消除气压效应估算黄土潜水的蒸发蒸腾强度

潜水蒸发蒸腾（ET_g）是干旱半干旱地区浅埋深地下水最主要的排泄方式,也是地下水系统中重要的均衡项。如果存在气压效应,用于估算地下水蒸发蒸腾强度的传统水位波动法则不适用。以黄土潜水为例,提出了一种基于水位变化和大气压变化规律的水位图方法,用于消除气压效应以获取潜水蒸发蒸腾强度。研究表明,大气压变化通常在午夜前,一般为22:00—24:00,会出现一个峰值,该时间段气压效应可以忽略,而且潜水蒸发蒸腾强度最小,此时潜水位的变化速率相当于净补给速率;在获取潜水净补给强度后,选择第二个时间段,0:00—4:00,此时潜水蒸发蒸腾强度最小,且气压一般处于连续下降阶段,可以用来估算气压效应系数。在此基础上,可利用水位均衡和水位波动法方便地估算潜水蒸发蒸腾强度。该方法数据获取容易,估算结果也较为准确。     

Application of MODFLOW and geographic information system to groundwater flow simulation in North China Plain, China

MODFLOW is a groundwater modeling program. It can be compiled and remedied according to the practical applications. Because of its structure and fixed data format, MODFLOW can be integrated with Geographic Information Systems (GIS) technology for water resource management. The North China Plain (NCP), which is the politic, economic and cultural center of China, is facing with water resources shortage and water pollution. Groundwater is the main water resource for industrial, agricultural and domestic usage. It is necessary to evaluate the groundwater resources of the NCP as an entire aquifer system. With the development of computer and internet information technology it is also necessary to integrate the groundwater model with the GIS technology. Because the geological and hydrogeological data in the NCP was mainly in MAPGIS format, the powerful function of GIS of disposing of and analyzing spatial data and computer languages such as Visual C and Visual Basic were used to define the relationship between the original data and model data. After analyzing the geological and hydrogeological conditions of the NCP, the groundwater flow numerical simulation modeling was constructed with MODFLOW. On the basis of GIS, a dynamic evaluation system for groundwater resources under the internet circumstance was completed. During the process of constructing the groundwater model, a water budget was analyzed, which showed a negative budget in the NCP. The simulation period was from 1 January 2002 to 31 December 2003. During this period, the total recharge of the groundwater system was 49,374 × 10⁶ m³ and the total discharge was 56,530 × 10⁶ m³ the budget deficit was −7,156 × 10⁶ m³. In this integrated system, the original data including graphs and attribution data could be stored in the database. When the process of evaluating and predicting groundwater flow was started, these data were transformed into files that the core program of MODFLOW could read. The calculated water level and drawdown could be displayed and reviewed online.     

Groundwater flow modelling of Hindon-Yamuna interfluve region, Western Uttar Pradesh

The study area Hindon -Yamuna interfluve region is underlain by a thick pile of unconsolidated Quaternary alluvial deposits and host multiple aquifer system. Excessive pumping in the last few decades, mainly for irrigation, has resulted in a significant depletion of the aquifer. Therefore, proper groundwater management of Hindon-Yamuna interfluve region is necessary. For effective groundwater management of a basin it is essential that careful zone budget study should be carried out. Keeping this in view, groundwater flow modelling was attempted to simulate the behavior of flow system and evaluate zone budget. Visual MODFLOW, pro 4.1 is used in this study to simulate groundwater flow. The model simulates groundwater flow over an area of about 1345 km² with a uniform grid size of 1000 m by 1000 m and contains three layers, 58 rows and 37 columns. The horizontal flows, seepage losses from unlined canals, recharge from rainfall and irrigation return flows were applied using different boundary packages available in Visual MODFLOW, pro 4.1. The river — aquifer interaction was simulated using the river boundary package. Simulated pumping rates of 500 m³/day, 1000 m³/day and 1500 m³/day were used in the pumping well package.The zone budget for the steady state condition of study area indicated that the total annual direct recharge is 416.10 MCM and the total annual groundwater draft through pumping is of the order of 416.63 MCM. Two scenarios were considered to predict aquifer system response under different conditions. Sensitivity analysis on model parameters was conducted to quantitatively evaluate the impact of varying model inputs. Based on the results obtained from the sensitivity analysis, it was found that the model is more sensitive to hydraulic conductivity and recharge parameter. Present study deals with importance of groundwater modelling for planning, design, implementation and management of groundwater resources.     

Review: Current and emerging methods for catchment-scale modelling of recharge and evapotranspiration from shallow groundwater

A review is provided of the current and emerging methods for modelling catchment-scale recharge and evapotranspiration (ET) in shallow groundwater systems. With increasing availability of data, such as remotely sensed reflectance and land-surface temperature data, it is now possible to model groundwater recharge and ET with more physically realistic complexity and greater levels of confidence. The conceptual representation of recharge and ET in groundwater models is critical in areas with shallow groundwater. The depth dependence of recharge and vegetation water-use feedback requires additional calibration to fluxes as well as heads. Explicit definition of gross recharge vs. net recharge, and groundwater ET vs. unsaturated zone ET, in preparing model inputs and reporting model results is necessary to avoid double accounting in the water balance. Methods for modelling recharge and ET include (1) use of simple surface boundary conditions for groundwater flow models, (2) coupling saturated groundwater models with one-dimensional unsaturated-zone models, and (3) more complex fully-coupled surface-unsaturated-saturated conceptualisations. Model emulation provides a means for including complex model behaviours with lower computational effort. A precise ET surface input is essential for accurate model outputs, and the model conceptualisation depends on the spatial and temporal scales under investigation. Using remote sensing information for recharge and ET inputs in model calibration or in model–data fusion is an area for future research development. Improved use of uncertainty analysis to provide probability bounds for groundwater model outputs, understanding model sensitivity and parameter dependence, and guidance for further field-data acquisition are also areas for future research.     

北京房山应急水源地地下水数值模拟及河流渗漏量预测

以北京房山岩溶水应急水源地为例,采用等效连续介质体概化地下水流系统,建立地下水流数值模型,评价地下水源汇项,分析地下水系统特征。运用MODFLOW中的河流（渠）子程序包,刻画地表河流和泉水与地下水的交换关系。经参数识别和验证,计算结果与实测数据拟合较好,能够比较准确的模拟水源地岩溶水系统。模拟和预测结果表明,水源地地区地下水与地表水联系密切,应急开采后,地下水系统由向河流排泄转变为河流渗漏补给地下水,可为应急水源地合理开发利用提供科学依据。     

Restoring groundwater levels after tunneling: a numerical simulation approach to tunnel sealing decision-making

Tunneling is often unpopular with local residents and environmentalists, and can cause aquifer damage. Tunnel sealing is sometimes used to avoid groundwater leakage into the tunnel, thereby mitigating the damage. Due to the high cost of sealing operations, a detailed hydrogeological investigation should be conducted as part of the tunneling project to determine the impact of sealing, and groundwater modeling is an accurate method that can aid decision-making. Groundwater-level drawdown induced by the construction of the Headrace water-conveyance tunnel in Sri Lanka dried up 456 wells. Due to resulting socio-environmental problems, tunnel sealing was decided as a remedy solution. However, due to the expectation of significant delays and high costs of sealing, and because the water pressure in the tunnel may prevent groundwater seepage into the tunnel during operation, there was another (counter) decision that the tunnel could remain unsealed. This paper describes groundwater modeling carried out using MODFLOW to determine which option—sealed or unsealed tunnel—is more effective in groundwater level recovery. The Horizontal Flow Barrier and River packages of MODFLOW were used to simulate sealed and unsealed tunnels, respectively. The simulation results showed that only through tunnel sealing can the groundwater level be raised to preexisting levels after 18 years throughout the study area. If the tunnel remains unsealed, about 1 million m³/year of water conveyed by the tunnel will seep into the aquifer, reducing the operational capacity of the tunnel as a transport scheme. In conclusion, partial tunnel sealing in high-impact sections is recommended.

     

基于MODFLOW的地下水流模型前处理优化

MODFLOW中现有的降水补给数据和井流数据是基于每个剖分网格输入的,导致基于MODFLOW建立大区域水流数值模型前处理的降水补给文件和井流文件存储开销过大、读取效率低。为此,通过改进现有的降水补给子程序包RCH及开发新的子程序包RAW,给出了一种基于面状补排项的数据输入新方法。改进后的MODFLOW程序通过读取RCH文件或RAW文件中每个分区的补排量数据,以及每个网格对应的分区编号,在程序内部实现了补排量向每个模型网格的分配。RAW子程序包实现了多层面状补排量的表达,可用于面状的地下水开采、农业回灌等源汇项的处理。相对于原始的源汇项数据存储方式,基于新方法建立的华北平原地下水流模型,RCH及RAW文件大小分别减小为原来的1/145和1/255,整个模型数据的读取时间的加速比为7.46。     

Quantitative assessment of the impact of an inter-basin surface-water transfer project on the groundwater flow and groundwater-dependent eco-environment in an oasis in arid northwestern China

Inter-basin water transfer projects (IBWTPs) can involve basins as water donors and water receivers. In contrast to most studies on IBWTPs, which mainly impact the surface-water eco-environment, this study focuses on the impacts of an IBWTP on groundwater and its eco-environment in a water donor basin in an arid area, where surface water and groundwater are exchanged. Surface water is assumed to recharge groundwater and a groundwater numerical simulation model was constructed using MODFLOW. The model was used to quantitatively evaluate the impact of an IBWTP located in the upstream portion of Nalenggele River (the biggest river in the Qaidam basin, Northwest China). The impact involved decrease in spring flow, drawdown of groundwater, reduction in oasis area, and an increase in species replacement of oasis vegetation in the midstream and downstream of the river. Results show that the emergence sites of springs at the front of the oasis will move 2–5 km downstream, and the outflow of springs will decrease by 42 million m³/a. The maximum drawdown of groundwater level at the front of the oasis will be 3.6 m and the area across which groundwater drawdown exceeds 2.0 m will be about 59.02 km², accounting for 2.71% of the total area of the oasis. Under such conditions, reeds will gradually be replaced by Tamarix, shrubs, and other alternative plant species. These findings have important implications for the optimization of water resource allocation and protection of the eco-environment in arid regions.     

陕北能源化工基地资源开发引起的植被生态风险

地下水和煤炭资源开发是否会破环生态环境,以及会给生态环境安全带来多大的风险,是陕北能源化工基地资源开发和生态环境保护中不可逾越的课题。以陕北能源化工基地生态环境最为脆弱的风沙滩地区为研究区,在研究地下水位埋深与植被生态关系的基础上,建立了不同地貌类型、不同潜水水位埋深对应的植被群落类型和植被指数的分布关系,利用Modflow软件建立了风沙滩地区地下水流数值模拟模型,采用蒙特卡洛方法建立了植被生态随机模型,根据地下水水位埋深与植被生态的关系实现了地下水流模型和植被生态模型的耦合求解,对地下水资源和煤炭资源开发可能引起的植被生态变化进行预测和风险评估。     

Response of riparian vegetation to water-table changes in the lower reaches of Tarim River, Xinjiang Uygur, China

The lower reaches of Tarim River in the Xinjiang Uygur region of western China had been dried out for more than 30 years before water began to be diverted from Konqi (Peacock) River via a 927-km-long channel in year 2000, aimed at improving the riparian ecological systems. Since then, eight intermittent water deliveries have been carried out. To evaluate the response of riparian vegetation to these operations, the groundwater regime and vegetation changes have been monitored along the 350-km-long stem of the river using a network of 40 dug wells at nine transects across the river and 30 vegetation plots at key sites. Results show that the water table rose remarkably, i.e. from a depth of 9.87 m before the water delivery to 3.16 m after the third water delivery. The lateral distance of affected water table extended to 1,050 m from the riverbank after the fourth water delivery. The riparian vegetation has changed in composition, type, distribution, and growing behavior. This shows that the water deliveries have had significant effects on restoration of riparian ecosystems.     

Numerical modeling the role of rubber dams on groundwater recharge and phreatic evaporation loss in riparian zones

Rubber dams have been widely built for their advantages in increase of flooding resources utilization in the north arid and semiarid plain regions of China. Rise in river water stage by the dams, particularly during the drought periods, increases lateral seepage of river water into groundwater, and thus groundwater table and phreatic evaporation loss in the riparian zones. In this study, a riparian area of the Baihe River in Nanyang of Henan Province, China was selected for investigation of influences of the river dams on the groundwater recharge and evaporation loss. A hydraulic model, HEC-RAS, was used for simulation of the river stage variations along the Baihe River, and a numerical groundwater model, MODFLOW, was applied for simulation of groundwater dynamics and estimation of river flow seepage into aquifer and evaporation loss. The results show that the dams increase river stages of 2–3 m during January 2000–December 2002. The increase in the captured groundwater recharge was 7.15–34.06 million m³/a and the increased phreatic evaporation loss occupies 10% of the increased recharge when four rubber dams were built.     

An automatic ordering method for streams in surface-water/groundwater interaction modeling

The widely used groundwater flow model MODFLOW offers a range of software packages to simulate the interaction between streams and groundwater in aquifer systems. However, these existing packages lack a general method to address the chaotic simulation sequences of stream segments and require these segments to be ordered by modelers as input to the code. Therefore, it is challenging to simulate a stream network divided into a large number of segments such as a canal irrigation system. In this study, the Streamflow Automatic Routing (SAR) package was developed, and an effective method is proposed to automatically determine the segment simulation sequence. The stream segment order in the SAR input file is arbitrary, which allows modifications of the stream network by removing segments directly and adding segments at the end of the segment group. This mainly includes two processes: scanning all the outlet channels of the water system and calling the recursive algorithm for each outlet channel of the water system. The SAR package was tested using a hypothetical stream–aquifer system and applied to a complex flow field in Aiding Lake of Turpan Basin, China. In the results, a close fitting between the simulation and observations shows that the SAR package precisely simulated the exchange flux between the steams and aquifer. The SAR package can significantly improve the efficiency of simulations in a complex stream network, and it can be widely used as a subroutine package of MODFLOW in agricultural irrigation areas where rivers and canals are interlaced.

     

龙湖周边机井开采对地下水流影响的数值模拟

人工湖、库和河流等将改变区域水文循环过程,特别是地表水与地下水交换关系。本文对郑州市规划的龙湖入渗水利用和龙湖周边机井布设方案进行比较分析。龙湖水体形成后,湖区与周围地下水位的2.5m落差将使湖水大量入渗补给地下水,大范围抬升湖区周围地下水位,龙湖周围低洼处将有发生盐碱化的危险,威胁到紧靠龙湖的西部国家森林公园和规划中的东北部生态回廊绿地。本文利用美国地质调查局(USGS)颁布的三维地下水数值模型(MODFLOW),模拟不同湖底防渗措施和机井开采方案下龙湖周围地下水位变化以及龙湖入渗量,对龙湖周边布井方案可行性和降低地下水效果加以分析和比较。     

河岸带土壤磷素空间分布及其对水文过程响应

野外观测太湖地区典型农业河岸带——浯溪荡河岸带土壤总磷（TP）和溶解性总磷（DTP）含量以及当地降雨量、河水水位和地下水水位,探讨了丰水年条件下该河岸带土壤TP和DTP的空间分布特征以及水文过程对其空间分布的影响。结果表明:①在水平方向上,土壤TP和DTP含量从远岸向近岸均呈现先减少后增加的变化趋势;在深度方向上,各断面TP和DTP含量随土层深度的增加均呈减少的变化趋势。②不同月份河水水位均低于地下水水位,地下水补给河水。河水水位和地下水水位随时间的变化规律与降雨量的相似,但具有一定的滞后性。③降雨是土壤水分运动的主要驱动力,降雨、河水水位以及地下水水位对河岸带土壤磷素空间分布的影响显著不同。     

GIS-based spatial and temporal prediction system development for regional land subsidence hazard mitigation

An integrated GIS-based approach for establishing a spatial and temporal prediction system for groundwater flow and land subsidence is proposed and applied to a subsidence-progressed Japanese coastal plain. Various kinds of fundamental data relating to groundwater flow and land subsidence are digitized and entered into a GIS database. A surface water hydrological cycle simulation is performed using a GIS spatial data operation for the entire plain, and the spatial and temporal groundwater infiltration quantity is hereby obtained. Through the data transformation from the GIS database to a groundwater flow code (MODFLOW), a 3D groundwater flow model is established and unsteady groundwater flow simulation for the past 21 years is conducted with results which compare satisfactorily with observed results. Finally, a Visual Basic code is developed for land subsidence calculations considering aquifer and aquitard deformation. Future land subsidence in the plain is predicted assuming different water pumping scenarios, and the results provide important information for land subsidence mitigation decision-making.     

Modeling groundwater/surface-water interactions in an Alpine valley (the Aosta Plain,NW Italy): the effect of groundwater abstraction on surface-water resources

A groundwater flow model of the Alpine valley aquifer in the Aosta Plain (NW Italy) showed that well pumping can induce river streamflow depletions as a function of well location. Analysis of the water budget showed that ～80% of the water pumped during 2 years by a selected well in the downstream area comes from the baseflow of the main river discharge. Alluvial aquifers hosted in Alpine valleys fall within a particular hydrogeological context where groundwater/surface-water relationships change from upstream to downstream as well as seasonally. A transient groundwater model using MODFLOW2005 and the Streamflow-Routing (SFR2) Package is here presented, aimed at investigating water exchanges between the main regional river (Dora Baltea River, a left-hand tributary of the Po River), its tributaries and the underlying shallow aquifer, which is affected by seasonal oscillations. The three-dimensional distribution of the hydraulic conductivity of the aquifer was obtained by means of a specific coding system within the database TANGRAM. Both head and flux targets were used to perform the model calibration using PEST. Results showed that the fluctuations of the water table play an important role in groundwater/surface-water interconnections. In upstream areas, groundwater is recharged by water leaking through the riverbed and the well abstraction component of the water budget changes as a function of the hydraulic conditions of the aquifer. In downstream areas, groundwater is drained by the river and most of the water pumped by wells comes from the base flow component of the river discharge.     

河岸带潜流层温度示踪流速计算方法

为揭示低温水影响下的河岸带潜流层的温度场和流场分布特性,利用野外水温水位实时监测试验,研究河岸带潜流层温度场在不同季节、不同空间位置上的分布特性,并利用水温资料计算获得地下水流速。结果表明:河岸带潜流层温度场在夏季和冬季分别呈现出"上暖下冷"和 "上冷下暖"的温度分层现象;通过对温度示踪方法的4种计算方法进行分析比较,得到Hatch相位法计算的地下水流速具有较高的准确性,在2014年12月15—31日时段内流速大小为1.03×10-4~7.96×10-4m/s,在空间上,断面深度增加,地下水流速降低,且不同深度流速曲线接近平行。     

Environmental changes after ecological water conveyance in the lower reaches of Heihe River,northwest China

This paper analyzed the dynamic change of the groundwater level by 6 years’ monitoring in field monitoring and the change of vegetation by the field survey and satellite remote sensing after watering in the lower reaches of Heihe River. The findings indicated: (1) the groundwater level elevation and the plant growth are closely related to the volume and the duration of watering. In general, groundwater level elevates dramatically and plants are growing much more vigorously after watering; (2) Watering incidence on groundwater keeps extending with the watering times increasing; (3) Plants grew rapidly in 100–400 m away from the water channel after watering. Watering incidence on vegetation reached 1,000 m; (4) In terms of the function and structure of ecosystem after watering in the lower reaches of Heihe River, the ecological water conveyance does not still reach the goal of ecological restoration at a large spatial scale at present. In addition, in order to solve fundamentally the problem of ecological environment worsens in the lower reaches of Heihe River, some suggestions and countermeasures are put forward.     

Steady flow rate to a partially penetrating well with seepage face in an unconfined aquifer

The flow rate to fully screened, partially penetrating wells in an unconfined aquifer is numerically simulated using MODFLOW 2000, taking into account the flow from the seepage face and decrease in saturated thickness of the aquifer towards the well. A simple three-step method is developed to find the top of the seepage face and hence the seepage-face length. The method is verified by comparing it with the results of previous predictive methods. The results show that the component of flow through the seepage face can supply a major portion of the total pumping rate. Variations in flow rate as a function of the penetration degree, elevation of the water level in the well and the distance to the far constant head boundary are investigated and expressed in terms of dimensionless curves and equations. These curves and equations can be used to design the degree of penetration for which the allowable steady pumping rate is attained for a given elevation of water level in the well. The designed degree of penetration or flow rate will assure the sustainability of the aquifer storage, and can be used as a management criterion for issuing drilling well permits by groundwater protection authorities.