Streamflow response of Belgian catchments to IPCC climate change scenarios

The IRMB (Integrated Runoff Model—F. Bultot) daily step conceptual model has been applied to eight Belgian catchments with areas ranging from 100 to 1200 km². These catchments are characterized by various infiltration rates and ground water storage capacities. The outputs of six GCMs (General Circulation Model) distributed by the IPCC (Intergovernmental Panel on Climate Change) and an earlier scenario have been used to perturb time series of hydrometeorological input data relevant to simulate the water cycle. This paper focuses on the impacts on streamflow and its surface and underground components, as well as on the occurrence of flood days and low flow days. Impacts are shown to be catchment and scenario dependent. Due to the scenario diversity, streamflow impacts are found to be either positive or negative. The trends are common to scenarios with the same patterns or to catchments with similar characteristics. For all but two scenarios, all the catchments present an increase of flood frequency. Nevertheless, for all the scenarios, catchments with prevailing surface flow are undergoing an increase in flood frequency during winter months.     

A regional model to assess the hydrological sensitivity of medium size catchments to climate variability

Catchment storage capacity is an important factor in the determination of catchment sensitivity to climate variability. Quantification of catchment sensitivity is in turn important in the regional assessment of the effects of possible climate change. In the present paper, an empirical regional model is proposed that quantifies catchment sensitivity as the ratio of present maximum reservoir storage to catchment storage capacity. Catchment storage capacity is defined theoretically using readily available catchment variables. Present maximum reservoir storage in a catchment, as determined from recession analysis, is expressed as a fraction of catchment storage capacity; the fraction defines catchment sensitivity and depends on storage capacity and annual net precipitation. Average annual conditions for present maximum reservoir storage and average annual net precipitation are used to test the developed model. Although the study used data from only 15 catchments in the Upper Loire region in France, the model proved statistically valid. Storage capacity calculated with the model compares favourably with the baseflow index and a storage index defined in previous research. Values of storage capacity are probable with respect to reported water resources in the area. With the model catchment sensitivity can easily be assessed. Flood or drought prone catchments can be identified as well as a catchment's sensitivity to a catchment-type transition (baseflow versus direct flow dominated catchments). © 1998 John Wiley & Sons, Ltd.     

不同时间尺度青海湖沉积物总有机碳对气候变化的敏感性

湖泊沉积物总有机碳（TOC）含量通常作为表征流域和湖泊生产力的指标,在亚洲季风区也常常被当作夏季风的代用指标,被广泛应用于气候与环境变化研究.本文梳理了过去千年、全新世以及冰期-间冰期时间尺度上青海湖沉积物TOC的变化特征,并探讨了其指示气候变化的敏感性与有效性.结果表明,过去千年青海湖沉积物TOC含量与区域暖季温度和降水表现出较为一致的周期性波动.通过对比全新世区域夏季温度、基于孢粉的降水定量重建结果,以及湖泊水位、风沙活动反映的湿度状况等,发现不能简单地将青海湖沉积物TOC含量或沉积通量作为夏季风强度或者季风降水强度的代用指标.青海湖沉积物TOC含量在冰期和间冰期表现出巨大的差异,指示了冰期-间冰期时间尺度上较大的温度与降水变幅.因此,不同地域条件及不同时间尺度下,湖泊沉积物TOC对气候变化的敏感性不同,将湖泊沉积物TOC含量作为亚洲夏季风的代用指标需要特别谨慎,特别是在高寒气候区.     

Estimating the sensitivity of runoff to climate change in an alpine-valley watershed of Xinjiang,China

ABSTRACT

The spatial-temporal variation of runoff in an inland basin is very sensitive to climate change. Investigation of runoff change in arid areas is typically limited by lack of meteorological and hydrogeological data. This study focused on runoff change in the Yarkand River source area of the Tarim Basin, China, with the aim of analysing the influence of climate change on the response characteristics of discharge. Sensitivity analysis was introduced to reflect the degree of influence of climate on runoff. Based on the sensitivity factors, over 30 sets of schemes including the IPCC Fourth Assessment Report were simulated using the MIKE 11/NAM rainfall–runoff model and the response of runoff was analysed. The results indicate that there are significant correlations and synchronous fluctuations between runoff and precipitation, evaporation and temperature. The characteristics of the sensitivity of runoff can be fitted well by Bi-Gaussian functions. The functions show that high sensitivity indexes mainly appear in the interval of 165 ± 100 m³ s^-1. The influence of precipitation on runoff is greater than that of other climate factors. Through simulation using the NAM model, we found that change of annual runoff was related to the initial climate condition. Annual runoff will have an increasing trend if it has a strong sensitivity to the initial meteorological condition. Moreover, the runoff decreases linearly with evaporation. Also it has a positive relationship with temperature and precipitation. Across the four seasons, the impact in summer and winter is greater than that in spring and autumn. Estimation of the spatial-temporal influence of climate on runoff could provide insight for water resource development in arid areas.

Editor Z.W. Kundzewicz Associate editor not assigned     

Response of snow cover and runoff to climate change in high Alpine catchments of Eastern Switzerland

A model study on the impact of climate change on snow cover and runoff has been conducted for the Swiss Canton of Graubünden. The model Alpine3D has been forced with the data from 35 Automatic Weather Stations in order to investigate snow and runoff dynamics for the current climate. The data set has then been modified to reflect climate change as predicted for the 2021–2050 and 2070–2095 periods from an ensemble of regional climate models.The predicted changes in snow cover will be moderate for 2021–2050 and become drastic in the second half of the century. Towards the end of the century the snow cover changes will roughly be equivalent to an elevation shift of 800 m. Seasonal snow water equivalents will decrease by one to two thirds and snow seasons will be shortened by five to nine weeks in 2095.Small, higher elevation catchments will show more winter runoff, earlier spring melt peaks and reduced summer runoff. Where glacierized areas exist, the transitional increase in glacier melt will initially offset losses from snow melt. Larger catchments, which reach lower elevations will show much smaller changes since they are already dominated by summer precipitation.     

Hydrological sensitivity of a large Himalayan basin to climate change

The present study sets out to investigate the sensitivity of water availability to climate change for a large western Himalayan river (the Satluj River basin with an area of 22 275 km² and elevation range of 500 to 7000 m), which receives contributions from rain, snow and glacier melt runoff. About 65% of the basin area is covered with snow during winter, which reduces to about 11% after the ablation period. After having calibrated a conceptual hydrological model to provide accurate simulations of observed stream flow, the hydrological response of the basin was simulated using different climatic scenarios over a period of 9 years. Adopted plausible climate scenarios included three temperature scenarios (T + 1, T + 2, T + 3 °C) and four rainfall scenarios (P ? 10, P ? 5, P + 5 and P + 10%). The effect of climate change was studied on snowmelt and rainfall contribution runoff, and total stream flow. Under warmer climate, a typical feature of the study basin was found to be reduction in melt from the lower part of the basin owing to a reduction in snow covered area and shortening of the summer melting season, and, in contrast, an increase in the melt from the glacierized part owing to larger melt and an extended ablation period. Thus, on the basin scale, reduction in melt from the lower part was counteracted by the increase from melt from upper part of the basin, resulting in a decrease in the magnitude of change in annual melt runoff. The impact of climate change was found to be more prominent on seasonal rather than annual water availability. Reduction of water availability during the summer period, which contributes about 60% to the annual flow, may have severe implications on the water resources of the region, because demand of water for irrigation, hydropower and other usage is at its peak at this time. Copyright © 2004 John Wiley & Sons, Ltd.     

Extreme value theory for precipitation: sensitivity analysis for climate change

Extreme value theory for the maximum of a time series of daily precipitation amount is described. A chain-dependent process is assumed as a stochastic model for daily precipitation, with the intensity distribution being the gamma. To examine how the effective return period for extreme high precipitation amounts would change as the parameters of the chain-dependent process change (i.e., probability of a wet day, shape and scale parameters of the gamma distribution), a sensitivity analysis is performed. This sensitivity analysis is guided by some results from statistical downscaling that relate patterns in large-scale atmospheric circulation to local precipitation, providing a physically plausible range of changes in the parameters. For the particular location considered in the example, the effective return period is most sensitive to the scale parameter of the intensity distribution.     

Streamflow sensitivity analysis to climate change for a large water‐limited basin

Partitioning precipitation (P) between streamflow (Q) and actual evapotranspiration (E_a) on a basin scale is controlled by climate change in combination with catchment characteristics. Fu's formulation of the Budyko framework was used to estimate Q as a function of two meteorological variables, P and potential evaporation (E_p), and one adjustable parameter reflecting characteristics of catchment conditions (ω). Results show that ω reflects the impacts of catchment characteristics on the partitioning of P between Q and E_a for the different water yielding regions. As predicted, Q was more sensitive to P than to comparable changes in E_p for the whole of the Yellow River Basin (YRB), a water‐limited basin, while it was shown to be highly sensitive to changes in P, E_p, and ω in the low water yielding region (LWYR) of the basin, followed by YRB and the high water yielding region of the basin. The high sensitivity of Q to P, E_p, and ω in LWYR indicates that the management of catchments within these zones is critical to the management of overall basin flow, mitigating impacts of climate change on Q. The Budyko framework, incorporating the adjustable parameter ω, outlines interactions between Q, climate, and characteristics specific to different water yielding regions. It also provides a new approach in understanding hydrological process response to climate change. Due to the obscure physical attributes of ω, an explanation of the parameter using soil or vegetation characteristics will aid in the understanding of the eco‐hydrological behaviour of catchments and help to provide more detailed catchment management options for which to mitigate climate change with respect to concerns regarding agricultural water usage. Copyright © 2013 John Wiley & Sons, Ltd.     

Assessing sensitivity of hydrologic responses to climate change from forested watershed in Mississippi

The climatic processes such as changes in precipitation, temperature and atmospheric CO₂ concentration can intensify the effects on water resources. An assessment of the effects of long‐term climate change on water resources is essential to the development of water quality improvement programs. This study was conducted in the Upper Pearl River Watershed (UPRW) in east‐central Mississippi to assess the effects of long‐term potential future climate change on average mean monthly stream flow from the five spatially distributed U. S. Geological Survey (USGS) gage stations in the UPRW using the Soil and Water Assessment Tool. The model was calibrated (January 1981 to December 1994) and validated (January 1995 to September 2008) using monthly measured stream flow data. The calibrated and validated model determined good to very good performance for stream flow prediction (R² and E from 0·60 to 0·86) between measured and predicted stream flow values. The root mean square error values (from 14 to 37 m³ s^?1) were estimated at similar levels of errors during model calibration and validation. The results showed that long‐term (50 years) average monthly stream flow sensitivity due to climate change effects was found the greatest as a result of percentage change in the precipitation followed by carbon dioxide (CO₂) concentration and temperature. The long‐term model simulation scenarios as compared with the base scenario for all five spatially distributed USGS gage stations in the UPRW estimated an average monthly stream flow decrease (from 54 to 67%) and average monthly stream flow increase (from 67 to 79%) depending on the spatial characteristics of the USGS gage stations. Overall, the results indicate that the UPRW hydrology is very sensitive to potential future climate changes and that these changes could stimulate increased streamflow generation from the watershed. Copyright © 2010 John Wiley & Sons, Ltd.     

The role of hydrological modelling uncertainties in climate change impact assessments of Irish river catchments

This study attempts to assess the uncertainty in the hydrological impacts of climate change using a multi-model approach combining multiple emission scenarios, GCMs and conceptual rainfall-runoff models to quantify uncertainty in future impacts at the catchment scale. The uncertainties associated with hydrological models have traditionally been given less attention in impact assessments until relatively recently. In order to examine the role of hydrological model uncertainty (parameter and structural uncertainty) in climate change impact studies a multi-model approach based on the Generalised Likelihood Uncertainty Estimation (GLUE) and Bayesian Model Averaging (BMA) methods is presented. Six sets of regionalised climate scenarios derived from three GCMs, two emission scenarios, and four conceptual hydrological models were used within the GLUE framework to define the uncertainty envelop for future estimates of stream flow, while the GLUE output is also post processed using BMA, where the probability density function from each model at any given time is modelled by a gamma distribution with heteroscedastic variance. The investigation on four Irish catchments shows that the role of hydrological model uncertainty is remarkably high and should therefore be routinely considered in impact studies. Although, the GLUE and BMA approaches used here differ fundamentally in their underlying philosophy and representation of error, both methods show comparable performance in terms of ensemble spread and predictive coverage. Moreover, the median prediction for future stream flow shows progressive increases of winter discharge and progressive decreases in summer discharge over the coming century.     

Evaluating the sensitivity of wetlands to climate change with remote sensing techniques

Wetlands are valuable ecosystems that provide many valuable services, yet many of these important ecosystems are at risk because of current trends in climate change. The Prairie Pothole Region (PPR) in the upper‐midwest of the United States and south‐central Canada, characterized by glacially sculpted landscapes and abundant wetlands, is one such vulnerable region. According to regional/global climate model predictions, drought occurrence will increase in the PPR region through the 21st century and thus will probably cause the amount of water in wetlands to decline. Water surface area (WSA) of Kidder County, ND, from 1984–2011 was measured by classifying TM/ETM+(Landsat Thematic Mapper / Enhanced Thematic Mapper Plus) images through the modified normalized difference water index. We then developed a linear model based on the WSA of these wetlands and historical climate data and used this to determine the wetland sensitivity to climate change and predict future wetlands WSA in the PPR. Our model based on Palmer drought severity index (PDSI) of the current year (PDSI_{t ? 0}) and of the previous two years (PDSI_{t ? 2}) can explain 79% of the annual wetland WSA variance, suggesting a high sensitivity of wetlands to drought/climate change. We also predicted the PPR wetlands WSA in the 21st century under A1B scenario (a mid‐carbon emission scenario) using simulated PDSI based on Intergovernmental Panel on Climate Change AR4 22‐model ensemble climate. According to our prediction, the WSA of the PPR wetlands will decrease to less than half of the baseline WSA (defined as the mean wetlands WSA of the 2000s) by the mid of the 21st century, and to less than one‐third by the 2080s, and will then slightly increase in the 2090s. This considerable future wetland loss caused only by climate change provides important implication to future wetland management and climate adaptation policy. Copyright © 2012 John Wiley & Sons, Ltd.     

Runoff and sediment loss responses to rainfall and land use in two agricultural catchments on the Loess Plateau of China

Soil erosion is a severe problem hindering sustainable agriculture on the Loess Plateau of China. Plot experiments were conducted under the natural rainfall condition during 1995–1997 at Wangdongguo and Aobao catchments in this region to evaluate the effects of various land use, cropping systems, land slopes and rainfall on runoff and sediment losses, as well as the differences in catchment responses. The experiments included various surface conditions ranging from bare soil to vegetated surfaces (maize, wheat residue, Robinia pseudoacacia L., Amorpha fruticosa L., Stipa capillata L., buckwheat and Astragarus adsurgens L.). The measurements were carried out on hill slopes with different gradients (i.e. 0 ° to 36 °). These plots varied from 20 to 60 m in length. Results indicated that runoff and erosion in this region occurred mainly during summer storms. Summer runoff and sediment losses under cropping and other vegetation were significantly less than those from ploughed bare soil (i.e. without crop/plant or crop residue). There were fewer runoff and sediment losses with increasing canopy cover. Land slope had a major effect on runoff and sediment losses and this effect was markedly larger in the tillage plots than that in the natural grass and forest plots, although this effect was very small when the maximum rainfall intensity was larger than 58·8 mm/h or smaller than 2·4 mm/h. Sediment losses per unit area rose with increasing slope length for the same land slope and same land use. The effect of slope length on sediment losses was stronger on a bare soil plot than on a crop/plant plot. The runoff volume and sediment losses were both closely related to rainfall volume and maximum intensity, while runoff coefficient was mainly controlled by maximum rainfall intensity. Hortonian overland flow is the dominant runoff process in the region. The differences in runoff volume, runoff coefficient and sediment losses between the catchments are mainly controlled by the maximum rainfall intensity and infiltration characteristics. The Aobao catchment yielded much larger runoff volume, runoff coefficient and sediment than the Wangdongguo catchment. Copyright © 2001 John Wiley & Sons, Ltd.     

Generating probabilistic estimates of hydrological response for Irish catchments using a weather generator and probabilistic climate change scenarios

In accounting for uncertainties in future simulations of hydrological response of a catchment, two approaches have come to the fore: deterministic scenario‐based approaches and stochastic probabilistic approaches. As scenario‐based approaches result in a wide range of outcomes, the role of probabilistic‐based estimates of climate change impacts for policy formulation has been increasingly advocated by researchers and policy makers. This study evaluates the impact of climate change on seasonal river flows by propagating daily climate time series, derived from probabilistic‐based climate scenarios using a weather generator (WGEN), through a set of conceptual hydrological models. Probabilistic scenarios are generated using two different techniques. The first technique used probabilistic climate scenarios developed from statistically downscaled scenarios for Ireland, hereafter called SDprob. The second technique used output from 17 global climate models (GCMs), all of which participated in CMIP3, to generate change factors (hereafter called CF). Outputs from both the SDprob and the CF approach were then used in combination with WGEN to generate daily climate scenarios for use in the hydrological models. The range of simulated flow derived with the CF method is in general larger than those estimated with the SDprob method in winter and vice versa because of the strong seasonality in the precipitation signal for the 17 GCMs. Despite this, the simulated probability density function of seasonal mean streamflow estimated with both methods is similar. This indicates the usefulness of the SDprob or probabilistic approach derived from regional scenarios compared with the CF method that relies on sampling a diversity of response from the GCMs. Irrespective of technique used, the probability density functions of seasonal mean flow produced for four selected basins is wide indicating considerable modelling uncertainties. Such a finding has important implications for developing adaptation strategies at the catchment level in Ireland. Copyright © 2011 John Wiley & Sons, Ltd.     

Estimating the sensitivity of mean annual runoff to climate change using selected hydrological models

Hydrological model sensitivity to climate change can be defined as the response of a particular hydrological model to a known quantum of climate change. This paper estimates the hydrological sensitivity, measured as the percentage change in mean annual runoff, of two lumped parameter rainfall-runoff models, SIMHYD and AWBM and an empirical model, Zhang01, to changes in rainfall and potential evaporation. These changes are estimated for 22 Australian catchments covering a range of climates, from cool temperate to tropical and moist to arid. The results show that the models display different sensitivities to both rainfall and potential evaporation changes. The SIMHYD, AWBM and Zhang01 models show mean sensitivities of 2.4%, 2.5% and 2.1% change in mean annual flow for every 1% change in mean annual rainfall, respectively. All rainfall sensitivities have a lower limit of 1.8% and show upper limits of 4.1%, 3.4% and 2.5%, respectively. The results for potential evaporation change are −0.5%, −0.8% and −1.0% for every 1% increase in mean annual potential evaporation, respectively, with changes rainfall being approximately 3–5 times more sensitive than changes in potential evaporation for each 1% change in climate. Despite these differences, the results show similar correlations for several catchment characteristics. The most significant relationship is between percent change in annual rainfall and potential evaporation to the catchment runoff coefficient. The sensitivity of both A and B factors decreases with an increasing runoff coefficient, as does the uncertainty in this relationship. The results suggest that a first-order relationship can be used to give a rough estimate of changes in runoff using estimates of change in rainfall and potential evaporation representing small to modest changes in climate. Further work will develop these methods further, by investigating other regions and changes on the subannual scale.     

Notable shifting in the responses of vegetation activity to climate change in China

The weakening relationship between inter-annual temperature variability and vegetation activity in the Northern Hemisphere over the last three decades has been reported by a recent study. However, how and to what extent vegetation activity responds to climate change in China is still unclear. We applied the Pearson correlation and partial correlation methods with a moving 15-y window to the GIMMS NDVI dataset from NOAA/AVHRR and observed climate data to examine the variation in the relationships between vegetation activity and climate variables. Results showed that there was an expanding negative response of vegetation growth to climate warming and a positive role of precipitation. The change patterns between NDVI and climate variables over vegetation types during the past three decades pointed an expending negative correlation between NDVI and temperature and a positive role of precipitation over most of the vegetation types (meadow, grassland, shrub, desert, cropland, and forest). Specifically, correlation between NDVI and temperature (P_NDVI-T) have shifted from positive to negative in most of the station of temperature-limited areas with evergreen broadleaf forests, whereas precipitation-limited temperate grassland and desert were characterized by a positive P_NDVI-P. This study contributes to ongoing investigations of the effects of climate change on vegetation activity. It is also of great importance for designing forest management strategies to cope with climate change.     

Water security in north China and countermeasure to climate change and human activity

This paper addresses the emergent issues by the case study of Haihe River Basin in North China. The advantage of the water international study and the background for the cause of these problems from natural change and in particular human activity are analyzed. The key points are addressed as four aspects: (a) the study of the water cycle process impacted by climate change and high intensity human activity; (b) water utilization related to new economic partner change, such as saving water model; (c) study on eco-hydrology, and the interaction of water and ecology impacted by climate change and human activity; and (d) reasonable water allocation that includs water diversion from south to north and saving water issue in the local areas. Several suggestions are proposed both on the study on the water cycle, which is a very important base of water security in north China, and on the application study of water resources and eco-environmental rehabilitation. These key issues will benefit both the advantage of water science and the sustainable development in China.     

全新世以来东北地区沼泽湿地发育过程及其对气候变化的响应

沼泽湿地是陆地生态系统的重要组成部分,在维护区域环境稳定中起着重要作用.随着社会经济的发展,人类活动导致湿地大面积退化和消失,严重影响了区域生态安全;恢复退化湿地已成为各国政府和学者关注的焦点.而了解历史时期沼泽湿地发育过程及影响因素则是建立合理湿地恢复目标的重要前提.东北地区是我国最大的沼泽湿地集中分布区,其中70%的湿地面临不同程度的退化威胁;但由于数据的缺乏,东北地区沼泽湿地发育过程及其与气候变化的关系仍不清楚.基于此,本研究系统分析了全新世以来东北地区沼泽湿地形成发育的动态变化过程,并探讨了东北地区不同区域沼泽湿地的发育规律及其对气候变化的响应机理.研究发现东北地区沼泽湿地约从12 ka（1 ka=1000 cal.）开始发育,在距今8.6 ka以后开始广泛形成,约有35%的沼泽湿地形成于全新世暖湿期（8.0-4.0 ka）;而沼泽湿地发育的高峰期则集中在全新世晚期.这种发育趋势与全球北方主要区域沼泽湿地大规模发育趋势显著不同.古气候重建表明,全新世早期东北地区气候温暖湿润,处在有利于沼泽发育的时期,促进了沼泽湿地的形成;而在全新世晚期,东北地区呈现冷湿的气候组合特征,冷湿的气候条件不利于有机质的分解,进而促进了沼泽湿地的大规模形成和发育.此外,研究结果也表明全新世以来东北地区不同区域沼泽湿地发育的时间和规模呈现显著的空间差异,而温度和降水则是影响不同区域沼泽湿地发育的最重要因素.本研究将为我国东北地区沼泽湿地的保护和恢复提供一定的理论和数据支持.     

Response of runoff to climate change in the Wei River basin,China

Abstract

Climate change will likely have severe effects on water shortages, flood disasters and the deterioration of aquatic systems. In this study, the hydrological response to climate change was assessed in the Wei River basin (WRB), China. The statistical downscaling method (SDSM) was used to downscale regional climate change scenarios on the basis of the outputs of three general circulation models (GCMs) and two emissions scenarios. Driven by these scenarios, the Soil and Water Assessment Tool (SWAT) was set up, calibrated and validated to assess the impact of climate change on hydrological processes of the WRB. The results showed that the average annual runoff in the periods 2046–2065 and 2081–2100 would increase by 12.4% and 45%, respectively, relative to the baseline period 1961–2008. Low flows would be much lower, while high flows would be much higher, which means there would be more extreme events of droughts and floods. The results exhibited consistency in the spatial distribution of runoff change under most scenarios, with decreased runoff in the upstream regions, and increases in the mid- and lower reaches of the WRB.

Editor Z.W. Kundzewicz; Associate editor D. Yang     

Growth characteristics and response to climate change of Larix Miller tree-ring in China

As one of the earliest species used in dendrochronological studies, Larix responds sensitively to climate change. In this study, nine larch species and one variety from eleven sites were collected to study the growth characteristics of tree-ring width using dendrochronological methods. Ten residual tree-ring chronologies were developed to analyze their relationships with regional standardized anomaly series by Pearson’s correlation analysis. The results suggest that most of the chronologies had significantl...