices used during the whole campaign, the results of the climate reconstruction supported a general warming of about 1 K characteristic for the 20th century, which followed an inexpressive cooler period typical for the most of the 19th century. In the last three to four decades the warming rate has been locally increasing up to 0.02 K/year. It was also shown that the snow cover played a dominant role in the penetration of the climate “signal” to depth and could considerably smooth down the subsurface response to the changes occurred on the surface.