Isotopic geochemistry of the groundwater system in arid and semiarid areas and its significance: a case study in Shiyang River basin, Gansu province, northwest China

 Shiyang River basin, located in the eastern part of Hexi Corridor in the middle Gansu province, NW China, is a typical arid to semiarid area. Within its drainage distance of merely 300 km, the groundwater system shows a gradual hydrochemical zonation from the upper reach to the lower reach, which is composed of hydrocarbonate, sulfate to chloride zones respectively. Variation in the saturation index (SI) of calcite and dolomite shows that, under arid to semiarid conditions, the drastic evaporation causes the groundwater quality to deteriorate in the lower reach. Isotopic compositions of H, O and He in the groundwater show that the groundwater recharge sources are mainly from meteoric water. δ³He–³He/²⁰Ne coordinates could clearly distinguish the water sources and mixing among them. In the Caiqi region, there is apparent mixing of the crevice water containing excess ⁴He with the overlying groundwater, which also implies a much lower circulation rate of the groundwater. Fairly high ³He/⁴He ratios of the groundwaters collected from the adjacent area of hidden faults along Qilian Mountains show the eminent input of mantle-derived helium, indicating that these faults not only cut the crust deeply, but are currently active. Received: 11 February 2000 · Accepted: 23 May 2000     

Evaluation of landscape changes and ecological degradation by GIS in arid regions: a case study of the terminal oasis of the Shiyang River,northwest China

The development and utilization of water and land resources in the Shiyang River basin are the highest among the inland rivers in northwestern China. Using GIS and the landscape structure analysis program FRAGSTATS, landscape metrics of a study area in the lake-district in Minqin Oasis in the lower reaches of Shiyang River basin were calculated and analyzed based on TM images from 1987 to 2001 at class level and landscape level, respectively. Transformation matrix of the landscape mosaics was also examined. The driving forces of landscape changes were analyzed, including the dynamics of runoff and groundwater resources and their exploitation, and influences of policies and market economy. The results showed that: (1) Patch number of farmland and desert decreased, but their mean patch area increased, indicating that reclamation and desertification was very serious in the study area. Contagion index for oasis increased and edge density and landscape diversity were reduced. (2) Farmland and desert areas have enlarged by 1,520.46 and 4,941.27 hm², respectively. This increase was at the cost of woodland and grassland, which shrank by 1,520.46 and 4,941.27 hm², respectively. (3) The net utilization of surface water decreased by 50% in the last 10 years, and dropped to 22.3 × 10⁶ m³ in the later 1990s. Exploitation of groundwater increased remarkably, up to 80 × 10⁶ m³ per year in the last 5 years. (4) The capability of the economic structure to withstand pressures of the market economy has depressed distinctly because of the simplified planting pattern, which is dominated by salinity-enduring cash crops, such as cotton. Based on the above analysis, strategies of ecological reconstruction in the lake-district were suggested.     

Eco-service value evaluation based on eco-economic functional regionalization in a typical basin of northwest arid area,China

Ecosystem services are the basis of human living and development. Land use has significant effects on the ecosystem structure and functions, even its services. Using the remote sensing (RS), geographical information system and ecological economy theory, this paper analyzed land use changes of different eco-economic functional areas in Manas River Basin during the period 1958–2006 using different stage RS images. This paper selects the evaluation method obtained by Costanza et al. and Xie Gaodi, and the ecological sensitivity coefficient analysis, which analyzed the variation characteristics of eco-service values of different eco-economic functional areas. The results showed that the land use pattern has changed greatly from 1958 to 2006. The area of farmland and industrial area increased rapidly, while the forest area, grassland, water area and unutilized area decreased greatly. The total eco-service value of the river basin decreased from 3,529.64 US$ × 10⁶ in 1958 to 2,559.88 US$ × 10⁶ in 2006. There was 27.47 % net loss of 969.76 US$ × 10⁶. The eco-service values of various land use types in the study area were close to the regional real values and the results were credible. There existed apparent temporal and spatial changes in the eco-service values of different eco-economic functional areas, and this significant change in the eco-service values was driven by economic development. Consequently, in view of eco-economic characteristics and ecological issues of various eco-economic functional areas, relevant strategies of ecological conservation were proposed for enhancing the general eco-service value of the river basin and realizing the regional sustainable development. The ‘‘yuan’’ is Chinese money unit (¥), US$1 = ¥6.27 (yuan).     

Environmental effects of water resource development and use in the Tarim River basin of northwestern China

The unbridled development and use of water resources in the Tarim River basin over the last 50 years have led to a serious degradation of soil (>12×10³ km² of land desertified between the 1960s and 1990s) and water quality (rise in maximum salinity was from 1.3 g l^–1 in 1960, to 4.0 g l^–1 in 1981–1984, and to 7.8 g l^–1 in 1998). Approximately 300 km of the lower reaches of the river course dried up between the 1950s and 1970s, seriously altering the downstream hydrological processes (a 4–6 m drop in groundwater levels from the 1960s to the 1980s, and 0.2 m yr^–1 thereafter) and ecosystems (67% and 50% decrease (1958–1978) in Populus euphratica forest acreage and biomass, respectively). Between the 1950s and 1990s, 3820 km² of P. euphratica forest and 200 km² of shrub- and grassland were lost in the lower reaches of the Tarim River. In this study, based on estimates of soil organic carbon in desertified lands, it has been found that in the last 30 years (1970–2000), approximately 112 Tg of organic carbon (28% originating in the 0–1.0 m soil profile) has been released into the atmosphere as a result of soil degradation in the Tarim River basin. Intensive anthropogenic disturbance has been one of the foremost factors leading to the deterioration of water resources in this region. The key to solving these problems is to enhance the scientific and technical level of monitoring, management, and restoration of water resources and associated water and soil components of local ecosystems.     

Environmental changes after ecological water conveyance in the lower reaches of Heihe River,northwest China

This paper analyzed the dynamic change of the groundwater level by 6 years’ monitoring in field monitoring and the change of vegetation by the field survey and satellite remote sensing after watering in the lower reaches of Heihe River. The findings indicated: (1) the groundwater level elevation and the plant growth are closely related to the volume and the duration of watering. In general, groundwater level elevates dramatically and plants are growing much more vigorously after watering; (2) Watering incidence on groundwater keeps extending with the watering times increasing; (3) Plants grew rapidly in 100–400 m away from the water channel after watering. Watering incidence on vegetation reached 1,000 m; (4) In terms of the function and structure of ecosystem after watering in the lower reaches of Heihe River, the ecological water conveyance does not still reach the goal of ecological restoration at a large spatial scale at present. In addition, in order to solve fundamentally the problem of ecological environment worsens in the lower reaches of Heihe River, some suggestions and countermeasures are put forward.     

甘肃北山柳园地区花岗岩类的年代学、地球化学特征及构造意义

北山柳园地区分布大量的花岗岩类岩石,岩石类型有花岗闪长岩、二长花岗岩、钾长花岗岩和斑状花岗岩.锆石SHRIMP U-Pb定年分析结果为花岗闪长岩的侵位年代为423±8 Ma辉铜山以东(HT-)钾长花岗岩和二长花岗岩的侵位分别为436±9 Ma和397±7 Ma.该区花岗质岩石都具有大离子亲石元素和轻稀土元素相对富集,K、Ni、Ta、P和Ti负异常的特征,属于准铝质到过铝质的高K花岗岩.花岗闪长岩无Sr和Eu负异常的特征,εNd(t)=-2.5～-0.8,其岩浆源于岩石圈地幔或是软流圈与岩石圈地幔相混合的岩浆熔融,并受到了含有火山弧组分的年轻地壳的混染.钾长花岗岩和二长花岗岩具有Sr和Eu负异常的特征,εNd(t)值分别为+1.4、-4.0～-2.0和-2.7～-0.3.HT-钾长花岗岩岩浆主要源于由于岩石圈地幔岩浆作用而导致上覆年轻地壳物质的部分熔融;花牛山附近(HN-)钾长花岗岩岩浆主要源于软流圈地幔部分熔融,可能受到了部分年轻地壳物质的混染;二长花岗岩岩浆主要源于年轻地壳的部分熔融.柳园地区4类花岗岩类岩石都是后碰撞构造背景下的岩浆产物,岩浆形成可能与俯冲板片断离有关.     

Water resources assessment in the Minqin Basin: an arid inland river basin under intensive irrigation in northwest China

The Minqin Basin is at the lower reach of the Shiyang River of Gansu province in northwest China. Dramatic decline in groundwater level has resulted from over-abstraction of groundwater since the late 1950s to satisfy increasing irrigation and other demands. Severe water shortage led to environmental degradation. To better understand the spatial–temporal variation of groundwater levels and to evaluate the groundwater resources in the region, a three-dimensional regional groundwater flow model was built and calibrated under transient condition. The MODFLOW program was used and the research area was discretized as a square network with cell size of 400 × 400 m. The model showed that the aquifer was under destructive stress, with a groundwater resource deficit of 260 million cubic meters per year (Mm³/year) on average. Since the inflow of surface water from the upstream basin has declined to about 100–150 Mm³/year in recent decades, the irrigation return flow had become the main recharge and accounted for 60.6% of total recharge; meanwhile, abstraction by pumping wells took 99.2% from the total groundwater discharge.     

A multi-method approach to quantify groundwater/surface water-interactions in the semi-arid Hailiutu River basin,northwest China

Identification and quantification of groundwater and surface-water interactions provide important scientific insights for managing groundwater and surface-water conjunctively. This is especially relevant in semi-arid areas where groundwater is often the main source to feed river discharge and to maintain groundwater dependent ecosystems. Multiple field measurements were taken in the semi-arid Bulang sub-catchment, part of the Hailiutu River basin in northwest China, to identify and quantify groundwater and surface-water interactions. Measurements of groundwater levels and stream stages for a 1-year investigation period indicate continuous groundwater discharge to the river. Temperature measurements of stream water, streambed deposits at different depths, and groundwater confirm the upward flow of groundwater to the stream during all seasons. Results of a tracer-based hydrograph separation exercise reveal that, even during heavy rainfall events, groundwater contributes much more to the increased stream discharge than direct surface runoff. Spatially distributed groundwater seepage along the stream was estimated using mass balance equations with electrical conductivity measurements during a constant salt injection experiment. Calculated groundwater seepage rates showed surprisingly large spatial variations for a relatively homogeneous sandy aquifer.     

Multi-tracer investigation of river and groundwater interactions: a case study in Nalenggele River basin,northwest China

Environmental tracers (such as major ions, stable and radiogenic isotopes, and heat) monitored in natural waters provide valuable information for understanding the processes of river–groundwater interactions in arid areas. An integrated framework is presented for interpreting multi-tracer data (major ions, stable isotopes (²H, ¹⁸O), the radioactive isotope ²²²Rn, and heat) for delineating the river–groundwater interactions in Nalenggele River basin, northwest China. Qualitative and quantitative analyses were undertaken to estimate the bidirectional water exchange associated with small-scale interactions between groundwater and surface water. Along the river stretch, groundwater and river water exchange readily. From the high mountain zone to the alluvial fan, groundwater discharge to the river is detected by tracer methods and end-member mixing models, but the river has also been identified as a losing river using discharge measurements, i.e. discharge is bidirectional. On the delta-front of the alluvial fan and in the alluvial plain, in the downstream area, the characteristics of total dissolved solids values, ²²²Rn concentrations and δ¹⁸O values in the surface water, and patterns derived from a heat-tracing method, indicate that groundwater discharges into the river. With the environmental tracers, the processes of river–groundwater interaction have been identified in detail for better understanding of overall hydrogeological processes and of the impacts on water allocation policies.     

石羊河流域城镇化用地空间扩展分析

石羊河流域是流域经济社会可持续发展研究的重点区域之一。为找出流域城镇化用地空间扩展的机理,从社会经济、区位交通、生态约束出发,开展了城镇空间扩展用地评价与预测研究。首先,利用改进的土地适宜性评价方法,找出城镇扩展可能性和各乡镇适宜性高值区的空间格局,发现其主要位于流域中部绿洲生态功能区,沿G30高速公路和312国道分布,以县城/城区为中心呈星形扩散。然后,利用经过精度检验的土地转化模型（LTM）,在适宜性评价因子的基础上模拟城镇扩张。结果表明：凉州区和金川区为流域发展的"两核",312国道天祝至永昌段、211省道凉州至民勤段、212省道永昌至金川段为流域发展的"三带"。上述结果可为政府制定流域发展规划提供参考。     

中国西北内陆干旱盆地地下水形成演化模式及其意义

随着系统理论分析方法的引入和同位素、遥感、计算机技术和先进物探手段等的应用,内陆干旱区的地下水勘查与研究得到迅速发展。本文以作者在中国西北地区近十几年的地下水勘查与研究成果为主要基础,将内陆干旱盆地平原区地下水划分为四级地下水流系统,即山前局部地下水流系统（Ｉ）、区域地下水流系统（Ⅱ）、滞流地下水流系统（Ⅲ）和细土平原区易变的局部地下水流系统（Ⅳ）。盆地地下水的形成演化和盐分迁移主要发生在Ｉ、Ⅱ和     

塔里木盆地东南缘新生代构造变形特征研究

塔里木盆地东南缘新生代变形特征研究对探讨阿尔金构造带新生代的活动特征及阿尔金构造带与西昆仑构造带的相互作用具有重要意义.本文在野外地质调查的基础上,结合地球物理和沉积学资料,探讨了塔里木盆地东南缘的新生代变形及演化特征.塔里木盆地东南缘新生代构造变形受西昆仑构造带、阿尔金构造带和车尔臣断裂带的控制,且变形由西向东减弱.西南部的构造样式主要表现为受西昆仑向北冲断作用控制的冲断构造;东南部为受阿尔金断层走滑作用控制的走滑-冲断构造;而北部则为受车尔臣断层走滑作用控制的基底卷入走滑-冲断构造.中新世,盆地东南缘受西昆仑构造带大规模的冲断活动影响,导致民丰山前盆地挠曲沉降和冲断层发育,而车尔臣断裂仅有微弱活动;上新世开始,构造变形扩展到整个研究区,不仅西昆仑构造带和车尔臣断裂带表现出强烈变形,而且阿尔金断层走滑作用强烈,导致北侧次级断层的强烈走滑冲断作用和若羌山前挤压挠曲盆地的形成.新生代时期,西昆仑构造带北向冲断作用要早于阿尔金构造带的走滑变形,阿尔金构造带的走滑作用对西昆仑构造带北向冲断构造有强烈的改造.     

Groundwater and surface-water interactions and impacts of human activities in the Hailiutu catchment,northwest China

The interactions between groundwater and surface water have been significantly affected by human activities in the semi-arid Hailiutu catchment, northwest China. Several methods were used to investigate the spatial and temporal interactions between groundwater and surface water. Isotopic and chemical analyses of water samples determined that groundwater discharges to the Hailiutu River, and mass balance equations were employed to estimate groundwater seepage rates along the river using chemical profiles. The hydrograph separation method was used to estimate temporal variations of groundwater discharges to the river. A numerical groundwater model was constructed to simulate groundwater discharges along the river and to analyze effects of water use in the catchment. The simulated seepage rates along the river compare reasonably well with the seepage estimates derived from a chemical profile in 2012. The impacts of human activities (river-water diversion and groundwater abstraction) on the river discharge were analyzed by calculating the differences between the simulated natural groundwater discharge and the measured river discharge. Water use associated with the Hailiutu River increased from 1986 to 1991, reached its highest level from 1992 to 2000, and decreased from 2001 onwards. The reduction of river discharge might have negative impacts on the riparian ecosystem and the water availability for downstream users. The interactions between groundwater and surface water as well as the consequences of human activities should be taken into account when implementing sustainable water resources management in the Hailiutu catchment.     

石羊河流域冰冻圈融水对出山径流的贡献及影响

气候变暖背景下,随着冰冻圈的持续萎缩,冰冻圈融水已成为寒区径流的重要组成部分和寒区水文过程的关键影响因子。以石羊河流域为研究区,2013年7月~2014年6月在系统采集大气降水、河水、泉水、井水、水库水、渠系水、冻土活动层地下水和冰雪融水样品基础上,应用稳定同位素示踪技术,定量评估了石羊河流域冰雪融水和冻土活动层地下水对出山径流的贡献量,结果表明：流域内大气降水、冻土活动层地下水和冰雪融水充分混合后以地下水的形式补给径流,大气降水、冻土活动层地下水和冰雪融水对出山径流的补给率分别为77%、20%和3%。依据多年冻土下界将山区分为冰雪冻土带和植被带,分析证实冰雪冻土带输出水量贡献了出山径流的82%,而植被带贡献了18%。流域出山口径流的补给带为海拔3300m以上,中游浅层地下水的补给带为海拔3700m以上。冰雪融水和冻土活动层地下水对7条支流出山径流的贡献率因自然地理状况而明显差异,东大河、西营河和金塔河降水对出山径流的贡献率分别为72%、78%和87%,相应的冻土活动层地下水贡献率为21%、17%和12%,冰雪融水为7%、5%和1%。降水对西大河、黄羊河、古浪河和大靖河出山径流贡献率分别为84%、91%、76%和73%,冻土活动层地下水对出山径流的贡献率依次为16%、9%、24%和27%。研究确认冻土活动层地下水已成为内陆河流域径流的重要组成部分,未来亟须进一步加强冻土活动层地下水水文机制的研究。

     

石羊河流域下游生态系统服务功能价值的评估

以石羊河流域下游民勤为主要研究范围, 对民勤县1994-2005年12 a间生态系统服务的价值进行了估算和对比分析. 结果表明, 1994年区域生态系统服务的总价值为9.976×10~8元, 2005年区域生态系统服务的总价值为8.475×10~8元, 12 a来区域内的生态系统服务价值下降了近1.501×10~8元. 由于缺乏对盐碱地、建筑用地等服务价值的相关研究信息, 该结果仅是对民勤生态系统服务价值的保守估算. 总的来说, 研究区域生态系统服务价值呈现快速下降趋势.     

Groundwater sustainability and groundwater/surface-water interaction in arid Dunhuang Basin,northwest China

The Dunhuang Basin, a typical inland basin in northwestern China, suffers a net loss of groundwater and the occasional disappearance of the Crescent Lake. Within this region, the groundwater/surface-water interactions are important for the sustainability of the groundwater resources. A three-dimensional transient groundwater flow model was established and calibrated using MODFLOW 2000, which was used to predict changes to these interactions once a water diversion project is completed. The simulated results indicate that introducing water from outside of the basin into the Shule and Danghe rivers could reverse the negative groundwater balance in the Basin. River-water/groundwater interactions control the groundwater hydrology, where river leakage to the groundwater in the Basin will increase from 3,114?×?10⁴ m³/year in 2017 to 11,875?×?10⁴ m³/year in 2021, and to 17,039?×?10⁴ m³/year in 2036. In comparison, groundwater discharge to the rivers will decrease from 3277?×?10⁴ m³/year in 2017 to 1857?×?10⁴ m³/year in 2021, and to 510?×?10⁴ m³/year by 2036; thus, the hydrology will switch from groundwater discharge to groundwater recharge after implementing the water diversion project. The simulation indicates that the increased net river infiltration due to the water diversion project will raise the water table and then effectively increasing the water level of the Crescent Lake, as the lake level is contiguous with the water table. However, the regional phreatic evaporation will be enhanced, which may intensify soil salinization in the Dunhuang Basin. These results can guide the water allocation scheme for the water diversion project to alleviate groundwater depletion and mitigate geo-environmental problem.     

The effects of human activities on oasis climate and hydrologic environment in the Aksu River Basin,Xinjiang, China

Under the influence of human activities, the differences in climate changes emerged obviously in the Aksu Oasis. The summer air temperature in Aksu City increased at a rate of 0.20°C·(10 annum)⁻¹, while the air temperature in Aler in summer decreased at a rate of −0.27°C·(10 annum)⁻¹. Human intervention has become the dominant factor in the the changes of water resources in the Aksu Oasis. Compared with the Xidaqiao hydrological station, which is located on the upper reaches of the Aksu River, the runoff ratio at the Aler hydrological station increased in summer and decreased in spring. Though the natural water inflow has increased in the last 50 years, irrigation diversion and water consumption for human activities have increased unceasingly due to the increased reclamation of land and the development of extensive agriculture. The water quality at the Xidaqiao station is in Grade I at different periods, and the water quality at the Aler station of the Tarim River is good because the river did not suffer from human disturbance before the large-scale development of oasis agriculture; but the salinity of river water increased from 0.67 g L⁻¹ in 1960 to 5.27 g L⁻¹ in 2000 at the Aler station after farmland development, reclamation and salt washing in the oasis. The geographic distribution of surface water resources has changed due to human activities and in turn affected groundwater replenishment, bringing about changes to groundwater table and quality.     

A Holocene dust record in arid central Asia inferred from Lake Barkol,northwest China

Grain-size distributions and detrital minerals were investigated for modern dust and for lacustrine sediment in Lake Barkol region, northwest China. Characteristics of the modern dust and lacustrine sediments, principle component analysis, and changes of quartz contents all suggest grain size 45–138 μm in the core sediment is the dust sensitive component. It indicates that high dust flux climate occurred at mid-Holocene (5.5–4.5 cal ka BP), corresponding to the high dust flux record in northwest Pacific and the drought interval of deserts in northwest China during the mid-Holocene. The strong dust activity is in contradiction with the climatic optimum recorded by the lacustrine evidence in Xinjiang. Different responses of the dust source region and watershed to the regional climate may have led to the inconsistency between dust and climate records during the mid-Holocene in arid central Asia.     

甘肃省石羊河流域径流多年变化特性研究

基于第三次甘肃省水资源调查评价收集的1956-2016年系列径流资料,补充至2018年,对甘肃省石羊河流域径流多年变化特性进行研究,主要对其变化趋势、突变年份、周期变化、年际变化特性进行研究。以降水补给为主的甘肃省石羊河流域径流量的大小,制约着地区经济的发展。经采用累积滤波器法和斯伯曼秩次相关法分析得出石羊河从北向南趋势由增向减的变化,采用滑动t检验法得出石羊河突变年份在1990年左右,采用谐波分析法得出石羊河北部周期为32年,南部径流周期不明显,径流年际变化较稳定。