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In water ecosystems, zoobenthos are one of the most important communities. Maintenance of healthy zoobenthos community is essential for water ecosystems remediation. Understanding the hydrology and water quality factors that drive the variation of zoobenthos is the priority for water ecosystems remediation. The present study used canonical correlation analysis to select the main habitat factors affecting zoobenthic communities based on field sampling of the river zoobenthos in the first pilot city for the construction of civilized water ecosystems in China—Jinan City. In addition, analysis was performed based on geoscience methods of Global Moran's I and Anselin local Moran's I spatial autocorrelation of main habitats factors. The results show that the key water quality physical factors affecting Jinan City zoobenthic communities were pH and conductivity; the key water quality chemical factors were K+, Na+, and permanganate index; and the key hydrological factor was water depth. The sodium ions and conductivity exhibited significant spatial autocorrelation in all seasons. And the regions exhibiting spatial autocorrelation were generally stable. Moreover, the characteristics of benthic animals are closely related to human activities of domestic sewage discharge in the central and agricultural activities in northern parts of the study area. All methods in this paper can be extended to the researches on other communities, for example, algae, zooplankton, and fish in water ecosystems. The methods and results in the paper can provide significant references for managers to protect and restore degraded water ecosystems in global water. [ABSTRACT FROM AUTHOR]

West Dongting Lake in China is important for human livelihoods and habitat of migratory waterfowl and other wildlife. The waterway re‐engineering and agriculture intensification have contributed to changes in hydrology, sediment, and vegetation on the floodplain. This paper describes an EcoPartnership program conducted by the U.S. Geological Survey, Wetland and Aquatic Research Center, and Beijing Forestry University. It focused on the development of a wetland ecosystem network in West Dongting Lake with technical support from the U.S. partner using a number of related studies to examine wetland vegetation dynamics from upstream to downstream along the tributaries. The results of U.S. studies showed that the regeneration potential of species might be altered by changes in climate and local environment, and seed bank depletion by germination may be a major conservation threat in a future with recurring droughts in swamps of the southeastern United States. In the monsoonal wetlands of West Dongting Lake, the soil seed bank could be used as a seed source for revegetation after hydrologic restoration with the introduction of certain foundational species and the removal of poplar plantations. Also, West Dongting Lake is at high ecological risk of mercury pollution. Wetland ecosystem monitoring may allow managers to use the information to predict effects of climate change, water level and flow changes on sedimentation, and to manage for desired vegetation to support waterfowl and ecosystem services. The cooperation of two countries through the EcoPartnership program is now well established and poised for extensive research projects in the future. [ABSTRACT FROM AUTHOR]

In this paper, grain‐size records of 128 surface samples and six sediment cores retrieved from freshwater marshes across the Sanjiang Plain were employed to reconstruct the marshes' hydrological variation during the Holocene and to discuss its links to the East Asian summer monsoon (EASM) variation. The grain‐size hydrological significance for the marshes' deposits was first interpreted by quantitative analyses of 128 modern samples. The results indicate that the sand fraction exhibits a higher level significance to modern water‐level conditions than other grain‐size parameters. Thus, the sand accumulation rates of the six cores were calculated and employed to reconstruct the Holocene hydrological regime of the marshes on the plain. Based on the cluster analysis, it can be identified that three higher water‐level stages occurred during 6.2–5.6 thousand yr BP, 5.6–4.5 thousand yr BP, and 2.8–2.4 thousand yr BP, whereas four lower water‐level stages occurred during ~8.0–6.2 thousand yr BP, 4.5–2.8 thousand yr BP, 2.4–0.7 thousand yr BP, and 0.7–0 thousand yr BP, respectively. Considering the prevalent monsoon climate on the modern Sanjiang Plain, it is reasonable to believe that the local water‐level fluctuations were mainly regulated by the EASM variation rather than local factors including flooding, waterway modification, depression infilling, and human activities. The higher water‐level stages were linked to a stronger EASM and vice versa. This study provides essential background datasets for understanding the potential controls on the marsh development and degradation on the Sanjiang Plain. [ABSTRACT FROM AUTHOR]

Abstract: Rapid degradation of global ecosystems seriously impacted the sustainable development of human society and economy. Understanding the heterogeneity of aquatic ecosystems is significantly helpful for ecological remediation. The success of restoration in Jinan City, the first pilot city for the construction of civilized freshwater ecology, will determine the fundamental improvement of the living environment of human beings in China. This paper studied the tempo‐spatial heterogeneity of aquatic ecosystems in Jinan using canonical correspondence analysis and random forest methods, based on data regarding aquatic ecology collected during field investigations from 2014 to 2015. Results showed that water depth and flow velocity in hydrological factors had the greatest impact on the distribution of fish and zoobenthos, and conductivity and total hardness in water quality factors had the greatest effect on both 2 communities; the biodiversity of fish and zoobenthos were better in the eastern than in the western region, and better in the mountain areas than in the plains; the quality of aquatic ecosystems in most regions of Jinan was in general good except for that in the 2 regions close to urban area that were severely affected by human activities. These results could provide a scientific basis for policymaking for ecological restoration and construction of civilized freshwater ecology, which will ensure successful maintenance and remediation of river ecosystems in the important city. This methodological framework could provide a reference for aquatic ecological rehabilitation both in China and worldwide. [ABSTRACT FROM AUTHOR]

Lakes in the Eastern Plain ecoregion of China are typically shallow, experience large disturbances, and are hydrologically connected to rivers. In recent years, lake eutrophication in this ecoregion has intensified due to human activities. To determine important regional nutrient criteria, the effects of hydrologic features and disturbances should be taken into account. In this paper, annual average data were used to construct stressor-response models for each hydrological lake type identified for lakes in the Eastern Plain ecoregion. In these models, total nitrogen (TN) and total phosphorus (TP) criteria were obtained from a chlorophyll a (Chl-a, response variable) threshold value. A Chl-a concentration of 4.73 μg L−1 was identified as this threshold value, which was based on the cyanotoxin limits associated with drinking water supply. The three lake types, which differed in hydrological structure, had significantly different TN and TP criteria. For example, lakes connected to the Yangtze River (T1) had a TN criterion ranging from 0.594 to 0.838 mg L−1, which was substantially higher than those for lakes that were never connected to the river (T3, 0.234-0.422 mg L−1). The exception to this trend occurred for lakes that were historically but not currently connected to the river (T2) due to P-limitation in this lake type. However, there was little variability in the TP criterion among T1, T2, and T3 lakes, the values of which ranged from 0.021 to 0.037, 0.023 to 0.042, and 0.028 to 0.041 mg L−1, respectively. [ABSTRACT FROM AUTHOR]

The effects of climate change and population growth in recent decades are leading us to consider their combined and potentially extreme consequences, particularly regarding hydrological processes, which can be modeled using a generalized extreme value (GEV) distribution. Most of the GEV models were based on a stationary assumption for hydrological processes, in contrast to the nonstationary reality due to climate change and human activities. In this paper, we present the nonstationary generalized extreme value (NSGEV) distribution and use it to investigate the risk of Niangziguan Springs discharge decreasing to zero. Rather than assuming the location, scale, and shape parameters to be constant as one might do for a stationary GEV distribution analysis, the NSGEV approach can reflect the dynamic processes by defining the GEV parameters　as functions of time. Because most of the GEV model is designed to evaluate maxima (e.g. flooding, represented by positive numbers), and spring discharge cessation is a ‛minima', we deduced an NSGEV model for minima by applying opposite numbers, i.e. negative instead of positive numbers. The results of the model application to Niangziguan Springs showed that the probability of zero discharge at Niangziguan Springs will be 1/80 in 2025, and 1/10 in 2030. After 2025, the rate of decrease in spring discharge will accelerate, and the probability that Niangziguan Springs will cease flowing will dramatically increase. The NSGEV model is a robust method for analysing karst spring discharge. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A geographic information system (GIS)-based analysis tool, the Taihu Basin Risk Assessment System ( TBRAS), is developed to perform scenario analysis of future flood risk changes in the Taihu Basin. The TBRAS integrates modules of climate modelling, hydrological and hydraulic modelling, dyke reliability analysis, socioeconomic analysis, and damage assessment. The results indicate that the TBRAS can provide a broad-scale simulation of the flooding processes and damage evaluation for the entire Taihu Basin. Future climate change by 2050 in precipitation alone can approximately result in four or five times of risk increase compared with the 2005 baseline risk. Socioeconomic changes alone can increase flood risk by four to six times. The paper reveals that, without any proactive responses, the combination of socioeconomic change, sea-level rise, and other climate changes can substantially increase the overall flood risks to 15-37 times of the present situation. We therefore conclude that both structural and non-structural measures for reducing flood risks are required and provide a set of response options for managing and adapting future flood risk changes. [ABSTRACT FROM AUTHOR]

Changes in precipitation can be expected to have a major influence on the frequency and severity of flooding in the Taihu Basin. As part of an integrated assessment of flood risk in the Taihu Basin, this paper addresses the hydrological conditions and the potential impacts of climate change on Taihu Lake water levels. The hydrological system is simulated by using the distributed hydrological model VIC ( Variable Infiltration Capacity), with future climate scenarios generated by the regional climate model PRECIS (Providing Regional Climates for Impacts Studies). The results indicate that maximum and mean flood water levels under the A2 and B2 scenarios for 2021-2050 will be higher than the levels during the baseline period (1961-1990), with larger increases under the B2 scenario than for the A2 scenario. The storm return periods leading to extreme water levels in the Taihu Lake in the future is projected to decrease significantly in comparison to the baseline period, implying the potential for the more frequent occurrence of major floods. These results indicate the importance of planning for future flood control in the Taihu Basin. [ABSTRACT FROM AUTHOR]

Wetlands are constantly affected by human activities such as landscaping, additional abstractions, and changes in catchment imperviousness, resulting in the reduction of wetland area and degeneration of water quality. Modelling of such anthropogenic factors should be explicitly considered, in order to provide better understanding of the hydrological impacts of wetland restoration. In this paper, the wetland module in a distributed hydrological model, SWAT, is modified to simulate the artificial water input to the designated wetlands. The impact and effect of recharging wetlands on local hydrological cycle, sea outflow and estuary ecology is discussed. The Qingdianwa depression, located in the north of Tianjin city, China, is used as a case study to investigate the effect of human activities on the natural eco-hydrological process as well as different restoration schemes. Water balance analysis shows that there is a significant shortage of water in the drier months, which also indicates that an external water source is required for wetland restoration. The selected restoration scheme of 0·8 m depth is effective in controlling runoff, whereas a depth of 1 m and above is required for maintaining the basic ecological function of the wetland. Such a scheme has an additional effect of increasing the average surface runoff and groundwater recharge during non-flood seasons by 37·65 and 45·4 million m3, respectively, which illustrated the importance of wetland restoration on local runoff, groundwater recharge and local ecology. The proposed method demonstrated that it is possible to select wetland restoration schemes that are beneficial to both hydrology and ecology. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The wetland ecosystem is particularly vulnerable to hydrological and climate changes. The Great Xing'an Mountain is such a region in China that has a large area of wetlands with rare human disturbance. The predictions of the global circulation model CGCM3 (the third-generation coupled global climate model from the Canadian Centre for Climate Modeling and Analysis) indicated that the temperature in The Great Xing'an Mountain will rise by 2-4°C over the next 100 years. This paper predicts the potential distributions of wetlands in this area under the current and warming climate conditions. This predication was performed by the Random Forests model, with 18 environmental variables, which will reflect the climate and topography conditions. The model has been proven to have a great prediction ability. The wetland distributions are primarily topography-driven in the Great Xing'an Mountains. Mean annual temperature, warmness index, and potential evapotranspiration ratio are the most important climatic factors in wetland distributions. The model predictions for three future climate scenarios show that the wetland area tends to decrease, and higher emission will also cause more drastic shrinkage of wetland distributions. About 30% of the wetland area will disappear by 2050. The area will decrease 62.47, 76.90, and 85.83%, respectively, under CGCM3-B1, CGCM3-A1B, and CGCM3-A2 by 2100. As for spatial allocation, wetlands may begin to disappear from the sides to the center and south to north under a warming climate. Under CGCM3-B1, the loss of wetlands may mainly occur in the south hills with flatter terrain, and some may occur in the north hills and intermontane plains. Under CGCM3-A1B, severe vanish of wetlands is predicted. Under CGCM3-A2, only a small area of wetlands may remain in the north of the high mountains. [ABSTRACT FROM AUTHOR]

The relationship between forests and streamflows has long been an important research interest in China. The purpose of this paper is to summarize progress and lessons learned from the forest-streamflow studies over the past four decades in China. To better measure the research gaps between China and other parts of the world, a brief global review on the findings from paired watershed studies over the past 100 years was also provided. In China, forest management shifted in the later 1990s from timber harvesting to forest restoration. Forest-streamflow research was accordingly changed from assessing harvesting impacts to evaluating both harvesting and forestation effects. Over the past four decades, Chinese forest hydrology research has grown substantially. Significant progress has been made on measuring individual processes, but little solid, long-term data were available to assess the relationship between forest changes and streamflows because of an absence of standard paired watersheds. In addition, misuse of statistical analyses was often found in the literature. A unique opportunity exists in China to study the forestation effects on streamflow as several large-scale forestation programs are being implemented. Such an opportunity should include a robust paired watershed design under an integrated watershed ecosystem framework to avoid repeating the lessons already learned. Recommendations on future forest-streamflow research directions in China are provided. [ABSTRACT FROM AUTHOR]

Using the combined methods of digital image processing of remote sensing data, a Geographical Information System (GIS) and analysis of historical books and maps, this paper aims to contribute to a better understanding of the processes and mechanisms of land-use and land-cover changes and hydrological variations during the last 2000 years in a hyper-arid environment. The southern and eastern Taklamakan Desert, one of the driest and ecologically most sensitive regions in China and characterized by a long history of human settlements, was chosen as the study area. A hydrological connection between the Keriya and Niya rivers in former times was recognized for the first time using satellite imagery. After transferring the notes and maps of historical times into a simplified modern map, it shows that the Lop Nuer decreased in size from a large lake in the Han Dynasty (206 BC to AD 220) to a much smaller one in the Qing Dynasty (AD 1644–1911). Areas settled in former times differ morphologically from the dune landscape in satellite imagery because of flat relief along dried river courses. A review of archaeological literature reinforces the fact that in the lower reaches of the Keriya and Niya rivers, in the interior of the Taklamakan Desert, irrigated agriculture was widely practised from ca. 200 BC to ca. AD 500. A possible climatic change toward drier conditions at ca. AD 500 is suggested as the cause of the abandonment of the cities in the desert and for the initial drying of the formerly large Lop Nuer Lake. [ABSTRACT FROM AUTHOR]

The extent and mechanisms by which precipitation extremes affect hydrological processes in the critical zone (CZ) of loess possessing a thick unsaturated zone remains poorly understood. To this end, we here employed a coupled liquid‒vapor‒heat‒airflow STEMMUS (simultaneous transfer of energy, mass, and momentum in unsaturated soil) model to investigate the impact of extreme precipitation, at both event and annual scales, on CZ hydrological processes within a semiarid loess site vegetated by apple trees on China's Loess Plateau. At the event scale, the vapor flux was two orders of magnitude lower than the liquid water flux. However, the thermal vapor flux penetrated to depths of 200 cm, whereas the isothermal liquid water flux only infiltrated to 100 cm during the study period, implying that thermal‐gradient‐driven vapor transfer is an important mechanism for deep‐layer recharge (DLR). At the annual scale, the DLR below 200 cm during extremely wet years was 6.5 times larger than that during extremely dry years. In contrast, extreme changes in climate had only limited impacts on evapotranspiration; the difference between extremely wet and extremely dry years averaged only 35 mm, much less than the difference in precipitation, which averaged 310 mm. However, the extremely dry years showed a higher ratio (0.58) between transpiration and evapotranspiration than did the extremely wet years (0.51). The findings reported here improve our understanding of CZ hydrological processes related to precipitation extremes in semiarid loess regions. Key Points: Thermal‐gradient‐driven vapor transfer is an important mechanism for deep‐layer recharge (DLR) in loessThe DLR below 200 cm during extremely wet years was 6.5 times larger than that during extremely dry yearsExtreme changes in precipitation had only limited impacts on evapotranspiration [ABSTRACT FROM AUTHOR]

Natural and anthropogenic factors have led to a series of fluvial sedimentation and hydrological changes in the lower West River, China. To evaluate the influence of human activities on the channel's morphology and examine the hydrological responses, we analyzed channel adjustments and changes of low water levels in the main river channel between Wuzhou and Zhaoqing that occurred over the recent decades. Due to a remarkable decrease in the suspended sediment concentration, the suspended sediment outputs during this period were larger than the sediment inputs for 27 consecutive years from 1987 to 2013. Therefore, the riverbed became a sediment source, with a high scouring of riverbed material. Between 2004 and 2014, the channel capacity of the lower reaches increased by 302.02 × 106 m3, and the average riverbed elevation decreased by 2.21 m, approximately 11.8% of which was caused by bed sediment loss induced by natural scour through sediment depletion; the remainder was caused by waterway engineering and sand mining, accounting for 0.8 and 87.4%, respectively. Approximately 91.3% of 1,312 river cross‐sections exhibited downcutting, indicating significant adjustment of the riverbed. This resulted in a substantial decline in the low water level in the 44‐km upstream section above Ducheng, which is located at the end of the tidal limit during dry seasons. However, this change was not noticeable in the section below Ducheng owing to the small water surface gradient and tidal influence. These findings reveal that human activities are a major driving force in the evolution of large rivers and the complexity of the hydrological responses to riverbed downcutting in a tidal reach, providing useful information for future river sand mining management and navigable engineering design of the lower West River and other rivers. [ABSTRACT FROM AUTHOR]

Afforestation to control soil erosion has been implemented throughout China over the past few decades. The long‐term hydrological effects, such as total water yield and baseflow, of this large‐scale anthropogenic activity remain unclear. Using six decades of hydrologic observations and remote sensing data, we explore the hydrological responses to forest expansion in four basins with contrasting climates across China. No significant change in runoff was found for the period 1970–2012 for the cold and dry Hailar River Basin in northeastern China. However, both forest expansion and reduced precipitation contributed to the runoff reduction after afforestation since the late 1990s. Similarly, afforestation and drying climate since the mid‐1990s induced a significant decrease in runoff for the Weihe River Basin in semi‐arid northwestern China. In contrast, the two wet basins in the humid southern China, Ganjiang River Basin and Dongjiang River Basin, showed insignificant changes in total runoff during their study periods. However, the baseflow in the winter dry seasons in these two watersheds significantly increased since the 1950s. Our results highlight the long‐term variable effects of forest expansion and local climatic variability on basin hydrology in different climatic regions. This study suggests that landuse change in the humid study watersheds did not cause dramatic change in river flow and that region‐specific afforestation policy should be considered to deal with forestation‐water quantity trade‐off. Conclusions from this study can help improve decision‐making for ecological restoration policies and water resource management in China and other countries where intensive afforestation efforts are taking place. Key Points: Both precipitation and afforestation explained reduction in runoff for dry basinsForest recovery did not result in significant changes in total runoff for two wet basinsDry season baseflow in two wet basins had an upward trend [ABSTRACT FROM AUTHOR]

The dynamic changes in the sediment discharge over 90 years from 1919 to 2008 in the Yellow River in China were assessed on the basis of annual rainfall series and annual sediment series in Shan County hydrological station. The key factors affecting sediment discharge, such as rainfall, and human activities were studied. Anomaly accumulation method and double mass curve were employed to test the stage changes of sediment discharge, and to determine the main factors of sediment decline. Results showed that the annual average sediment discharge under natural conditions was about 16 × 108 t, but the measured annual average sediment during 1919-2008 was 12.71 × 108 t. The highest annual average during the study period was 39.10 × 108 t in 1933 while the lowest was 1.77 × 108 t in 2008. Sediment discharge in the Yellow River experienced two low sediment stages (1924-1931 and 1979-2008) and a high sediment stage (1932-1971), respectively. Since 1979, there was a significant decreasing trend in the sediment discharge, and the main influencing factor was fierce human activities. Annual average sediment discharge in the post-development period (1979-2008) was 69.7% lower than that in the pre-development period (1919-1978), with average reduction of 81 and 19% caused by human activities and rainfall, respectively. These results provide important evidence for making protecting policy for water resources quality and environmental safety of the Yellow River. [ABSTRACT FROM AUTHOR]

This article explains the Global Energy and Water Cycle Experiment (GEWEX)-Asian Monsoon Experiment (GAME). GEWEX was conducted under the umbrella of the World Climate Research Program and was led by Professor Yasunari from Japan. GAME research focused on water and energy cycles of Eurasia. Intensive field work carried out in eastern Siberia, the Tibetan Plateau, Central China, and Thailand has resulted in new insights into hydrological and meteorological processes. The papers in this issue focus on the hydrological characteristics of the GAME region.

GLDAS2.0 provides long‐term fine resolution gridded hydrometeorological data sets, which are necessary for water‐related studies, particularly in some transboundary rivers that are partially without observation. Yet, GLDAS2.0 has only been validated at limited locations, and few studies have been conducted to develop approaches to correct the GLDAS2.0 data for transboundary rivers. This work assessed the GLDAS2.0 data and developed approaches to correct their uncertainties for studies in large transboundary rivers in the Tibetan Plateau and Northeast China (NC). To achieve these goals, observational data from 1982 to 2010 and a water and energy budget‐based distributed hydrological model including biosphere after calibration and validation were employed. We find that the GLDAS2.0 data (except for wind speed) can reasonably replicate observed seasonal variations. However, its specific humidity and wind speed have large uncertainty, and precipitation has large uncertainty in summer. In NC, the trends of its precipitation, air temperature, downward longwave radiation, and wind speed are consistent with the observations. In the Yarlung Tsangpo, Lancang, and Nu Rivers, the trends of all GLDAS2.0 data reproduce the observation very well, that is, wetting, warming, and dimming trends. Validations show that the corrections are effective and the corrected forcing data can be successfully used in hydrological simulation with improved performance than the raw GLDAS2.0 data, which demonstrates the usefulness of the methodology and corrected forcing data to hydrometeorological studies in transboundary rivers in China as well as in other nearby regions/countries. Plain Language Summary: GLDAS2.0 provides long‐term hydrometeorological data sets, which are necessary for water‐related studies, particularly in some transboundary rivers that are partially without observation. This work assessed GLDAS2.0 data and developed approaches to correct their uncertainties for studies in large transboundary rivers in the Tibetan Plateau (TP) and Northeast China (NC). In NC, the trends of GLDAS2.0 precipitation, air temperature, downward longwave radiation, and wind speed are consistent with observations. In TP, the trends of all the GLDAS2.0 data reproduce observation very well. Validations show that the corrections are effective and the corrected data have improved performance than raw GLDAS2.0 data in hydrological simulation. Key Points: Specific humidity and wind speed have large uncertainty, and precipitation has large uncertainty in summerTrends of precipitation, air temperature, downward longwave radiation, and wind speed are consistent with observationEquations are developed to reduce forcing data uncertainty, and validations show that the equations are effective [ABSTRACT FROM AUTHOR]

Characterizing the upper tail of flood peak distributions remains a challenge due to the elusive nature of extreme floods. China has experienced some of the most extreme floods on Earth and is therefore an important setting for extreme flood research. Here, we examine the upper tail of flood peaks over China based on a comprehensive flood dataset that integrates systematic observations from 1759 stream gaging stations and 14,779 historical flood surveys. Floods with large upper tail ratios (i.e., flood peak discharge normalized by sample 10‐yr flood) cluster spatially in the windward regions of mountainous terrain with basin mean annual rainfall of around 550 mm. Large upper tail ratio floods are associated with a mixture of rainfall generation processes. These processes are characterized by anomalous moisture transport (e.g., zonal water vapor pathways) and/or synoptic configurations (e.g., blocking), with respect to flood‐producing storms for annual flood peaks. Downscaling simulations with the Weather Research and Forecasting model for the 1939, 1963, and 2016 floods over the North China Plain region highlight the role of interactions between complex terrain and large‐scale environment in defining the world envelope curve of flood peaks. The upper‐tail floods demonstrate a combination of ingredients producing extreme rainfall. Our results provide important insights to extreme floods in China and a frame of reference for assessing the largest floods on Earth. Key Points: We examine the upper tail of flood peaks based on the most comprehensive dataset of flood records to date across ChinaComplex terrain and mean annual rainfall are two key elements in dictating the distribution of upper tail ratiosAnomalous moisture transport provides the fundamental distinction between large upper tail ratio floods and annual flood peaks [ABSTRACT FROM AUTHOR]

Long‐term, accurate soil moisture (SM) estimates are crucial for climate, hydrology, and agriculture. Multisource SM products are available at high spatiotemporal coverage, but their uncertainties have yet to be fully evaluated in China. Ten SM products (i.e., reanalysis, assimilation, and satellite) were intercompared and evaluated over 18 hydroclimatic regions of China during 2000–2018 at different scales. The results show that all SM products share similar spatial patterns but exhibit significant differences in regions and products. The interannual fluctuations and differences between these products are relatively small, except for the anomalies of ESA CCI ACTIVE and PASSIVE in southern China. At a seasonal scale, the estimates of NCEP R2, ACTIVE, and PASSIVE for specific regions are significantly different from other products. Moreover, all SM products correlate well with precipitation in summer and have their own dominant areas. Among them, ERA5 shows a comprehensive potential for application in China. The temporal correlation coefficient (R), root mean square difference (RMSD), and standard deviation (σ) demonstrate that ERA5 performs better in southern China, while CLSM performs better in the northeast and throughout China, with R exceeding 0.7 for both products. For the Equitable Threat Score (ETS), ERA5 has a better overall performance with scores greater than 0.03 distributed in more regions of China, followed by ACTIVE and CFSR/CFSV2. This study not only provides a reasonable reference for the targeted selection of SM products in different hydroclimatic regions of China but also establishes a preliminary data basis for the integration of multiple products. Key Points: Ten soil moisture products from multiple sources were intercompared and evaluated in 18 hydroclimatic regions of China during 2000–2018All products share similar spatial patterns to precipitation in China, but with subtle interannual and seasonal variationThe optimal SM products are found in different regions of China, among which ERA5 shows the superior overall performance(R>0.7&ETS¯>0.03) [ABSTRACT FROM AUTHOR]

Reliable information on the dynamics of hydrological changes is crucial for the social and economic stabilities and sustaining developments in arid Central Asia. However, the few long‐term hydrological records limit understanding of the relationship between meltwater runoff and climate changes, because the short‐term observations show a paradoxical runoff trend with climate warming across Central Asia. Here, we made a systematic analysis on the 10Be exposure ages of the river terraces developed in the eastern Tarim Basin and reconstructed the hydrological regime changes during the past 170 ka. These data, together with the ages of the river terraces in the water source areas, suggest that the exposure ages of river terraces in the eastern Tarim Basin reflect the depositional time of alluvial sediments. The meltwater runoff displays an inverse relation with the North Hemisphere Summer Insolation and temperature changes on both orbital and millennial time scale, indicating that low temperatures favor high runoff fluxes. The observed correlation between the hydrological regimes and temperature changes suggests that the runoff will decrease and thus climate will become drying with global warming in arid Central Asia. Plain Language Summary: Reliable information on the dynamics of hydrological changes is crucial for the social and economic stabilities and sustaining developments in arid Central Asia. However, the short‐term observations show a paradoxical runoff trend with climate warming across Central Asia. In order to understand the association of hydrological regimes with climate changes in arid Central Asia, particularly the hydrological changes on the context of global warming, this study reconstructs the hydrological changes in the eastern Tarim Basin over the past 170 ka. Our results show that the high runoff occurred during low temperature periods in the past. The inverse correlation between the hydrological regimes and temperatures in this study indicates that the runoff will decrease and climate will become drying with global warming in the future. More conservative water management policies should be taken for the sustaining development and water security in Central Asia. Key Points: 10Be exposure ages of river terraces in the eastern Tarim Basin reflect the depositional dates of alluvial sedimentsThe runoff in central Asia displays an inverse relation with global temperature changesHigh runoffs and humid climates occurred during cold periods over the past 170 ka, indicating a climate drying with global warming [ABSTRACT FROM AUTHOR]

The dry‐wet abrupt alternation (DWAA) event, which is defined as the phenomenon of dry (or wet) spells abruptly following wet (or dry) spells, magnifies the influence of individual wet and dry events. The dynamic evolution of DWAA events has not been studied for different climate zones of China that is particularly susceptible to dry and wet extremes. This study explores the future changes in the abrupt alternations between dry and wet extremes across 10 climate divisions of China, with a thorough assessment of dry and wet conditions using the Standardized Precipitation Evapotranspiration Index (SPEI). We take advantage of an ensemble of regional climate model simulations including the Providing Regional Climate Impacts for Studies (PRECIS) experiment and five CORDEX East Asia experiments to produce high‐resolution climate information for a baseline period of 1975–2004 and a future period of 2069–2098. Our findings disclose that a total of 70% of China's land area suffered from the DWAA events at least once during 1975–2004. The wet‐dry alternation event is projected to become more frequent in summer, and a prominent increase in the number of dry‐wet alternation events is expected to occur in spring over most parts of China. Moreover, an increasing number of DWAA events with intensified magnitude is projected to strike the North China Plain dominated by warm temperature and humid zone, which is the most densely populated region of the country and is also the largest agriculture production area. Our findings also reveal a strong positive correlation between DWAA and heavy rainfall. The 95th percentile rainfall event contributes most to the wet‐dry alternation event for most climate divisions of China. Plain Language Summary: The emerging disaster of dry‐wet abrupt alternation (DWAA) has been receiving increasing attention due to its compound effects on agricultural production and socioeconomic development. Since China is exposed to dry and wet hydrological extremes as well as their interconnections, a first attempt is made in this study to explore the historical evolution and the future change in the abrupt shifts between dry and wet extremes for different climate divisions of China. Our findings reveal that a total of 70% of China's land area suffered from DWAA events at least once from 1975 to 2004. More importantly, the DWAA is expected to occur more frequently and intense by the end of the 21st century, especially for the North China Plain which is the most densely populated region of the country and is also the largest agricultural production area. Moreover, the summertime wet‐dry alternation is expected to become more frequent for most climate divisions of China, while the dry‐wet alternation event is projected to occur more frequently in spring over East China. These findings provide meaningful insights into the development of adaptation strategies for enhancing society's resilience to compound extremes in a changing climate. Key Points: A total of 70% of China's land area suffered from the dry‐wet abrupt alternation events at least once during 1975–2004The dry‐wet abrupt alternation events are projected to occur more frequently with greater intensity in the North China PlainThe 95th percentile rainfall event contributes most to the wet‐dry alternation event for most climate divisions of China [ABSTRACT FROM AUTHOR]

Global climate change is likely to affect reference evapotranspiration (ET0), which is important for agricultural water resources and food security. Analysis of ET0 changes is also important for understanding climate change and its impacts on hydrology. In this study, ET0 was calculated from 2020 to 2099 in nine agricultural regions and the entire country of China utilizing the Penman–Monteith method based on bias‐corrected climate data from the global climate models MIROC‐ESM‐CHEM, NorES1‐M, IPSL‐CM5A‐LR, GFDL‐ESM 2M and HadGEM2‐ES under future climate change scenarios. The spatiotemporal characteristics of seasonal and annual ET0 and climatic variables were analysed based on the Mann–Kendall test with trend‐free prewhitening (TFPW‐MK) and Sen's slope estimator. Sensitivity coefficient and multivariate regression were used to identify factors controlling the change in ET0. The results showed that seasonal and annual air temperature and precipitation both increased under all climate scenarios, and the majority of relative humidity and wind speed values showed downward trends during 2020–2099. The lowest annual ET0 values were found in the NECR and QTR, and the SCR had the maximum ET0. Both the TFPW‐MK and slope statistics showed an upward trend of seasonal ET0 during 2020–2059 under all scenarios. During 2060–2099, seasonal ET0 values showed a slight and nonsignificant downward trend under RCP 2.6, while upward trends were produced in other scenarios. Areas with high ET0 values were located in the SCR, GXR and HHHR, while low ET0 values mainly occurred in the NECR and QTR. The ET0 for the four seasons in the SCR was higher than that in the other regions, and the summer ET0 was the highest compared with that in the other seasons overall. For the attribution assessment, Tavg is the main controlling variables to ET0 trends under the interaction of multiple climatic factors though RH is the most sensitive. [ABSTRACT FROM AUTHOR]

Healthy plankton communities form the basis of healthy aquatic ecosystems. By elucidating the mechanisms of mutual feedback between plankton and habitat processes and identifying key driving factors can enhance the success rate of ecosystem restoration. However, previous studies suffered from a lack of consideration for temporal and spatial variation in aquatic biome. In this study, three sets of samples were collected in May, September and October 2015 from 59 sampling sites in Jinan, a pilot city for water ecological civilization project, China. Canonical correspondence analysis was performed on the vast amount of data obtained from the samples to analyse the driving effects of various hydrological and water quality factors on plankton. The analysis results indicated that the development of plankton communities in Jinan were primarily driven by (1) hydrological factors of water depth, river width and flow velocity; (2) water quality physical factors of water temperature and conductivity and (3) water quality chemical factors of pH, chemical oxygen demand, biochemical oxygen demand, carbonate and sulphate contents. These results will provide in‐depth theoretical and technical direction for the restoration of aquatic ecosystems in the first pilot city in China and other regions worldwide. [ABSTRACT FROM AUTHOR]

Fast socio‐economic development in agriculture and urbanization resulted in increasing nutrient export by rivers, causing coastal eutrophication in China. In addition, climate change may affect hydrology, and as a result, nutrient flows from land to sea. This study aims at a better understanding of how future socio‐economic and climatic changes may affect coastal eutrophication in China. We modeled river export of total dissolved nitrogen (TDN) and phosphorus (TDP) in 2050 for six scenarios combining socio‐economic pathways (SSPs) and Representative Concentration Pathways (RCPs). We used the newly developed MARINA 2.0 (Model to Assess River Inputs of Nutrients to seAs) model. We found that global change can make coastal eutrophication control in China more difficult. In 2050 coastal waters may be considerably more polluted or considerably cleaner than today depending on the SSP‐RCP scenarios. By 2050, river export of TDN and TDP is 52% and 56% higher than in 2012, respectively, in SSP3‐RCP8.5 (assuming large challenges for sustainable socio‐economic development, and severe climate change). In contrast, river export of nutrients could be 56% (TDN) and 85% (TDP) lower in 2050 than in 2012 in SSP1‐RCP2.6 (assuming sustainable socio‐economic development, and low climate change). Climate change alone may increase river export of nutrients considerably through hydrology: We calculate 24% higher river export of TDN and 16% higher TDP for the SSP2 scenario assuming severe climate change compared to the same scenario with low climate change (SSP2‐RCP8.5 vs. SSP2‐RCP2.6). Policies and relevant technologies combining improved nutrient management and climate mitigation may help to improve water quality in rivers and coastal waters of China. Plain Language Summary: Fast socio‐economic development has resulted in increasing nutrient export by rivers, causing coastal eutrophication in China. In addition, climate change may affect river discharge, and as a result, nutrient flows from land to sea. We explored how future socio‐economic and climatic changes may affect coastal eutrophication in China. We found that in 2050 coastal waters may be considerably more polluted or considerably cleaner than today depending on the socio‐economic development and climate change. By 2050, river export of total dissolved nitrogen (TDN) and phosphorus (TDP) is 52% and 56% higher than in 2012, respectively, in a scenario assuming large challenges for sustainable socio‐economic development and severe climate change. In contrast, river export of nutrients could be 56% (TDN) and 85% (TDP) lower in 2050 than in 2012 in the scenario assuming sustainable socio‐economic development and low climate change. Climate change alone may increase river export of nutrients considerably: we calculate 24% higher river export of TDN and 16% higher TDP for a scenario assuming severe climate change compared to the same scenario with low climate change. Policies combining improved nutrient management and climate mitigation may help to improve water quality in rivers and coastal waters of China. Key Points: In 2050, rivers in China may be more polluted or cleaner, depending on socio‐economic and climatic changesClimate change may increase nutrient pollution in rivers and coastal eutrophication in ChinaCoastal eutrophication can be reduced by nutrient management and climate mitigation [ABSTRACT FROM AUTHOR]

Understanding the dominant causes of streamflow alteration and effects of the current water diversion scheme is beneficial for sustainable management of water resources in an arid area. This study presents a quantitative attribution of the run‐off changes between headstreams and mainstream from 1960 to 2015 using the Choudhury–Yang equation and evaluates the effects of 18 times of ecological water conveyance in the lower reaches of the Tarim River Basin (TRB). Our results suggest that climate change was the primary determinant of increase of the streamflow in the headstreams from 2000 to 2015. While in the mainstream, human activities played a dominant role in deduction in the streamflow with the contribution of 54.8–355.6%. Eighteen episodes of ecological water conveyance have a positive effect on rising groundwater level and are highly related to seed falling time of Shrub and Perennial herbaceous and Annual herbaceous except for Arbor. It indicates that restoring the long‐term drying of the lower reaches through continuous water conveyance is feasible, although the existing programme has not restored the entire riparian system. Our study suggests that it is necessary to adopt an integrated approach for water resources allocation rather than relying on a single tributary contribution in the TRB. [ABSTRACT FROM AUTHOR]

Understanding the variability in soil hydraulic conductivity in the mountainous headwaters is critical to the modeling of mountainous runoff and the water resources management of river basins, especially in the arid and semiarid areas. In this study, a total of 32 soil profiles with five layers within 0-70 cm were sampled under different land cover types: forest, meadow, high coverage grassland (HCG), medium coverage grassland (MCG), and barren land in the upper stream of the Heihe river watershed, Northwest China. Saturated hydraulic conductivity ( KS) was measured for each sample. The vertical variation of KS and soil hydrological response under different land covers were analyzed. Results show that KS value in layer 5 was significantly lower than the values of above four layers. KS decreased in the order of forest, meadow, HCG, MCG, and barren land, corresponding to the degree of vegetation degradation. The KS decreased with depth under forest, HCG, and barren land, but increased first and then decreased under meadow and MCG. The dominant stormflow paths for different land covers were different: forest was dominated by deep percolation, HCG was dominated by subsurface flow (SSF), meadow was prevailed by Hortonian overland flow and had no SSF, while MCG and barren land were also dominated by Hortonian overland flow, but still formed SSF. This result provides important information for improving the accuracy of mountainous hydrological modeling and, in turn, leading to sustainable management of water resources in the study watershed. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Watershed delineation is a required step when conducting any spatially distributed hydrological modelling. Automated approaches are often proposed to delineate a watershed based on a river network extracted from the digital elevation model (DEM) using the deterministic eight-neighbour (D8) method. However, a realistic river network cannot be derived from conventional DEM processing methods for a large flat area with a complex network of rivers, lakes, reservoirs, and polders, referred to as a plain river network region (PRNR). In this study, a new approach, which uses both hydrographic features and DEM, has been developed to address the problems of watershed delineation in PRNR. It extracts the river nodes and determines the flow directions of the river network based on a vector-based hydrographic feature data model. The river network, lakes, reservoirs, and polders are then used to modify the flow directions of grid cells determined by D8 approach. The watershed is eventually delineated into four types of catchments including lakes, reservoirs, polders, and overland catchments based on the flow direction matrix and the location of river nodes. Multiple flow directions of grid cells are represented using a multi-direction encoding method, and multiple outflows of catchments are also reflected in the topology of catchments. The proposed approach is applied to the western Taihu watershed in China. Comparisons between the results obtained from the D8 approach, the 'stream burning' approach, and those from the proposed approach clearly demonstrate an improvement of the new approach over the conventional approaches. This approach will benefit the development of distributed hydrological models in PRNR for the consideration of different types and multiple inlets and outlets of catchments. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Understanding the mechanisms of river runoff variation is important for the effective management of water resources in arid and semi-arid regions. This study uses long-term observational data as a basis for examining the effects of human activities and climate change on the runoff variation of Jinghe River Basin, a typical arid inland basin in northwest China. A distributed hydrological model called the Soil and Water Assessment Tool, combined with a sequential cluster method and a separation approach, was used to quantify and distinguish the effects of human activities and climate change on runoff. The hydrological sequence before 1981 can be considered natural. However, human activities have significantly affected runoff since 1981. The runoff reduction caused by human activities between 1981 and 2008 accounted for 85.7% of the total reduction in the downstream of Jinghe River, whereas that caused by climatic variation was only 14.3%. This observation suggests that human activities are the major driver of runoff variation in the basin. Although the role of climate change in driving runoff variation has been identified to be prevalent and dominant in arid regions, this study highlights the importance of human activities. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Shallow groundwater is an important source of water for the maintenance and restoration of ecosystems in arid environments, which necessitates a deeper understanding of its complex spatial and temporal dynamics driven by hydrological processes. This study explores the dominant hydrological processes that control the shallow groundwater dynamics in the Gobi Desert-riparian-oasis system of the lower Heihe River, a typical arid inland river basin located in northwestern China. The groundwater level and temperature were monitored in 14 shallow wells at 30-min intervals during the 2010-2012 period. After combining this information with meteorological and hydrological data, a comprehensive analysis was conducted to understand the dynamic behaviour of the shallow groundwater system and to determine the dominant factors that control the groundwater flow processes. The results of the study indicate notably large temporal and spatial variations in both the groundwater level and temperature. Noticeable fluctuations in the groundwater level (0.5-1 m) and temperature (4-8 °C) were observed in the riparian zone, evidencing a clear river influence. In comparison, the groundwater fluctuations in the Gobi Desert were more stable (the annual variations of the water table were less than 0.5 m, and the water temperature varied by no more than 2 °C). Strong variations in the groundwater table (1.5-5.0 m/year) and temperature (1.5-6.5 °C), mainly caused by surface flood irrigation and groundwater pumping, were observed in the oasis area. The investigated sites were categorized into three types that reflect the dominant hydrological processes: (1) the riparian zone, dominated by riverbank filtration and groundwater evapotranspiration; (2) the Gobi Desert area, controlled by groundwater evaporation and lateral recharge; and (3) the oasis area, dominated by groundwater evapotranspiration as well as surface-groundwater interactions caused by human activities. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Hydrological processes change from the impacts of climate variability and human activities. Runoff in the upper reaches of the Hun-Taizi River basin, which is mainly covered by forests in northeast China, decreased from 1960 to 2006. The data used in this study were based on runoff records from six hydrological stations in the upper reaches of the Hun-Taizi River basin. Nonparametric Mann-Kendall statistic was used to identify change trends and abrupt change points and consequently analyze the change characteristics in hydrological processes. The abrupt change in the annual runoff in most subcatchments appeared after 1975. Finally, the effects of climate change and land cover change on water resources were identified using regression analysis and a hydrology model. Results of the regression analysis suggest that the correlation coefficients between precipitation and runoff prior to the abrupt change were higher compared with those after the abrupt change. Moreover, using hydrology model analysis, the water yield was found to increase because of the decrease in forest land. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT The Yangtze floodplain is characterized by numerous large (surface area > 1 km2; ∼25% are > 10 km2) and shallow lakes (maximum depth mainly < 5 m). Floodplain lakes are inherently dynamic and important sites for biogeochemical cycling, biodiversity as well as human resources. Importantly, the degree of hydrological connectivity between lakes and river channels is affected by climate, geomorphic processes as well as cultural disturbance of the catchment. This study investigated the long-term (∼200 years) interaction between a shallow floodplain lake (Taibai Lake; area 25 km2, mean depth 3·2 m) and the Yangtze River using high-resolution multi-proxy analysis (diatoms, geochemistry, and grain size) of a 210Pb-dated sediment core. Diatom assemblages in Taibai Lake exhibited a strong temporal succession and were successively dominated by Aulacoseira granulata (planktonic), Gyrosigma acuminatum (periphytic), and the facultatively planktonic Nitzschia palea over the past 200 years. Eutrophication as inferred by diatom inferred-total phosphorous (DI-TP), however, only started around 1990 with TP concentration increasing from 65 to 95 µg L−1. Prior to 1950 DI-TP was constant and detrended correspondence analysis axis 1 sample scores (of the diatom assemblages) were not correlated with DI-TP concentration suggesting that there were other stressors driving changes in the diatom assemblage besides nutrients. We used sediment grain size as a proxy for hydrological connectivity; median grain size is strongly correlated with the abundance of A. granulata ( R2 = 0·67). A comparison of the diatom stratigraphy with physical and geochemical proxies suggested that Taibai Lake shifted from a riverine-influenced, turbid algae-macrophyte mixed state to a clearwater macrophyte-dominated state around 1950 AD, primarily due to the changes in the hydrological regime of the floodplain resulting from land reclamation and building of reservoirs. After 1990 AD, the lake ecosystem deteriorated following continuous input of nutrients from agriculture and aquaculture, shifting to a hyper-eutrophic algae-dominated state. These results indicate the dynamic nature of floodplain ecosystems and the complexity of multiple stressors affecting them over decadal timescales and the long-term interaction between anthropogenic and natural forcing processes. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

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The article presents a study which analyzed hydrological daily discharge time series of the Shaligunlanke Station in China based on data mining theory and technology. Results showed that the annual process of the daily discharge can be divided into five segments. Dynamic time warping (DTW) was used to look for similarities in the discharge process. The study also showed that data mining is a feasible approach to discover hidden information in the historical hydrological data.

The article presents a study on the shift trend and step changes for runoff time series in the Shiyang River basin in northwest China. It states that seven statistical test approaches were used to determine the shift trends and step changes in the study. It discusses that Mann-Kendall test, Spearman's Rho test, linear regression and Hurst exponent were utilized to detect past and future shift trends for runoff time series, while the distributed-free CUSUM test, cumulative deviations and the Worsley likelihood ratio test were employed to detect step changes for the same time series. Results showed that the annual runoff from Zamu, Huangyang and Gulang rivers demonstrate statistically significant decreasing trends.

The article presents a comparison of three methods for examining vineyard evapotranspiration (ET) in the arid desert regions of China. The methods compared include field Water Balance (WB), Eddy Covariance (EC) and Bowen Ratio-Energy Balance (BREB). The variations of the total ET estimated by EC and BREB are similar at hourly or daily timescale with a slight difference in values. Results show that these methods provided similar estimate of the total ET at various timescales and can be used to estimate ET from vineyards in arid conditions.

The article presents a study which focuses on the improvement of the peak flow rate equation used in the Chemicals, Runoff, and Erosion from Agricultural Management Systems (CREAMS) model, to be used in the Loess Plateau in China. The significance of the measure of the peak flow rates in CREAMS in soil conservation plans and engineering projects are discussed. The methods and results of the study and observations are also discussed. The new equation for the peak flow rate in CREAMS is also presented.

This article presents a study regarding the isotropic variation in the lake water balance at the Yamdruk-tso basin found in southern Tibetan Plateau. It discusses that the use of stable isotopes is a practical tool in the study of the lake water budget, which is one way to study the hydrological cycle in the large numbers of inland lakes on the Tibetan Plateau. It mentions that the isotope record of the sediments at the Tibetan Plateau is believed to reflect the climatic and environmental changes.

The article presents a study on an automatic mapping of snow cover depletion curves using remote sensing data under conditions of frequent cloud cover and temporary snow. The study formulates a methodology to produce accurate snow cover depletion curves automatically using high temporal resolution optical remote sensing data such as Terra Moderate Resolution Imaging Spectroradiometer (MODIS). Moreover, the said method based on Terra MODIS was used in a case study carried in the lower and middle reaches of the Kaidu River Watershed in China. Results of the case study suggest that the approach in making accurate snow cover depletion curves automatically under conditions of frequent cloud cover and temporary snow cover using high temporal resolution optical sensing data, were successful.

This article discusses a study which estimated the evolution of vegetation cover and its hydrological impact in the Mekong River basin in the 21st century. The researchers used climatic predictions, a dynamic global vegetation model, terrestrial biogeochemical model, and the distributed hydrological model. They indicated a significant change in vegetation type mainly on the Tibetan Plateau in China and in mountainous areas, with the degree of change differing for each special report on emissions scenario. They suggested that changes in river discharge will be slowed due to changes in evapotranspiration.

The article reports on the study of the historical climate variations and climate change in the Brahmaputra basin such as Tibetan plateau (TP), Himalayan belt and the floodplains (FP). The study analyses the historical trends in temperature and precipitation of the TP, FP, and Himalayan belt through a global 100 year monthly high resolution dataset. It shows that precipitation in the basin is determined by the strength by the monsoons. It expresses that El Niño Southern Oscillation teleconnection does not have an important role in the changes in monsoon precipitation. The study also demonstrates the relationship among air temperature, FP, TP, and the strength of the monsoon.

The Global Energy and Water Cycle Experiment (GEWEX) Asian Monsoon Experiment (GAME) reanalysis datasets are the products of four-dimensional data assimilations (4DDA) of meteorological observations made from April 1998 to October 1998. These datasets were created using the most recently updated 4DDA schemes of the Japan Meteorological Agency (JMA) during the GAME reanalysis project (1999-2001) as well as radiosonde observations made during the intensive observation period of the GAME project (April 1998-October 1998). Two versions of reanalyses products have been released officially: Ver. 1.1 and Vet. 1.5. One of the greatest differences between the two versions is the representation of snow cover: Ver. 1.1 used climatological snow data, while Vet. 1.5 used satellite-derived snow information. Here, we describe how snow cover modifications and land surface schemes differ between the two versions and how changes in surface processes affect surface fluxes. The use of satellite-derived snow information produced a difference in surface fluxes over the Tibetan Plateau, especially for May. We also compare surface fluxes estimated by the long-term reanalysis (JRA25) product of the JMA as well as GAME reanalysis product with in situ observations by the Asian Automatic Weather Station (AWS) Network (AAN). Radiosonde observations made 4 times daily were incorporated into the atmospheric field of the 4DDA GAME reanalysis and resulted in a good correspondence between the reanalyses products and surface observations, especially for July. The use of satellite-derived snow information as a boundary condition also had improved flux results over the Tibetan Plateau in May. [ABSTRACT FROM AUTHOR]

1. At a local scale, the species composition, diversity and spatial variation of wetland plant communities are determined primarily by spatial and temporal heterogeneity in their environments. Less is known about variation at a landscape-level. The floodplain of the Changjiang (Yangtze) River in China includes hydrologically connected, subtropical wetlands with different hydrological characteristics. 2. We examined seed-bank species composition and richness in marshes of two contrasting hydrological types: permanent marshes, fed by local runoff, and lakeshore marshes more closely connected to the regulated river. Lakeshore marshes are flooded annually to depth of approximately 1 m and during flooding they support an alternate, aquatic vegetation type. The soil seed bank in March was a comparative estimator of species diversity. At the beginning of the growing season it included seeds from both phases of alternating vegetation types associated with the annual hydrological cycle. 3. A regional pool of 101 species was detected in the seed banks of six wetlands associated with the river and its tributaries: 56 occurred in permanent marshes and 59 in lakeshore marshes, with only 15 common to both. Species rarefaction curves indicated that more species occurred in permanent than lakeshore marshes at equal numbers of individuals sampled. However, the more heterogeneous lakeshore seed banks were estimated (Chao 2) to have greater total species richness (81) than permanent marsh (60). 4. Analysis using S&3x00F8;rensen's coefficient of similarity and DCA ordination revealed complex variation, with much greater differences between hydrological types than within them, irrespective of geographical distance. The types also differed significantly in the composition of four functional groups of species. 5. Despite the potential for dispersal of propagules via the annually pulsing river system (hydrochory), at a regional and landscape scale, diversity is maintained largely by largescale temporal hydrological heterogeneity and smaller scale spatial and topographic heterogeneity. [ABSTRACT FROM AUTHOR]

The hydrological response to climate change in the Tarim River Basin was investigated by analysing the hydrological, temperature and precipitation data of the past 50 years. The long-term trend of the hydrological time-series, including air temperature, precipitation, and streamflow, was examined by using both parametric and non-parametric techniques and the plausible association between streamflow and climate change by the method of grey correlation analysis. The results show that the study area became warmer in the last few decades. The air temperature experienced a significant monotonic increase by 5%; the precipitation showed a significant decrease in the 1970s and then a major increase in the 1980s and 1990s, with average annual precipitation up by 6-8 mm per decade. A step change occurred in both temperature and precipitation around 1986, with mean temperature and precipitation increasing from 67°C and 146 mm before 1986 to 7.3°C and 180 mm respectively after 1986. The temperature has risen by nearly 1 °C over the past 50 years, possibly resulting from the impact of global climate change. Streamflows in the Aksu River and the Yarkant River have shown a significant (P < 0.05) tendency of increase. This is particularly the case for the Aksu River. The coefficients of streamflow increase in the Aksu and Yarkant Rivers are 0.41 and 0.13 respectively. The results of grey correlation analysis show that in the Aksu River, which is located in the northwest of the basin, the impact of precipitation on streamflow is much greater than that of temperature. However, in the Hotan River, which is located in the southwest of the basin, the impact of temperature on streamflow is much greater than that of precipitation. This is likely to be related to the geographic distribution of the headstreams of the rivers. [ABSTRACT FROM AUTHOR]

The interactions of nature and society are intimately reflected in the degradation of the vast, yet diverse, landscapes and ecosystems of arid western China. The development of agriculture, especially irrigation, has altered rivers, soils and ecosystems so much that major ecological rehabilitation and restoration efforts have been needed since 1950. The catchments of the Tarim River in southern Xinjiang (the Tarim Basin) and of the Black River (Hei He) in Gansu Province and western Inner Mongolia provide examples of the benefits, difficulties and conflicts involved in dryland water management. In the early stages of the human development of these catchments, agriculture depending on irrigation using water from these inland rivers was encouraged. The over-exploitation of these water resources led to such ecological problems as desiccation of lakes, drying out of rivers, degradation of soils and vegetation and lowering of groundwater levels, with consequent environmental and economic impacts. Since 1990 several high-cost, national projects to re-establish ecosystems have been initiated. Water is now released from dams in the headwaters of the rivers in order to restore water flows to the dried out lake basins. Such schemes have inevitably led to social problems and difficulties for the people who depended on the water from the dams for local irrigation. The contrasts in adjustments and attitudes over the use of water for agriculture and other economic activities, as opposed to schemes of restoration of ecosystems and ecological engineering, stem largely from two issues; inconsistent provision of information from the scientific community, and differing ideologies, namely environmental protection versus economic development. [ABSTRACT FROM AUTHOR]