Assessing Wind Erosion: A Review of Recent Measurement Techniques

Wind erosion represents a formidable environmental challenge and has serious negative impacts on soil health and agricultural productivity, particularly in arid and semi-arid areas. The complex dynamics of wind erosion make its large-scale monitoring and quantification a daunting task. To facilitate the monitoring and quantification of wind erosion, various scientific approaches and methods have been employed. These include sophisticated wind erosion equations and models, wind tunnel experiments, and the application of radionuclides. Additionally, researchers have assessed soil physicochemical properties, used anemometers for wind speed measurement, and deployed dust collectors for particle capture. Remote sensing technologies, wind erosion monitoring stations, and evaluations of wind barriers have also been utilized. Recently, the adoption of machine learning methods has gained popularity. Despite their value, each of these techniques has limitations in capturing the full spectrum of the wind erosion process. This paper examines these limitations and assesses the effectiveness of each method in the context of wind erosion studies. It also outlines directions for future research and suggests pathways that could enhance the understanding and management of wind erosion.

Dry/wet climate zoning and delimitation of arid areas of Northwest China based on a data-driven fashion

The division of arid areas is important in water and land resources management, planning and for a long-term agricultural, economic and social planning. Northwest China （NW） dominates the main arid areas in China. There is thus a need to adopt adequate concepts relative to the scope of arid areas of NW China and identify its climate types and characteristics. In this study, we analyzed climatic data over the last 30 years （1981-2010） from 191 stations in three provinces and three autonomous regions of NW China. The factor-cluster analysis technique （FC）, an objective and automated method was employed to classify the dry/wet climate zones. The traditional methods with predefined thresholds were adopted for providing a comparison with FC. The results showed that the wet/dry climate zones by FC were mainly distributed along mountains, rivers and desert borders. Climate-division boundaries relied heavily on the major terrain features surrounding the grouped stations. It also showed that the climate was dry in the plain sandy areas but relatively wet in the high mountain areas. FC method can reflect the climate characteristics more fully in NW China with varied and complicated topography, and outperform the tradi- tional climate classifications. Arid areas of NW China were defined as four climate types, including five resultant classes in FC classifications. The Qinling and Da Hinggan Mountains were two important boundaries, besides main administrative boundaries. The results also indicated that there are some differences between two traditional clas- sifications. The precipitation moved and fluctuated to an extent, which confirmed that climate change played an important role in the dry/wet climate zoning, and the boundaries of dry/wet climate zones might change and migrate with time. This paper is expected to provide a more in-depth understanding on the climate characteristics in arid areas of NW China, and then contribute to formulate reasonable water and land management planning and agri- cultural production programs.

Measuring and modeling two-dimensional irrigation infiltration under film-mulched furrows

Furrow irrigation with film-mulched agricultural beds is being promoted in the arid region of northwest China because it improves water utilization. Two-dimensional infiltration patterns under film-mulched furrows can provide guidelines and criteria for irrigation design and operation. Our objective was to investigate soil water dynamics during ponding irrigation infiltration of mulched furrows in a cross-sectional ridge-furrow configuration, using laboratory experiments and mathematical simulations. Six experimental treatments, with two soil types （silt loam and sandy loam）, were investigated to monitor the wetting patterns and soil water distribution in a cuboid soil chamber. Irrigation of mulched furrows clearly increased water lateral infiltration on ridge shoulders and ridges, due to enhancement of capillary driving force. Increases to both initial soil water content （SWC） and irrigation water level resulted in increased wetted soil volume. Empirical regression equations accurately estimated the wetted lateral distance （Rl） and downward distance （Rd） with elapsed time in a variably wetted soil medium. Optimization of model parameters followed by the Inverse approach resulted in satisfactory agreement between observed and predicted cumulative infiltration and SWC. On the basis of model calibration, HYDRUS-2D model can accurately simulate two-dimensional soil water dynamics under irrigation of mulched furrows. There were significant differences in wetting patterns between unmulched and mulched furrow irrigation using HYDRUS-2D simulation. The Rd under the mulched furrows was 32.14% less than the unmulched furrows. Therefore, film-mulched furrows are recommended in a furrow irrigation system.

Invariance in the Seasonal Median Dates for Mono-Modal Monsoonal Rainfall Distribution over the Semi-Arid Ecotone of Sub-Saharan West Africa

Seasonal distribution of mono-modal, monsoonal rainfall across the semi-arid ecotone of sub-Saharan of West Africa is highly variable and unpredictable. The ever-present risk of drought and crop failure in this environment often results in food shortages that are met by emergency food aid. Humanitarian assistance planners would be better prepared for such interventions in a timely manner if they have reliable indicators that forewarn the impending failure of the rains. A good indicator would be a characteristic of the seasonal rainfall distribution that can be shown to be reasonably invariant over time and space. The objective of this study is to investigate whether such invariance existed for the seasonal median date (meaning the date when 50% of the seasonal total occurs). Such invariance is expected since the sun’s cyclic declination forces the advance and retreat of the Inter-tropical Front over West Africa. We examined the statistical properties of the seasonal median date for 1349 station-years of rainfall records for 30 rainfall stations in Burkina Faso and Niger with coordinates ranging from 9.88° to 18.5° north latitude and -4.77° to 13.2° longitude. The results showed that the median date was quite narrowly distributed over years with rather weak dependence on geographical coordinates. It can therefore be used as a reasonable ex-ante indicator of the success or failure of the rains as the rainy season progress.

区域主要作物生产实体水-虚拟水耦合流动过程解析与评价

水安全是粮食安全的刚性基础.在农业生产过程中(产前、产中、产后)自然-经济-社会(三元)因素驱动下,其水资源消耗形成实体水-虚拟水(二维)嵌入转化、互为反馈、相互影响的耦合流动过程.本文基于实体水-虚拟水"二维三元"耦合流动理论,集成构建了以水量为参数的区域作物生产广义实体水-虚拟水耦合流动过程量化方法,并应用于我国"丝绸之路经济带"沿线西部六省,对其1985~2013年主要作物实体水-虚拟水耦合流动过程进行解析与评价.揭示了区域作物生产实体水-虚拟水耦合流动现象,发现六省间水资源消耗与流动存在资源与经济效益的此消彼长现象.表明以农田尺度实体节水为目标的资源单视角传统农业水资源管理理念,已不足以实现多空间尺度水资源的资源-经济同步高效利用的管理目标,而具有资源-经济-社会三重意义的区域农业全产业链实体水-虚拟水统筹管理应为有效解决思路.基于此,初步提出三点思考:(1)现代农业节水应实体水-虚拟水统筹考虑;(2)需加快突破农业生产实体水-虚拟水耦合流动量化、评价方法与调控关键技术;(3)建议基于农业全产业链视角,建立基于实体水-虚拟水二维度理论的农业水资源管理体系,确保实现各阶段水资源管理"三条红线".

Feedbacks between vegetation restoration and local precipitation over the Loess Plateau in China

The implementation of large-scale vegetation restoration over the Chinese Loess Plateau has achieved clear improvements in vegetation fraction,as evidenced by large areas of slopes and plains being restored to grassland or forest.However,such large-scale vegetation restoration has altered land-atmosphere exchanges of water and energy,as the land surface characteristics have changed.These variations could affect regional climate,especially local precipitation.Quantitatively evaluating this feedback is an important scientific question in hydrometeorology.This study constructs a coupled land-atmosphere model incorporating vegetation dynamics,and analyzes the spatio-temporal changes of different land use types and land surface parameters over the Loess Plateau.By considering the impacts of vegetation restoration on the water-energy cycle and on land-atmosphere interactions,we quantified the feedback effect of vegetation restoration on local precipitation across the Loess Plateau,and discussed the important underlying processes.To achieve a quantitative evaluation,we designed two simulation experiments,comprising a real scenario with vegetation restoration and a hypothetical scenario without vegetation restoration.These enabled a comparison and analysis of the net impact of vegetation restoration on local precipitation.The results show that vegetation restoration had a positive effect on local precipitation over the Loess Plateau.Observations show that precipitation on the Loess Plateau increased significantly,at a rate of 7.84 mm yr^(-2),from 2000 to 2015.The simulations show that the contribution of large-scale vegetation restoration to the precipitation increase was about 37.4%,while external atmospheric circulation changes beyond the Loess Plateau contributed the other 62.6%.The average annual precipitation under the vegetation restoration scenario over the Loess Plateau was 12.4%higher than that under the scenario without vegetation restoration.The above research results have important theoretical and practical significance for the ecological protection and optimal development of the Loess Plateau,as well as the sustainable management of vegetation restoration.

Spatiotemporal variation in water footprint of grain production in China

Water shortage has become a significant constraint to grain production in China.A more holistic approach is needed to understand the links between grain production and water consumption.Water footprint provides a framework to assess water utilization in agriculture production.This paper analyzes the spatiotemporal variation in water footprint of grain production(WFGP)in China from 1951 to 2010.The results show that,jointly motivated by the improvement of agricultural production and water use efficiency,WFGP in all areas showed a decreasing trend.National average WFGP has decreased from 3.38 to 1.31 m^(3)·kg^(–1).Due to regional differences in agricultural production and water use efficiency,spatial distribution of WFGP varies significantly and its pattern has changed through time.Moreover,WFGP may show significant differences within areas of similar climatic conditions and agricultural practices,indicating that there is a strong need to improve the management of water use technology.Statistical analysis revealed that regional differences in grain yield are the main cause for variations in spatiotemporal WFGP.However,the scope for further increases in grain yield is limited,and thus,the future goal of reducing WFGP is to decrease the water use per unit area.