Three-Dimensional Tidal Model and Its Application to Numerical Simulation of Water Quality in Coastal Waters

The turbulence mechanism plays an important part in the mixing process and momentum transfer of turbulence. A three-dimensional Prandtl mixing length tidal model has been developed to simulate tidal flows and water quality. The eddy viscosities and diffusivities are computed from the Prandtl mixing length model. In order to model the water quality of an estuary or coastal area many interdependent processes need to be simulated. These may be conveniently separated into three main groups: transport and mixing processes, biochemical interaction of water quality variables and the utilization and re-cycling of nutrients by living matter. The model simulates full oxygen and nutrient balance, primary productivity and the transport, reaction mechanism and fate of pollutants over tidal time-scales. The model is applied to numerical simulation of tidal flows and water quality in Dalian Bay. The model has been calibrated against a limited data set of historical water quality observations and in general demonstrates excellent agreement with all available data.

A Three-Dimensional Water Quality Model and Its Application to Jiaozhou Bay, China

A three-dimensional coupled physical and water quality model was developed and applied to the Jiaozhou Bay to study water quality involving nutrients, biochemical oxygen demand, dissolved oxygen, and phytoplankton that are closely related to eutrophication process. The physical model is a modified ECOM-si version with inclusion of flooding/draining processes over the intertidal zone. The water quality model is based on WASP5 which quantifies processes governing internal nutrients cycling, dissolved oxygen balance and phytoplankton growth. The model was used to simulate the spatial distribution and the temporal variation of water quality in the Jiaozhou Bay for the period of May 2005 to May 2006. In addition, the effect of reduction of riverine nutrients load was simulated and evaluated. The simulated results show that under the influence of nutrients discharged from river, the concentrations of nutrients and phytoplankton were higher in the northwest and northeast of the bay, and decreased from the inner bay to the outer. Affected by strong tidal mixing, the concentrations of all state variables were vertically homogeneous except in the deeper regions where a small gradient was found. Obvious seasonal variation of phytoplankton biomass was found, which exhibited two peaks in March and July, respectively. The variation of riverine waste loads had remarkable impact on nutrients concentration in coastal areas, but slightly altered the distribution in the center of the bay.

Three-dimensional physical simulation and optimization of water injection of a multi-well fractured-vuggy unit

With complex fractured-vuggy heterogeneous structures, water has to be injected to facilitate oil pro- duction. However, the effect of different water injection modes on oil recovery varies. The limitation of existing numerical simulation methods in representing fractured- vuggy carbonate reservoirs makes numerical simulation difficult to characterize the fluid flow in these reservoirs. In this paper, based on a geological example unit in the Tahe Oilfield, a three-dimensional physical model was designed and constructed to simulate fluid flow in a fractured-vuggy reservoir according to similarity criteria. The model was validated by simulating a bottom water drive reservoir, and then subsequent water injection modes were optimized. These were continuous （constant rate）, intermittent, and pulsed injection of water. Experimental results reveal that due to the unbalanced formation pressure caused by pulsed water injection, the swept volume was expanded and consequently the highest oil recovery increment was achieved. Similar to continuous water injection, intermit- tent injection was influenced by factors including the connectivity of the fractured-vuggy reservoir, well depth, and the injection-production relationship, which led to a relative low oil recovery. This study may provide a constructive guide to field production and for the devel- opment of the commercial numerical models specialized for fractured-vuggy carbonate reservoirs.

Three-Dimensional Water-Quality Simulation for River Based on VOF Method

In the present study, considering the transport and transformation processes of variables, a threedimensional water quality model for the river system was established, which coupled the volume of fluid(VOF) method with the k-ε turbulence mathematical model. Then, the water hydrodynamic characteristics and transport processes for BOD_5, NH_(3^-)N and TP were analyzed. The results showed that the water surface of convex bank was a little lower than that of concave bank due to the centrifugal force near the bend, and most concentrations were inferior to the type Ⅴ standard indexes of surface water environmental quality. The model validation indicated that the errors between the simulated and monitored values were comparatively small, satisfying the application demands and providing scientific basis and decision support for the restoration and protection of water quality.

The 3D simulation and optimized management model of groundwater systems based on eco-environmental water demand

Through the study of mutual process between groundwater systems and eco-environmental water demand, the eco-environmental water demand is brought into groundwater systems model as the important water consumption item and unification of groundwater抯 economic, environmental and ecological functions were taken into account. Based on eco-environmental water demand at Da抋n in Jilin province, a three-dimensional simulation and optimized management model of groundwater systems was established. All water balance components of groundwater systems in 1998 and 1999 were simulated with this model and the best optimal exploitation scheme of groundwater systems in 2000 was determined, so that groundwater resource was efficiently utilized and good economic, ecologic and social benefits were obtained.

Three-dimensional numerical modelling of water quality in Dahuofang Reservoir in China

A three-dimensional eutrophication model was applied to assist the management of Dahuofang Reservoir in China.Transport processes were obtained from the three-dimensional,finite volume hydrodynamic model.The hydrodynamic model was verified for a one-year time period in 2006.Our simulation reproduced intra-annual variation of stratification.The simulated variation of vertical thermal structures also matched observations.The water quality model included 8 state variables,including dissolved oxygen,phytoplankton as carbon,carbonaceous biochemical oxygen demand,ammonium nitrogen,nitrate and nitrite nitrogen,ortho-phosphorus,organic nitrogen,and organic phosphorus.Sensitivity of the parameters has been analyzed to decide which process would affect the water quality in the simulation.The water quality verification suggested the model successfully computed the temporal cycles and spatial distributions of key water quality components.The comparison between water quality components before and after the first phase of the water conveyance project suggests that the project has a slight effect on the reservoir ecosystem.The model could be used as a tool to guide physico-biological engineering design or management strategies for Dahuofang Reservoir.

Simulation of water temperature distribution in Fenhe Reservoir

In order to evaluate the need of controlling the temperature of water discharged from the Fenhe Reservoir, the reservoir water temperature distribution was examined. A three-dimensional mathematical model was used to simulate the in-plane and vertical distribution of water temperature. The parameters of the model were calibrated with field data of the temperature distribution in the Fenhe Reservoir. The simulated temperature of discharged water is consistent with the measured data. The difference in temperature between the discharged water and the natural river channel is less than 3 ℃ under the current operating conditions. This will not significantly impact the environment of downstream areas.

Water resource utilization characteristics and driving factors in the Hainan Island

The scarcity of water resources caused by the unique topography and uneven rainfall distribution in Hainan Island has become a major factor restricting local development. In order to provide effective and scientific reference basis for the overall water resource utilization status and solving this problem, this study calculated the water resource utilization situation of Hainan Island from 2017 to 2021 in detail using methods including water resource ecological footprint analysis. Furthermore, a spatial correlation analysis was conducted to examine the island's water resource utilization characteristics, and the driving factors behind the changes in water resource utilization over the past five years were analyzed using the LMDI model. The results show that:(1) During the study period, the water resource ecological footprint in Hainan Island exhibited a slow growth trend, while the ecological carrying capacity showed a downward tendency.The per capita ecological deficit of water resources remains relatively high, and the water consumption per 10 000 yuan GDP in the whole land continues to decrease, indicating that the overall pressure on water resource demand remains high with significant regional differences accompanied by the efficiency of water resource utilization steadily improving at the same time;(2) Agricultural water use accounts for the highest proportion in the entire water use structure, while ecological water use represents the smallest share, with a year-on-year increase, indicating that Hainan Island highlights the agricultural development and is increasingly conscious of the ecological environment;(3) Significant spatial differentiation in water resource utilization characteristics exists in Hainan Island, with the western region being a hot spot aggregation area for per capita water resource ecological footprint, per capita ecological carrying capacity of water resources, water consumption per 10 000 yuan GDP, while it is a cold spot cluster area for per capita ecological deficit of water resources. The opposite holds true for the eastern region of Hainan Island;(4) Economic and technological factors have a major impact on the changes in water resource ecological footprint within the designated area. Among them, economic factors drive the growth of the water resource ecological footprint in Hainan Island, and exacerbate local water resource consumption, while technological factors negatively contribute to the amount of water resource utilization in Hainan Island, indicating that advanced technology has improved water resource utilization efficiency and significantly reduced water resource consumption.

基于BP-DEMATEL的山西省冬小麦水足迹影响因素识别

针对山西省冬小麦水足迹历史演变及关键影响因素识别问题,分析了1993—2021年山西省冬小麦水足迹历史演变规律,利用BP神经网络-决策实验室(BP-DEMATEL)模型对冬小麦水足迹演变的关键影响因素进行识别,将其分为驱动型因素及特征型因素,并揭示了影响因素之间的作用机制。结果表明:1993—2021年山西省冬小麦水足迹及单位水足迹均呈下降趋势;2021年山西省冬小麦总水足迹为27亿m^(3)(蓝水占比57%),单位水足迹为1 122 m^(3)/t,与前期高点相比分别下降38%(较1994年)和21%(较1993年);气温、相对湿度和灌溉面积为冬小麦水足迹演变的关键驱动型因素,化肥施用量和农业机械总动力为关键特征型因素。

黄河流域关中平原城市群水资源利用效率与公平性评价

为提高黄河流域城市群水资源利用效率与公平性,推动黄河流域生态保护与高质量发展,以关中平原城市群为例,在采用水足迹与水行星边界方法分析水资源可持续利用水平的基础上,运用超效率SBM模型与GML指数探讨了城市群的水资源利用效率,并利用基尼系数与贡献系数评价了用水公平程度对城市群的影响。结果表明:2010—2019年,关中平原城市群水足迹、水赤字和灰水足迹分别下降了4.52%、3.62%和59.79%,水资源的不可持续性和水污染状况得到改善;水资源利用效率不高且未呈现增长趋势,技术效率与技术进步之间未实现良性互动;水资源占用相对公平,但水污染同城市发展及水资源承载能力之间的公平程度均有明显下降。

基于系统动力学模型的山东省水资源生态足迹预测

在资源环境可持续发展和生态文明建设得到重视的时代,水资源的供需均衡是衡量一个区域社会经济发展的重要因素,而与水资源有关的生态足迹相关概念被越来越多的专家和学者所采用,是一个具有关键意义的衡量指标。然而,在这方面的研究中,现有学者主要集中于现状的分析与探讨,缺乏对未来的预测。经济蓬勃、人口稠密的山东省存在由于社会经济的快速发展而导致的水资源供需紧张的问题,亟需寻求保障水资源和社会经济协调发展的可持续方案。根据水资源生态足迹模型和山东省水资源供需系统动力学模型,设计SD1 (维持现状)、SD2(发展经济)、SD3 (节约用水)和SD4 (综合开发)等情景对2022-2050年山东省水资源生态足迹和生态承载力进行预测。结果表明,2022-2050年情景SD1~SD4下山东省水资源的人均生态足迹的平均数值分别为0.408、0.447、0.319和0.412 hm^(2)/人,水资源的人均生态承载力的平均数值都为0.130 hm^(2)/人,由此导致0.278、0.317、0.189和0.282 hm^(2)/人的人均水资源生态亏损;水资源生态压力指数和水资源生态经济协调指数均值分别为3.149、3.458、2.466和3.188及1.257、1.242、1.304和1.259,山东省未来情景下水资源利用压力较大,不安全利用的状态将会持续。从水资源生态足迹的角度对4种情景进行比较,综合发展型情景SD4具有合适的评价指标,既能保证经济发展,也能减少水资源利用的不安全程度,山东省未来发展应采取此类情景,但同时要提高各行业用水效率、加强全社会节水意识,既“开源”又“节流”,才能保障水资源的可持续发展。

基于LMDI模型的湖北省农业水足迹时空分布与驱动力研究

结合水足迹理论和传统农业用水核算方法,分析2005—2020年湖北省各市州农业水足迹时空演变特征,并利用LMDI模型对农业水足迹变化量进行驱动力因素分解。结果表明:1)湖北省农业水足迹呈现先上升再下降的波动趋势;湖北省各市州农业水足迹存在明显的时空分布差异,这是自然因素和经济因素共同作用的结果。2)各驱动力对湖北省农业水足迹变化的影响程度为经济效应>技术效应>人口效应,经济效应对农业水足迹变化量的贡献值,达53.72%,技术效应和人口效应的贡献值分别为32.86%和13.42%;其中,经济效应对农业水足迹起正向驱动作用,技术效应和人口效应对农业水足迹起到反向驱动的作用。研究结论拓展了长江流域农业水足迹及驱动力分析,同时对于提高农业可持续发展、增加农业用水效率有指导意义。

基于足迹家族的银川市产业可持续发展评价

为积极响应黄河流域生态保护和高质量发展先行区建设,探究银川市各产业资源开发力度及可持续发展状况,通过足迹家族计算方法量化2011—2020年银川市各产业足迹,并利用资源环境压力指数法及Tapio脱钩模型对银川市产业可持续发展状况进行评价,最后采用对数平均迪氏指数法(LMDI)对各产业驱动机制进行分析。结果表明:1)近10年银川市水足迹呈现“V”型变化趋势,2016年达到最低值1.03×106 hm^(2),水足迹主要以农业为主,占70%以上;银川市碳足迹与生态足迹呈现逐步上升趋势,工业在碳足迹与生态足迹中均占主导地位,分别占95%和85%左右。2)水资源压力指数整体呈现“V”型变化趋势,最大值与最小值相差约3倍;碳排放压力指数呈现倒“L”型变化趋势,2019年压力指数达到最大值220;生态压力指数呈现“波浪”型上升趋势,2020年压力指数接近220,表明资源环境压力在逐步上升。3)农业可持续发展评价整体表现良好,工业整体表现为较差,生活及生态产业呈现良好至差的态势。4)各产业环境承载力和足迹生产效益因素对产业发展具有促进作用,水资源消耗量、碳排放量和环境污染程度分别对农业、工业、生活及生态产业起主要抑制作用。研究表明,银川市农业足迹变化幅度不大且经济发展迅速,可持续发展趋势良好;工业资源环境压力大幅上升且经济上升缓慢,不利于可持续发展;生活及生态产业资源环境压力上升速率大于经济发展速率,可持续发展能力逐步下降。

长江流域水资源利用效率及影响因素研究--基于Shephard水资源距离函数

分析长江流域水资源利用效率、时空分布特征及影响因素,对于解决长江流域水资源问题和促进长江经济带发展至关重要。为科学评价长江流域水资源利用效率及空间分布差异,以2012—2020年长江流域11个省(市、自治区)为研究对象,构建Shephard水资源距离函数的随机前沿模型,对长江流域水资源利用效率及影响因素进行实证分析并探究长江流域水资源利用效率时空分异特征。研究表明:1)通过计算水足迹发现,长江流域各省水足迹消费总量趋于稳定,上游省份用水量较少,中下游省份水资源消费量较大,省际水足迹总量差异显著,农业生产是水足迹主要的来源,其次是工业用水;2)运用Shephard水资源距离函数的随机前沿模型计算长江流域水资源利用效率发现,省与省之间差异显著,空间上呈现“中游低,上下游高”的特征,并有逐年降低的趋势;2012—2020年上游省份水资源利用效率自西向东递减,中下游省份水资源利用效率在低水平上保持稳定并有降低趋势;3)选取的影响因素指标系数均通过了显著性检验,水资源禀赋的系数显著为负,表明人均水资源拥有量提高对长江流域水资源利用效率有正向促进作用;经济发展水平的系数显著为负,表明经济发展对水资源效率提升有推动作用;城镇化率的系数显著为负,表明城镇化水平越高,水资源的利用效率高,但影响程度较低;而第三产业占GDP的比重的系数显著为正,表明产业结构调整对水资源利用效率起抑制性作用。最后针对研究结果,提出以下对策建议:建立跨部门协调机制,加强水资源管理和监测;推动区域合作,加强信息共享;优化产业结构,促进可持续发展。

基于灰水足迹的长江经济带耕地利用生态效率时空分异特征

长江经济带面临水生态环境污染制约下的农业发展困境,水环境约束下耕地利用生态效率的提升成为平衡耕地利用中经济效益与生态效益的关键手段,对于探索生态可持续的耕地利用模式、实现农业绿色发展具有重要意义。该研究以灰水足迹为视角,基于SBM-Undesirable模型、空间自相关分析及马尔可夫链模型探明2000—2020年长江经济带耕地利用生态效率时空格局及演变趋势。研究表明:1)长江经济带2000—2020年平均灰水足迹值呈现先增后减趋势,2015年后下降态势更为明显。在空间上呈现为“东西高,中部低”的空间分布特征,灰水足迹高值区域主要集中在粮食主产区省份。2)2000—2020年长江经济带耕地利用生态效率持续下降,效率均值处于0.5~0.8之间,存在较大提升空间。在空间上呈现高值区域多沿水系分布的特点。3)长江经济带市域耕地利用生态效率存在显著空间正相关性,以研究时段演变趋势来看,耕地利用生态效率的演进存在路径依赖,难以实现“跨越式”提升。因受到邻域背景影响,在空间上易显现出“俱乐部收敛”现象,“高-高集聚”与“低-低集聚”分布更为常见。可在农业生产重点区域采用差异化精准农业模式,需重视区域间动态协同发展,完善联防联治的面源污染防控机制,积极引导耕地利用生态效率高值区域逐步形成集中连片,同时对于耕地利用生态效率低效区提供财政与政策支持。研究结果可为各地区探索耕地利用可持续发展模式与农业生产活动中水生态环境保护提供参考依据。

Melt Evolution above a Spontaneously Retreating Subducting Slab in a Three-Dimensional Model

Dehydration of the subducting slab favors the melting of the surrounding mantle. Water content and melt evolution atop a spontaneously retreating subducting slab are reported in a three- dimensional （3-D） model. We find that fluids, including water and melts in the rocks, vary substantially along the trench, which cannot be found in two-dimensional （2-D） models. Their maxima along the subducting slab are mainly located at about 50 to 70 and 120 to 140 kin. Volumetric melt production rate changes spatially and episodically atop the slab, which may reflect the intensity and variations of volcanoes.

河北省水资源生态足迹分析与预测

科学预测河北省未来的水资源生态足迹和生态承载力,对于区域水资源可持续利用具有重要意义。利用系统动力学(SD)法和生态足迹模型构建河北省水资源利用SD模型,设计现状延续型情景ES1、经济发展型情景ES2、节约用水型情景ES3和协调发展型情景ES4等4类不同发展情景,对现状(2006~2021年)和未来(2022~2050年)水资源生态足迹进行评价与预测。结果表明:①对于现状年份,人均水资源生态足迹呈缓慢下降趋势,人均水资源生态承载力呈波动变化,水资源处于生态赤字,表明水资源利用处于不安全状态,但水资源利用效率越来越高。②对于预测年份,4类发展情景的人均水资源生态足迹和水资源生态压力指数均呈增长趋势,水资源均处于生态赤字,并且亏损程度逐年严重。虽然万元GDP水资源生态足迹均呈下降趋势,未来的水资源利用效率越来越高,但未来水资源利用压力仍过大。③情景ES4是最适宜的情景,既能以适当的速度保证河北省未来社会经济发展,又能降低水资源生态压力。河北省在未来水资源利用过程中,需从多方面采取积极行动,以确保水资源可持续利用发展。

基于SD模型的张掖盆地水资源生态足迹核算与预测

根据水资源生态足迹模型,通过构建张掖盆地水资源利用SD模型,设计5类不同情景来核算和预测现状(2000—2020年)和未来(2021—2050年)张掖盆地水资源生态足迹和生态承载力。结果表明:对于现状,人均水资源生态足迹、生态承载力和生态盈亏均值分别为3.517、0.272和-3.245 hm^(2)/人,水资源生态压力指数和生态足迹强度均值分别为12.969和2.822 hm^(2)/104元;农业用水在张掖盆地水资源生态足迹核算中占绝对优势但占比在下降,农业领域是节水的重点且潜能较大;水资源生态足迹强度明显下降(降幅90.21%),证明了张掖盆地用水效率的上升;张掖盆地的水资源利用压力较大。平均而言,预测期内张掖盆地不同情景中人均水资源生态足迹均大于人均水资源生态承载力,由此导致人均水资源生态亏损的出现;各情景下水资源生态压力指数和生态足迹强度均值分别为12.932、13.483、10.055、12.698和9.846及0.281、0.206、0.201、0.281和0.196 hm^(2)/104元,未来时间里张掖盆地的水资源利用仍然处于不安全的状态。2021—2050年张掖盆地无法有效缓解水资源利用紧张的状况,需采用经济发展与水资源保护兼顾的发展方案,推荐政府部门采用情景ZS 5。因此,张掖盆地未来水资源利用需要全社会、各部门的通力合作,不断提高水资源利用效率,大力推进节约用水措施和技术的普及与应用,才能确保水资源的可持续利用。

中国灰水和碳足迹减污降碳空间联合网络研究

当前,中国面临着污染治理与碳减排的双重挑战,减污降碳成了社会经济绿色转型的重要抓手。该文以减污降碳为背景,利用2012年和2017年多区域投入产出表,分析2012年和2017年中国30个地区间贸易产生的灰水足迹与碳排放量,并采用社会网络分析法,从网络关系的视角,对2012年和2017年省际间灰水足迹和二氧化碳空间联合网络特征进行实证分析。结果表明:(1)山东、河南和江苏等经济规模较大的地区灰水足迹和碳排放量较大,海南、青海和宁夏等经济规模较小的地区灰水足迹和二氧化碳排放较小。(2)山西和内蒙古是主要的灰水足迹和碳排放净流出区域,广东、浙江和江苏是主要的灰水足迹净流入区域,地区发展和交通因素是灰水足迹和碳排放流动差异的主要原因。(3)在2012年和2017年中国省际灰水足迹和二氧化碳的空间联合关系中,所有地区均处于空间网络中。个体特征表明,西北经济规模较小的地区以溢出效应为主,经济规模较大的地区以接收其他地区的溢出关系为主,这是产品或服务流动导致的。研究结果可为制定科学的水资源管理和碳减排政策提供依据。

基于生态足迹模型的民乐县水资源可持续利用分析

本文利用水资源生态足迹模型,以干旱少雨、经济落后的民乐县作为研究对象,从农业、工业、生活、生态4个用水账户出发,计算和分析了民乐县2015—2022年的水资源生态足迹和水资源生态承载力,并以此为基础,对水资源生态盈亏、压力指数及万元GDP水资源生态足迹值进行计算,评价分析了民乐县在此期间的水资源可持续利用状态。研究结果表明,民乐县水资源生态亏损程度严重,水资源整体上处于不可持续利用状态,安全程度极低。从计算的生态用水足迹值来看,民乐县目前的用水比例不利于生态环境的改善;由计算的万元GDP水资源生态足迹值可知,民乐县水资源利用效率不高,必须采取措施扭转目前的不利局面。分析结果可为县级层面的区域水资源利用和管理提供参考。