CHARACTERISTICS OF WATER TRANSFORMATION AND ITS EFFECTS ON ENVIRONMENT IN THE ARID REGION —A case study in Alar irrigation region of Xinjiang, China

1　ＣＨＡＲＡＣＴＥＲＩＳＴＩＣＳＯＦＷＡＴＥＲＴＲＡＮＳ ＦＯＲＭＡＴＩＯＮＩＮＡＲＩＤＬＡＮＤＴｈｅｒｅｇｕｌａｒｉｔｉｅｓｏｆｗａｔｅｒｔｒａｎｓｆｏｒｍａｔｉｏｎｉｎｓｔｒｅａｍｆｏｒｍｉｎｇａｒｅａｓａｎｄｓｔｒｅａｍｄｉｓａｐｐｅａｒｉｎｇａｒｅａｓａｒｅｖｅｒｙｄｉｆｆｅｒｅｎｔ.Ｉｎｓｔｒｅａｍｆｏｒｍｉｎｇａｒｅａｓ ,ｗａｔｅｒｔｒａｎｓｆｏｒｍａｔｉｏｎｉｓｍａｉｎｌｙｆｒｏｍ ｐｒｅｃｉｐｉｔａｔｉｏｎ ,ｓｎｏｗｍｅｌｔａｎｄｉｃｅｍｅｌｔｗａｔｅｒｔｏｓｕｒｆａｃｅｗａｔｅｒ…     

Characteristics of water transformation and its effects on environment in the arid region

The characteristics of water balance in arid regions is that the streams are formed in mountain area and continuously evaporates and infiltrates in the process of flowing to plain area, streams finally disappear in the desert or flow into the lakes, which are the low reaches of the rivers. But the distribution and transformation of water in Xinjiang, China have changed under the influences of human activities. The influences of human activities take place in a short time and regionally, especially in arid land where water is the key factor of environment. Water inside of oasis has increased, and water out of oasis or at the lower reaches of the river has decreased. Human activities have caused the environment changes in both positive and negative aspects by changing the circulation and distribution of water. Under the influence of human activities, oases in Xinjiang have expanded, meanwhile some lakes have contracted desertification is serious, natural vegetation has declined and natural environment out of oasis has degenrated. Foundation item: Under the auspices of the National Natural Science Foundation of China(49771009). Biography: LI Xin(1940 -), male, a native of Anhui Province, professor. His research interest includes water resources.     

黑河中游地区作物用水效率比较及种植结构调整方向研究

黑河流域地处西北干旱区,水资源短缺是限制其中游绿洲农业发展、下游生态环境保护的首要原因。该流域的中游绿洲农业用水约占总用水量的80%,因此农业节水对流域发展至关重要。在干旱区绿洲农业节水探索中,众多学者主张通过节水技术来提高用水效率,而关于农业种植结构调整对农业节水影响的定量研究较少。本文采用2012年黑河流域蒸散发数据、土地利用数据、降水数据和农业经济统计数据,定量分析黑河中游主要作物需水特征和用水效率差异,尝试从调整作物种植结构角度为其绿洲农业节水提供依据。结果表明：(1)研究区4种主要作物中,玉米生长期需水量最大,其次为小麦、油菜和大麦;(2)考虑降水补给,发现大麦和油菜生长需水可很大程度上依赖降水,而小麦和玉米则需要灌溉,且玉米灌溉需水量远超小麦;(3)作物用水效率由高到低依次为大麦、油菜、小麦和玉米。从用水效率角度而言,考虑种植区位,在黑河中游适当扩大小麦种植规模更有利于提高中游农业用水效率。     

PRESSURE OF WATER SHORTAGE ON AGRICULTURE IN ARID REGION OF CHINA

1INTRODUCTIONWiththedevelopmentoftheworld,waterdemandisincreasing,especiallywiththegrowthofpopulationinthelast50years,waterdemandforirrigationhasgreatlyincreasedforfoodproduction.Inthearidandsemi-aridareas,watershortagebecomesaheavierproblemtorestrictfoodproduction,localeconomyandenvironmentalprotection.China,with22%ofthetotalpopulationintheworld,hasonly8%offreshwaterintheglobe;watershortagehasaffectedagricultureandresident'slifeinthenorthernChina.SomescientistsindicatedthatChina'swaters…     

Hydrological Processes in the Huaihe River Basin,China: Seasonal Variations,Causes and Implications

Understanding streamflow changes in terms of trends and periodicities and relevant causes is the first step into scientific management of water resources in a changing environment. In this study, monthly streamflow variations were analyzed using Modified Mann-Kendall(MM-K) trend test and Continuous Wavelet Transform(CWT) methods at 9 hydrological stations in the Huaihe River Basin. It was found that: 1) streamflow mainly occurs during May to September, accounting for 70.4% of the annual total streamflowamount with Cv values between 0.16–0.85 and extremum ratio values between 1.70–23.90; 2) decreased streamflow can be observed in the Huaihe River Basin and significant decreased streamflow can be detected during April and May, which should be the results of precipitation change and increased irrigation demand; 3) significant periods of 2–4 yr were detected during the 1960 s, the 1980 s and the 2000 s. Different periods were found at stations concentrated within certain regions implying periods of streamflow were caused by different influencing factors for specific regions; 4) Pacific Decadal Oscillation(PDO) has the most significant impacts on monthly streamflow mainly during June. Besides, Southern Oscillation Index(SOI), North Atlantic Oscillation(NAO) and the Ni?o3.4 Sea Surface Temperature(Ni?o3.4) have impacts on monthly streamflow with three months lags, and was less significant in time lag of six months. Identification of critical climatic factors having impacts on streamflow changes can help to predict monthly streamflow changes using climatic factors as explanatory variables. These findings were well corroborated by results concerning impacts of El Nino-Southern Oscillation(ENSO) regimes on precipitation events across the Huaihe River Basin. The results of this study can provide theoretical background for basin-scale management of water resources and agricultural irrigation.     

WATER RESOURCES TRANSFORMATION AND WATER QUALITY VARIATION IN THE URUMQI RIVER BASIN

ＷＡＴＥＲＲＥＳＯＵＲＣＥＳＴＲＡＮＳＦＯＲＭＡＴＩＯＮＡＮＤＷＡＴＥＲＱＵＡＬＩＴＹＶＡＲＩＡＴＩＯＮＩＮＴＨＥＵＲＵＭＱＩＲＩＶＥＲＢＡＳＩＮＱｕＹａｏｇｕａｎｇ（曲耀光）；ＬｕｏＨｏｎｇｚｈｅｎ（骆鸿珍）（ＬａｎｚｈｏｕＩｎｓｔｉｔｕｔｅｏｆＧ...     

PRIMARY ANALYSIS ON GROUNDWATER, SOIL MOISTURE AND SALINITY IN FUKANG OASIS OF SOUTHERN JUNGGAR BASIN

１INTRODUCTIONSoilandlandformarethemoreimportantenviron－mentalfactorsaffectingthedistributionofvegetationinabasinwhenthemeteorologicconditionissimilaronalargescale，especiallyspatialandtemporalvariationsofthesoilmoistureandsaltcontent．Inaridareasthesoil…     

Vegetation-environment relationships between northern slope of Karlik Mountain and Naomaohu Basin, East Tianshan Mountains

Based on data from 22 sample plots and applying the Canonical Correspondence Analysis (CCA),this paper discusses the vegetation-environment relationships between the northern slope of Karlik Mountain and Naomaohu Basin,which is situated in the easternmost end of the Tianshan Mountains,Xinjiang Uygur Autonomous Region,China.For the zonal vegetation,community diversity of mountain vegetation is higher than that of the desert vegetation due to environmental factors.The CCA ordination diagram revealed that the composition and distribution of vegetation types are mainly determined by altitude,soil pH and soil salt content.With increasing elevation,the soil pH and total salt content decrease but the contents of soil organic matter,soil water,total nitrogen and total phosphorus increase gradually.In the CCA ordination diagrams,the sample plots and main species can be divided into five types according to their adaptations to the environmental factors.Type I is composed of desert vegetation distributed on the low mountains,hills,plains and deserts below an elevation of 1900 m;type II is distributed in the mountain and desert ecotone with an elevation of 1900-2300 m,and includes steppe desert,desert steppe and wetland meadow;type III is very simply composed of only salinized meadow;type IV is distributed above an elevation of 2300 m,containing mountain steppe,meadow steppe,subalpine meadow and alpine meadow;type V only contains salinized meadow.The results show that with increasing elevation,species combination changes from the xerophytic shrubs,semi-shrubs and herbs distributed in the low altitude zone with arid climate to the cold-tolerant perennial herbs growing in the high altitudinal zone with cold climate.     

遥感及再分析降水产品在缺资料干旱内陆盆地的适用性评估

山区降水较集中,但降水测站多位于山谷或人口密集区,代表性差。遥感和再分析降水产品能提供时空分布连续的数据,不受地形条件限制。柴达木盆地中心属干旱荒漠区,水是制约该区开发的首要条件,其四周属高寒山区,降水相对较多,但降水监测十分薄弱。为获取该区相对精确的降水时空分布信息,本文评估了4套高分辨率降水产品（CMADS、TRMM、GPM和MSWEP）的适用性。首先基于地面站点数据评估它们在不同时空尺度上的精度,并分析它们在柴达木盆地的空间分布和年内分配特征。然后,以盆地东南隅的无测站山区香日德河流域为研究区,利用降水产品驱动SWAT模型来评估它们的分布式水文模拟适用性。结果表明：(1) MSWEP在年、月尺度上与站点降水的吻合程度最高（R≥0.79,PBIAS=0.5%）,其次是GPM和TRMM,CMADS精度最低（R≥0.64,PBIAS=5.8%）;(2)从降水精度与站点高程的关系来看,降水产品在相对低海拔区容易高估站点降水,而在相对高海拔区常低估实际降水;(3)在香日德河流域,MSWEP(NSE=0.64)在基准期（2009—2012年）的径流模拟表现明显好于其它降水产品（NSE=0.3...     

Hydrological services by mountain ecosystems in Qilian Mountain of China: A review

Hydrological service is a hot issue in the current researches of ecosystem service, particularly in the upper reaches of mountain rivers in dry land areas, where the Qilian Mountain is a representative one. The Qilian Mountain, where forest, shrubland and grassland consist of its main ecosystems, can provide fresh water and many other ecosystem services, through a series of eco-hydrological process such as precipitation interception, soil water storage, and fresh water provision. Thus, monitoring water regulation and assessing the hydrological service of the Qilian Mountain are meaningful and helpful for the healthy development of the lower reaches of arid and semi-arid areas. In recent 10 years, hydrological services have been widely researched in terms of scale and landscape pattern, including water conservation, hydrological responses to afforestation and their ecological effects. This study, after analyzing lots of current models and applications of geographical information system (GIS) in hydrological services, gave a scientific and reasonable evaluation of mountain ecosystem in eco-hydrological services, by employing the combination of international forefronts and contentious issues into the Qilian Mountain. Assessments of hydrological services at regional or larger scales are limited compared with studies within watershed scale in the Qilian Mountain. In our evaluation results of forest ecosystems, it is concluded that long-term observation and dynamic monitoring of different types of ecosystem are indispensable, and the hydrological services and the potential variation in water supplement on regional and large scales should be central issues in the future research.     

Coupling mechanism of rural settlements and mountain disasters in the upper reaches of Min River

Human settlements are the place where human beings live,among which the rural settlements can be regarded as a reflection of human-land relationship in mountain areas because their vertical distribution is greatly influenced by the specific geographical environment and ecological conditions of mountains.Based on field investigation,this paper uses physical,geographical,and ecological theories to make a comprehensive study of rural settlements and mountain disasters in the upper Min River,which is an ecologically fragile area with high-frequency disasters（collapse,landslide,debris flow,etc.） and a minority inhabit district.By applying these modern scientific theories,this paper attempts to shed some light on the relationship between rural settlements and mountain disasters.Consequently,an in-depth understanding of this relationship was achieved as follows：（1） Rural settlements and mountain disasters are mainly distributed in the intercepted flows of water and soil; and both quantity and quality of arable lands in mountains are important indicators of these flows.（2） The Small Watershed Management Project is a complex system of rural settlements and mountain disasters that interacts with and constrains the ecological system.By this project,the human survival will be better guaranteed.Being fundamental for the ecological reconstruction,the coupling mechanism of rural settlements and mountain disasters is not only an engine to promote harmonious development between human and nature,but also a bridge to link them.     

Effects of RapidEye imagery’s red-edge band and vegetation indices on land cover classification in an arid region

Land cover classification (LCC) in arid regions is of great significance to the assessment, prediction, and management of land desertification. Some studies have shown that the red-edge band of RapidEye images was effective for vegetation identification and could improve LCC accuracy. However, there has been no investigation of the effects of RapidEye images’ red-edge band and vegetation indices on LCC in arid regions where there are spectrally similar land covers mixed with very high or low vegetation coverage information and bare land. This study focused on a typical inland arid desert region located in Dunhuang Basin of northwestern China. First, five feature sets including or excluding the red-edge band and vegetation indices were constructed. Then, a land cover classification system involving plant communities was developed. Finally, random forest algorithm-based models with different feature sets were utilized for LCC. The conclusions drawn were as follows: 1) the red-edge band showed slight contribution to LCC accuracy; 2) vegetation indices had a significant positive effect on LCC; 3) simultaneous addition of the red-edge band and vegetation indices achieved a significant overall accuracy improvement (3.46% from 86.67%). In general, vegetation indices had larger effect than the red-edge band, and simultaneous addition of them significantly increased the accuracy of LCC in arid regions.     

Cryotic climate conditions and their eventual implication in the high-mountain surface of the Nevado de Toluca volcano,Mexico

The state of the cryosphere in tropical regions is of great importance because the temperature around the glaciers, permafrost and snow cover always fluctuates near the melting point. These thermal conditions and their high sensitivity to climate change cause the accelerated disappearance of these elements; therefore, it is important to know the climatic factors that regulate them, as well as the physical characteristics of each cryospheric element. Unlike glaciers, permafrost and snow cover have not been widely studied. In recent decades, the study of the glacial and periglacial environment has been carried out in intertropical mountains. However, despite the altitude of their relief and the frequent occurrence of snowfall in tropical high mountains, the conditions that determine such events have been barely analyzed; and in the case of Mexico, the volume of snowfall and its thickness have not been quantified either, as well as their corresponding duration. Consequently, this work is aimed to analyze the temperature and precipitation conditions that determine the snowfall at the higher part of the Nevado de Toluca volcano; at the same time, the conditions of the cryotic climate and their possible implication on the surface are studied. The analysis of data from 1965 to 2016, using frequency statistics, allowed to realize that snowfall occurs with low intensity, its accumulation being less than 10 cm thick and 10 mm of snow water equivalent, which causes the snowpack to stay only a few weeks on average. At the same time, it was determined that there is a significant increase in the number of freeze-thaw cycles. Therefore, due to the climate conditions and their influence on the mountain surface, it is probable that the bedrock is subject to a greater gelifraction dynamics, and the unconsolidated soil surface increases; the combination of the above could cause a greater geomorphological dynamic over time, particularly due to debris flows, and by water and wind erosion of the surface. This work is intended to serve as a reference for the high mountain environment in the intertropical regions.     

THE BALANCE BETWEEN SUPPLY AND DEMAND OF WATER RESOURCES AND THE WATER—SAVING POTENTIAL FOR AGRICULTURE IN THE HEXI CORRIDOR

The Hexi Corridor is an important base of agriculture development in Northwest China. According to recent statistics, there are 65.94×10⁸m³ of water resources available in the Hexi Corridor. At present, net consumption in development and utilization is 43.33×10⁸m³. Water supply and demand reach a balance on the recent level of production, but loss of evaporation and evapotranspiration is as much as 25.69×10⁸m³. So net use efficiency of water resources is 59%. Based on analyzing balance between water and land considering ecological environment at present, there exists the serious water shortage in the Shiyang River system where irrigation lands have overloaded. There is a comparative balance between supply and demand of water resource in the Heihe River system; and the Sule River system has some surplus water to extend irrigation land. Use of agriculture water accounts for 83.3% and ecological forest and grass for 6.9%. The Hexi Corridor still has a great potential for water saving in agriculture production. Water-saving efficiency of irrigation is about 10% by using such traditional technologies as furrow and border-dike irrigation and small check irrigation, and water-saving with plastic film cover and techniques of advanced sprinkler and drip/micro irrigation etc. cansave more than 60% of irrigated water. Incremental irrigation area for water-saving potential in the Hexi Corridor has been estimated as 56% – 197% to original irrigation area. So the second water sources can be developed from water saving agriculture in the Hexi Corridor under Development of the Western Part of China in large scale. This potential can be realized step by step through developing the water-saving measures, improving the ecological condition of oasis agriculture, and optimizing allocation of water resources in three river systems. Foundation item: Under the auspices of the Key innovation Project Engineering of Chinese Academy of Sciences (KZcx-1-10-03) Biography: GAO Qian-zhao (1942 –), male, a native of Changzhou, Jiangsu, Professor and supervisor of Ph. D students. His research interests include hydrology and rational utilization of water resources in the arid zone.     

干旱区县域土地整治分区实证研究——以新疆奇台县为例

在系统分析奇台县自然条件、社会经济、整治潜力、生态环境等信息的基础上,构建土地整治分区指标体系,运用因子分析和聚类分析法,以GIS平台划定土地整治分区,揭示了该县域土地利用现状及存在突出问题,提出该县域各区土地整治的方向和重点任务。研究结果表明,影响类似于奇台这样典型干旱区县域土地整治分区的因子主要集中在年降水量、灌溉保证度、农用地质量;日照、水土匹配系数;非农人口比重、人均居民点面积;林地覆盖率等方面。然而,由于干旱区县域的情况千差万别,在具体实施土地整治过程中,只能因地制宜,发挥各自优势,才能实现土地整治的综合效益。     

Determining critical support discharge of a riverhead and river network analysis: Case studies of Lhasa River and Nyangqu River

A riverhead is the demarcation point of continuous water channel and seasonal channel, which is characterized by a critical flow that can support a continuous water body. In this study, the critical support discharge(CSD) is defined as the critical steady flows required to form the origin of a stream. The CSD is used as the criterion to determine the beginning of the riverhead, which can be controlled by hydro-climate factors(e.g., annual precipitation, annual evaporation, or minimum stream flow in arid season). The CSD has a close correlation with the critical support/source area(CSA) that largely affects the density of the river network and the division of sub-watersheds. In general, river density may vary with regional meteorological and hydrological conditions that have to be considered in the analysis. In this paper, a new model referring to the relationship of CSA and CSD is proposed, which is based on the physical mechanism for the origin of riverheads. The feasibility of the model was verified using two watersheds(Duilongqu Basin of the Lhasa River and Beishuiqu Basin of the Nyangqu River) in Tibet Autonomous Region to calculate the CSA and extract river networks. A series of CSAs based on different CSDs in derived equation were tested by comparing the extracted river networks with the reference network obtained from a digitized map of river network at large scales. Comparison results of river networks derived from digital elevation model with real ones indicate that the CSD(equal to criterion of flow quantity(Q_c)) are 0.0028 m~3/s in Duilongqu and 0.0085 m~3/s in Beishuiqu. Results show that the Q_c can vary with hydro-climate conditions. The Q_c is high in humid region and low in arid region, and the optimal Q_c of 0.0085 m~3/s in Beishuiqu Basin(humid region) is higher than 0.0028 m~3/s in Duilongqu Basin(semi-arid region). The suggested method provides a new application approach that can be used to determine the Q_c of a riverhead in complex geographical regions, which can also reflect the effect of hydro-climate change on rivers supply in different regions.     

Climate change and glacier area variations in China during the past half century

Glacier variations in the Tibetan Plateau and surrounding mountain ranges in China affect the livelihood of over one billion people who depend on water from the Yellow, Yangtze, Brahmaputra, Ganges and Indus rivers originating in these areas. Based on the results of the present study and published literature, we found that the glaciers shrank 15.7% in area from 1963 to 2010 with an annual area change of -0.33%. The shrinkage generally decreased from peripheral mountain ranges to the interior of Tibet.The linear trends of annual air temperature and precipitation at 147 stations were 0.36°C(10a)~(-1) and 8.96 mm(10a)~(-1) respectively from 1961 to 2010. The shrinkage of glaciers was well correlated with the rising temperature and the spatial patterns of the shrinkage were influenced by other factors superimposed on the rising temperature such as glacier size, type, elevation, debris cover and precipitation.     

Water Consumption of a Six-Year-Old River Red Gum Plantation in the Southern Zagros Mountains, Iran

Water is the most important limiting factor in the development of arid environments; therefore, optimization of water use is a necessity in desert reclamation projects. Evapotranspiration of a 6-year-old river red gum (Eucalyptus camaldulensis Dehnh.) plantation, located in a sedimentation basin of an artificial recharge of the Gareh Bygone Plain groundwater system in Iran’s southern Zagros Mountains, was studied during a 7-month period. A neutron moisture probe was used to monitor soil water changes in the root zone. Soil water depletion following rapid drainage for blocks receiving relatively high, medium and low volumes of floodwater were 809.6, 312.4, and 203.1 mm, respectively, for a 150-day period. Soil water potential during most of the study period was below -1.5 MPa. This study proves that river red gum in not a suitable species for desertification control where water conservation is of vital importance. Flood irrigation of trees on 8 Aug. 1991 provided the opportunity to throw doubt upon the claim of summer dormancy of river red gum.     

A dynamic model for exploring water-resource management scenarios in an inland arid area: Shanshan County,Northwestern China

Water scarcity is a challenge in many arid and semi-arid regions; this may lead to a series of environmental problems and could be stressed even further by the effects from climate change. This study focused on the water resource management in Shanshan County, an inland arid region located in northwestern China with a long history of groundwater overexploitation. A model of the supply and demand system in the study area from 2006 to 2030, including effects from global climate change, was developed using a system dynamics (SD) modeling tool. This SD model was used to 1) explore the best water-resource management options by testing system responses under various scenarios and 2) identify the principal factors affecting the responses, aiming for a balance of the groundwater system and sustainable socio-economic development. Three causes were identified as primarily responsible for water issues in Shanshan: low water-use efficiency, low water reuse, and increase in industrial water demand. To address these causes, a combined scenario was designed and simulated, which was able to keep the water deficiency under 5% by 2030. The model provided some insights into the dynamic interrelations that generate system behavior and the key factors in the system that govern water demand and supply. The model as well as the study results may be useful in water resources management in Shanshan and may be applied, with appropriate modifications, to other regions facing similar water management challenges.     

基于GEE的黄河流域植被时空变化及其地形效应研究

黄河流域作为中国东部平原的生态屏障,研讨其植被覆盖的时空变化有助于生态环境治理。本文利用GEE平台,基于Landsat数据通过像元二分模型反演了1990—2020年黄河流域植被覆盖度（FVC）,并通过Theil-Sen Median趋势分析和Mann-Kendall检验方法剖析FVC的时空变化趋势,挖掘出FVC趋势变化与海拔、坡度、坡向等地形因子之间的响应关系。结果表明：(1)黄河流域FVC整体呈现西北低东南高的空间分布趋势,其中低等FVC占整个流域面积的45%,主要集中于西北部干旱半干旱地区;(2)流域中部植被覆盖改善明显,占整个流域的57.07%,西北部和东南部退化程度相对较高;(3)植被覆盖受地形效应影响较为显著,在坡度大于40°及高程（-31～637 m）时高等级FVC占比较高,坡度8～18°及高程1852～2414 m范围内植被改善效果相对较好。结果可以为黄河流域生态环境保护及高质量发展提供科学支撑。