D. I. Siegel's research while affiliated with Syracuse University and other places

Publications (77)

Article
The interpretation of aquifer responses to pumping tests is an important tool for assessing aquifer geometry and properties, which are critical in the assessment of water resources or in environmental remediation. However, the responses of aquifers, measured by time-drawdown relationships in monitoring wells, are nonunique solutions that are affect...
Article
Although northern peatlands represent a globally significant reservoir for carbon, considerable uncertainty exists concerning solute transport systems within large (>1000 km²) peat deposits. We therefore delineated geochemical gradients linked to groundwater recharge and discharge along a 6 km transect within the 1200 km² Red Lake Peatland of north...
Article
We report the results of analysis and interpretation of 19,278 predrilling groundwater samples from water wells in the Appalachian Basin for dissolved methane collected from 2009 to 2012 (11,309 samples from northeastern Pennsylvania and 7969 samples from a western area that included north-central West Virginia, eastern Ohio, and southwestern Penns...
Article
Chesapeake Energy Corporation funded consultants and the authors of this paper through their organizations of employment and, in the case of Donald Siegel, privately to do basic research on this temporal data set and prepare the paper. The authors of this report did all analysis and writing. The opinions and conclusions expressed in this paper are...
Conference Paper
Prairie wetlands are ubiquitous features of the Great Plains of North America, and provide important habitat for amphibians and migratory waterfowl. Complex hydrological controls maintain brackish surface pond salinities in closed-basin wetlands, which are sensitive to regional dry/wet climate cycles. In order to better understand hydrogeological c...
Article
Full-text available
Peatlands are the dominant landscape element in many northern watersheds where they can have an important influence on the hydrology of streams. However, the capacity of peatlands to moderate stream flow during critical dry periods remains uncertain partly due to the difficulty of estimating discharge from extensive peat deposits. We therefore used...
Article
Unconventional natural gas production in the Marcellus and Utica formations of the Northeastern United States raises concerns about potential impacts to shallow groundwater. We examined and interpreted 13,040 analyses from pre-drilling groundwater samples from domestic water wells in Northeastern (NE) Pennsylvania and 8,004 samples from water wells...
Article
The close interplay between hydraulic and biotic processes controls the evolution of ecosystems in large, circumboreal peatlands and the degree to which they lose, gain or sequester carbon. In peatlands, biota significantly alters surficial acid–base equilibrium and solute chemistry by releasing dissolved organic compounds into surface and pore wat...
Article
Recent studies in northeastern Pennsylvania report higher concentrations of dissolved methane in domestic water wells associated with proximity to nearby gas-producing wells.1,2 We test this possible association by using Chesapeake Energy's baseline dataset of over 11,300 dissolved methane analyses from domestic water wells, densely arrayed in Brad...
Article
We report the results of two independent laboratory investigations to evaluate total and leachable concentrations of glycols, glycol ethers, phenol, and other compounds in representative Type I and Type I/II Portland cement products that United States Environmental Protection Agency (EPA), The American Society of Testing and Materials (ASTM) and ot...
Article
Full-text available
We investigated the hydrochemical setting of Lake Taihu (eastern China) to determine how different land use types influence the variability of surface water chemistry in different water sources to the lake. Major water types within the watershed range from caclium-magnesium bicaxrbonate water, typical of relatively pristine water, highly ocntaminat...
Article
Full-text available
Ground water recharge is assumed to occur primarily at raised bog crests in northern peatlands, which are globally significant terrestrial carbon reservoirs. We synoptically surveyed vertical profiles of peat pore water δ18O and δ2H from a range of bog and fen landforms across the Glacial Lake Agassiz Peatlands, northern Minnesota. Contrary to our...
Chapter
During the twentieth century, the science of hydrogeology focused on establishing and refi ning fundamental principles and developing tools to study groundwater flow, well hydraulics, hydrogeochemistry, and contaminant hydrogeology. By the end of the century, the science evolved to assimilate principles and expertise from other disciplines, includi...
Article
Peatlands represent a critical component of the Global Carbon Cycle serving as both a major source and sink for greenhouse gases. Although a broad consensus exists that the carbon balance of these wet-waterlogged deposits is intimately linked to hydrological processes, considerable uncertainty still exists with regard to the dynamics of these linka...
Article
A new integrated catchment model for salinity has been developed to assess the transport of road salt from upland areas in watersheds to streams using readily accessible landscape, hydrologic, and meteorological data together with reported salt applications. We used Fishkill Creek (NY) as a representative watershed to test the model. Results showed...
Article
1] The conceptual model of hyporheic exchange below river steps may oversimplify exchange flow paths if it depicts a uniform pattern of downstream-directed upwelling. This research used nonmobile, porous bed flume experiments and hydrodynamic simulation (CFD) to characterize hyporheic flow paths below a river step with a hydraulic jump. Bed slope w...
Article
This research examined hydrostatic groundwater model (MODFLOW) predictive adequacy and sensitivity in simulating hyporheic flow paths across a river step with a hydraulic jump. In a companion paper, we used flume and hydrodynamic model analysis to develop a refined conceptual model depicting these flow paths with zones of downwelling and upstream-d...
Article
Full-text available
The academic community continues to believe that the formal scholarly publishing process separates sound research from shoddy or biased counterparts. Unfortunately, scholarly publishing may not be able to effectively fulfill its role as a gatekeeper much longer. As soon as the “publish or perish
Article
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We report the results of a synoptic ("snapshot") sampling of inorganic and isotopic geochemistry of surface water and groundwater during base flow in Red Canyon Creek watershed (Wyoming, USA) to evaluate how mixing of waters and geochemical processes modify stream-water chemistry. Our synoptic approach of studying the geochemistry of a stream mimic...
Article
We investigated the difference in DOM reactivity in northern peatlands using C/N ratios of the peat, DOM, and inorganic constituents (DIC/ammonium). Previous studies have shown a difference in reactivity between the bog and fen environments using 14C. In sedge-dominated peatlands, the 14C content of the products of respiration, CH4 and DIC are esse...
Article
The 1200 sq km Red Lake peatland in northern Minnesota has been the focus of an ongoing study of carbon-groundwater interactions for over 30 years. This large continuous expanse of peatland contains several major bog complexes, each of which covers over 100 sq. km. Each bog complex has 1) a forested bog crest that grades downslope into 2) gently sl...
Article
The incorporation of increasingly multidisciplinary aspects of geoscience curricula into a traditional geology field camp requires compromises. Among these, decisions about projects to reduce or eliminate and course prerequisites are two of the most challenging. Over the past 10 yr, the University of Missouri's geology field camp has completed a tw...
Article
Full-text available
The Changjiang and the Jiulong Estuaries, located in eastern and southeastern China, respectively, have different geomorphologic and tidal processes as well as anthropogenic development in their associated watersheds. Sediments in the Changjiang estuary mostly consist of SiO2, CaO and MgO (mean percentages of 63.9, 4.34 and 2.35%), whereas sediment...
Article
Full-text available
Mountain streams are a common source in Central America for community water supplies (CWS). These streams become dewatered by the CWS during dry season low flows, with potential impacts on hydraulic gradients, hyporheic exchange flow, terrestrial-aquatic linkages, and nutrient dynamics, which may ultimately affect aquatic and riparian micro-ecosyst...
Article
The Urban Schoolyards project is a two year partnership with a university Earth Science Department and the surrounding urban elementary schools. The goal of the project was to develop the capacity of elementary teachers to teach earth science lessons using their schoolyards and local parks as field sites. The university personnel developed lessons...
Article
We found a consistent distribution pattern for radiocarbon in dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and methane replicated across spatial and temporal scales in northern peatlands from Minnesota to Alaska. The 14C content of DOC is relatively modern throughout the peat column, to depths of 3 meters. In sedge-dominated pe...
Article
We found a consistent distribution pattern for radiocarbon in dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and methane replicated across spatial and temporal scales in northern peatlands from Minnesota to Alaska. The 14C content of DOC is relatively modern throughout the peat column, to depths of 3 m. In sedge-dominated peatlan...
Article
Subduction of the Pacific plate beneath the Mariana forearc releases fluids to the overlying mantle wedge that ascend, producing serpentinite “mud” that discharges on the ocean floor. As part of Leg 195 of the Ocean Drilling Program cores were obtained from drill-holes into the mud volcanoes. We report the isotopic composition of Sr in water squeez...
Article
This study describes unusual temporal variations in streamwater isotopic and geochemical composition in a 3rd order stream, Red Canyon Creek, draining carbonate-rich catchments in the southeastern flank of Wind River Range (WY). Although the isotopic ratios of oxygen in precipitation increased from about -30 0/00 to -15 0/00 during winters of 2005-...
Data
Subduction of the Pacific plate beneath the Mariana forearc releases fluids to the overlying mantle wedge that ascend, producing serpentinite "mud" that discharges on the ocean floor. As part of Leg 195 of the Ocean Drilling Program cores were obtained from drill-holes into the mud volcanoes. We report the isotopic composition of Sr in water squeez...
Article
Temporary storage of surface water at channel sides and pools significantly affects water and solute transport downstream in watersheds. Beavers, natural "stream channel engineers", build dams which obstruct stream flow and temporarily store water in small to large ponds within stream channels. These ponds substantially delay water movement and inc...
Article
Scaling biogeochemical processes across complex regional landscapes remains one of the most important challenges for deciphering the global methane cycle. For the past 30 years we have investigated the coupling of climate, groundwater, and methane cycling in the Glacial Lake Agassiz peatlands in northern Minnesota. Periodic droughts perturb the loc...
Article
The University of Missouri's Branson Geology Field Camp has integrated a series of environmental geology components into its curriculum, including hydrogeology and geophysics. In this paper, we present the results of a dye tracing experiment carried out by undergraduate students as the capstone field experiment of an optional advanced hydrogeology...
Article
Subduction of the Pacific plate beneath the Mariana forearc releases hydrous fluids which move upward along fractures and react with fault gouge and fractured harzburgitic mantle rocks to produce serpentinite "mud" that discharges with cold water as springs on the ocean floor. This mud accumulates as seamounts, tens of km wide and up to two km high...
Article
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[1] Measurements of solute concentrations from previously unstudied watersheds throughout west Siberia suggest that warming and permafrost degradation will likely amplify the transport of dissolved solids to the Kara Sea and adjacent Arctic Ocean. We present concentrations of Ca2+, K+, Mg2+, Na+, Si, Cl-, SO 42-, HCO3-, inferred alkalinity, and tot...
Article
At present the dynamics of local and regional flow systems in large peat basins has only been imperfectly characterized. Over 20 years of study in the GLAP for example has continued to uncover new layers of complexity not only with regard to the geometry of these flow systems but also their interactions with climate, geology, and biological process...
Article
Recent studies propose that ebullition (i.e. bubbling) may be an important and underrepresented mechanism for methane emissiions from peatlands to the atmosphere. Some of these studies suggest that the geometry of the primary pore system imposes the main constraint on bubble transport within peat deposits. We tested this hypothesis by analyzing cor...
Conference Paper
Doing large-scale experiments arguably best teaches hydrogeology students about the physics of subsurface flow. We present the results of a unique, large-scale, tracer experiment done at the 2006 Branson Geology Summer Field Camp (University of Missouri) to instruct students on the physics of solute transport. The hydrogeology students dyed the ent...
Article
2 ABSTRACT: Many major North American watersheds are connected by canals and diversions, allowing fi sh migration across watersheds. Unique geochemical "signatures" of watershed waters may be useful as natural tracers if they are incorporated into fi sh earstones (otoliths). We tested this hypothesis by measuring concentrations of dissolved Ca, Na,...
Article
Organic acids supply most of the acidity in the surface waters of bogs in peatlands. Yet, the fundamental geochemical properties of peatland organic acids are still poorly known. To assess the geochemical properties of typical organic acid assemblages in peatlands, we used a triprotic analog model for peat pore waters and surface waters in the Glac...
Article
Large raised bogs and patterned fens cover 56% of the landscape in the Glacial Lake Agassiz region of northern Minnesota (USA). Organic acids supply most of the acidity in the surface water of the bogs, but groundwater upwelling from the underlying glacial deposits neutralizes these organic acids within deep peat. Substantial concentrations of orga...
Article
Measurements of solute concentrations from watersheds located throughout West Siberia suggest that warming and permafrost degradation will amplify the transport of dissolved solids to the Kara Sea and adjacent Arctic Ocean. We present concentrations of Ca2+, K+, Mg2+, Na+, Si, Cl-, SO42-, HCO3- and total dissolved solids (TDS) from 94 streams and r...
Article
This paper presents the results of a hydrogeochemical study of the Lake Junin watershed, Peru, to evaluate the controls over chemical composition of water in this remote Andean site. Stream, spring, and lake waters in the Lake Junin basin are all Ca 2C and HCO 3 K type. Evaporation has enriched the d 18 O of the lake water by about 6‰ compared to t...
Article
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This paper presents the results of a study on the geochemistry of Fe in a minerotrophic wetland in Central New York. Fine-scale geochemical trends in the peat and peat porewater were investigated to evaluate detailed vertical profiles of Fe in solution. Two sites within the wetland were examined: one site adjacent to an agricultural field receiving...
Article
Models of near-stream hyporheic exchange flows are difficult to prepare because geomorphic stream features and adjacent subsurface characteristics both affect groundwater-surface water interaction. Inverse models of the results of in-stream tracer tests characterize net short time-scale hyporheic exchange along reaches, but not the actual physical...
Article
Peatlands are a major terrestrial source and sink of atmospheric methane, which is transported to the land surface by diffusion, advection and ebullition. Methane production is mostly related to seasonal variations in soil temperature and fluxes of labile carbon. We report the results of a study to explore the extent to which temperature variations...
Article
This report discusses how we developed and implemented an interactive upper division/graduate level class project based on a fictional trichloroethylene contamination incident as part of our spring-2003 semester hydrogeology curriculum at Syracuse University. The "truth" of the contamination was based on a hypothetical Visual MODFLOW and MT3D compu...
Article
Full-text available
[1] Peatlands deform elastically during precipitation cycles by small (±3 cm) oscillations in surface elevation. In contrast, we used a Global Positioning System network to measure larger oscillations that exceeded 20 cm over periods of 4–12 hours during two seasonal droughts at a bog and fen site in northern Minnesota. The second summer drought al...
Article
We report the results of an isotopic study designed to determine the source of solutes and carbon dioxide in the famed Saratoga Springs (New York) mineral waters. These waters have thousands of milligrams per liter total dissolved solid concentrations and are highly charged with carbon dioxide gas. The spring waters are cold (˜12 °C) and there is n...
Article
Recent field studies from northern Minnesota indicate that deep ebullition fluxes may be a major component of the methane cycle in large peat basins. Zones of overpressure were discovered under raised bogs across the Glacial Lake Agassiz peatlands in which biogenic gas bubbles accumulate in semi-elastic compartments confined by dense wood layers. I...
Article
Raised bogs and municipal waste landfills harbor large populations of methanogens within their domed deposits of anoxic organic matter. Although the methane emissions from these sites have been estimated by various methods, limited data exist on the activity of the methanogens at depth. We therefore analyzed the stable isotopic signature of the por...
Article
The Croton Reservoir that provides water to New York City periodically has color problems in late fall. Consequently, a synoptic sampling of 92 streams draining wetlands in the watershed was done to determine whether water color is related to dissolved organic carbon, iron and manganese concentrations. In addition, major solute concentrations were...
Article
Three-dimensional ground-water modeling experiments were done to test the hypothesis that regional ground-water flow is an important component of the water budget in the Glacial Lake Agassiz Peatlands of northern Minnesota. Previous data collected from the Glacial Lake Agassiz Peatlands suggest that regional ground-water flow discharges to these pe...
Article
Numerical simulations indicate that mechanical dispersive mixing can be the dominant mass transport mechanism in large peatlands. Dispersive mixing driven by lateral flow can drive solute fluxes from the mineral soil upward to the peat surface and thereby explain observed patterns of bog and fen in large peatlands. Longitudinal and transverse dispe...
Article
To elucidate the roles of hydrology and vegetation in belowground carbon cycling within peatlands, radiocarbon values were obtained for pore water dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), CH4, and peat from the Glacial Lake Agassiz peatland. The major implication of this work is that the rate of microbial respiration within...
Article
This study evaluates relationships between vegetation and stable isotope distribution within a large, northern peat-accumulating wetland. Concentration and δ13C for both porewater and emitted methane were obtained from June–September for two systems characterized by different plant assemblages and hydrologic regimes: a Carex -dominated fen and a Sp...
Article
Ground-water flow simulations are used to evaluate the importance of three parameters on vertical flow in peatlands: regional slope, permeability of the mineral soil underlying the peat, and peatland topography. Our results indicate that the extent of vertical ground-water flow in peatlands is primarily controlled by mineral soil permeability. Loca...
Article
During the past decade or longer, large amounts of data on the concentrations of dissolved aromatic hydrocarbons have been obtained from routine monitoring of leaky underground storage tanks (USTs). Commonly, aromatic hydrocarbon concentration data is interpreted only within the context of regulatory maximum allowable concentration levels. We show...
Article
A study was undertaken to explore whether the isotopic compositions of Pb and Sr are useful to distinguish mixtures of uncontaminated groundwater, seawater, and landfill leachate at the Fresh Kills landfill, Staten Island, New York. Ratios of 87Sr/86Sr ranged from 0.7088 to 0.7137 and could be used to distinguish Sr that was derived from seawater f...
Article
Full-text available
The probable limits of the carbon budget of the Rapid River Watershed, within the greater Glacial Lake Agassiz Peatland in northern Minnesota, were evaluated using a Monte Carlo simulation approach. Carbon enters the peatlands in groundwater, precipitation, and primary productivity. Carbon leaves the peatlands by groundwater and surface water outfl...
Article
Hydrochloric acid and calcium and sodium chloride salt solutions were passed through humified bog peat cores of 1m length to determine values for the material properties governing solute transport: hydraulic conductivity, effective porosity, and dispersivity. Chloride passed through the bulk peat cores about twice as fast as predicted from chloride...
Article
Raised bogs represent end-products of peatland development that are generally assumed to be decoupled from the regional groundwater system. However, the development of two peat mounds in northern Minnesota was driven by three major reversals in its groundwater-flow regime. A 4000-year record of groundwater flow was reconstructed by stratigraphic st...
Article
Bogs and fens from northern Minnesota produce large quantities of CH4, which may be either emitted to the atmosphere or stored in below-ground reservoirs. The identity of the organic materials that support CH4 production has been uncertain, but we present evidence that a significant fraction of surface emission and below-ground CH4 is derived from...
Article
NORTHERN peatlands can act as either important sources or sinks for atmospheric carbon1,2. It is therefore important to understand how carbon cycling in these regions will respond to a changing climate. Existing carbon balance models for peatlands assume that fluid flow and advective mass transport are negligible at depth3,4, and that the effects o...
Article
The Malloryville Wetland Complex, a small kettle-hole peatland, contains a diversity of peatland types. The wetland has a ‘rich’ side that contains wetland vegetation associated with solute-rich, near-neutral pH (minerotrophic) water, and a ‘poor’ side containing vegetation that grows in solute-poor and acidic (ombrotrophic) water. Vertical head gr...
Article
(1) The hydrogeology of a spring-fen mound, water track, and raised bog in the remote Lost River peatland, northern Minnesota, was investigated by measurements of the groundwater levels and chemistry of groundwater in observation wells. (2) Water-level measurements indicate that all the major physiographic features in the mire--a raised bog, spring...
Article
Detailed hydrologic investigations of peat landforms in the Red Lake Peatlands have revealed that groundwater flow is significantly related to the type of landform and vegetation community present at a given site. Hydrogeologic modeling of shallow groundwater systems suggests that bedrock topography is an important, perhaps the vital, boundary cond...
Article
A recent hydrologic and pore-water chemistry study of the 7,500 km[sup 2] Lake Agassiz Peatlands in northern Minnesota suggest that local groundwater flow through the peat in the Lake Agassiz Peatland is superimposed on a regional flow system. Discharge of the regional flow system into the peasants through the underlying lacustrine sediments contro...

Citations

... Similarly, simply telling one to "listen to the facts" of technology does not build trust [as per Kahneman (2011) and Duffy (2018)], particularly if opponents have a good reason not to trust technology companies or governmental agencies. Facts alone will not change minds [refer to, e.g., Siegel (2016) and Siegel (2019)]. A campaign would have to build credibility with opponents, by using someone they trust to spread the message, "cognitive-infiltration and persuasion" in the terms of Sunstein and Vermeule (2009, p. 224). ...
... For example, numerous high-latitude peatlands of the northern hemisphere, are at least partly located on carbonate rocks (United Kingdom, Siberia or western China). In addition, even when they are not directly located on carbonate rocks, interactions may exist; through the export of peatland-derived acidic waters which accelerate the dissolution of carbonates downstream (Calmels et al., 2014;Wallin et al., 2010), or through the water supply of peatland from carbonate catchments (Chasar et al., 2000;Levy et al., 2016). ...
... The contaminant that has been identified as the most common problem in PA is methane (CH 4 ), the chief component of natural gas ( Brantley et al., 2014 ). Many studies investigating groundwater quality in shale gas basins have focused on contamination by such anomalous CH 4 ( Hammond, 2016 ;Hammond et al., 2020 ;Li and Carlson, 2014 ;Molofsky et al., 2013 ;Nicot et al., 2017c ;Osborn et al., 2011 ;Sherwood et al., 2016 ;Siegel et al., 2015aSiegel et al., ,b, 2016Smith et al., 2016 ;Wen et al., 2017Wen et al., , 2016. Here 'anomalous CH 4 ' is used to denote dissolved or free-phase CH 4 found in groundwater that is putatively derived from the effects of recent human activities related to shale gas development. ...
... This explains why some researchers have observed correlations between concentrations of CH 4 and chloride (Cl) in groundwater in PA and New York (Harkness et al., 2017;Kreuzer et al., 2018). Appalachian Basin brine salts may be observed in groundwater either because brine migration is ongoing today or because Appalachian Basin brine fluids trapped in small pores in aquifers are still being flushed out today (Llewellyn, 2014;Siegel et al., 2016Siegel et al., , 2015bSiegel et al., , 2015aWarner et al., 2012). ...
... Classroom lectures are used to teach fundamental knowledge of groundwater such as Darcy's law and water balance, as well as to tackle multidisciplinary topics that might be raised from students with potentially diverse backgrounds. For example, Siegel and McKenzie (2004) presented a real-world contamination project that divides students into three groups and culminates in a day-long mock trial. Neupauer (2008) described a semester-long project that integrates classroom theories into weekly assignments. ...
... This overview paper only touches on some of her work. Additional research has been published on streamflow statistics (Glas et al., 2019a), effectiveness of BDAs on shifting stream geochemistry and morphology (Davis et al., 2021;Pearce et al., 2021aPearce et al., , 2021bWade et al., 2020), and pedagogical practices (Bauer et al., 2009;Lautz et al., 2007;Russoniello and Lautz, 2020). Lautz also implemented a cross-disciplinary graduate studies program that brought together Master's and PhD students interested in research at the intersection of water and energy (EMPOWER, https ://empower.syr.edu/). ...
... This overview paper only touches on some of her work. Additional research has been published on streamflow statistics (Glas et al., 2019a), effectiveness of BDAs on shifting stream geochemistry and morphology (Davis et al., 2021;Pearce et al., 2021aPearce et al., , 2021bWade et al., 2020), and pedagogical practices (Bauer et al., 2009;Lautz et al., 2007;Russoniello and Lautz, 2020). Lautz also implemented a cross-disciplinary graduate studies program that brought together Master's and PhD students interested in research at the intersection of water and energy (EMPOWER, https ://empower.syr.edu/). ...
... The research area was a peatland where runoff occurs on and below the peat soil surface. As a result, lateral and vertical water infiltration occurred in the peat soil column [24,32]. Therefore, direct observation of changes in groundwater level, rainfall intensity, and evapotranspiration in the field was crucial. ...
... Similarly, simply telling one to "listen to the facts" of technology does not build trust [as per Kahneman (2011) and Duffy (2018)], particularly if opponents have a good reason not to trust technology companies or governmental agencies. Facts alone will not change minds [refer to, e.g., Siegel (2016) and Siegel (2019)]. A campaign would have to build credibility with opponents, by using someone they trust to spread the message, "cognitive-infiltration and persuasion" in the terms of Sunstein and Vermeule (2009, p. 224). ...
... As the subsurface component of the water cycle, groundwater circulation ( Duffy and Al-Hassan, 1988 ;Nativ et al., 1997 ) is an important hydrological process in terrestrial environments that supplies renewable fresh water and maintains the base flow of surface water systems. Groundwater circulation below the undulant water table in a basin with multiple wave lengths has been found to occur in the form of hierarchically nested flow systems, i.e., a composition of local, intermediate and regional flow systems ( Tóth, 1963 ;Freeze and Cherry, 1979 ;Engelen and Kloosterman, 1996 ;Schwartz and Zhang, 2003 ;Liang et al., 2010 ;Liang et al., 2013 ;Anderson and Siegel, 2013 ). In addition, such nested groundwater flow sys- Jiang et al. (2014) with 3 stagnation points, SP1, SP2 and SP3. ...