Water quality changing trends of the Miyun Reservoir

In order to simulate changes in the water quality of the Miyun Reservoir dueto continuous descent of surface water level, a 3-D ecological hydrodynamic model was developedthrough coupling the water quality analysis simulation program (WASP) with the environmental fluiddynamics code (EFDC). The model was then calibrated and verified. Four scenarios (S1, S21, S22 andS23) were simulated using the model. Results show that the water quality of the Miyun Reservoirunder conditions of low surface water level is apparently affected by different amounts of inflowand different total phosphorus (TP) loadings. The chlorophyll-a concentration might exceed 10 μg/Lin many areas of the Miyun Reservoir (This limitative value is seen as a critical value ofeutrophication) when large loadings of TP enter due to the amount of inflow increasing. Results ofscenario S23 indicate that control of TP loadings can decrease chlorophyll-a concentrationeffectively, and the water quality of the Miyun Reservoir will improve or retain its status quo.

Long-term variations in runoff of the Syr Darya River Basin under climate change and human activities

In this study,we analyzed the hydrological and meteorological data from the Syr Darya River Basin during the period of 1930–2015 to investigate variations in river runoff and the impacts of climate change and human activities on river runoff.The Syr Darya River,which is supplied by snow and glacier meltwater upstream,is an important freshwater source for Central Asia,as nearly half of the population is concentrated in this area.River runoff in this arid region is sensitive to climate change and human activities.Therefore,estimation of the climatic and hydrological changes and the quantification of the impacts of climate change and human activities on river runoff are of great concern and important for regional water resources management.The long-term trends of hydrological time series from the selected 11 hydrological stations in the Syr Darya River Basin were examined by non-parametric methods,including the Pettitt change point test and Mann-Kendall trend tests.It was found that 8 out of 11 hydrological stations showed significant downward trends in river runof f.Change of river runoff variations occurred in the year around 1960.Moreover,during the study period(1930–2015),annual mean temperature,annual precipitation,and annual potential evapotranspiration in the river basin increased substantially.We employed hydrological sensitivity method to evaluate the impacts of climate change and human activities on river runoff based on precipitation and potential evapotranspiration.It was estimated that human activities accounted for over 82.6%–98.7%of the reduction in river runoff,mainly owing to water withdrawal for irrigation purpose.The observed variations in river runoff can subsequently lead to adverse ecological consequences from an ecological and regional water resources management perspective.

A new theoretical solution of the effect of atmospheric pressure on water level

Based on the partial differential equation governing the effect of atmospheric pressure on water level of confined well,deriving the boundary condition and considering the seepage water between well and aquifer,the author obtained the analytical solution of water level change in time domain under the action of an atmospheric pressure history with the Laplace transform method.This solution is composed of two terms:stable and retarded terms.The stable term is the multiplication of barometric efficiency and simultaneous atmospheric pressure,and it implies the value of water level after infinite time when the atmospheric pressure is a constant from the time in question.The retarded term is the transient process due to the time lag of water exchange between well and aquifer.From the solution,it is obtained that the interference of atmospheric pressure on water level is the integral superimposition of the contribution of all atmospheric pressure changes before the time in question.So that,we further found out the response function of pulsive atmospheric pressure history.Calculation shows:① The pulsive response function starts from zero and tends to a steady value,which is proportional to the barometric efficiency,when the time tends to infinity;② The retarded time depends on the mechanical property of aquifer and the radius of well.The larger the seepage coefficient,the smaller the radius of well and the thicker the aquifer,then the shorter the retarded time gets.This solution can be used as the theoretical basis for further analysis of the atmospheric effect and practical correcting method in the future.

Risk analysis of dynamic control of reservoir limited water level by considering flood forecast error

Flood control forecast operation mode is one of the main ways for determining the upper bound of dynamic control of flood limited water level during flood season. The floodwater utilization rate can be effectively increased by using flood forecast information and flood control forecast operation mode. In this paper, Dahuofang Reservoir is selected as a case study. At first, the distribution pattern and the bound of forecast error which is a key source of risk are analyzed. Then, based on the definition of flood risk, the risk of dynamic control of reservoir flood limited water level within different flood forecast error bounds is studied. The results show that, the dynamic control of reservoir flood limited water level with flood forecast information can increase the floodwater utilization rate without increasing flood control risk effectively and it is feasible in practice.

Modeling the impacts of drying trend scenarios on land systems in northern China using an integrated SD and CA model

Climate-induced drought has exerted obvious impacts on land systems in northern China.Although recent reports by the Intergovernmental Panel on Climate Change(IPCC) have suggested a high possibility of climate-induced drought in northern China,the potential impacts of such drying trends on land systems are still unclear.Land use models are powerful tools for assessing the impacts of future climate change.In this study,we first developed a land use scenario dynamic model(iLUSD) by integrating system dynamics and cellular automata.Then,we designed three drying trend scenarios(reversed drying trend,gradual drying trend,and acceleration of drying trend) for the next 25 years based on the IPCC emission scenarios and considering regional climatic predictions in northern China.Finally,the impacts of drying trend scenarios on the land system were simulated and compared.An accuracy assessment with historic data covering 2000 to 2005 indicated that the developed model is competent and reliable for understanding complex changes in the land use system.The results showed that water resources varied from 441.64 to 330.71 billion m3 among different drying trend scenarios,suggesting that future drying trends will have a significant influence on water resource and socioeconomic development.Under the pressures of climate change,water scarcity,and socioeconomic development,the ecotone(i.e.,transition zone between cropping area and nomadic area) in northern China will become increasingly vulnerable and hotspots for land-use change.Urban land and grassland would have the most prominent response to the drying trends.Urban land will expand around major metropolitan areas and the conflict between urban and cultivated land will become more severe.The results also show that previous ecological control measures adopted by the government in these areas will play an important role in rehabilitating the environment.In order to achieve a sustainable development in northern China,issues need to be addressed such as how to arrange land use structure and patterns rationally,and how to adapt to the pressures of climate change and socioeconomic development together.

佳木斯市2011年-2020年地表水生态环境质量变化研究

采用Spearman秩相关系数法,对松花江佳木斯市2011年-2020年期间主要污染指标变化趋势进行了分析。计算结果表明,2011年-2020年佳木斯上断面的高锰酸盐指数、化学需氧量、氨氮和总磷,佳木斯下断面的化学需氧量和总磷,江南屯断面的化学需氧量,同江断面的高锰酸盐指数、化学需氧量和总磷,汤旺河口内断面的化学需氧量、氨氮和总磷,梧桐河口内断面的化学需氧量和总磷呈显著下降趋势;其余监测断面的这几项监测指标无显著变化。对污染物的年际变化进行了分析,并探讨了地表水环境质量变化原因。

基于2次全国制图的土壤可蚀性因子变化趋势

2011年第1次全国水利普查水土保持专项普查基于全国各省(区、市)土壤类型图和土种志剖面数据,制作首张全国土壤可蚀性因子分布图(简称2011版K值)。为了提高土壤侵蚀评价的准确性和可信度,2022年利用全国土系调查数据和随机森林制图方法对中国土壤可蚀性因子分布图进行更新(简称2022版K值)。以全国水蚀区2011版和2022版的土壤可蚀性因子(简称K值)为研究对象,分别在流域尺度和不同土壤类型下对K值大小及空间分布进行研究。结果表明:2022版全国平均K值(0.0298 t·hm^(2)·h/(MJ·mm·hm^(2)))略低于2011版K值(0.0323 t·hm^(2)·h/(MJ·mm·hm^(2))),说明全国水土流失治理发展状况有向好的趋势。其中栗钙土、暗棕壤、盐碱土等土壤类型K值的降低幅度最大,潮土、褐土、黄壤等土壤类型的K值则有所升高。K值降低主要与退耕还林、土壤改良等政策措施的出台和布设有关,升高则与集约化耕作及坡地侵蚀有关。该结果可为水土流失动态监测及治理成效评价提供科学依据。

水位变化下浅埋盾构隧道开挖面渗透力与稳定性研究

为分析临江地区透水地层浅埋盾构开挖面渗流作用下的稳定性,结合安庆市沿江东路管廊盾构段典型断面,建立浅埋盾构三维流固耦合数值模型,分析水位变化、土体力学性质对开挖面稳定性影响以及渗透力的变化规律,明确浅埋盾构渗透作用下开挖面的失稳形式,建立区别于传统破坏模型的圆台-弧转体数学模型,提出一种基于极限分析上限法且考虑渗透力作用的极限支护压力的计算方法,并与已有研究结果相对比,验证该方法的可行性;根据该方法分析水位、土体力学参数、盾构掘进参数对极限支护压力的影响。研究结果表明:黏聚力及内摩擦角增加会导致破坏区高度显著减小,而水位增加会导致破坏区高度及长度显著增加;开挖面上渗透力随开挖面与拱顶的距离增大而增大,渗透力随水位变化呈线性变化,平均渗透力随水位变化率为2.75 kN·m^(-3);极限支护压力随黏聚力、水位呈线性变化,随摩擦角呈非线性变化;结合开挖面前方土层土体力学性质,极限支护压力随水位变化率为5.11~5.75 kPa,与实测土仓压力变化率6.38 kPa较吻合,控制土仓压力在80 kPa以上时能有效保证开挖面稳定。

芡实对沿淮富营养化水体的净化效果研究

为了解乡土水生植物芡实对沿淮农村富营养化河流净化效果,在模拟沿淮农村地区富营养化河流的水池中种植芡实,定期监测水体中的总氮(TN)、氨氮(NH_(4)^(+)-N)、总磷(TP)、化学需氧量(COD_(Cr))、酸碱度(pH)、可溶性盐含量(EC)、溶解氧(DO)的数值变化,综合分析芡实对富营养化河流的净化效果。结果表明,芡实作为沿淮地区乡土水生植物,对富营养化的河流有着净化作用。芡实在生长过程中能吸收水体95.53%~98.45%的NH_(4)^(+)-N和99.50%~99.65%的TP,净化效果好。芡实对富营养河流中TN和COD_(Cr)的净化效果不明显,而且水体中的pH上升11.05%~11.61%,EC值增加21.12%~22%,DO增加3.82~21.77倍。芡实作为一种乡土水生植物,对沿淮地区富营养化河流具有显著的净化潜力。

三峡水库运行后汉口—九江河段水位变化特征及成因

大型水库的修建引起坝下游的水位调整,进而对河势、航运、防洪及生态等产生显著影响。为探究汉口—九江河段水位变化特征及成因,采用M-K分析法分析1988—2022年汉口、黄石港和九江站的水位变化趋势,并使用基于距平残差的水位变幅分析方法和一维水动力模型,分析河道冲淤、下游水位和阻力变化对不同特征流量下水位变化的影响。研究结果表明:①三峡成库前,除九江站枯水位呈显著性下降趋势,各级流量下的水位均没有显著性变化趋势。②三峡成库后,九江站的水位变化趋势与建库前相同;汉口站、黄石港站在12000 m^(3)/s和20000 m^(3)/s下的水位呈显著性下降趋势,12000 m^(3)/s时降幅分别为0.072、0.045 m/a,20000 m^(3)/s时降幅分别为0.048、0.027 m/a;水位变化的临界转换流量约为30000 m^(3)/s,在该流量附近水位未出现明显变化;当流量大于30000 m^(3)/s时,水位呈非显著性上升趋势,45000 m^(3)/s下的升幅分别为0.037、0.049 m/a。③临界转换流量以下水位下降的主导作用为河道冲刷,临界流量附近的水位未出现明显变化源于阻力增大作用接近抵消了河道冲刷的影响,临界转换流量以上的水位上升源于阻力增大作用更加明显,个别年份的洪水位上升显著源于下游水位顶托作用明显。

基于耦合融雪模块WAS模型的流域径流模拟与组分解析

【目的】在气候变化背景下,深入解析径流组分对识别降水模式改变、气温升高等气候变化下的径流响应具有重要意义。为提高WAS模型在高寒山区的径流模拟精度,从而支撑径流组分的准确深入解析。【方法】以毛家村水库上游流域为例,采用度日因子法与双温度阈值法综合构建了融雪模块,将其与WAS模型进行耦合,并将改进后WAS模型应用于2001—2020年毛家村水库流域径流模拟与组分解析。根据水源与演化路径不同,将径流划分为基流、降雨地表径流和融雪地表径流3部分,并根据年内不同时期水文过程的主导因素不同,利用不同时期的实测径流分别对地下水参数、土壤参数和融雪参数进行逐步分级率定。【结果】结果显示:耦合融雪模块WAS模型相较于原WAS模型,在春季融雪期的模拟精度有显著提升,改进后WAS模型在率定期与验证期NSE分别为0.85、0.78,R^(2)分别为0.93、0.91,优于原WAS模型的模拟效果。径流组分解析结果显示,季节尺度上,基流、降雨地表径流、融雪地表径流对春季径流的贡献分别为58.1%、19.1%、22.8%,对夏季径流的贡献分别为30.7%、67%、2.3%,秋、冬季径流中,无融雪地表径流,基流、降雨地表径流对秋季径流的贡献分别为46.4%、53.6%,对冬季径流的贡献分别为78.8%、21.2%;年尺度上,基流、降雨地表径流和融雪地表径流对总径流的贡献分别为41.7%、53.6%和4.8%。【结论】WAS模型无论改进前后均可以从总体上模拟出径流的长期动态变化,耦合融雪模块的WAS模型可以更加精准的模拟出春季融雪期径流过程,提高了模型在高寒山区的适用性。降雨地表径流是该流域径流的主要组成部分,其次为基流,融雪地表径流最少。但融雪对于抑制春季径流衰减具有重要作用,基流是构成冬、春两季径流的主要部分,对于维持冬季与春季径流水平具有重要意义。

基于逐步回归分析的峡江水库对吉安水位顶托作用量化分析

峡江水库建设对赣江干流水位的顶托作用主要影响着上游吉安河段的水文情势变化,分析回水顶托作用下引起的水位变化以及解析河段水位抬升成因机制对研究水利工程修建改变河道水力特点的防洪减灾工作具有重要意义。基于历史实测水位和流量数据,构建计算水位顶托效果的逐步回归预测模型,利用皮尔逊相关分析定量评估水位顶托效果与各因素之间的相关性和影响程度,随后援用逐步回归方法量化分析了峡江水库运行对吉安水位顶托作用,即建立水位顶托效果与各因素之间的多元回归方程并验证方程的可靠性。结果表明:①基于逐步回归分析的预测模型模拟精度高,水位和流量要素模拟效果均良好,模拟水位过程与实测过程基本保持一致,在模拟流量方面也能够较好地再现实测过程且水位预测模型的各项评价指标优于流量预测模型;②水位顶托效果与峡江水库实测水位存在极强正相关性,与吉安实测水位和吉安水位落水过程存在中等正相关性,与吉安实测流量存在中等负相关性,与吉安水位涨水过程存在微弱负相关性;③多元逐步回归方程的修正后决定系数R2为0.892,表明方程拟合度较高且通过了后续的准确性检验,可表征吉安实测水位、吉安实测流量、峡江水库实测水位、吉安水位涨落过程的多重驱动作用。

晋西黄土区典型造林整地措施对土壤水分动态的影响

【目的】探究晋西黄土区典型造林树种和水平阶整地措施对0~180 cm土层土壤水分动态的影响,为植被恢复及流域综合治理提供参考依据。【方法】以晋西黄土残塬区蔡家川流域典型工程措施水平阶以及主要造林树种刺槐Robinia pseudoacacia和侧柏Platycladusorientalis为研究对象,于2019年5—9月生长季开展土壤水分定位监测,并采用配对试验,对自然坡面刺槐林地与侧柏林地土壤水分进行同步观测,分析不同植被和水平阶整地综合影响下的土壤水分特征及对降雨事件的响应,评价典型工程措施对不同植被土壤含水量的影响。【结果】生长季不同植被类型、水平阶整地前后的土壤含水量的变化与降雨量的变化密切相关,不同样地平均土壤含水量由高到低依次为水平阶侧柏林地(18.68%)、自然坡面侧柏林地(16.19%)、水平阶刺槐林地(16.10%)、自然坡面刺槐林地(15.42%)。较之自然坡面,水平阶整地措施能够分别提高侧柏林地和刺槐林地土壤含水量15.38%、4.41%。根据土壤水分垂直变化特征,水平阶整地可以提升土壤水分的活跃层、次活跃层深度:水平阶侧柏林地活跃层、次活跃层深度范围为0~80 cm,相对于自然坡面侧柏林地提升深度33%;水平阶刺槐林地活跃层、次活跃层深度范围为0~140 cm,相对于自然坡面刺槐林地提升深度40%。【结论】土壤含水量的动态变化与降雨量、工程措施、植被作用关系密切,水平阶是开展黄土残塬小流域生态恢复的有效工程措施,且水平阶侧柏林地提升效果要优于水平阶刺槐林地。图3表3参37.

内蒙古草原内陆河流域水文循环要素时空演变及驱动因素

[目的]开展内蒙古草原内陆河流域水文循环要素对植被动态和气候变化的响应研究,对于内蒙古草原内陆河流域的生态保护及区域水资源开发利用具有重要的理论意义。[方法]以内蒙古草原内陆河流域为研究区,基于多源遥感、气候气象、水文等数据,采用趋势检验、显著性检验和相关性分析等方法,对流域水文循环要素的时空演变及驱动因素进行相关分析。[结果](1)流域蒸散发呈显著上升趋势(0.994 mm/a),降水量呈显著下降趋势(2.69 mm/a),土壤水分呈增加趋势,其中子流域锡林河径流呈下降趋势,巴拉格尔河径流呈上升趋势;(2)生长季植被总体呈增加趋势,植被归一化指数(NDVI)、总初级生产力(GPP)和叶面积指数(LAI)整体呈东高西低的阶梯状空间分布格局,气温整体呈现上升趋势;(3)植被变化与蒸散发(ET)、土壤水分(SSM)呈正相关,气温和蒸散发整体上呈现显著正相关(R=0.699,p=0.01),空间相关性由西向东递增;气温和径流呈负相关,和土壤水分在流域东、西部呈显著负相关性。[结论]流域水文循环变量(降水、蒸散发、土壤水分、径流量)随着植被增加而增加;降水、土壤水分和径流量随气温上升而减少,蒸散发随气温上升而增加。

拓扑路由特征演化趋势分析

在时间的维度上,互联网的拓扑特征是持续在动态变化的。理解互联网拓扑路由的演化趋势有助于发现互联网的发展规律和特征,未来能够帮助预测未开发的新技术及新政策对互联网拓扑和路由的影响。主要从3个角度对互联网的拓扑特征的演化趋势进行分析。一是互联网的静态拓扑特征的演化趋势,例如聚类系数、节点度的幂律分布;二是网络的扁平化趋势;三是AS之间的依赖程度。最后,分析发现了互联网的拓扑特征动态变化特点。

义昌江流域水质水量演变规律分析

研究义昌江流域降水量、径流量和水质指标演变规律,可为流域水资源开发利用、水环境保护和水生态改善提供数据支撑。运用线性趋势回归检验法研究其变化趋势,采用有序聚类分析法对其进行突变分析;分析水质指标时空变化,并进行水质评价;基于Pearson相关分析和双累积曲线法,研究义昌江流域水质变化的原因。结果表明:降水量、径流量、溶解氧、高锰酸盐指数、氨氮、粪大肠菌群变化趋势不明显。一般情况下,下游大冲口断面水质比上游断面好;从季节变化来看,冬季水质大部分合格、水质较好;从年变化来看,水质变化波动;径流对溶解氧、氨氮的影响比降水和水温更大,水温对高锰酸盐指数、粪大肠菌群的影响比降水和径流更大;水质指标变化受自然因素和人类活动共同影响。

炎陵县“十三五”期间地表水水质评价及变化趋势分析

炎陵县是洣水的发源地,对该县域内的地表水水质进行评价,并对其变化趋势进行分析,可为环境管理及河道治理提供有力的技术支撑。分析结果表明:炎陵县“十三五”期间,太和断面主要水质指标高锰酸盐指数、化学需氧量、生化需氧量、氨氮、总磷等均呈下降趋势,综合水质指数呈显著下降趋势,说明5年来太和断面水质呈显著好转趋势;晏公潭断面主要水质指标高锰酸盐指数、化学需氧量、氨氮、总磷等均呈下降趋势,综合水质指数呈不显著下降趋势,说明5年来晏公潭断面水质呈好转趋势,但不显著。

基于趋势分析和Kendall算法的辽河水质分析

文章通过选取辽河干流6处典型断面,以COD和NH3-N作为评价指标,深入剖析辽河的水质污染状况及其变化趋势。通过应用Kendall算法以及趋势分析法,系统地分析了2020—2022年间辽河各监测断面水质的变化趋势与特征。结果表明:虽然各断面的COD和NH3-N浓度整体保持相对稳定,但部分断面仍呈现出不显著的上升趋势。该成果可为辽河水质治理提供一定参考。

广东省海外高层次人才政策变迁及发展趋势

海外高层次人才是我国参与国际竞争的关键资源。在广东省深入推进人才强省建设的背景下,研究广东省海外高层次人才政策的变迁及发展趋势,识别社会需求的渐进变化和政府战略的动态调整,从而为未来政策优化提供理论依据和实践指引,同时为其他地区构建海外高层次人才吸引与留住机制提供参考经验。以近30年(1993—2022年)广东省政策文献为研究对象,采取政策文献量化分析的研究方法,探讨广东省海外高层次人才政策在不同阶段的变迁路径和政策特征。研究结果显示:广东省海外高层次人才政策经历了体系初建期、逐步完善期和创新发展期3个阶段;政策变迁特征包括政策对象逐步聚焦于高精尖缺人才、扶持主体逐渐向产业界倾斜,以及政策导向从管理转变为服务,从引进转变为吸引。基于研究发现,提出广东省海外高层次人才政策的发展趋势:未来将更加注重关键领域海外高层次人才的引进,更加注重粤港澳大湾区协同发展,更加注重产业界对海外高层次人才的引进。

广东省近岸海域海面地形模型建立

广东省近岸海域缺少高精度海面地形模型,无法准确为广东省无缝垂直基准面提供可靠标定与统一转换。将长达19年水位数据的验潮站作为基准站,对其他长期、中期验潮站通过平均海面传递方法进行加密,并结合水准联测数据得到验潮站沿岸海面地形值,最终采用反距离加权法建立广东省近岸海域海面地形模型。评估结果表明该模型误差优于3.2 cm,明显高于有关参考文献给出的成果精度,对广东省陆海基准统一转换研究具有很高的参考和使用价值。