Use of stable isotopes to understand run‐off generation processes in the Red River Delta

This paper presents the use of stable isotopes of water for hydrological characterization and flow component partitioning in the Red River Delta (RRD), the downstream section of the Red River. Water samples were collected monthly during 2015 from the mainstream section of the river and its right bank tributaries flowing through the RRD. In general, δ¹⁸O and δ²H river signatures were depleted in summer–autumn (May–October) and elevated in winter–spring (November–April), displaying seasonal variation in response to regional monsoon air mass contest. The Pacific equatorial–maritime air mass dominates in summer and the northern Asia continental air mass controls in winter. Results show that water of the RRD tributaries stems solely from local sources and is completely separated from water arriving from upstream subbasins. This separation is due to the extensive management of the RRD (e.g., dykes and dams) for the purposes of irrigation and inundation prevention. Mainstream river section δ¹⁸O and δ²H compositions range from ?10.58 and ?73.74‰ to ?6.80 and ?43.40‰, respectively, and the corresponding ranges inside the RRD were from ?9.35 and ?64.27‰ to ?2.09 and ?15.80‰. A combination of data analysis and hydrological simulation confirms the role of upstream hydropower reservoirs in retaining and mixing upstream water. River water inside the RRD experienced strong evaporation characterized by depleted d‐excess values, becoming negative in summer. On the other hand, the main stream of the Red River has d‐excess values around 10‰, indicating moderate evaporation. Hydrograph separation shows that in upstream subbasins, the groundwater fraction dominates the river flow composition, especially during low flow regimes. Inside the RRD, the river receives groundwater during the dry season, whereas groundwater replenishment occurs in the rainy season. Annual evaporation obtained from this hydrograph separation computation was about 6.3% of catchment discharge, the same order as deduced from the difference between subbasin precipitation and discharge values. This study shows the necessity to re‐evaluate empirical approaches in large river hydrology assessment schemes, especially in the context of climate change.     

Review on snowmelt runoff simulation in mountain regions,Northwest China北大核心CSCD

Snowmelt runoff is a valuable water resource in Northwest China. In the past few decades, progress has been achieved in snowmelt runoff simulation in mountainous areas, including observation and simulation of snow melt process, improvement and development of distributed snow melt runoff model, and ability for application of snow melt runoff model with temporal and spatial distribution driving data. The development of interpolation algorithm, remote sensing and data assimilation technology provides data support for the widespread application of distributed snowmelt runoff model in northwest mountainous regions of China. Climate warming and economic and social development will further aggravate the contradiction between supply and demand of water resources in the arid regions of Northwest China, which requires higher precision and detail spatial and temporal resolution of snowmelt runoff simulation. Based on the progress and challenges on snowmelt runoff simulation in mountainous regions of Northwest China, following studies need more attention：the mechanism of snow accumulation and ablation, snow cover spatial and temporal distribution monitoring and high precision of snow distribution data acquisition, quantitative climate change impact on river basin snowmelt runoff. © 2022 The authors.     

Assessing flood hazard using flood marks and analytic hierarchy process approach: a case study for the 2013 flood event in Quang Nam,Vietnam

The production of flood hazard assessment maps is an important component of flood risk assessment. This study analyses flood hazard using flood mark data. The chosen case study is the 2013 flood event in Quang Nam, Vietnam. The impacts of this event included 17 deaths, 230 injuries, 91,739 flooded properties, 11,530 ha of submerged and damaged agricultural land, 85,080 animals killed and widespread damage to roads, canals, dykes and embankments. The flood mark data include flood depth and flood duration. Analytic hierarchy process method is used to assess the criteria and sub-criteria of the flood hazard. The weights of criteria and sub-criteria are generated based on the judgements of decision-makers using this method. This assessment is combined into a single map using weighted linear combination, integrated with GIS to produce a flood hazard map. Previous research has usually not considered flood duration in flood hazard assessment maps. This factor has a rather strong influence on the livelihood of local communities in Quang Nam, with most agricultural land within the floodplain. A more comprehensive flood hazard assessment mapping process, with the additional consideration of flood duration, can make a significant contribution to flood risk management activities in Vietnam.     

黑河中游水土资源开发利用现状及水资源生态环境安全分析

黑河流域水资源产生于南部祁连山区,主要消耗于中游农业灌溉区。对黑河流域水文资料分析计算发现,流域出山水资源量多年变化比较稳定,最枯年和最丰年水资源量之比为 1:2,丰枯变化幅度与长江以南丰水河流相当。多年平均水资源量为32．31×10⁸ m³／a,近10年中游水资源开发利用量稳定在34×10⁸ m³／a以上,仅中游地区对水资源的开发利用率达120％左右。目前国际上公认的人均水资源量紧缺线为 1000～1700 m³／a,黑河流域水资源开发利用具有反复转化多次重复利用的特点,用这个指标无法全面评价黑河流域水资源的安全状况。     

Water Ice in 2060 Chiron and Its Implications for Centaurs and Kuiper Belt Objects

The deviation from the power-law decline of the optical flux observed in GRB 970228 and GRB 980326 has been used recently to argue in favor of the connection between gamma-ray bursts and supernovae. We consider an alternative explanation for this phenomenon, based on the scattering of a prompt optical burst by 0.1 M middle dot in circle dust located beyond its sublimation radius 0.1-1 pc from the burst. In both cases, the optical energy observed at the time of the first detection of the afterglow suffices to produce an echo after approximately 20-30 days, as observed. Prompt optical monitoring of future bursts and multiband photometry of the afterglows will enable us to test simple models of dust reprocessing quantitatively and to predict source redshift.     

近50年中国干湿气候界线波动及其成因初探

文中在 10a际尺度上详细分析了中国干湿气候界线波动与气候的干湿变化 ,得出 :过去 5 0a中国干湿气候界线波动显著 ,区域差异大 ,呈现出整体移动和东西、南北相异波动的特征。 2 0世纪 6 0～ 70年代中国干湿气候存在一次突变 ,由较湿润变为干旱 ,但各地干旱程度不同。干湿气候界线波动与气候的干湿变化具有显著的年代际特征。在此基础上分析了气候界线波动的可能原因 ,中国干湿气候界线的波动与气候的干湿变化是西太平洋副热带高压强度位置导致的东南季风、孟加拉湾暖流所导致的西南季风以及高原季风、中纬度西风环流等综合作用的结果。中国各地区干湿位相变化不一致 ,区域差异大 ,是不同环流以及环流的不同强弱组合所致。东南季风、西南季风、高原季风、中纬度西风环流、西太平洋副热带高压的年代际变化是过去 5 0a中国干湿气候界线波动与气候干湿变化年代际变化的根本原因。 2 0世纪 6 0～ 70年代的干湿突变 ,是整个北半球大气环流异常的结果     

Study on Mineralization Age of Xiaoban Gold Deposit, Fujian Province

The Xiaoban gold deposit is a large-size deposit recently found in middle area of Fujian Province. It belongs to magmatic hydrothermal type occurred in Mayuan Group metamorphic rocks of Middle Proterozoic and is controlled by low angle fault (detachment) structures. The contents of Au in Mayuan Group metamorphic rocks, Caledonian-Indosinian deformed granite and early Yanshanian granite are higher with Au enrichment coefficient of 2.06-5.68, 5.11 and 6.67 than those in other geological bodies. And the higher enrichment coefficients (>2) of Ag, S, Sn and Te are similar to those of gold ore. Meanwhile, the distribution of Au in Mayuan Group metamorphic rocks and early Yanshanian granite with a low D-value (0.58 and 0.67) is favorable to gold mineralization. REE characteristics of gold ore, ratios of (LREE/HREE), (La/Sm)n, (Yb/Lu)n, (La/Tb)n and (Sm/Nd)n are similar to Mayuan Group metamorphic rocks, only non or little normal Eu abnormal of ore is dissimilar to metamorphic rocks. The δ(34S) of the gold ore, with a high homogenization, is (-4.7×10-3)-(-2.7×10-3). The study of inclusion indicates 180-249 ℃ of mineralization temperature, 3.69 %-11.81 % of salinities and 0.869-0.991 g/cm3 of densities of mineralization fluid. Based on hydrogen and oxygen isotope (δ(18O)=11.0×10-3-11.7×10-3, δ(D)=(-48×10-3)-(-62×10-3)) and initial w(87Sr)/w(86Sr) =0.715,combining to the analysis of geological history, regional metamorphism and magamtic activity, the authors confirm that the source for the ore fluid was mainly from magmatic, partly from metamorphic water, and with a little influence of meteoric water. Isotopic dating made on Rb-Sr isochron age of 182 Ma, by using alteration minerals of gold-ores from the deposit, indicates that the mineralization occurs in early Yanshanian epoch. This is close to the age of 187 Ma of the Anchun magmatite with a similar alteration and gold mineralization to the Xiaoban gold deposit. The age of early Yanshanian epoch of the Xiaoban gold is indentical with the characteristics of southern China gold metallogenic belt and the geotectonic evolution of the transition from paleo-Asian system and paleo-Tethyan system to paleo-Pacific active continental margin in eastern Asia.     

Uncertainty Analysis of the Parameters of the Temperature-index Method: A Case Study of Shiyi Glacier in Qilian Mountains

In order to assess the performance of the common temperature-index melt model at both spatial and temporal scale in Qilian Mountains, we performed the sensitivity and uncertainty analysis on the parameters of a common temperature-index method and evaluated the glacier mass balance on a small alpine glacier, which is separated into two relatively independent branches, with the daily mass balance and the meteorological data in the summer of 2011 and 2012. Sensitivity analysis was conducted by perturbation analysis and uncertainty analysis was carried out by Generalized Likelihood Uncertainty Estimation (GLUE) for different conditions. The results showed that the temperature-index method could properly capture the diurnal variability of the glacier mass balance. But strong equifinality of model parameter existsed in model calibration due to the uncertainty in the parameters. The model was very sensitive to changes in the value of K_ice, followed by the K_snow and T_s. It was also found that the GLUE approaches could estimate and derive the posterior distributions of 3 parameters properly. Moreover, there existed an acceptable range, which ensured high precision under different conditions.     

Spatial and temporal of variations of alpine vegetation cover in the source regions of the Yangtze and Yellow Rivers of the Tibetan Plateau from 1982 to 2001

Spatial and temporal variations in alpine vegetation cover have been analyzed between 1982 and 2001 in the source regions of the Yangtze and Yellow Rivers on the Tibetan Plateau. The analysis was done using a calibrated-NDVI (Normalized Difference Vegetative Index) temporal series from NOAA-AVHRR images. The spatial and temporal resolutions of images are 8 km and 10 days, respectively. In general, there was no significant trend in alpine vegetation over this time period, although it continued to degrade severely in certain local areas around Zhaling and Eling Lakes, in areas north of these lakes, along the northern foot of Bayankala Mountain in the headwaters of the Yellow River, in small areas in the Geladandong region, in a few places between TuoTuohe and WuDaoliang, and in the QuMalai and Zhiduo belts in the headwaters of the Yangtze River. Degradation behaves as vegetation coverage reduced, soil was uncovered in local areas, and over-ground biomass decreased in grassland. The extent of degradation ranges from 0 to 20%. Areas of 3×3 pixels centered on Wudaoliang, TuoTuohe, QuMalai, MaDuo, and DaRi meteorological stations were selected for statistical analysis. The authors obtained simple correlations between air temperature, precipitation, ground temperature and NDVI in these areas and constructed multivariate statistical models, including and excluding the effect of ground temperature. The results show that vegetation cover is sensitive to variations in temperature, and especially in the ground temperature at depths of ∼40 cm. Permafrost is distributed widely in the study area. The resulting freezing and thawing are related to ground temperature change, and also affect the soil moisture content. Thus, degradation of permafrost directly influences alpine vegetation growth in the study area.     

The impact of the development of water resources on environment in arid inland river basins of Hexi region, Northwestern China

Water resources use is a key parameter in the hydrological cycle, especially in arid inland of Northwest China, groundwater movement and circulation processes are closely related to the surface water, while recoverable and renewable groundwater mainly comes from the conversion of surface river water, and there is extensive transfer among rainfall, surface water and groundwater. Human activity, in particular, large-scale water resources exploitation and development associated with dramatic population growth in the last decades, has led to tremendous changes in the water regime. There are misuse and wastage of surface water with traditional multi-channel irrigation for most rivers, which in turn leads to over-exploitation of groundwater to augment supplies. This situation has been exacerbated by rapid population growth and socio-economic development, with decreased irrigational systems return to groundwater due to the irrigation system in the middle reaches of rivers in the Hexi region becoming better. The investigations of this study revealed that over the last decades, man-made oases have developed rapidly in various inland river basins. With the increasing human demand for water, the contradiction between water demand and water supply is becoming increasingly acute and the amount of groundwater usage significantly increased. Notwithstanding the annual surface water from mountains is relatively stable in the Hexi region, the recharges of groundwater have been reduced by 11.1%, with a maximum reduction of 50% in the Shiyang River basin. Groundwater abstraction increased by approximately six times, particularly in the Shiyang River basin, groundwater abstraction exceeds recharge by 4.1×10⁸ m³ year⁻¹ in recent decades. Consequently, the groundwater level has declined widely by 3–16 m, with a maximum decline of 45 m in several groundwater observation wells in the Minqin basin on the lower reaches of the Shiyang River basin. These cause serious human activity-induced environmental problems, such as water-quality deterioration, vegetation degradation, soil salinization and land desert desertification, etc. It is suggested that modernized irrigation technology and new regulation to cover water resources management and allocation with the river basins are urgently needed to achieve a sustainable development. The aim of this study is to analyze the impact of the development of water resources on the environment in arid inland river basins in Northwestern China, which were analyzed by comparing the three main river basins (i.e., the Shuilei, the Heihe and the Shiyang River basins) with different water resources development cases.