Impacts of land-use and climate changes on ecosystem productivity and carbon cycle in the cropping-grazing transitional zone in China

Terrestrial ecosystems are both a carbon source and sink, therefore play an important role in the global carbon cycle that act as a link of interactions between human activities and climate changes[1,2]. Climate change impacts ecosystem carbon cycle through af- fecting biological processes, e.g. plant photosynthesis, respiration, and soil carbon decomposition. Land-use change directly modifies the distribution and structure of terrestrial ecosystems and hence the carbon storage and fluxes. Usi…     

Impact of land-use change on hydrological processes in the Maying River basin, China

Since the 1960s, dramatic changes have taken place in land-use patterns characterized by the persistent expansion of cultivated land and a continuous decrease in natural woodland and grassland in the arid inland river basins of China. It is very important to assess the effects of such land-use changes on the hydrological processes so vital for water resource management and sustainable development on the catchment scale. The Maying River catchment, a typical arid inland watershed located in the middle of the Hexi Corridor in northwest China, was the site chosen to investigate the hydrological responses to land-use changes. The annual runoff, base flow, maximum peak flow, and typical seasonal runoff in both spring and autumn flood periods were selected as the variables in the hydrological processes. Statistical-trend analysis and curvilinear regression were utilized to detect the trends in hydrological variables while eliminating the climatic influence. The relationship between cultivated land-use and hydrological variables was analyzed based on four periods of land-use variation data collected since 1965. A runoff model was established composed of two factors, i.e., cultivated land use and precipitation. The impact of land use changes, especially in the large ar- eas of upstream woodland and grassland turned into cultivated lands since 1967, has resulted in a mean annual runoff decrease of 28.12%, a base flow decline of 35.32%, a drop in the maximum peak discharge of 35.77%, and mean discharge decreases in spring and autumn of 36.05% and 24.87% respectively, of which the contribution of cultivated land expansion to the influence of annual runoff amounts to 77%-80%, with the contribution to the influence of spring discharge being 73%-81%, and that to the influence of base flow reaching 62%-65%. Thus, a rational regulation policy of land use patterns is vitally important to the sustainable use of water resources and the proper development of the entire catchment.     

五台山新生代隆升剥露的磷灰石裂变径迹研究

五台山是中国三级地貌重要分界线之一太行山脉海拔最高的山,其隆升历史的研究对中国三级地貌形成时代的确定具有重要意义.沿五台山最高峰北台顶向北自上而下至山根和阜平县境内长城岭地区海拔最高点向东自上而下至山根两条剖面,分别采集一系列岩石样品,最后挑选16个样品进行磷灰石裂变径迹研究.通过对封闭径迹长度分布直方图的分析,表明五台山样品自晚白垩纪末以来一直在单调冷却,即五台山在持续地隆升;通过对样品径迹年龄-高程图的分析,同时结合热史模拟及Excel数据拟合,表明晚白垩纪末以来五台山的隆升为分阶段幕式过程,共经历了三期快速隆升：74～58 Ma、46～31 Ma及15 Ma左右.五台山晚白垩纪末以来的隆升与太行山其他地区及周边张宣隆起、泰山等其他山系的隆升在时间上存在对应关系,所以,五台山新生代隆升为区域性构造演化的一部分.     

Study on spatial pattern of land-use change in China during 1995—2000

Land-use/cover change has become an event being of paramount importance to the study of global environmental change[1,2]. Land-cover change is closely related to the terrestrial surface material cycles and life-support processes[3], i.e., the interaction …     

Effects of land-use/cover change on hydrological processes using a GIS/RS-based integrated hydrological model: case study of the East River,China

Abstract

An integrated model, combining a surface energy balance system, an LAI-based interception model and a distributed monthly water balance model, was developed to predict hydrological impacts of land-use/land-cover change (LUCC) in the East River basin, China, with the aid of GIS/RS. The integrated model is a distributed model that not only accounts for spatial variations in basin terrain, rainfall and soil moisture, but also considers spatial and temporal variation of vegetation cover and evapotranspiration (ET), in particular, thus providing a powerful tool for investigating the hydrological impact of LUCC. The model was constructed using spatial data on topography, soil types and vegetation characteristics together with time series of precipitation from 170 stations in the basin. The model was calibrated and validated based on river discharge data from three stations in the basin for 21 years. The calibration and validation results suggested that the model is suitable for application in the basin. The results show that ET has a positive relationship with LAI (leaf area index), while runoff has a negative relationship with LAI in the same climatic zone that can be described by the surface energy balance and water balance equation. It was found that deforestation would cause an increase in annual runoff and a decrease in annual ET in southern China. Monthly runoff for different land-cover types was found to be inversely related to ET. Also, for most of the scenarios, and particularly for grassland and cropland, the most significant changes occurred in the rainy season, indicating that deforestation would cause a significant increase in monthly runoff in that season in the East River basin. These results are important for water resources management and environmental change monitoring.

Editor Z.W. Kundzewicz     

Effects of climate and land-use change on green-water variations in the Middle Yellow River,China

Abstract

Water resources management should cover both blue water and green water. For green-water management at the river drainage basin scale, the green-water coefficient (C _gw) is adopted, defined as the ratio of annual green water to annual precipitation. Based on data from the Middle Yellow River basin, China, for the period 1950 to 2007, we studied the temporal variation in C _gw in response to some influencing factors. A decreasing trend in C _gw was found. The influence of changes in land management on C _gw, reflected by an increase in the area (A _sw) of soil and water conservation measures, is emphasized. Using multiple regression analysis, the contributions of A _sw and the 5-year moving averages of annual precipitation and air temperature were estimated as 51, 37 and 12%, respectively. The results may provide useful information for better management of water resources, including green and blue water flows in the Yellow River basin.

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

Citation Xu, J.-X., 2013. Effects of climate and land-use change on green-water variations in the Middle Yellow River, China. Hydrological Sciences Journal, 58 (1), 1–12.     

Simulating the impacts of land-use and climate change on water resource availability for a large south Indian catchment

Abstract

A monthly rainfall-runoff model was calibrated for a large tropical catchment in southern India. Various land-use and climatic change scenarios were tested to assess their effects on mean annual runoff and assured water yield at the Bhavanisagar Reservoir in Tamil Nadu, India. The largest increase in runoff (19%) came from converting forest and savanna (the indigenous control scenario) to agriculture. Mean annual runoff decreased by 35% after conversion to commercial forest and 6% after partial conversion to tea plantations. The predicted climate scenarios of reduced dry season rainfall decreased the annual runoff by 5% while enhanced annual rainfall caused a 17% increase in runoff. Even if land-use and climate changes had relatively large effects on runoff, the changes in reservoir yield which can be assured every year, were often less severe. This was probably due to the buffering effect of the reservoir and variation in the mean annual runoff.     

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     

Attribution of runoff change in the alpine basin: a case study of the Heihe Upstream Basin,China

Quantifying the relative contributions of different factors to runoff change is helpful for basin management, especially in the context of climate change and anthropogenic activities. The effect of snow change on runoff is seldom evaluated. We attribute the runoff change in the Heihe Upstream Basin (HUB), an alpine basin in China, using two approaches: a snowmelt-based water balance model and the Budyko framework. Results from these approaches show good consistency. Precipitation accounts for 58% of the increasing runoff. The contribution of land-cover change seems unremarkable for the HUB as a whole, where land-cover change has a major effect on runoff in each sub-basin, but its positive effect on increasing runoff in sub-basins 1 and 3 is offset by the negative effect in sub-basin 2. Snow change plays an essential role in each sub-basin, with a contribution rate of around 30%. The impact of potential evapotranspiration is almost negligible.

EDITOR D. Koutsoyiannis

ASSOCIATE EDITOR S. Huang     

Plausible impact of global climate change on water resources in the Tarim River Basin

Combining the temperature and precipitation data from 77 climatological stations and the climatic and hydrological change data from three headstreams of the Tarim River: Hotan, Yarkant, and Aksu in the study area, the plausible association between climate change and the variability of water resources in the Tarim River Basin in recent years was investigated, the long-term trend of the hydrological time series including temperature, precipitation, and stream-flow was detected, and the possible association between the El Nino/Southern Oscillation (ENSO) and these three kinds of time series was tested. The results obtained in this study show that during the past years, the temperature experienced a significant monotonic increase at the speed of 5%, nearly 1℃rise; the precipitation showed a significant decrease in the 1970s, and a significant increase in the 1980s and 1990s, the average annual precipitation was increased with the magnitude of 6.8 mm per decade. A step change occurred in both temperature and     

Climate change and consequences on the water cycle in the humid Xiangjiang River Basin,China

Anthropogenic activities have altered the climate and led to changes in the water cycle. Understanding the climate change and hydrological responses is critical to derive adaptive strategies for sustainable water resources management. In this study, we diagnosed the trends of primary climate elements and hydrological components during the past half century (1960–2009) for the humid Xiangjiang River Basin in central-south China at multiple temporal and spatial scales. The air temperature trend demonstrated an overall warming climate but with a quicker pace in recent years; however, the wind speed reduced significantly in the early period, and this downtrend had largely disappeared after the mid-1990s. Under such a shifting climate, the hydrological responses were not monotonic during the past 50 years: the evapotranspiration behaved in a decreasing trend in the early 35 years (1960–1994), followed by an uptrend in the later period (1995–2009). The stepwise analysis of soil water content and baseflow demonstrated a wetting trend followed by a drying one but with a steeper slope, indicating an accelerated drying trend which may cause a concern in stream water availability especially in the dry season. Spatial trend analysis showed that some areas experienced a downtrend (drying) in the dry season, but most areas had an uptrend (wetting) in the wet season for the whole study period. Overall, the analyses of temporal and spatial changes are useful for decision makers to deal with the continuing changes in climate and hydrology. This study also highlighted the necessity of climate change studies at multiple temporal and spatial scales.     

Projection of surface water resources in the context of climate change in typical regions of China

Climate change and its impact on hydrological processes are overarching issues that have brought challenges for sustainable water resources management. In this study, surface water resources in typical regions of China are projected in the context of climate change. A water balance model based on the Fu rational function equation is established to quantify future natural runoff. The model is calibrated using data from 13 hydrological stations in 10 first-class water resources zones of China. The future precipitation and temperature series come from the ISI-MIP (Inter-Sectoral Impact Model Intercomparison Project) climate dataset. Taking natural runoff for 1961–1990 as a baseline, the impacts of climate change on natural runoff are studied under three emissions scenarios: RCP2.6, RCP4.5 and RCP8.5. Simulated results indicate that the arid and semi-arid region in the northern part of China is more sensitive to climate change compared to the humid and semi-humid region in the south. In the near future (2011–2050), surface water resources will decrease in most parts of China (except for the Liaozhong and Daojieba catchments), especially in the Haihe River Basin and the middle reaches of the Yangtze River Basin. The decrement of surface water resources in the northern part of China is more than that in the southern part. For the periods 2011–2030 and 2031–2050, surface water resources are expected to decrease by 12–13% in the northern part of China, while those in the southern part will decrease by 7–10%.

EDITOR D. Koutsoyiannis

ASSOCIATE EDITOR R. Hirsch     

Climate change impact on water resources availability: case study of the Llobregat River basin (Spain)

ABSTRACT

Climate change may have significant consequences for water resources availability and management at the basin scale. This is particularly true for areas already suffering from water stress, such as the Mediterranean area. This work focused on studying these impacts in the Llobregat basin supplying the Barcelona region. Several climate projections, adapted to the spatiotemporal resolution of the study, were combined with a daily hydrological model to estimate future water availability. Depending on the scenario and the time period, different assessment indicators such as reliability and resilience showed a future decrease in water resources (up to 40%), with drought periods becoming more frequent. An additional uncertainty analysis showed the high variability of the results (annual water availability ranging from 147 hm³/year to 274 hm³/year), thus making accurate projections difficult. Finally, the study illustrates how climate change could be taken into account to provide adaptive measures for the future.

Editor M.C. Acreman; Associate editor J. Thompson     

Quantifying the effects of climate change and human activities on runoff in the water source area of Beijing,China

Abstract

Quantitative assessment of the effects of climate change and human activities on runoff is very important for regional sustainable water resources adaptive management. In this study, the non-parametric Mann-Kendall test is used to identify the trends in and change points of the annual runoff with the aim of analysing the changing characteristics of the hydrological cycle. The study presents the analytical derivation of a method which combines six Budyko hypothesis-based water–energy balance equations with the Penman-Monteith equation to separate the effects of climate change and human activities. The method takes several climate variables into consideration. Results based on data from the Yongding River basin, China, show that climate change is estimated to account for 10.5–12.6% of the reduction in annual runoff and human activities contribute to 87.4–89.5% of the runoff decline. The results indicate that human activities are the main driving factors for the reduction in runoff.

Editor Z.W. Kundzewicz; Associate editor C.Y. Xu     

Impact assessment of climatic and land-use changes on flood runoff in southeast Queensland

Abstract

Over the past century, land-use has changed in southeast Queensland, and when coupled with climatic change, the risk of flooding has increased. This research aims to examine impacts of climate and land-use changes on flood runoff in southeast Queensland, Australia. A rainfall–runoff model, RORB, was calibrated and validated using observed flood hydrographs for one rural and one urbanized catchment, for 1961–1990. The validated model was then used to generate flood hydrographs using projected rainfall based on two climate models: the Geophysical Fluid Dynamics Laboratory Climate Model 2.1 (GFDL CM2.1) and the Conformal-Cubic Atmospheric Model (CCAM), for 2016–2045. Projected daily rainfall for the two contrasting periods was used to derive adjustment factors for a given frequency of occurrence. Two land-use change scenarios were used to evaluate likely impacts. Based on the projected rainfall, the results showed that, in both catchments, future flood magnitudes are unlikely to increase for large flood events. Extreme land-use change would significantly impact flooding in the rural catchment, but not the urbanized catchment.

Editor Z.W. Kundzewicz; Associate editor Y. Gyasi-Agyei     

River discharge,land use change,and surface water quality in the Xiangjiang River,China

To compare the impacts of river discharge on the surface water quality of the Xiangjiang River in China, 12 surface water quality parameters recorded at 31 sampling sites from January 1998 to December 2008 along the river and its main tributaries were analyzed. Significantly higher concentrations of total nitrogen, ammoniacal nitrogen, and total phosphorus, and biochemical oxygen demand were observed during low‐flow periods than during high‐flow periods, implying a higher risk to local residents drinking untreated water during low‐flow periods. Pollution indexes, including the inorganic pollution index and integrated pollution index (IPI), were negatively related to impervious surface area (ISA) and cropland area (CLA) when ISA (CLA) was less than 160 (3000) km². However, the relationship was positive when ISA (CLA) was larger than 160 (3000) km², which provided a reasonable explanation for the observed spatial patterns of water quality. Distinct increasing temporal trends for two kinds of pollution indexes were also found. The annual ISA was significantly related to the rapid degradation of water quality from 1998 to 2008, with correlation coefficient (r) values of 0.816 (p = 0.002) and 0.711 (p = 0.014) for the organic pollution index (OPI) and IPI, respectively. However, annual rainfall was negatively correlated with the two indexes with r values of 0.785 (p = 0.002) and 0.448 (p = 0.093) for OPI and IPI, respectively. Our study highlights that decision makers should be more aware of recent increases in the pollution of the Xiangjiang River, especially at downriver sites and during low‐flow periods. Copyright © 2013 John Wiley & Sons, Ltd.     

Impact of climatic change on streamflow in the upper reaches of the Minjiang River,China

Abstract

Characteristics of hydroclimatic change in the upper reaches of the Minjiang River are analysed using data collected over the past 50 years. The effect of autocorrelation of time series on trend analysis is removed by adopting a pre-whitening technique. Long-term hydrometeorological trend and abrupt changes are analysed by the Mann-Kendall test. The results were validated by the linear trend and Spearman methods. Correlations between runoff change with air temperature and with precipitation were studied with the Pearson method. The results clearly show that average air temperature in the upper reaches of the river is increasing, and precipitation decreasing, with differences in spatio-temporal distribution. Runoff change has a clear positive correlation with precipitation. Meteorological change, especially in precipitation, is the key governing influence of runoff volume. The annual runoff decrease, especially the decrease of inflow in spring and autumn and earlier appearance and longer duration of the low-flow season, will impact greatly on irrigation and municipal water supply. Therefore, relevant measures and further study are necessary.

Editor Z.W. Kundzewicz; Associate editor Q. Zhang

Citation Huang, X.R., Zhao, J.W., Li, W.H., and Jiang, H.X., 2013. Impact of climatic change on streamflow in the upper reaches of the Minjiang River, China. Hydrological Sciences Journal, 59 (1), 154–164.     

Assessing climate change impacts on the ecohydrology of the Jinghe River basin in the Loess Plateau,China

Abstract

Quantifying the impacts of climate change on the hydrology and ecosystem is important in the study of the Loess Plateau, China, which is well known for its high erosion rates and ecosystem sensitivity to global change. A distributed ecohydrological model was developed and applied in the Jinghe River basin of the Loess Plateau. This model couples the vegetation model, BIOME BioGeochemicalCycles (BIOME-BGC) and the distributed hydrological model, Water and Energy transfer Process in Large river basins (WEP-L). The WEP-L model provided hydro-meteorological data to BIOME-BGC, and the vegetation parameters of WEP-L were updated at a daily time step by BIOME-BGC. The model validation results show good agreement with field observation data and literature values of leaf area index (LAI), net primary productivity (NPP) and river discharge. Average climate projections of 23 global climate models (GCMs), based on three emissions scenarios, were used in simulations to assess future ecohydrological responses in the Jinghe River basin. The results show that global warming impacts would decrease annual discharge and flood season discharge, increase annual NPP and decrease annual net ecosystem productivity (NEP). Increasing evapotranspiration (ET) due to air temperature increase, as well as increases in precipitation and LAI, are the main reasons for the decreasing discharge. The increase in annual NPP is caused by a greater increase in gross primary productivity (GPP) than in plant respiration, whilst the decrease in NEP is caused by a larger increase in heterotrophic respiration than in NPP. Both the air temperature increase and the precipitation increase may affect the changes in NPP and NEP. These results present a serious challenge for water and land management in the basin, where mitigation/adaption measures for climate change are desired.

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

Citation Peng, H., Jia, Y.W., Qiu, Y.Q., and Niu, C.W., 2013. Assessing climate change impacts on the ecohydrology of the Jinghe River basin in the Loess Plateau, China. Hydrological Sciences Journal, 58 (3), 651–670.     

The impact of land use change on water balance in Zhangye city,China

Land use change has a significant effect on water balance, especially in arid region, such as Northwest China. In this paper, we analyze the effect of land use change on water balance in terms of the amount of water supply and demand from economic perspective. It's the first time to extend the basic 48 sectors input-output table to include water and land accounts that involved into multiple production processes for Zhangye city. We then perform the improved ORANI-G model, a single region Computable General Equilibrium (CGE) model, to analyze the effect of land use change on water balance under three scenarios. Subsequently, scenario-based simulation results are interpreted through selected sectors from agricultural, industrial, and service sectors respectively. Finally, the effect of land use change on water balance is analyzed through the difference between business-as-usual and land use unchanged scenarios. The results show that the extent of effect on water balance is different among sectors. Specifically, from the perspective of absolute value, service sectors are the largest, followed by industrial sectors, and the agricultural sectors are the least. Conversely, in terms of percentage change of land use, the largest extent of effect occurs in agricultural sectors. Additionally, with the rapid urbanization and the development of social economy, water balance in industrial sectors and service sectors will be stricken and reconstructed to a new high level. Simulation results also show that agricultural land shrinking will mitigate water scarcity distinctly, which indicates that balance the relationship among different stakeholders is imperative to guarantee water transformation from agricultural sectors to industrial and service sectors.     

长江上游区域蒸发皿蒸发量变化及其对水分循环的影响

利用长江上游最近30年(66个测站)蒸发皿蒸发量和最近50年(90个测站)的7种气象要素,分析了蒸发皿蒸发量的区域变化趋势和影响蒸发皿蒸发量变化的因素;针对7个水文站的年径流量变化,探讨了蒸发皿蒸发量变化后对水分循环的影响.结果表明,长江上游蒸发皿蒸发量的变化可以划分为三个分区,研究区域东西两侧(青藏高原和大巴山一带)为显著减少区,分别命名为RⅠ和RⅡ,中间(云贵高原北部到黄土高原南缘以及由二者包围的四川盆地一带)为显著增大区,命名为RⅢ区.影响区域蒸发皿蒸发量变化的原因各有不同,青藏高原一带(RⅠ区)蒸发皿蒸发量减少的原因可归结于太阳辐射强度和风动力扰动减弱所致.大巴山一带(RⅡ区)减少原因是太阳辐射强度、风动力扰动强度、湿度条件都在显著下降所引起的.云贵高原到四川盆地一带(RⅢ区)蒸发皿蒸发量增加是环境气温强烈升高,导致其上空大气水汽含量显著减少,大气很干燥,引发蒸发过程加强所致.蒸发皿蒸发量发生变化的直接后果就是导致水分循环强弱发生变化,对于RⅠ区,尽管蒸发皿蒸发量减少,由于降水量和径流量增加的作用,这一区域的水分循环有所加强.在RⅡ区,降水量、径流量和蒸发量都在减少,因此RⅡ区水分循环显著减弱.在RⅢ区,降水量和径流量同时减少,而蒸发量增大,水量消耗增大,因此RⅢ区水分循环有减弱趋势.