Modeling for Inter-Basin Groundwater Transfer Identification: The Case of Upper Rift Valley Lakes and Awash River Basins of Ethiopia

Groundwater movement beneath watershed divide is one component of the hydrological cycle that is typically ignored due to difficulty in analysis. Numerical ground-water models, like TAGSAC, have been used extensively for predicting aquifer responses to external stresses. In this paper TAGSAC code was developed to identify the inter-basin groundwater transfer (IBGWT) between upper Awash River basin (UARB) and upper rift valley lakes basin (URVLB) of Ethiopia. For the identification three steady state groundwater models (for UARB, URVLB and for the two combined basins) were first created and calibrated for the 926 inventoried wells. The first two models are conceptualized by considering the watershed divide between the two basins as no-flow. The third model avoids the surface water divide which justifies IBGWT. The calibration of these three models was made by changing the recharge and hydrogeologic parameters of the basins. The goodness of fit indicators (GoFIs) obtained was better for the combined model than the model that describes the URVLB. Furthermore, the hydraulic head distribution obtained from the combined model clearly indicates that there is a groundwater flow that doesn’t respect the surface water divide. The most obvious effect of IBGWT observed in these two basins is that it diminishes surface water discharge from URVLB, and enhances discharge in the UARB. Moreover, the result of this study indicates potential for internal and cross contamination of the two adjacent groundwater.

Impact of transferred water on the hydrochemistry and water quality of surface water and groundwater in Baiyangdian Lake,North China

The hydrochemical composition of surface water and groundwater is a key parameter for understanding the evolution of water and its quality.In particular,little is known about the impact of transferred water on surface water and groundwater.In this study,Baiyangdian Lake was selected as a typical area for extensive groundwater exploration and surface water transfer in the North China Plain.Surface water and groundwater samples were sampled in dry/wet seasons and then analyzed before/after the water transfer,respectively.Generally,surface water and groundwater are extensively hydrologically connected based on hydrochemical evidence.It was found that the hydrochemical composition of the shallow groundwater is affected by the surface water and that the water quality of the deep groundwater is stable.However,inter-aquifer recharge processes from the shallow groundwater to the deep groundwater existed in the anthropogenic region impacted with high nitrate-ion concentrations.Also,the hydrochemical composition of the surface water and groundwater was dominated by rock-weathering and evaporation-precipitation processes.Due to the existence of the deep vadose zone in the alluvial fan,Na^(+)was exchanged into soil matrices during the leakage of the surface water.In addition,the transferred water resulted in surface water with good quality,and it also played as an important recharge source to groundwater.As the most important water resource for irrigation and drinking,deep groundwater should be paid more attention in the alluvial fan with frequent water transfer and extensive groundwater exploration.

Analysis of Asynchronism-Synchronism of Regional Precipitation in Inter-Basin Water Transfer Areas

The local characteristics of multi-dimensional modeling method of multivariate copula. A new modeling remedy this defect. Different types of copula distribution random variables are seldom considered in the general method, called pair-copula construction, is introduced to functions are allowed to be introduced in this method. Correspondingly, the related characteristics of complex multivariate can be described by a cascade of pair-copula acting on two variables at a time. In the analysis of asynchronism-synchronism of regional precipitation in WED inter- basin water transfer areas, the pair-copula construction method is compared with the general modeling method of mul- tivariate copula. The results show that the local dependence structure would exist among hydrologic variables even in three-dimensional cases. In this situation, the general modeling method of multivariate copula would face difficulties in fitting distribution. However, the pair-copula construction method could capture the local information of hydrologic variables efficiently by introducing different types of copula distribution functions. Moreover, the compensation ca- pacity of water resources is strong in different hydrological areas of WED water transfer project. The asynchronous frequency of wetness and dryness is 69.64% and the favorable frequency for water transfer is 46.15%.

西辽河平原地下水失衡及其与土地利用的互馈关系

西辽河平原是我国北方重要的生态屏障,但是生态环境脆弱。2004年以来农田灌溉用水增加,地下水水位持续下降。为查明区域地下水失衡、生态效应及其影响因素,开展了西辽河平原地下水水位统测和长期监测,采用空间相关性分析、水均衡分析、土地利用转移矩阵、对地下水水位变化贡献度分析等方法,分析了区域地下水均衡状况及其与土地利用的互馈关系。结果表明:西辽河平原2020年地下水水位比2004年平均下降2.23 m,地下水储存量年均减少10.90×10^(8) m^(3);平原中部农业集中灌溉区地下水水位下降幅度较大,尤其通辽科尔沁区地下水水位下降最为明显;西辽河平原地下水开采量对地下水水位下降的贡献度为33%,科尔沁区超过50%;地下水水位下降区水位埋深从4.71 m下降至8.34 m,导致草地退化,面积减少,覆盖度下降;西辽河平原地下水可持续开采量为24.28×10^(8) m^(3)/a。用于农业灌溉的地下水开采量增大是造成地下水水位下降的主要原因,为防止地下水水位持续下降,提出了提高节水灌溉能力,调整种植结构、引入外源水及压缩地下水开采量等综合治理建议。该研究成果可为区域农业种植规划、地下水管理与保护提供技术支撑。

南水北调前后北京平原区地下水和地面沉降演变特征

超量开采地下水引发的地面沉降已成为制约北京区域社会经济可持续发展的重要因素之一。2014年12月,南水北调中线工程正式通水,每年向北京输水超过10×10^(8)m^(3),改变了北京供水格局,也为地下水压采、涵养及控制地面沉降创造了条件。本文利用多种监测数据,分析南水进京前后,北京平原区地下水和地面沉降的变化;研究不同水位变化模式下不同岩性及深度土层的变形特征;计算土层不同变形阶段的弹性和非弹性储水率;并对黏性土层产生较大残余变形和滞后变形的原因进行了探讨。结果表明:①2015~2020年,平原区大部分地区第一至第四含水层组地下水位逐渐上升,地面沉降呈减缓的趋势。②第二和第三压缩层组是沉降主要贡献层,除平各庄和榆垡站外,其余各站第三压缩层组沉降占比逐渐增大,沉降主控层有向深部转移的规律。③平原区北部和东部,第二和第三压缩层组对应的地下水位由降转升。在水位下降阶段,土层呈塑性和蠕变变形;水位上升阶段,土层以塑性变形为主,部分时间出现弹性变形,具有黏弹塑性。平原区南部,地下水位始终持续下降,土层变形始终呈塑性和蠕变变形。含水砂层则主要呈弹性变形。④土层变形的不同阶段,弹性和非弹性储水率并不是恒定的,随着地下水位下降,储水率呈减小的趋势。⑤黏性土层存在较大残余变形和变形滞后的原因,一是非弹性储水率大于弹性储水率,二是黏性土层的弱渗透性。

邻接已建地下室深大基坑支护结构设计实践

随着城市地下空间开发利用的迅猛发展,临近甚至邻接已建地下结构的项目也越来越多,如何利用已有地下结构或其支护结构成为面临的新课题。本文以某综合体项目基坑支护设计为例,阐述了项目特点及支护结构选型,并根据项目特点,针对与已建地下室及原围护结构间传力转换体系、支锚刚度引起的变形协调和地下水处理等关键问题提出了处理措施。工程实践表明,利用已有地下结构作为支撑点是可行的,但需要考虑支撑计算长度引起的支锚刚度变化,其可通过调整支撑杆件布置、加强截面参数及覆板边桁架等措施实现。

Assessment of rehabilitation strategies for lakes affected by anthropogenic and climatic changes: A case study of the Urmia Lake, Iran

Over the last three decades,more than half of the world's large lakes and wetlands have experienced significant shrinkage,primarily due to climate change and extensive water consumption for agriculture and other human needs.The desiccation of lakes leads to severe environmental,economic,and social repercussions.Urmia Lake,located in northwestern Iran and representing a vital natural ecosystem,has experienced a volume reduction of over 90.0%.Our research evaluated diverse water management strategies within the Urmia Lake basin and prospects of inter-basin water transfers.This study focused on strategies to safeguard the environmental water rights of the Urmia Lake by utilizing the modeling and simulating(MODSIM)model.The model simulated changes in the lake's water volume under various scenarios.These included diverting water from incoming rivers,cutting agricultural water use by 40.0%,releasing dam water in non-agricultural seasons,treated wastewater utilization,and inter-basin transfers.Analytical hierarchy process(AHP)was utilized to analyze the simulation results.Expert opinions with AHP analysis,acted as a multi-criteria decision-making tool to evaluate the simulation and determine the optimal water supply source priority for the Urmia Lake.Our findings underscore the critical importance of reducing agricultural water consumption as the foremost step in preserving the lake.Following this,inter-basin water transfers are suggested,with a detailed consideration of the inherent challenges and limitations faced by the source watersheds.It is imperative to conduct assessments on the impacts of these transfers on the downstream users and the potential environmental risks,advocating for a diplomatic and cooperative approach with adjacent country.This study also aims to forecast the volumes of water that can be transferred under different climatic conditions—drought,normal,and wet years—to inform strategic water management planning for the Urmia Lake.According to our projection,implementing the strategic scenarios outlined could significantly augment the lake's level and volume,potentially by 3.57×109–9.38×109 m3 over the coming 10 a and 3.57×109–10.70×109 m3 in the subsequent 15 a.

基于迁移模型的土壤与地下水环境的综合利用风险标准评估

本研究以某化工企业为例,采用多层次土壤和地下水修复目标值计算模型(P20模型),结合实地监测数据和污染物迁移模拟,对场地进行了综合环境风险评估。研究采集了地下水样品,并通过对苯、氯苯、1,4-二氯苯等污染物的监测,发现区域内地下水受到较为严重的化学污染。通过Ogata Banks和Domenico模型的应用,模拟了污染物在地下水中的迁移趋势,为场地的治理与修复提供了科学依据。

风对砂土非饱和带水汽热运移规律影响研究

针对目前以非饱和带土体水汽热运移对类似铁路、公路工程以及污染物运移影响根本认识不足的问题,基于室内砂土土柱试验,开展了在一定热辐射条件下,考虑风速(0、0.56、1.44 m/s)对砂土非饱和带水汽热运移规律影响研究。结果表明:温度控制系统和风速控制系统工作以后,风速的增大一方面降低了土表的温度梯度,并减缓着水分的流失,另一方面加快土表水分的流失作用,2种机制共同影响着土体的含水率变化。蒸发速率受到温度梯度的影响,随着温度梯度以及基质势作用下气态水向上运移速率趋于稳定,土体的瞬时蒸发量在40 h之后也趋于稳定。总结的经验可供今后类似项目借鉴。

生态调水对民勤盆地地下水位变化的影响分析

民勤绿洲是河西走廊石羊河流域下游将巴丹吉林沙漠和腾格里沙漠分割的一块绿洲,对于这两大沙漠的合拢有着极其重要的意义,也对河西走廊的生态保障有着不凡的作用。本文基于GIS平台,利用石羊河流域智慧水资源管理平台采集的数据,分析了民勤盆地地下水位年内、年际变化特征和地下水位埋深的空间分布规律。结果表明,近5年内民勤盆地地下水位年内变化波动较大,年际变化相对平稳,处于回升状态,平均回升0.33 m。当地管理部门应继续合理规划水资源配比,以实现水资源的可持续发展。

Justification of public investment initiatives on water transfer systems as an instrument for water balances in Spain: the case of the Júcar–Vinalopówater transfer system

One of the most controversial issues in recent years in water management has been finding a balance between available resources and water needs related to certain territories. The changes brought about by a new awareness over the need to preserve the environment, the social perception of the ownership of the river channels, the need for adjust financial costs arising from the waterworks and the compliance with European standards urgently require redesign of water supply policies in force at this time. The Júcar-Vinalopó water transfer, considered as an historic aspiration for many years in the region, has been regarded as a key element for solving the depletion of groundwater in a large area located in the southeast of the Iberian Peninsula, mainly for irrigation purposes. In this paper we present an approach to the economic aspects related to the implementation of the project, its investment and financing arrangements and the question of the subsequent management with the impact of the well-known “recovery cost principle', highlighting the current difficulties in carrying out projects of this size, due to severe limitations, as social and economic conditions of the transfer.

生态输水对塔里木河中下游地表水及地下水水质的影响

在塔里木河流域生态输水工程背景下,以塔里木河流域地表水与地下水为研究对象,通过在塔里木河中上游、中游及下游设置固定监测样点,连续开展水域水质监测。结果表明:随着输水时间的延长,水体中pH呈先降低后增加的趋势,COD含量在输水中期和退水初期达到最高值,BOD5和NO_(2)^(-)N含量呈先增加后降低,易沉固体含量则呈持续降低趋势;生态输水期COD、BOD5和TP含量在地下水和地表水间差异不显著,输水结束后差异逐渐显著;中下游各区域地表水水质指标含量均高于地下水;BOD5含量、易沉固体含量在地表水与地下水间相关性极显著(P<0.01),地表水中易沉固体含量与地表水BOD5含量、地下水BOD5与地表水COD含量、地下水中易沉固体含量与地表水BOD5含量、COD含量之间均显著相关(P<0.05)。生态输水降低了流域中下游地表水及地下水pH和易沉固体含量,增加了水体中COD和BOD5含量,由生态输水造成的地表水对地下水水质的影响具有滞后效应。因此,在生态输水过程中要关注输水量控制,防止上中游灌区排水注入干流,保证中下游区域水环境良好,有效促进胡杨林生态系统恢复,实现生态输水工程的生态价值。

地下水停采后地面沉降区地下水氟的演化规律: 以沧州市为例

南水北调工程极大改善了我国北方的用水问题,进一步减少了深层地下水的开采量,缓解了华北平原地下水长期亏损的情况,但其对区域地下水水化学演化的影响尚未可知。以地面沉降典型分布区沧州市为研究对象,研究南水北调工程通水及地下水停采后对地下水水化学的影响。采集2017年及2021年区域第Ⅲ、Ⅳ层承压地下水样品,探究水化学特征,并通过SBAS-InSAR技术进一步评估区域年均地面形变量,分析地下水停采后区域水质及氟时空变化的影响。研究发现:压缩开采后深层地下水氟含量略微降低,高值区面积减小,高pH、TDS和ρ(HCO_(3)^(-)),低ρ(Ca^(2+))的地下水环境有利于氟的富集;水化学类型没有改变,地下水盐分含量升高,岩盐、萤石溶解更充分;同时,全区地面沉降量及沉降速率较南水北调工程实施前明显放缓,东南部存在小面积地面抬升区。地面沉降的减缓抑制了隔水层黏土压密释水,减弱黏土孔隙高氟水的直接释放,侧向径流补给占比上升,含水层得到的有效补给变多,使得区域地下水中氟浓度降低。但较长的水力停留时间及水岩相互作用,可促使沉积物蒸发岩溶解迁移进入地下水中,使得近海区域深层地下水中盐分含量升高。研究成果对沧州市饮用水安全和水资源管理提供了科学依据。

南水北调中线工程河南省受水城市地下水生态系统服务价值评估

选取南水北调中线工程河南省受水城市为典型研究区域,综合运用市场价值法、替代工程法和等效替代法等对南水北调中线工程河南省受水城市2008—2019年地下水生态系统服务价值进行评估。结果表明:河南省11个受水城市中,地下水生态系统服务价值最高的是郑州市,变化较为稳定的是平顶山市、漯河市和许昌市,变化最剧烈的是鹤壁市。郑州市2019年地下水生态系统服务价值为213.17亿元,其中,调节服务价值最高,支持服务和供给服务价值次之,社会服务价值最低;在各指标中水源涵养指标占总价值比例最高,预防地面沉降指标次之,科研教育指标占比最小。河南省受水城市2008—2019年多年平均生态系统服务价值为1030.37亿元,变化趋势为先下降后上升,转折点出现在2013年,原因是地下水压采、南水北调中线工程置换地下水、植树造林、水土保持等措施增加了地下水资源量。研究结果可为南水北调中线工程受水城市生态环境效益评价及地下水保护提供参考依据。

渗流作用下的中深层地埋管换热器传热分析

考虑地下水渗流的影响,基于移动线热源模型提出一种中深层地埋管换热器半解析模型。基于Fluent软件建立数值模型,并对已知进口流体温度和已知总热输入功率两种边界条件下的数值模型、半解析模型和忽略渗流的半解析模型进行对比。结果发现,两种边界条件下的半解析模型在前期均具有较大误差,而在中后期均与数值模型吻合得较好,其精度高于忽略渗流的半解析模型,尤其是在地下水渗流速度较大的时候。结果表明所提出的半解析模型可用于分析渗流作用下的中深层地埋管传热。

单井U型地埋管换热器传热特性与热渗耦合特性分析

在“双碳”目标下,浅层地热能供暖(冷)作为一种新型的清洁能源利用形式得到广泛使用。为提高浅层地热能的利用效率,以我国北方某综合能源供暖(冷)项目土壤源热泵系统为研究对象,构建单井U型地埋管换热器的三维非稳态传热模型,并利用Fluent软件分析其传热特性与热渗耦合特性。选取4.0,4.5,5.0 m等3个不同埋管间距和106.0,113.0,120.0 m等3种不同埋管深度,对地埋管换热器的换热总量及单位井深换热量分别进行对比分析。分析结果表明,埋管间距为4.0 m、埋管深度为106.0 m时,单井地埋管换热器的换热效果最佳。对无渗流和有渗流及不同渗流速度下地埋管换热器温度场进行对比分析,结果表明,地下水渗流会对地埋管换热器换热效率带来正向影响,并且随着渗流速度的增加,换热效果更好。上述分析为实际工程的地埋管方案设计提供参考依据。

Implications of Declining Ground Water and Water Quality in the Greater Okefenokee Swamp Basin for Survival and Recovery of Federally Endangered and Threatened Marine and Aquatic Species and Critical Habitat in the US Southeastern Coastal Plain Ecoregion—Part 2

The Floridan aquifer system underlies the United States (US) Southeastern Coastal Plain Physiographic Region. Anthropogenic groundwater declines in that regional karst aquifer system, via semi-confining zones, have been documented in published literature for decades. These anthropogenic groundwater declines reduce surfacewater levels and flows, which increases saltwater intrusion and alters the physical, chemical, and biological integrity of the nation’s waters, in violation of the US Clean Water Act (CWA) of 1972. Historic groundwater declines from mining and other anthropogenic groundwater withdrawals from this regional karst aquifer system already threaten the survival and recovery of marine and aquatic federally endangered and threatened species, as well as existing and proposed critical habitat for those species within the Southeastern Coastal Plain Ecoregion. Examples of marine and aquatic species and their designated critical habitat adversely affected by groundwater declines in the Greater Okefenokee Swamp Basin of this ecoregion include the federally endangered south Atlantic Distinct Population Segments (DPS) of the Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus), shortnose sturgeon (Acipenser brevirostrum), and oval pigtoe mussel (Pleurobema pyriforme), as well as the federally threatened Gulf subspecies of the Atlantic sturgeon (Acipenser oxyrinchus desotoi) and Suwannee moccasinshell (Medionidus walkeri). In 2020, rules were adopted by two federal agencies allowing significant further degradation of the physical, chemical, and biological integrity of the nation’s waters that are essential for maintaining federally listed species and their habitat in this Ecoregion. The US Fish and Wildlife Service (USFWS) has acknowledged the harm to these species and critical habitat from mining and additional groundwater alterations, but no comprehensive Areawide Environmental Impact Statement (AEIS), similar to the AEIS required for mining within the Peace River Basin, has been conducted for any of the numerous mining projects that are expanding and proposed within the Greater Okefenokee Swamp Basin to evaluate all indirect and cumulative adverse impacts to all federally listed species.

塔里木河下游地下水位对植被的影响

对塔里木河下游断流河道2000～2002年9个地下水监测断面和18个植被样地的实地监测资料分析表明,地下水埋深对天然植被的组成、分布及长势有直接关系.地下水位的不断下降和土壤含水率大大丧失是引起塔里木河下游植被退化的主导因子.塔里木河下游的四次输水对其下游地下水位抬升起到了积极作用,河道附近地下水位呈逐级抬升过程,横向影响范围达1000 m左右,纵向上,表现为上段地下水抬升幅度较大(达84%),下段抬升幅度较小(6%).随着地下水位的抬升,天然植被的响应范围由第一次输水后的200～250 m,扩展到第四次输水的800 m.

基于多匝环形线圈的核磁共振信号响应计算与试验研究

核磁共振接收信号的质量主要受探测天线的传递特性影响,当传递特性较差时,严重影响测量效果.结合目前国内外核磁共振找水仪天线的研制情况,给出了接收天线传递特性的计算方法,根据数值计算结果讨论了影响传递特性的天线参数.利用吉林大学研制的核磁共振找水仪进行实际测试,结果证明与讨论结果一致.本文得出的传递特性影响因素和接收信号质量评估方法,可以为不同类型核磁共振找水仪天线的设计提供依据,将促使核磁共振方法在复杂地形环境找水及隧道、矿井灾害水源探测等方面得到有效应用.

大型水源地开采地下水导致的盐分迁移和污染

以河南省新乡市为例,通过分析地下水渗流、水化学和同位素的时空特征,对大型水源地长期开采地下水所导致的溶质迁移进行了研究。研究表明,大型水源地长期集中开采地下水,形成了较大面积和较深的地下水位降落漏斗,改变了地下水自北部山前冲洪积斜地向南部的冲积平原渗流的运动格局,地下水中盐分和污染物随着地下水渗流而迁移,北部污染严重的地下水和南部微咸水都向漏斗区运移。因此,双向迁移的结果,使得水源地附近水质变差,污染程度加重。