A multi-method approach to quantify groundwater/surface water-interactions in the semi-arid Hailiutu River basin,northwest China

Identification and quantification of groundwater and surface-water interactions provide important scientific insights for managing groundwater and surface-water conjunctively. This is especially relevant in semi-arid areas where groundwater is often the main source to feed river discharge and to maintain groundwater dependent ecosystems. Multiple field measurements were taken in the semi-arid Bulang sub-catchment, part of the Hailiutu River basin in northwest China, to identify and quantify groundwater and surface-water interactions. Measurements of groundwater levels and stream stages for a 1-year investigation period indicate continuous groundwater discharge to the river. Temperature measurements of stream water, streambed deposits at different depths, and groundwater confirm the upward flow of groundwater to the stream during all seasons. Results of a tracer-based hydrograph separation exercise reveal that, even during heavy rainfall events, groundwater contributes much more to the increased stream discharge than direct surface runoff. Spatially distributed groundwater seepage along the stream was estimated using mass balance equations with electrical conductivity measurements during a constant salt injection experiment. Calculated groundwater seepage rates showed surprisingly large spatial variations for a relatively homogeneous sandy aquifer.     

Interaction between groundwater, the hyporheic zone and a Chalk stream: a case study from the River Lambourn, UK

Understanding the processes controlling groundwater/surface-water interaction is essential for effective resource management and for protecting sensitive ecosystems. Through intensive monitoring of Chalk groundwater, shallow gravel groundwater and surface water in the River Lambourn, UK, using a combination of hydrochemical and hydrophysical techniques, a complex pattern of interactions has been elucidated. The river is broadly in hydraulic contact with the streambed sediments and adjacent gravels and sands, but these deposits are mainly hydraulically separate from the underlying Chalk at the site. The hydraulic relationship between the river and underlying alluvium is variable, involving components of groundwater flow both parallel and transverse to the river and with both effluent and influent behaviour seen. While the gravel aquifer is significant in controlling groundwater/surface-water interaction, its importance as a route for flow down the catchment is likely to be modest compared with river discharge. The hydrological complexity revealed in a geological setting typical of lowland UK Chalk streams has implications both for investigation methods and for management such as in the setting of environmental objectives in the European Water Framework Directive.     

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.     

Groundwater pollution due to sugar-mill effluent, at Sonai, Maharashtra, India

 Analyses of 126 samples collected from 18 dug wells in the shallow basaltic aquifer over a period of 7 months have revealed spatial as well as temporal changes in the chemical properties of groundwater. While the temporal changes have been attributed to dilution and concentration phenomena governed by climatic factors, the spatial variations in the geochemical characteristics of groundwater appeared to be related to pollution due to effluents from the Mula Sugar Factory. The cause of groundwater pollution is the effluent carried by a stream flowing through the area. Fluctuations in the groundwater table, influent water quality character of the stream, less capacity to accommodate large volume of effluent and occurrence of zero base flow (under natural conditions) in the stream are the factors favoring infiltration of constituents of waste water into the underlying weathered basaltic aquifer. Pollutants have entered into the shallow aquifer by downward percolation through the zone of aeration to form a recharge mound at the water table and, further, lateral movement below the water table. The plume of polluted groundwater has a lateral extent of a few meters in the upstream area and more than 400 m on either side of the stream in the downstream part. The zone of polluted groundwater has an areal extent of more than 3.5 km². Groundwater is the only source available for drinking and agricultural purposes. It is recommended that the base of the lagoons and the stream used for release of plant effluent should be waterproofed for the protection of groundwater in the Sonai area. Received: 30 April 1997 · Accepted: 23 September 1997     

Development of a hydrogeological conceptual wetland model in the data-scarce north-eastern region of Kilombero Valley,Tanzania

Understanding groundwater/surface-water interactions in wetlands is crucial because wetlands provide not only a high potential for agricultural production, but also sensitive and valuable ecosystems. This is especially true for the Kilombero floodplain wetland in Tanzania, which represents a data-scarce region in terms of hydrological and hydrogeological data. A comprehensive approach combining hydrogeological with tracer-based assessments was conducted, in order to develop a conceptual hydrogeological wetland model of the area around the city of Ifakara in the north-eastern region of Kilombero catchment. Within the study site, a heterogeneous porous aquifer, with a range of hydraulic conductivities, is underlain by a fractured-rock aquifer. Groundwater chemistry is mainly influenced by silicate weathering and depends on groundwater residence times related to the hydraulic conductivities of the porous aquifer. Groundwater flows from the hillside to the river during most of the year. While floodwater close to the river is mainly derived from overbank flow of the river, floodwater at a greater distance from the river mainly originates from precipitation and groundwater discharge. Evaporation effects in floodwater increase with increasing distance from the river. In general, the contribution of flood and stream water to groundwater recharge is negligible. In terms of an intensification of agricultural activities in the wetland, several conclusions can be drawn from the conceptual model. Results of this study are valuable as a base for further research related to groundwater/surface-water interactions and the conceptual model can be used in the future to set up numerical flow and transport models.     

Enhancement of aquifer vulnerability indexing using the analytic-element method

Indexing methods are used for the evaluation of aquifer vulnerability and establishing guidelines for the protection of ground-water resources. The principle of the indexing method is to rank influences on groundwater to determine overall vulnerability of an aquifer to contamination. The analytic element method (AEM) of ground-water flow modeling is used to enhance indexing methods by rapidly calculating a potentiometric surface based primarily on surface-water features. This potentiometric map is combined with a digital-elevation model to produce a map of water-table depth. This is an improvement over simple water-table interpolation methods. It is physically based, properly representing surface-water features, hydraulic boundaries, and changes in hydraulic conductivity. The AEM software, SPLIT, is used to improve an aquifer vulnerability assessment for a valley-fill aquifer in western New York State. A GIS-based graphical user interface allows automated conversion of hydrography vector data into analytic elements.     

Hydrogeological investigation of an oasis-system aquifer in arid southeastern Morocco by development of a groundwater flow model

Groundwater of the Tafilalet oasis system (TOS) is an important water resource in the lower Ziz and Rheris valleys of arid southeastern Morocco. The unconfined aquifer is exploited for domestic consumption and irrigation. A groundwater flow model was developed to assess the impact of climatic variations and development, including the construction of hydraulic structures, on the hydrodynamic behavior of the aquifer. Numerical simulations were performed by implementing a spatial database within a geographic information system and using the Arc Hydro Groundwater tool with the code MODFLOW-2000. The results of steady-state and transient simulations between 1960 and 2011 show that the water table is at equilibrium between recharge, which is mainly by surface-water infiltration, and discharge by evapotranspiration. After the commissioning of the Hassan Addakhil dam in 1971, hydraulic heads became more sensitive to annual variations than to seasonal variations. Heads are also influenced by recurrent droughts and the highest water-level changes are recorded in irrigated areas. The model provides a way of managing groundwater resources in the TOS. It can be used as a tool to predict the impact of different management plans for the protection of groundwater against overexploitation and deterioration of water quality.     

The dependence of stream depletion by seasonal pumping on various hydraulic characteristics and engineering factors

Compensation pumping is used to alleviate deficiencies in streamflow discharge during dry seasons. Short-term groundwater pumping can use aquifer storage instead of catchment-zone water until the drawdown reaches the edge of the stream. The capacitance is a complex, dimensionless parameter of an aquifer system that defines the delayed effect on streamflow when there is groundwater pumping. This parameter is a function of aquifer hydraulic characteristics, pumping time, and distance between the well and stream edge; the latter can involve stream leakance and vertical leakance of an associated aquitard. Three typical hydraulic cases of combined water systems (major catchment-zone wells close to the stream and compensation pumping wells) were classified depending on their capacitance structure (i.e. the relationship between surface water and groundwater): (1) perfect hydraulic connection between the stream and aquifer; (2) imperfect hydraulic connection between the stream and aquifer; and (3) essentially imperfect hydraulic connection between the stream and the underlying confined aquifer. The impact of various hydraulic characteristics and engineering factors on stream depletion was examined by conceptual and numerical modeling. To predict the suitability and efficiency of a combined water system application, regression tests were undertaken on unit stream depletion and capacitance, and power dependencies were defined.     

运用地下水对潮汐的响应识别压力传导系数

在地下水扩散方程中,压力传导系数是描述地下水运动的重要参数。传统的方法是通过抽水或注水给地下水系统一个扰动,监测地下水水位的响应,由此计算含水层的压力传导系数。文章提出用潮汐衰减率方法识别含水层压力传导系数,其适用于滨海区承压含水层的参数识别。在推导出解析解的基础上,通过数值拟合、最小二乘法、牛顿迭代法求得含水层的压力传导系数,提出潮汐衰减率的概念,建立余切函数与潮汐衰减率的线性关系,用线性关系中的斜率和截距识别压力传导系数。用潮汐衰减率方法识别出的压力传导系数与其实际值相等,说明该方法是正确有效的。潮汐信号衰减率与海水振荡的余切函数线性相关。数值仿真表明,该方法可以准确地估算出含水层的压力传导系数。潮汐衰减率方法具有少打井,经济高效等优点。潮汐衰减率方法为实际工程应用提供了可靠的理论基础,它可以用于部分实际工程中。该方法的局限性在于需要提供含水层的部分参数,如含水层的长度、海水波动振幅、频率等。     

Groundwater response to serial stream stage fluctuations in shallow unconfined alluvial aquifers along a regulated stream (West Virginia,USA)

Groundwater response to stream stage fluctuations was studied in two unconfined alluvial aquifers using a year-long time series of stream stages from two pools along a regulated stream in West Virginia, USA. The purpose was to analyze spatial and temporal variations in groundwater/surface-water interaction and to estimate induced infiltration rate and cumulative bank storage during an annual cycle of stream stage fluctuation. A convolution-integral method was used to simulate aquifer head at different distances from the stream caused by stream stage fluctuations and to estimate fluxes across the stream–aquifer boundary. Aquifer diffusivities were estimated by wiggle-matching time and amplitude of modeled response to multiple observed storm events. The peak lag time between observed stream and aquifer stage peaks ranged between 14 and 95 hour. Transient modeled diffusivity ranged from 1,000 to 7,500 m²/day and deviated from the measured and calculated single-peak stage-ratio diffusivity by 14–82 %. Stream stage fluctuation displayed more primary control over groundwater levels than recharge, especially during high-flow periods. Dam operations locally altered groundwater flow paths and velocity. The aquifer is more prone to surface-water control in the upper reaches of the pools where stream stage fluctuations are more pronounced than in the lower reaches. This method could be a useful tool for quick assessment of induced infiltration rate and bank storage related to contamination investigations or well-field management.     

Estimates of groundwater discharge to a coastal wetland using multiple techniques: Taylor Slough, Everglades National Park, USA

Quantifying water exchange between a coastal wetland and the underlying groundwater is important for closing water, energy and chemical budgets. The coastal wetlands of the Florida Everglades (USA) are at the forefront of a large hydrologic restoration project, and understanding of groundwater/surface-water interactions is needed to comprehend the effects of the project. Four independent techniques were used to identify water exchange at varying spatial and temporal scales in Taylor Slough, Everglades National Park. The techniques included a water-budget study and measurements of hydraulic head gradients, geochemical tracers, and temperature. During the 18-month study, the four methods converged as to the timing of groundwater discharge, typically between June and September, contemporaneous with the wet season and increasing surface-water levels. These results were unexpected, as groundwater discharge was predicted to be greatest when surface-water levels were low, typically during the dry season. Either a time lag of 1?C5?months in the response of groundwater discharge to low surface-water levels or precipitation-induced groundwater discharge may explain the results. Groundwater discharge was a significant contributor (27?%) to the surface water in Taylor Slough with greater rates of discharge observed towards the coastline in response to seawater intrusion.     

River–groundwater connectivity in a karst system,Wellington, New South Wales,Australia

The characterization of river–aquifer connectivity in karst environments is difficult due to the presence of conduits and caves. This work demonstrates how geophysical imaging combined with hydrogeological data can improve the conceptualization of surface-water and groundwater interactions in karst terrains. The objective of this study is to understand the association between the Bell River and karst-alluvial aquifer at Wellington, Australia. River and groundwater levels were continuously monitored, and electrical resistivity imaging and water quality surveys conducted. Two-dimensional resistivity imaging mapped the transition between the alluvium and karst. This is important for highlighting the proximity of the saturated alluvial sediments to the water-filled caves and conduits. In the unsaturated zone the resistivity imaging differentiated between air- and sediment-filled karst features, and in the saturated zone it mapped the location of possible water- and sediment-filled caves. Groundwater levels are dynamic and respond quickly to changes in the river stage, implying that there is a strong hydraulic connection, and that the river is losing and recharging the adjacent aquifer. Groundwater extractions (1,370 ML, megalitres, annually) from the alluvial aquifer can cause the groundwater level to fall by as much as 1.5 m in a year. However, when the Bell River flows after significant rainfall in the upper catchment, river-leakage rapidly recharges the alluvial and karst aquifers. This work demonstrates that in complex hydrogeological settings, the combined use of geophysical imaging, hydrograph analysis and geochemical measurements provide insights on the local karst hydrology and groundwater processes, which will enable better water-resource and karst management.     

Groundwater recharge in suburban areas of Hanoi,Vietnam: effect of decreasing surface-water bodies and land-use change

Over-exploited groundwater is expected to remain the predominant source of domestic water in suburban areas of Hanoi, Vietnam. In order to evaluate the effect on groundwater recharge, of decreasing surface-water bodies and land-use change caused by urbanization, the relevant groundwater systems and recharge pathways must be characterized in detail. To this end, water levels and water quality were monitored for 3 years regarding groundwater and adjacent surface-water bodies, at two typical suburban sites in Hanoi. Stable isotope (δ¹⁸O, δD of water) analysis and hydrochemical analysis showed that the water from both aquifers and aquitards, including the groundwater obtained from both the monitoring wells and the neighboring household tubewells, was largely derived from evaporation-affected surface-water bodies (e.g., ponds, irrigated farmlands) rather than from rivers. The water-level monitoring results suggested distinct local-scale flow systems for both a Holocene unconfined aquifer (HUA) and Pleistocene confined aquifer (PCA). That is, in the case of the HUA, lateral recharge through the aquifer from neighboring ponds and/or irrigated farmlands appeared to be dominant, rather than recharge by vertical rainwater infiltration. In the case of the PCA, recharge by the above-lying HUA, through areas where the aquitard separating the two aquifers was relatively thin or nonexistent, was suggested. As the decrease in the local surface-water bodies will likely reduce the groundwater recharge, maintaining and enhancing this recharge (through preservation of the surface-water bodies) is considered as essential for the sustainable use of groundwater in the area.

     

Quantification of River Nile/Quaternary aquifer exchanges via riverbank filtration by hydrochemical and biological indicators,Assiut, Egypt

This study approach seeks to characterize the hydraulic interactions between the Nile and the Quaternary aquifer via riverbank filtration (RBF) in Abu Tieg area, Assuit Governorate. The substantial removal/reduction of the most problematic substances during percolation of Nile water into abstraction wells was investigated using physico-chemical and biological indicators. Four sites with 11 municipal wells (20–750 m from the Nile) tapping the alluvial aquifer that is fed by the riverbank infiltrate were monitored. Bank-filtrated water was compared with those of the Nile and groundwater. Results showed that infiltrated Nile water ratio into the wells ranged from 39 to 80% reflecting the effect of distance from the Nile. Removal efficiency of total algal, total and faecal coliforms in bank-filtered water was 99.9%, while turbidity removal ranged from 93 to 98%. Fe, Mn and Zn in the bank-filtered water were relatively higher than those in the Nile, but were still under the allowable standards except those of Mn. LSI and WQI for the bank-filtered water indicated that the water was ranked as non-corrosive and of excellent quality. Comparison of physico-chemical and microbiological characteristics of the bank-filtered water with those of the Nile and groundwater showed the high efficiency of RBF as a treatment technology with minimal cost compared to conventional methods.     

Prediction criteria for groundwater potential zones in Kemuning District,Indonesia using the integration of geoelectrical and physical parameters

The presence of groundwater is strongly related to its geological and geohydrological conditions.It is,however,important to study the groundwater potential in an area before it is utilized to provide clean water.Werner-Schlumberger’s method was used to analyze the groundwater potential while hydraulic properties such as soil porosity and hydraulic conductivity were used to determine the quality and ability of the soil to allow water’s movement in the aquifer.The results show that the aquifer in the Sekara and Kemuning Muda is at a depth of more than 6 meters below the ground level with moderate groundwater potential.It is also found that the aquifer at depths of over 60 m have high groundwater potential.Moreover,soil porosity in Kemuning is found to be average while the ability to conduct water was moderate.This makes it possible for some surface water to seep into the soil while the remaining flows to the rivers and ditches.     

Modeling stream-aquifer interactions in a shallow aquifer, Choele Choel Island, Patagonia, Argentina

A groundwater/surface-water interaction model was developed for the shallow alluvial aquifer of the Choele Choel Island in Patagonia, Argentina. In this semiarid climate, agriculture is sustained by an irrigation/drainage system. During the irrigation season, seepage losses through unlined distribution canals in irrigated fields contribute to elevated groundwater levels, jeopardizing fruit productivity in some areas. Moreover, high stream stages during the irrigation season interfere with groundwater drainage. The model utilized MODFLOW and its stream package, and was successfully calibrated for a historical irrigation season. Modeling results indicate that drainage through streams is significantly higher than drainage through artificial drains. The stream/aquifer relationship proved very responsive to water table rises caused by irrigation. This response manifested as changes in the gaining/losing character of stream reaches. A synthetic run aimed at isolating the effect of streamflow changes on groundwater levels showed that the effect of higher streamflows dissipates toward the interior of the island, disappearing completely at the island center. Even though some results were qualitative, the model helped to provide a better understanding of the coupled system to elucidate some of the causes of a rising water table on the island.

Influences of groundwater extraction on flow dynamics and arsenic levels in the western Hetao Basin,Inner Mongolia,China

Data on spatiotemporal variations in groundwater levels are crucial for understanding arsenic (As) behavior and dynamics in groundwater systems. Little is known about the influences of groundwater extraction on the transport and mobilization of As in the Hetao Basin, Inner Mongolia (China), so groundwater levels were recorded in five monitoring wells from 2011 to 2016 and in 57 irrigation wells and two multilevel wells in 2016. Results showed that groundwater level in the groundwater irrigation area had two troughs each year, induced by extensive groundwater extraction, while groundwater levels in the river-diverted (Yellow River) water irrigation area had two peaks each year, resulting from surface-water irrigation. From 2011 to 2016, groundwater levels in the groundwater irrigation area presented a decreasing trend due to the overextraction. Groundwater samples were taken for geochemical analysis each year in July from 2011 to 2016. Increasing trends were observed in groundwater total dissolved solids (TDS) and As. Owing to the reverse groundwater flow direction, the Shahai Lake acts as a new groundwater recharge source. Lake water had flushed the near-surface sediments, which contain abundant soluble components, and increased groundwater salinity. In addition, groundwater extraction induced strong downward hydraulic gradients, which led to leakage recharge from shallow high-TDS groundwater to the deep semiconfined aquifer. The most plausible explanation for similar variations among As, Fe(II) and total organic carbon (TOC) concentrations is the expected dissimilatory reduction of Fe(III) oxyhydroxides.     

Combined electrical resistivity tomography and magnetic resonance sounding investigation of the surface-water/groundwater interaction in the Urema Graben,Mozambique

This study focusses on the hydrogeology of Urema Graben, especially possible interactions between surface water and groundwater around Lake Urema, in Gorongosa National Park (GNP). Lake Urema is the only permanent water source for wildlife inside GNP, and there are concerns that it will disappear due to interferences in surface-water/groundwater interactions as a result of changes in the hydraulic environment. As the lake is the only permanent water source, this would be a disaster for the ecosystem of the park. The sub-surface geology in Urema Graben was investigated by 20 km of electrical resistivity tomography (ERT) and three magnetic resonance sounding (MRS) surveys. The average depth penetration was 60 and 100 m, respectively. The location of the ERT lines was decided based on general rift morphology and therefore orientated perpendicular to Urema Graben, from the transitional areas of the margins of the Barue platform in the west to the Cheringoma plateau escarpments in the east. ERT and MRS both indicate a second aquifer, where Urema Lake is a window of the first upper semi-confined aquifer, while the lower aquifer is confined by a clay layer 30–40 m thick. The location and depth of this aquifer suggest that it is probably linked to the Pungwe River which could be a main source of recharge during the dry season. If a dam or any other infra-structure is constructed in Pungwe River upstream of GNP, the groundwater level will decrease which could lead to drying out of Urema Lake.     

Controls on groundwater flow in the Bengal Basin of India and Bangladesh: regional modeling analysis

Groundwater for domestic and irrigation purposes is produced primarily from shallow parts of the Bengal Basin aquifer system (India and Bangladesh), which contains high concentrations of dissolved arsenic (exceeding worldwide drinking water standards), though deeper groundwater is generally low in arsenic. An essential first step for determining sustainable management of the deep groundwater resource is identification of hydrogeologic controls on flow and quantification of basin-scale groundwater flow patterns. Results from groundwater modeling, in which the Bengal Basin aquifer system is represented as a single aquifer with higher horizontal than vertical hydraulic conductivity, indicate that this anisotropy is the primary hydrogeologic control on the natural flowpath lengths. Despite extremely low hydraulic gradients due to minimal topographic relief, anisotropy implies large-scale (tens to hundreds of kilometers) flow at depth. Other hydrogeologic factors, including lateral and vertical changes in hydraulic conductivity, have minor effects on overall flow patterns. However, because natural hydraulic gradients are low, the impact of pumping on groundwater flow is overwhelming; modeling indicates that pumping has substantially changed the shallow groundwater budget and flowpaths from predevelopment conditions.     

Using subsurface metazoan fauna to indicate groundwater–surface water interactions in the Nakdong River floodplain, South Korea

Hydrological interactions between surface water and groundwater (GW) can be described using hydrochemical and biological methods. Surface water–groundwater interactions and their effects on groundwater invertebrate communities were studied in the Nakdong River floodplain in South Korea. Furthermore, the GW-Fauna-Index, a promising new index for assessing the strength of surface-water influence on groundwater, was tested. The influence of surface water on groundwater decreased with increasing depth and distance from the river. While hydrochemistry prevailingly reflected the origin of the waters in the study area (i.e. whether alluvial or from adjacent rock), faunal communities seemed to display an affinity to surface-water intrusion. Fauna reacted quickly to changes in hydrology, and temporal changes in faunal community structure were significantly linked to the hydrological situation in the floodplain. The metazoan faunal community and the GW-Fauna-Index allow a distinction between surface and subsurface waters with varying degrees of exchange. The results indicate that hydrological conditions are reflected by faunal assemblages on a high spatiotemporal resolution, and that surface-water intrusion can be estimated using the GW-Fauna-Index.