Impacts of water resource planning on regional water consumption pattern: A case study in Dunhuang Oasis, China

Water resources are critical for the existence and development of oases in endorheic basins.Thus,to enable sustainable development,it is fundamentally important to understand how to allocate and use these resources in a reasonable way.We therefore simulated and analyzed changes in water consumption pattern within the Dunhuang Oasis of China under three scenarios using a system dynamic model that corresponds to different water consumption pattern.This was done to assess the impacts of regional water resource planning(comprehensive planning of the rational use of water resource and protection of ecosystem services in the Dunhuang Basin)on water consumption pattern within the Dunhuang Oasis.The first of these,Scenario 1,is a baseline in which the status quo is maintained,while Scenario 2 incorporates the comprehensive effects of agricultural water-saving irrigation measures with an inter-basin water diversion project,and Scenario 3 focuses on ecological rehabilitation.In the baseline Scenario 1,the total water consumption within the Dunhuang Oasis increased progressively while agricultural water consumption remained extremely high and threatened overall ecological security.In contrast,Scenario 2 would decrease agricultural water consumption by almost 5.30×10^7 m^3 following the implementation of water-saving practices.The additional water allocated from an inter-basin water diversion project would play an important role in alleviating ecological strain on the oasis.Finally,in Scenario 3,the total irrigated land must be decreased to 20.6×10^3 hm^2 by 2025 assuming that water supply for ecosystem restoration would be at least 50%of the total consumption.Although water resource planning plays a very important role in alleviating the ecological water crisis within the oasis,it is necessary to consider the suitable scale of oasis with regard to current water consumption pattern.

Comparison of water resources management between China and the United States

As the world’s top two economies,the United States(U.S.)and China face a number of similar water resources problems.Yet,few studies have been done to systematically compare policies and approaches on water resources management between China and the U.S.This study compares water resources policies of China and the U.S.in the areas of national authority,water supply,water quality,and ecosystem use of the water to draw lessons learned and shed light on water resources management in China,the U.S.,and the rest of the world.The lessons learned from the comparison include six aspects.1)New paradigms of people-water harmony and a water-saving society are urgently needed to address the pressing water crisis and achieve the United Nations Sustainable Development Goals(UN SDGs).2)A comprehensive,consistent,forward-looking national policy is necessary to achieve sustainable use of water resources.3)Empowerment of river basin commissions with comprehensive authority over the integrative management of air,land,water,and biological resources in the river basin could significantly enhance the benefits and effectiveness of economic development and environmental protection.4)Expansion of water exchange through market mechanisms among water users promotes efficient and beneficial water uses.5)Use of water for ecosystem services should be an integral part of water resources management.China has set up a national blueprint for achieving ecological civilization;maintaining appropriate amounts of flow in rivers and lakes for maintenance of wildlife and fisheries and ecosystems should be institutionalized as part of this national strategy as well.6)By sharing their rich experiences and lessons in water resources management,economic development,and ecological protection with other countries,China and the U.S.can help the world to achieve global human-water harmony and the UN SDGs.

Performance evaluation of CLM5.0 in simulating liquid soil water in high mountainous area,Northwest China

The model performance in simulating soil water content(SWC) is crucial for successfully modeling earth’s system,especially in high mountainous areas.In this study,the performance of Community Land Model 5.0(CLM5.0) in simulating liquid SWC was evaluated against observations from nine in-situ sites in the upper reach of the Heihe River Watershed(HRW),Northwest China.The CLM5.0 shows reliable performance in the study area with correlation coefficients(R) ranging between 0.79–0.93,root mean standard errors(RMSE)ranging between 0.044–0.097 m^(3)/m^(3),and the mean bias(BIAS) ranging between-0.084–0.061 m^(3)/m^(3).The slightly worse performance of CLM5.0 than CLM4.5 on alpine meadow and grassland is mainly caused by the revised canopy interception parameterization.The CLM5.0 overestimates interception and underestimates evapotranspiration(ET) on both alpine meadow and grassland during the growth period.The systematical overestimations at all the grassland sites indicate that the underestimation of ET is much larger than the overestimation of interception on grassland during growth period,while the errors of simulated interception and ET are partially canceled out on alpine meadow.Moreover,the underestimation of ET is more responsible for the overestimation of SWC than the overestimation of interception in the high mountainous area.It is necessary to estimate reasonable empirical parameter α(proportion of leaf water collection area) in interception parameterization scheme and further improve the dry surface layerbased soil evaporation resistance parameterization introduced in CLM5.0 in future researches.The performance of CLM5.0 is better under completely frozen stage than thawing stage and freezing stage,because of low variations of liquid SWC caused by extremely low hydraulic conductivity of soils.The underestimation of liquid SWC under frozen state is caused by underestimation of soil temperature,which leads to more ice mass and less liquid water in total water content.

Challenges of agriculture and food systems issues in China and the United States

China and the United States are the two most significant nations in the contemporary global food and agricultural network.In addition,they are two of the most important innovators with respect to the development of new crop varieties,agro-technologies,farm products,markets and consumer issues,such as consumer resistance to genetically modified foods,among others.In the face of an ever-complex web of interactions,technologies and products among producers and consumers in both nations,there are far more structural similarities than differences in the food and agriculture sectors of these two nations.This essay,adopting some of the themes of the Sino-American Symposium on Future Issues Affecting Quality of Life,presents a limited but representative comparative assessment of three of the most important shared challenges impacting the agricultural sectors of China and the United States for the period from 2000 to the present including 1)environmental challenges related to agricultural water supply,2)declines in farm labor and rural population,and 3)growing food-related concerns and challenges.For both nations,excessive and unsustainable groundwater consumption has lowered water tables and limited crop production.Rural populations and farm workforces in both nations are also declining,leading to labor challenges in both nations.Finally,concerns regarding food safety are also very similar with major challenges to the farm sector associated with consumer resistance to genetically modified food crops and sanitation issues linked to lengthening supply chains.All of these issues threaten the development of sustainable agricultural production systems.

Evaluation of Precipitation Datasets from TRMM Satellite and Down-scaled Reanalysis Products with Bias-correction in Middle Qilian Mountain,China

Accurate estimates of precipitation are fundamental for hydrometeorological and ecohydrological studies,but are more difficult in high mountainous areas because of the high elevation and complex terrain.This study compares and evaluates two kinds of precipitation datasets,the reanalysis product downscaled by the Weather Research and Forecasting(WRF)output,and the satellite product,the Tropical Rainfall Measuring Mission(TRMM)Multisatellite Precipitation Analysis(TMPA)product,as well as their bias-corrected datasets in the Middle Qilian Mountain in Northwest China.Results show that the WRF output with finer resolution perfonns well in both estimating precipitation and hydrological simulation,while the TMPA product is unreliable in high mountainous areas.Moreover,bias-corrected WRF output also performs better than bias-corrected TMPA product.Combined with the previous studies,atmospheric reanalysis datasets are more suitable than the satellite products in high mountainous areas.Climate is more important than altitude for the\falseAlarms'events of the TRMM product.Designed to focus on the tropical areas,the TMPA product mistakes certain meteorological situations for precipitation in subhumid and semiarid areas,thus causing significant"falseAlarms"events and leading to significant overestimations and unreliable performance.Simple linear bias correction method,only removing systematical errors,can significantly improves the accuracy of both the WRF output and the TMPA product in arid high mountainous areas with data scarcity.Evaluated by hydrological simulations,the bias-corrected WRF output is more reliable than the gauge dataset.Thus,data merging of the WRF output and gauge observations would provide more reliable precipitation estimations in arid high mountainous areas.

Development of an Instant Correction and Display System of Numerical Weather Prediction Products in China

This paper presents the development of numerical prediction products(NPP) correction and display system(NPPCDS) for rapid and effective post-processing and displaying of the T213 NPP(numerical prediction products of the medium range numerical weather prediction spectral model T213L31) through instant correction method. The NPPCDS consists of two modules: an automatic correction module and a graphical display module. The automatic correction module automatically corrects the T213 NPP at regularly scheduled time intervals, while the graphical display module interacts with users to display the T213 NPP and its correction results. The system helps forecasters extract the most relevant information at a quick glance without extensive post-processing. It is simple, easy to use, and computationally efficient, and has been running stably at Huludao Meteorological Bureau in Liaoning Province of China for the past three years. Because of its low computational costs, it is particularly useful for meteorological departments that lack advanced computing capacity and still need to make short-range weather forecasting.

Elemental Analysis of Soil Phosphorus Neighborhoods Using SEM, Spectral Mapping and GIS

The utility of GIS （geographic information system） methods and spatial statistical analysis on spectral maps of sediment samples were examined. Detailed elemental maps are often constructed using energy dispersive X-ray techniques and SEM （scanning electron microscopy）. The elemental neighborhood associations of a single element, P （phosphorus）, were quantified at a magnification of 3,000 ×. For each of the 170,000 pixels on the images which displayed a strong P concentration, neighborhoods from 0.1μm^2 to 12 μm^2 were examined for associated elemental concentrations. PCA （principal component analysis） revealed two significant neighborhood types associated with P in samples of pH 4, and three neighborhood types at pH 8. These neighborhoods corresponded to Mg-P associations commonly found to be chemically prevalent in river sediments impacted by agricultural operations. Discriminant analysis showed that the greatest accuracy in predicting sample pH could be achieved by using a neighborhood size of 12 ~m2. Potassium at relatively large neighborhood sizes was the element most significant in predicting pH. While many of the chemical associations in close proximity to P could be predicted and explained through mineral solubility, spatial analysis provided some interesting insights into the structure of the samples. Results also indicted differences in the spatial scale associated with different processes.

A Modified Groundwater Module in SWAT for Improved Streamflow Simulation in a Large, Arid Endorheic River Watershed in Northwest China

Interactions between surface water and groundwater are dynamic and complex in large endorheic river watersheds in Northwest China due to the influence of both irrigation practices and the local terrain. These interactions interchange numerous times throughout the middle reaches, making streamflow simulation a challenge in endorheic river watersheds. In this study, we modified the linear-reservoir groundwater module in SWAT(Soil and Water Assessment Tools, a widely used hydrological model) with a new nonlinear relationship to better represent groundwater processes; we then applied the original SWAT and modified SWAT to the Heihe River Watershed, the second largest endorheic river watershed in Northwest China, to simulate streamflow. After calibrating both the original SWAT model and the modified SWAT model, we analyzed model performance during two periods: an irrigation period and a non-irrigation period. Our results show that the modified SWAT model with the nonlinear groundwater module performed significantly better during both the irrigation and non-irrigation periods. Moreover, after comparing different runoff components simulated by the two models, the results show that, after the implementation of the new nonlinear groundwater module in SWAT, proportions of runoff components changed-and the groundwater flow had significantly increased, dominating the discharge season. Therefore, SWAT coupled with the non-linear groundwater module represents the complex hydrological process in the study area more realistically. Moreover, the results for various runoff components simulated by the modified SWAT models can be used to describe the hydrological characteristics of lowland areas. This indicates that the modified SWAT model is applicable to simulate complex hydrological process of arid endorheic rivers.

Semi-supervised Support Vector Regression Model for Remote Sensing Water Quality Retrieving

This paper proposed a semi-supervised regression model with co-training algorithm based on support vector machine, which was used for retrieving water quality variables from SPOT 5 remote sensing data. The model consisted of two support vector regressors (SVRs). Nonlinear relationship between water quality variables and SPOT 5 spectrum was described by the two SVRs, and semi-supervised co-training algorithm for the SVRs was es-tablished. The model was used for retrieving concentrations of four representative pollution indicators―permangan- ate index (CODmn), ammonia nitrogen (NH3-N), chemical oxygen demand (COD) and dissolved oxygen (DO) of the Weihe River in Shaanxi Province, China. The spatial distribution map for those variables over a part of the Weihe River was also produced. SVR can be used to implement any nonlinear mapping readily, and semi-supervis- ed learning can make use of both labeled and unlabeled samples. By integrating the two SVRs and using semi-supervised learning, we provide an operational method when paired samples are limited. The results show that it is much better than the multiple statistical regression method, and can provide the whole water pollution condi-tions for management fast and can be extended to hyperspectral remote sensing applications.

Evaluation of the SMOS and SMAP soil moisture products under different vegetation types against two sparse in situ networks over arid mountainous watersheds, Northwest China

Assessment of the suitability of satellite soil moisture products at large scales is urgently needed for numerous climatic and hydrological researches, particularly in arid mountainous watersheds where soil moisture plays a key role in landatmosphere exchanges. This study presents evaluation of the SMOS(L2) and SMAP(L2_P_E and L2_P) products against ground-based observations from the Upstream of the Heihe River Watershed in situ Soil Moisture Network(UHRWSMN) and the Ecological and Hydrological Wireless Sensor Network(EHWSN) over arid high mountainous watersheds, Northwest China.Results show that all the three products are reliable in catching the temporal trend of the in situ observations at both point and watershed scales in the study area. Due to the uncertainty in brightness temperature and the underestimation of effective temperature, the SMOS L2 product and both the SMAP L2 products show "dry bias" in the high, cold mountainous area. Because of the more accurate brightness temperature observations viewing at a constant angle and more suitable estimations of single scattering albedo and optical depth, both the SMAP L2 products performed significantly better than the SMOS product.Moreover, comparing with station density of in situ network, station representation is much more important in the evaluation of the satellite soil moisture products. Based on our analysis, we propose the following suggestions for improvement of the SMOS and SMAP product suitability in the mountainous areas: further optimization of effective temperature; revision of the retrieval algorithm of the SMOS mission to reduce the topographic impacts; and, careful selection of in situ observation stations for better representation of in situ network in future evaluations. All these improvements would lead to better applicability of the SMOS and SMAP products for soil moisture estimation to the high elevation and topographically complex mountainous areas in arid regions.

Applicability of cosmic-ray neutron sensor for measuring soil moisture at the agricultural-pastoral ecotone in northwest China

Accurate monitoring of soil moisture is crucial in hydrological and ecological studies.Cosmic-ray neutron sensors(CRNS)measure area-average soil moisture at field scale,filling a spatial scale gap between in-situ observations and remote sensing measurements.However,its applicability has not been assessed in the agricultural-pastoral ecotone,a data scarce semiarid and arid region in Northwest China(APENC).In this study,we calibrated and assessed the CRNS(the standard N0 method)estimates of soil moisture.Results show that Pearson correlation coefficient,RP,and the root mean square error(RMSE)between the CRNS soil moisture and the gravimetric soil moisture are 0.904 and less than 0.016 m3 m–3,respectively,indicating that the CRNS is able to estimate the area-average soil moisture well at our study site.Compared with the in-situ sensor network measurements(ECH2O sensors),the CRNS is more sensitive to the changes in moisture in its footprint,which overestimates and underestimates the soil moisture under precipitation and dry conditions,respectively.The three shape parameters a0,a1,a2 in the standard calibration equation(N0 method)are not well suited to the study area.The calibrated parameters improved the accuracy of the CRNS soil moisture estimates.Due to the lack of low gravimetric soil moisture data,performance of the calibrated N0 function is still poor in the extremely dry conditions.Moreover,aboveground biomass including vegetation biomass,canopy interception and widely developed biological soil crusts adds to the uncertainty of the CRNS soil moisture estimates.Such biomass impacts need to be taken into consideration to further improve the accuracy of soil moisture estimation by the CRNS in the data scarce areas such as agricultural-pastoral ecotone in Northwest China.

Watershed science:Linking hydrological science with sustainable management of river basins

Over the past decades,a number of water sciences and management programs have been developed to better understand and manage the water cycles at multiple temporal and spatial scales for various purposes,such as ecohydrology,global hydrology,sociohydrology,supply management,demand management,and integrated water resources management(IWRM).At the same time,rapid advancements have also been taking place in tracing,mapping,remote sensing,machine learning,and modelling technologies in hydrological research.Despite those programs and advancements,a water crisis is intensifying globally.The missing link is effective interactions between the hydrological research and water resource management to support implementation of the UN Sustainable Development Goals(SDGs)at multiple spatial scales.Since the watershed is the natural unit for water resources management,watershed science offers the potential to bridge this missing link.This study first reviews the advances in hydrological research and water resources management,and then discusses issues and challenges facing the global water community.Subsequently,it describes the core components of watershed science:(1)hydrological analysis;(2)water-operation policies;(3)governance;(4)management and feedback.The framework takes into account water availability,water uses,and water quality;explicitly focuses on the storage,fluxes,and quality of the hydrological cycle;defines appropriate local water resource thresholds through incorporating the planetary boundary framework;and identifies specific actionable measures for water resources management.It provides a complementary approach to the existing water management programs in addressing the current global water crisis and achieving the UN SDGs.

A new method for instant correction of numerical weather prediction products in China

This paper presents a new correction method, "instant correction method(ICM)", to improve the accuracy of numerical prediction products(NPP) and provide weather variables at grid cells. The ICM makes use of the continuity in time of the forecast errors at different forecast times to improve the accuracy of large scale NPP. To apply the ICM in China, an ensemble correction scheme is designed to correct the T213 NPP(the most popular NPP in China) through different statistical methods. The corrected T213 NPP(ICM T213 NPP) are evaluated by four popular indices: Correlation coefficient, climate anomalies correlation coefficient, root-mean-square-errors(RMSE), and confidence intervals(CI). The results show that the ICM T213 NPP are more accurate than the original T213 NPP in both the training period(2003–2008) and the validation period(2009–2010). Applications in China over the past three years indicate that the ICM is simple, fast, and reliable. Because of its low computing cost, end users in need of more accurate short-range weather forecasts around China can benefit greatly from the method.

土壤水文属性及其对水文过程影响研究的进展、挑战与机遇

土壤水文属性对水文过程、能量过程、碳氮循环过程及各过程间相互作用有重要影响。首先简要回顾近30年来土壤水文属性的研究进展,包括土壤水文属性的监测分析、土壤水文属性对水文过程的影响机理,以及不同尺度土壤水文属性对水文过程的影响差异及联系。其次,论述土壤水文属性研究的挑战与机遇。最后介绍祁连山区土壤水文属性对水文过程的影响及多尺度特征研究。力求加深对土壤水文属性变异规律及其对水文过程影响机理的认知,发展土壤水文学和山区水文学,支持水资源科学管理和区域可持续发展。

流域科学与水资源管理

流域是水资源管理的基本单位。基于水资源文献的综合分析,讨论了自20世纪以来水资源管理概念、目标及途径的变迁,提出建立流域科学,以流域为研究对象,以揭示流域生态水文过程的客观规律为前提,采用现代管理科学理论和方法,应用先进工程技术手段优化配置水资源,满足人类活动及生态系统的多种需求,促进社会、经济及环境的可持续发展。并且指出流域科学的内涵应包括:①水资源的调查、监测和模拟;②水资源利用多目标设定;③水资源分配机制;④水资源管理指标的确定与评价;⑤水资源管理决策机构;⑥水资源管理反馈分析与人类活动调控。

宇宙射线中子法在西北农牧交错带土壤水分测量中的适用性研究

准确监测土壤水分在水文学和生态学研究中至关重要.宇宙射线中子传感器(CRNS)能测量田间尺度上的区域平均土壤水分,填补了原位观测与遥感反演之间的空间尺度缺陷.但是其在中国西北农牧交错带这样一个数据缺乏的干旱-半干旱地区的适用性研究还很缺乏.本研究校准并评估了CRNS(标准N0方法)估算土壤水分的性能.结果显示CRNS和烘干法土壤水分之间的皮尔逊相关系数(RP)和均方根误差(RMSE)分别为0.904和0.016m3m–3.这意味着CRNS能够很好地估计研究区的平均土壤水分.与原位观测网(ECH2O)测量的土壤水分相比,CRNS对环境中水分的变化更加敏感,表现为降雨时的高估和土壤干燥时的低估.标准校准方程(N0方法)中的三个形状参数a0、a1、a2在本研究区适用性受限,对其进行经验校准提高了CRNS土壤水分估算的准确性.由于缺少低烘干法土壤水分数据,因此在极端干燥的条件下,校准后的N0方法性能依旧不好.此外,包括植被生物量、林冠截留和广泛发育的生物土壤结皮在内的地上生物量增加了CRNS土壤水分估算的不确定性.需要考虑这些生物量的影响,以进一步提高CRNS在如中国西北农牧交错带这类数据缺乏地区中估算土壤水分的准确性.

流域科学:连接水文学与流域可持续管理的枢纽

近几十年来,为了更好地认识和管理不同时空尺度的水循环,许多水科学和管理项目相继问世,如生态水文学、全球水文学、社会水文学、供水管理、需水管理和水资源综合管理(Integrated Water Resources Management, IWRM)等.与此同时,示踪、制图、遥感、机器学习和模拟等先进技术也广泛应用于水文过程和水资源研究中.尽管如此,全球水危机仍日益加剧.究其原因在于水文水资源研究和管理之间未能在不同时空尺度建立有效的链接和交流来实现联合国可持续发展目标.流域是水资源管理的基本单元,流域科学有望搭建水文水资源研究与管理之间的桥梁.本文首先回顾水文研究和水资源管理的进展,进而讨论了全球水资源界面临的问题和挑战.在此基础上,提出了流域科学的四个核心组成部分:(1)水文分析;(2)水资源政策;(3)综合治理;(4)管理与反馈.该构架综合考虑水资源拥有量和用水量及水质,量化水循环的储存、通量和质量,基于地球环境边界条件理论确定当地水资源阈值;提出水资源管理的具体可行措施.流域科学为应对当前全球水危机和实现联合国可持续发展目标提供了互补性水资源管理途径.