Spatial-temporal Variation Characteristics of Water Quality in the Lower Reaches of the Nenjiang River

As an important river in the western part of Jilin Province,the lower reach of the Nenjiang River is an important wetland water source conservation area in Jilin Province.Within the watershed,it governs the Momoge Wetland,the Xianghai Wetland,and the Danjiang Wetland in Jilin Province.The main problem in the lower reaches of the Nenjiang River is the uneven distribution of water resources in time and space,and the intensification of land salinization.Zhenlai County and Da an City in the Nenjiang River Basin have sufficient surface water resources,with surface water as the drinking water source.Baicheng City and Tongyu County have scarce surface water resources,and both use groundwater as their domestic water source.The main polluted section in the basin is the Xianghai Reservoir,and the annual water quality evaluation is Class V.However,the water quality of the Tao er River,the main stream of the Nenjiang River,is significantly better than that of the Xianghai Reservoir.In order to better study the water environmental pollution situation in the Nenjiang River basin,monitoring data from five sections of non seasonal rivers in the basin from 2012 to 2021 were selected for studying water quality.This in-depth exploration of the water pollution status and river water quality change trends in the Nenjiang River basin is of great significance for future rural development,agricultural pattern transformation,and the promotion of water ecological civilization construction.

Changes in groundwater levels and the response of natural vegetation to transfer of water to the lower reaches of the Tarim River

Restoration and reconstruction of the degraded Tarim River ecosystem is an important challenge. A goal of an ecological water conveyance project is to protect and restore the natural vegetation in the lower reaches of Tadm River by transferring water from Bosten Lake, through the river channel, to the lower reaches. This study describes the changes in groundwater depth during the water transfer and the respondence of riparian vegetation to alterations in groundwater levels. The results indicate that groundwater depth along the Tarim River channel has a significant spatial-temporal component. Groundwater levels closest to the river channel show the most immediate and pronounced changes as a response to water transfer while those further away respond more slowly, although the observed change appears to be longer in duration. With a rise in the groundwater level, natural vegetation responded with higher growth rates, biomass and biodiversity. These favorable changes show that it is feasible to protect and restore the degraded natural vegetation by raising the groundwater depth. Plant communities are likely to reflect the hysteresis phenomenon, requiting higher water levels to initiate and stimulate desired growth than what may be needed to maintain the plant community. Because different species have different ecologies, including different root depths and densities and water needs, their response to increasing water availability will be spatially and temporally heterogenous. The response of vegetation is also influenced by microtopography and watering style. This paper discusses strategies for the protection and restoration of the degraded vegetation in the lower reaches of the Tarim River and provides information to complement ongoing theoretical research into ecological restoration in add or semi-arid ecosystems.

Water sources of plants and groundwater in typical ecosystems in the lower reaches of the Heihe River Basin

Stable oxygen and hydrogen isotopic compositions （δ18O and δD） of soil water and shallow groundwater of a riparian forest, an artificial shrub forest, and Gobi of the lower reaches of the Heihe River Basin are used to study the recharge water sources of those ecosystems. IsoSource software is used to determine the δ180 values for root water of Populous euphratica and Tamarix ramosissima in the riparian forest ecosystem, Haloxylon ammodendron in the artificial shrub forest, and Reaumuria soongorica in the Gobi, as well as for local soil water and groundwater, and precipitation in the upper reaches of the Heihe River Basin. Our results showed that soil water and shallow groundwater of the riparian forest and the artificial shrub forest were recharged by river water which originated from precipitation in the upper reaches, and strong evaporation occurred in the artificial shrub forest. Soil water of the Gobi was not affected by Heihe River water due to this area being far away from the river channel. The main water sources of Populous euphratica were from 40-60-cm soil water and groundwater, and of Tamarix ramosissima were from 40-80-cm soil water in the riparian forest ecosystem. In the artificial forest, Haloxylon ammodendron used 200-cm saturated-layer soil water and shallow groundwater. The Reaumuria soongorica mainly used soil water from the 175-200-cm depth in the Gobi. Therefore, soil water and groundwater are the main water sources which maintain survival and growth of the plants in the extremely arid regions of the lower reaches of the Heihe River Basin.

REMOTE SENSING APPLICATION RESEARCH OF WATER POWER AT THE INITIAL EXPLOITING STAGE IN THE LOWER REACHES OF YALONG RIVER

There are abundant water power resources in the Yalong River which are suitable for the large hydroelectric engineering. But a reliability study should be made for the valley which liable to frequent earthquakes. The color infrared aerophotos, multi-spectral photography and thermal infrared scanning had been specially done besides MSS image, processing. Researches on remote sensing applications to engineering geology, hydrogeology, deformation of neo-tectonics, Iandslide, mud-rock flow, ecological environment and geographical information system had been carried out by more than 20 research units.

Diagnosing anomalous characteristics of atmospheric water cycle structure during seasonal-scale drought events:A case study in middle and lower reaches of Yangtze River

Anomalous characteristics of the atmospheric water cycle structure are highly significant to the mechanisms of seasonal-scale meteorological droughts.They also play an important role in the identification of indicative predictors of droughts.To better understand the causes of seasonal meteorological droughts in the middle and lower reaches of the Yangtze River(MLRYR),characteristics of the atmospheric water cycle structure at different drought stages were determined using standardized anomalies.The results showed that the total column water vapor(TCWV)was anomalously low during drought occurrence periods.In contrast,there were no anomalous signals at the drought persistence and recovery stages in the MLRYR.Moreover,there was no significant temporal correlation between the TCWV anomaly and seasonal-scale drought index(the 3-month standardized precipitation index(SPI_(3))).During drought events,water vapor that mainly originated from the Bay of Bengal was transported southwest of the MLRYR.Meanwhile,the anomalous signal of water vapor transport was negative at the drought appearance stage.At the drought persistence stage,the negative anomalous signal was the most significant.Water vapor flux divergence in the MLRYR showed significant positive anomalous signals during drought events,and the signal intensity shifted from an increasing to a decreasing trend at different drought stages.In addition,a significant positive correlation existed between the anomaly of water vapor flux divergence and regional SPI_(3).Overall,water vapor flux divergence is more predictive of droughts in the MLRYR.

黄河下游花园口以上河道滞沙指标研究

水沙搭配关系是影响黄河下游河道冲淤调整的重要因素,局部河段滞沙则是改善下游水沙关系的有效手段之一。小浪底水库运用后,河槽沿程冲刷不均衡,河床粗化,细沙补给不足,输沙效率明显降低。分析黄河下游河道冲淤特性及水沙演进规律,建立不同类型洪水滞沙河段(花园口以上河段)与排洪瓶颈河段(高村—艾山河段)的冲淤关系。基于滞沙对河道行洪和稳定性的影响,以排洪瓶颈河段不淤积为约束,提出洪水滞沙的水沙优化配置指标。中泥沙洪水滞沙指标为:洪水平均流量为1800~3700 m^(3)/s,平均含沙量为66~235 kg/m^(3)。

黄河下游高效输沙指标及输沙水量研究

研究提出黄河下游高效输沙的定义和内涵,依据小浪底水库运用方式和黄河不同时段河道水量的功能定位,将汛期的洪水水量定义为狭义输沙水量,汛期的平水期和非汛期水量的主要功能为满足生态、灌溉、发电等需求,不作为输沙水量。建立了单位输沙水量与排沙比及流量含沙量之间的定量关系,提出了高效输沙流量和含沙量指标的定量计算方法,在现状下游河道过流能力条件下,计算了满足高效输沙要求的流量与含沙量搭配指标。提出了维持下游河道全年一定冲淤水平的利津断面狭义输沙水量计算方法,当进入下游年沙量为3亿t时,维持下游河道全年冲淤平衡的利津断面洪水输沙水量为56.2亿~69.6亿m^(3)。

基于分解-预测-灰狼优化集成模型的水质预测研究

准确的水质预报及关键因素识别是流域水环境控制及水资源保护的重要依据。针对地表水水质评价指标的多样性以及原始数据的非线性、非平稳的特征,在改善传统的分解-预测-集成时间序列预测框架之上,提出了一种基于集合经验模态分解(EEMD)和灰狼优化集成策略(GWO)数据预测模型。该模型采用集合经验模态分解方法对数据进行分解,得到不同频率的分解分量,再分别运用Elman神经网络、长短记忆神经网络(LSTM)和支持向量回归(SVR)作为基学习器进行预测,然后利用灰狼动态优化集成策略对预测结果进行集成,最后,以长江下游水质断面的数据对模型有效性进行评估,并与单一预测模型和平均集成策略的预测模型进行对比。研究结果表明,该模型在误差评价指标和DM检验上表现优异,相较于其他模型更具优势,其中,对于溶解氧的预测,相较于平均集成策略的预测模型,通过灰狼优化集成模型的平均绝对误差(MAE)、均方根误差(RMSE)以及Theil不等系数(TIC)分别降低了16.29%、13.17%、13.24%,对于最终水质等级的预测正确率为98.6%,证明该模型能够准确预测水质等级并识别关键影响因素,进而为水环境污染治理提供科学依据。

长江安徽段江湖连通性及生物通道恢复研究

江湖阻隔是导致长江中下游江湖复合生态系统衰退的最主要原因,江湖连通和生物通道恢复是流域生态修复的重要措施之一。通过现场调查等方法研究了华阳河湖群、菜子湖、升金湖和安庆西江古道等与长江干流的阻隔现状及连通性特征,在此基础上探讨了技术和管理层面存在的问题并提出对策建议。结果发现:依托涉水工程建设开展恢复河湖生物通道的做法可以有效缓解江湖复合生态系统的衰退,尤其是以“过鱼设施建设、季节性灌江纳苗、生态水网建设”相结合的生物通道恢复方案具有技术可行性。相关成果可为长江中下游江湖连通性及生物通道恢复、国家水网建设提供有益的参考。

黄河下游水资源承载力与粮食生产韧性时空耦合及驱动因素

[目的]探究黄河下游水资源承载力与粮食生产韧性协同发展水平,为推动水资源保护利用和粮食生产协调发展提供新的政策视角。[方法]基于水资源承载力和粮食生产韧性评价指标体系,采用熵权法测算2010—2021年黄河下游水资源承载力和粮食生产韧性指数,运用耦合协调度模型和核密度估计分析两者协调发展时空演变特征,同时借助地理探测器探究影响两者耦合协调度的主导因子和交互因子。[结果]时间维度上,水资源承载力与粮食生产韧性耦合协调度由0.484 0上升至0.747 6,耦合协调度类型由濒临失调上升至中级协同;空间维度上,两者耦合协调度最高值出现在山东省济南市,最低值集中在河南省境内;年降水量、居民生活用水量、城市绿地面积、耕地面积和财政支农力度5项因子是两者协调发展的主导驱动因子,各主导因子的交互作用解释力表现呈现为双因子增强或非线性增强的特征。[结论]黄河下游水资源承载力和粮食生产韧性耦合协调度逐年上升并逐渐呈现出“东高西低”的空间分布特征,同时两大系统发展日趋紧密,交互作用逐渐增强。

黄河下游高村-孙口段冲淤变化及影响因素定量分析

为探究黄河过渡段河道滩槽演变规律,采用实测水沙和大断面数据,分析近年来高孙段河床冲淤、水沙条件和河床形态的演变,以年和汛期为时间尺度,用灰色关联度分析河槽冲淤量与水沙条件及河床形态的关联程度。结果表明,近年来高孙段以冲刷为主,汛期是年内输沙的主要时期;高村断面来沙系数可以分为波动减小(2002~2017年)和快速增加(2018~2019年)两大阶段,而河床形态中水力半径和宽深比变化趋势完全相反,糙率存在增大趋势;高村断面的水沙条件及河床形态与高孙段河道冲淤具有较高的关联程度,河床形态比水沙条件具有更高的相关性。

水位变化条件下植被对下荆江河段岸坡稳定性影响分析

针对下荆江河段典型的上黏下砂二元岸坡,选用香根草-高羊茅组合植物护坡型式,综合考虑植物根系锚固作用及植被蒸腾作用,利用GeoStudio软件模拟岸坡强度指标和热力学指标,运用单因子分析方法研究河道水位下降幅度M、水位下降速率R、初始水位I因素对岸坡稳定性的影响,并运用灰色关联分析方法对比三种因素对岸坡稳定性的影响程度。结果表明:在水位下降过程中,岸坡稳定安全系数先快速下降,后趋于稳定;岸坡稳定性受水位快速下降的影响最大,当下降速率小于1 m/d时,素土岸坡能保持在基本稳定状态;当下降速率大于3 m/d时,岸坡失稳破坏。植被有助于提升岸坡的稳定性,有植被岸坡与素土岸坡相比,其稳定安全系数最大可提升4.33%;岸坡稳定安全系数与M、R、I三种影响因素的关联度在有植被条件下依次有所下降,最大降低3.73%。本文研究结果明确了水位变化条件下植被对下荆江岸坡的稳固效果,可为生态护岸工程的设计提供基础支撑。

汉江中下游水质时空特征及环境流量确定

近年来,汉江中下游水质问题频发,且河道内环境流量尚未明确,严重威胁沿岸用水安全。为探明汉江中下游水质时空分布特征和河道环境流量,收集调研了2015—2019年汉江中下游黄家港、襄阳、皇庄、沙洋、潜江、仙桃和汉川等7个控制断面的pH、溶解氧、高锰酸盐指数、氨氮、总磷5项水质指标,基于水质单因子评价方法分析了水质时空变化特征。通过建立一维水动力-水质模型,构建了基于保障各控制断面水质的环境流量计算方法;根据不同水源的输入,计算了汉江中下游河道环境流量,并提出了保障方案。结果表明,汉江中下游丰水期氨氮和枯水期总磷在皇庄以下断面均未达到Ⅱ类水标准,氨氮沿程变化不明显,总磷从上游至下游逐渐升高。环境流量保障需结合引江济汉补水工程和丹江口下泄流量,丰水期和枯水期当引调长江水分别为500 m^(3)/s和350 m^(3)/s时,还需丹江口水库分别下泄214 m^(3)/s和315 m^(3)/s才能满足河道内的环境流量。研究为汉江中下游水质安全保障和合理分配丹江口水资源提供了参考。

水质保护与用水效率的主从博弈稳健优化模型及其应用

水资源系统的复杂不确定性为可靠的水资源优化配置带来挑战。为实现水质保护与用水效率均衡,基于量化水资源系统不确定性的稳健参数建立了主从博弈稳健优化模型,并采用稳健对等转换法和模糊满意度算法进行联合求解。以汉江中下游流域为研究区域,结果表明:主从博弈稳健模型的均衡解劣于确定性多目标模型的优化解,模型以牺牲目标最优值为代价提高了可靠性;不确定性影响均衡解的决策范围,高不确定度下均衡解范围更宽,能够为不确定性下提升决策策略的适应性提供依据。相比于单目标的水质保护稳健模型与经济发展稳健模型,主从博弈稳健模型能提供更均衡的水资源配置方案。模型的敏感性分析揭示了目标层对稳健参数变化的响应规律。本研究可为不确定情景下水资源冲突管理提供适应性稳健决策方法。

具有时滞效应的air2stream河流水温模型及应用研究

高精度河流水温模型对于深入了解水温的时空变化特征和河流生态修复具有重要意义。基于数据驱动的air2stream模型在保证预测精度的同时,避免了计算的复杂性,已成为河流水温模拟常用的模型。由于水的热惯性及水文条件等的影响,河流水温变化往往显著滞后于气温变化,而air2stream原模型并未考虑滞后效应,导致该模型在流量未知情况下实际精度偏低。为解决该问题,采用气温-水温皮尔逊相关系数计算时滞天数,构建具有时滞的air2stream新模型,进一步根据长江中下游地区两个监测站的多年实测数据验证新模型的有效性和稳定性。结果表明:新模型在不引进额外观测数据的条件下具有更高精度且性能更稳定。相比原模型,在两个监测站新模型的均方根误差分别降低约4.29%和5.85%。新模型具有精度高、水文要素需求少的特点,可为长江中下游的水环境影响评价和生态保护提供依据。

甘肃省黑河下游河水漫溢的时空演变及其影响因素

生态输水是干旱区内陆河流域退化生态系统恢复的主要措施,而流域下游的河水漫溢直接关系到绿洲的恢复成效。基于1987—2021年全球地表水体数据集,结合流域内自然环境和人类活动等数据,通过GEE平台构建的水体频率,即像素点在特定时间段内观测到水体的次数与总观测次数的比率,分析了黑河下游生态输水前、后河水漫溢的时空演变及其影响因素。结果表明:分水前1987—2001年正义峡、哨马营和狼心山的年均径流量分别为8.86×10^(8)、5.28×10^(8)、4.27×10^(8)m^(3),分水后2002—2021年分别为11.99×10^(8)、8.12×10^(8)、6.70×10^(8)m^(3),狼心山-东居延海段的年均径流量(即绿洲可利用水资源量)为6.17×10^(8)m^(3),时间上主要集中在4—5和9—10月;分水后永久性水体面积逐渐增加且主要集中在东居延海,2004年后东居延海出现永久性水体,水体频率最高出现在哨马营-狼心山段河道两侧,其次是东居延海及其外围区域,东河、西河及西居延海水体频率相对较低;分水前河水漫溢主要是由自然水文过程引起的,同时也受到中游人类活动的较大影响,分水后河水漫溢与生态输水量呈显著正相关(P<0.01),下游年蒸发量和人类活动均与河水漫溢呈显著负相关(P<0.01)。建议兴建和修缮黑河下游水利设施,改善下游河水漫溢的时空分布不均性,保障下游生态系统的健康与安全。

长江下游桥区动态自适应自主航行决策方法

针对长江下游桥区环境复杂且时变,存在特殊航行规则、可航水域受限等问题,提出一种自主航行决策方法。在该类水域,基于数字化交通环境模型,结合导航模型、船舶操纵运动数学模型(MMG)、航向航迹控制方法构建自动航行模型。以航行规则和良好船艺为前提计算可行操纵区间,依靠时序滚动框架消除剩余误差和自适应目标船(TS)机动,求取自主航行决策方案。仿真结果表明:该方法能自适应时变环境,实现自适应多目标避让,并沿推荐航线安全通过,为桥区水域自主航行提供一种自适应的决策方法。

黄河下游近期来水来沙年内年际波动特征研究

为探究近20 a来黄河下游水沙新情势,基于花园口站1997—2020年实测资料,并对比同时段潼关站水沙数据,从趋势性、变异性、周期性、年内分布及水沙搭配5个方面,系统分析黄河下游来水来沙年内年际波动特征。结果表明,两站水量呈显著增加趋势、沙量呈显著减少趋势;潼关站水、沙量分别在2018年、2004年突变,花园口站水、沙量分别在2017年、2001—2002年显著突变;潼关站水、沙量变化主周期分别为14、13 a,平均周期为9.5 a,花园口站水、沙量变化主周期分别为13、12 a,平均周期为8 a;基于上述分析,将研究时段划分为5个阶段,各阶段两站流量年内分布不均匀度相近,经历了减小-增大的交替过程,含沙量年内分布有所差别;潼关站来沙系数、水沙系数分别呈逐阶段减小、增大趋势,花园口站来沙系数先减小后回升,水沙系数前期较小,Ⅱ—Ⅳ阶段增大,第Ⅴ阶段减小。在天然水沙变化与人工水沙调控综合作用下,近期黄河下游水沙过程呈明显的阶段性变化特征,水沙搭配总体相对较优。

长江上游关键区主汛期典型涝年气候成因辨析

为从更精细的角度分析长江上游主汛期典型涝年的降雨特征及气候成因,将长江上游分为5个关键区,利用长江上游1961~2021年282个雨量站逐日降雨资料,通过Morlet小波分析等方法分析长江上游及5个关键区主汛期降雨特征并找出长江上游典型涝年进行分类,最后对不同型降雨典型涝年的水汽输送及气候成因进行了探讨。研究表明:(1)长江上游与金沙江、长江上游干流降雨量的年际波动总体较为一致,异常涝年的出现时间也较为一致,嘉陵江、岷沱江流域年际波动的阶段性突变较为明显,乌江流域的年际波动则较为平稳;长江上游及5个关键区降雨量周期变化较为一致,均存在3 a左右的振荡周期。(2)长江上游典型涝年5个关键区降雨可分为3类,分别为关键区一致多型、关键区四多一少型及关键区三多两少型。(3)长江上游主汛期不同型降雨的水汽输送来源存在一定差异,关键区一致多型及关键区四多一少型水汽输送主要来自西太平洋及孟加拉湾,而关键区三多两少型水汽输送主要来自西太平洋及南海。(4)青藏高原积雪偏多有利于长江上游降水量偏多;关键区一致多型一般发生于暖海温向冷海温转折变化的年份,而关键区四多一少型及关键区三多两少型一般发生在冬季海温偏冷的年份。