Subsurface Water Flow Research Articles

Morphostructural Development of Gunungsewu Karst, Jawa Island

DOI: 10.17014/ijog.v8i2.157Gunungsewu Karst (also known as Sewu karst in the literature) is synonymous with morphology of a carbonate terrain dominated by hills crowned by accordant-level tops that developed in a humid tropical environment by comparatively more rapid dissolution and denudation. In addition, the hills are sinoid to cone-shaped. Surface drainage is negligible compared to subsurface water flow. Abandoned channel segments and spatial arrangements of karst hills have been found to correspond with fracture patterns that are genetically associated with the regional compression direction of Jawa Island. Images derived from space platforms show many landform patterns that were neither known from ground-based nor from aerial photograph study. Landforms arranged in ring, multi-ring, spiral, polygonal, and long linear to serpentine patterns are common beside the expected depressions of dolines, poljes, and uvalas. The orientations of the long linear ridges appear to change systematically from those near the coast to those located inland. These linear ridges are interpreted as depositional fronts, most likely representing breaker zones. The youngest depositional ridge fronts, located nearest to the present shoreline, are parallel to the geological strike of Jawa Island. Toward the island’s interior, linear depositional fronts deviate in orientation by as much as 40o. This is now interpreted to have resulted from counterclockwise rotation of the Gunungsewu microplate since the late Middle Miocene. Similar CCW rotations are indicated by the paleomagnetic orientations of igneous rocks located farther east in the southern range of the island. Active tectonics is expressed in stage-wise net uplift of Gunungsewu whereas regional tilting appears negligible. Stacked and often paired river terraces (thus suggesting land uplift) have been used to relatively date paleoarcheological finds. Very recent uplift on the coast show up in lazy-V limestone notch profiles, and occasionally by stacked notches. At the Klayar coast, slight northward tilt of a few degrees are expressed as counter-regional inclination of a subrecent abrasion platform.

Effects of spatial information of soil physical properties on hydrological modeling based on a distributed hydrological model

The spatial distribution of soil physical properties is essential for modeling and understanding hydrological processes. In this study, the different spatial information (the conventional soil types map-based spatial information (STMB) versus refined spatial information map (RSIM)) of soil physical properties, including field capacity, soil porosity and saturated hydraulic conductivity are used respectively as input data for Water Flow Model for Lake Catchment (WATLAC) to determine their effectiveness in simulating hydrological processes and to expound the effects on model performance in terms of estimating groundwater recharge, soil evaporation, runoff generation as well as partitioning of surface and subsurface water flow. The results show that: 1) the simulated stream flow hydrographs based on the STMB and RSIM soil data reproduce the observed hydrographs well. There is no significant increase in model accuracy as more precise soil physical properties information being used, but WATLAC model using the RSIM soil data could predict more runoff volume and reduce the relative runoff depth errors; 2) the groundwater recharges have a consistent trend for both cases, while the STMB soil data tend to produce higher groundwater recharges than the RSIM soil data. In addition, the spatial distribution of annual groundwater recharge is significantly affected by the spatial distribution of soil physical properties; 3) the soil evaporation simulated using the STMB and RSIM soil data are similar to each other, and the spatial distribution patterns are also insensitive to the spatial information of soil physical properties; and 4) although the different spatial information of soil physical properties does not cause apparent difference in overall stream flow, the partitioning of surface and subsurface water flow is distinct. The implications of this study are that the refined spatial information of soil physical properties does not necessarily contribute to a more accurate prediction of stream flow, and the selection of appropriate soil physical property data needs to consider the scale of watersheds and the level of accuracy required.

Modelling the interaction of surface and subsurface water flow by linking TOPMODEL and MODFLOW

A coupled ground water–surface water model was used to quantify the hydrological processes in a lowland watershed. The model was constructed by coupling TOPMODEL and MODFLOW without writing new code for the integrated model. Meteorological, land use and soil type data for the Tenmile watershed, USA, were used to run TOPMODEL, which partitions precipitation into evapotranspiration, runoff and recharge. The ground water model, MODFLOW, is driven by recharge derived from TOPMODEL and provides water table elevation and baseflow. The coupled model was calibrated and validated with stream discharge and ground water head data for the period 1968 to 1972. Nash-Sutcliffe model efficiency (E) and correlation coefficient (r) were used to evaluate model behaviour. The model demonstrated good performance, with average E and r values greater than 0.7 for stream flow and ground water head during calibration and validation. Despite obvious challenges in harmonising the different spatial and temporal discretisation in surface water and ground water models, the results from this study demonstrate that the coupled model is capable of simulating hydrological processes in the study area and that with further improvements, it can be a useful tool for integrated management of surface water and ground water resources.

Statistical Change Detection in Water Cycle over Two Decades and Assessment of Impact of Urbanization on Surface and Sub-Surface Water Flows

Urbanization is termed as physical transformation of landscapes that alter the natural regime of the environment of its surrounding resulting in further changes in macro as well as micro climate of the region [1]. Urban areas are continually facing problems of water scarcity and urban flash floods. Recent news from IPCC report 2010, CIESIN’s Global Rural Urban Mapping Project [2] and World Water Vol. 7 2007, it is clear that urban land area has doubled and affected the hydrological cycle. The components of hydrological cycle affected are Infiltration, Runoff and Evaporation and the causing components are derived by studies as land use, land cover, water withdrawal and urban developments. Thus water availability, water recharge and water cycle are all destabilized in course or urban development. The paper is an attempt to correlate and identify the periodical changes in urban water cycle, during urbanization of Bhopal City, India, during last twenty years and above. The observations are based on GIS mapping of the study area from 1991 to 2009 using rational method of runoff and recharge calculations and statistical analysis of related built-up areas. Also change in natural course of drainages with the help of GIS imageries which have been detected during twenty years that help to observe the adaptation of natural system to urban course. Also the observations show an interesting relation which can be used for further research and sustainable development [3].

Three‐phase compositional modeling of CO2 injection by higher‐order finite element methods with CPA equation of state for aqueous phase

Most simulators for subsurface flow of water, gas, and oil phases use empirical correlations, such as Henry's law, for the CO2 composition in the aqueous phase, and equations of state (EOS) that do not represent the polar interactions between CO2and water. Widely used simulators are also based on lowest‐order finite difference methods and suffer from numerical dispersion and grid sensitivity. They may not capture the viscous and gravitational fingering that can negatively affect hydrocarbon (HC) recovery, or aid carbon sequestration in aquifers. We present a three‐phase compositional model based on higher‐order finite element methods and incorporate rigorous and efficient three‐phase‐split computations for either three HC phases or water‐oil‐gas systems. For HC phases, we use the Peng‐Robinson EOS. We allow solubility of CO2in water and adopt a new cubic‐plus‐association (CPA) EOS, which accounts for cross association between H2O and CO2 molecules, and association between H2O molecules. The CPA‐EOS is highly accurate over a broad range of pressures and temperatures. The main novelty of this work is the formulation of a reservoir simulator with new EOS‐based unique three‐phase‐split computations, which satisfy both the equalities of fugacities in all three phases and the global minimum of Gibbs free energy. We provide five examples that demonstrate twice the convergence rate of our method compared with a finite difference approach, and compare with experimental data and other simulators. The examples consider gravitational fingering during CO2sequestration in aquifers, viscous fingering in water‐alternating‐gas injection, and full compositional modeling of three HC phases.

Impact of dumped sediment structures on hydrological modelling in the artificial Chicken Creek catchment, Germany

Revealing the hydrological impact of sediment structures promises a better understanding of the influence of the spatial variability of sediment properties on the hydrological patterns and processes at the catchment scale. To improve the knowledge of structure-process interactions in initial ecosystems, the 6-ha artificial Chicken Creek Catchment in Germany was investigated by the Transregional Collaborative Research Centre 38 (SFB/TRR 38). Sediment structures called pour-ribs, which are dumped by stackers during the construction process, lead to differently compacted sediment zones, which increase the spatial variability of sediments’ hydraulic properties. Although levelled afterwards by bulldozers, the majority of these structures remain in the subsurface. To analyse the effects of pour-ribs on the hydrological catchment’s behaviour, the process-based spatially distributed Water balance Simulation Model (WaSiM-ETH) was applied. The results show that the consideration of pour-ribs improves the runoff simulation and significantly affects the simulated soil moisture patterns and, thereby, the initial stage of the ecosystem development. Compacted zones act as hydraulic barriers and inhibit subsurface lateral water flow, whereas non-compacted zones constitute areas with increased water storage capacity. Both effects cause reduced catchment runoff. Moreover, disregarding of the pour-ribs was identified as a source of model uncertainty in previous studies. A further outcome of this study is the importance of a global sensitivity analysis as a tool for model improvement. Finally, the results stress the importance of considering the variability of sediment properties for hydrological modelling at the catchment scale.

Dryland Riparian Ecosystems in the American Southwest: Sensitivity and Resilience to Climatic Extremes

Drylands make up over 40% of the earth’s land surface (Noy-Meir 1973; Reynolds and others 2007). In these arid and semiarid landscapes, surface and subsurface water flows create mesic riparian environments (Kingsford 2006; Stromberg and Tellman 2009). Dryland riparian areas sustain water-limited plants and animals that cannot withstand upland conditions year-round, thereby supporting regional diversity (Sabo and others 2005; Lite and others 2005). Dryland rivers are also characterized by occasional large, high-intensity floods that rework the bed geomorphology and increase riparian heterogeneity. This combined variation in water availability and flood disturbance creates spatiotemporally complex and unique landscapes (Soykan and Sabo 2009; Soykan and others 2012). The hydrology of desert riparian ecosystems has been extensively altered by human activities including stream diversion and groundwater extraction, and is expected to undergo further change in response to changing climates (Patten 1998). Globally, increasing temperatures associated with climate change are expected to intensify the water cycle, leading to greater rates of evapotranspiration, more water in the atmosphere, and more-frequent intense storms (Huntington 2006; IPCC 2007). More intense storms are likely to increase flood intensity over the next 50 years (Dominguez and others 2012). In the American Southwest in particular, warmer sea surface temperatures could spur stronger and more-frequent El Nino-associated winter storms (Garfin and Lenart 2007). Perhaps of greater importance are projected increases in aridity. Average precipitation is expected to increase at a global scale, but some regions, including the American Southwest, are expected to experience substantial decreases in average annual rainfall as well as increases in frequency and intensity of droughts (Seager and others 2007). As aridity increases, streams and riparian zones undergo declines in surface flow and depth to groundwater; there are declines, as well, in the extent of river segments with perennial (vs. intermittent or ephemeral) stream flow. Given that rivers and their riparian corridors function as keystone elements of arid and semiarid landscapes, climate change will have far reaching effects on regional biota (Stromberg and others 2010). Nevertheless, the extent of biotic change for riparian ecosystems in coming decades will be tempered by the fact that for desert rivers, climatic and hydrologic variation is the norm (Milly and Received 30 May 2012; accepted 13 September 2012

A terrain-following grid transform and preconditioner for parallel, large-scale, integrated hydrologic modeling

A terrain-following grid formulation (TFG) is presented for simulation of coupled variably-saturated subsurface and surface water flow. The TFG is introduced into the integrated hydrologic model, ParFlow, which uses an implicit, Newton Krylov solution technique. The analytical Jacobian is also formulated and presented and both the diagonal and non-symmetric terms are used to precondition the Krylov linear system. The new formulation is verified against an orthogonal stencil and is shown to provide increased accuracy at lower lateral spatial discretization for hillslope simulations. Using TFG, efficient scaling to a large number of processors (16,384) and a large domain size (8.1 Billion unknowns) is shown. This demonstrates the applicability of this formulation to high-resolution, large-spatial extent hydrology applications where topographic effects are important. Furthermore, cases where the analytical Jacobian is used for the Newton iteration and as a non-symmetric preconditioner for the linear system are shown to have faster computation times and better scaling. This demonstrates the importance of solver efficiency in parallel scaling through the use of an appropriate preconditioner.

An integrated solution of the overland and subsurface flow along a sloping soil layer

Flow profiles of surface water passing over a vegetation-free area under a uniform rainfall are investigated by a semi-analytical approach. The ground is considered to be pervious and the soil layer of finite thickness is assumed homogeneous. The Navier–Stokes equations and Biot’s theory of poroelasticity are employed to govern the surface water flow and subsurface water flow, respectively. Since the velocity distributions appear to be still a function of the water depth, a numerical technique is necessary to find the flow profiles on the ground before solving the flow velocity and discharge. A dimensionless parameter related to soil porosity and permeability is proposed to reveal its effect on surface and subsurface water flow. The water depths at the upper boundary for surface water flow also verify the previous research. The present solutions are compared to the conventional solutions and numerical solutions to show the validation.

Glacitectonic sedimentary and hydraulic processes at an oscillating ice margin

An assemblage of subglacial, ice-terminal and proglacial landforms and sediments provides evidence for the relationship between ice-marginal glacitectonics, sedimentary processes and subglacial and proglacial hydraulic processes at a retreating late Devensian ice margin in north-central Ireland. Deltas were deposited in glacial lakes impounded between the retreating ice margin and the southern Sperrin Mountains, followed by outwash and end moraine formation as the ice margin retreated south. Sediments within the moraines show evidence for ice margin oscillation from two opposing ice margins, including subglacial bedrock rafts and breccias which are separated by glacitectonic shears with silty partings. In adjacent outwash, vertically-disturbed proglacial sands, gravels and silts located in front of moraine positions attest to high hydraulic pressure and subsurface water flow during ice oscillation. The relationship between sedimentary and hydraulic processes in the ice margin region is described by a depositional model which links glacitectonic thrusting and subsurface water flow during ice oscillation to formation of subglacial, ice-terminal and proglacial sediments. The evidence presented in this paper shows that subglacial and proglacial morphosedimentary processes and patterns of sediment deposition are mediated by the presence of proglacial permafrost, which helps direct processes and patterns of groundwater flow.

Influences of shifts in climate, landscape, and permafrost on terrestrial hydrology

This study has simulated the terrestrial hydrology associated with different climate, landscape, and permafrost regime scenarios for the field case example of the relatively well characterized coastal catchment of Forsmark, Sweden. The regime scenarios were selected from long‐term simulation results of climate, topographical, shoreline, and associated Quaternary deposit and vegetation development in this catchment with a time perspective of 100,000 years or more and were used as drivers for hydrological simulations with the three‐dimensional model MIKE SHE. The hydrological simulations quantify the responses of different water flow and water storage components of terrestrial hydrology to shifts from the present cool temperate climate landscape regime in Forsmark to a possible future Arctic periglacial landscape regime with or without permafrost. The results show complexity and nonlinearity in the runoff responses to precipitation changes due to parallel changes in evapotranspiration, along with changes in surface and subsurface water storage dynamics and flow pathways through the landscape. The results further illuminate different possible perspectives of what constitutes wetter/drier landscape conditions, in contrast to the clearer concept of what constitutes a warmer/colder climate.

Transient flow between aquifers and surface water: analytically derived field-scale hydraulic heads and fluxes

Abstract. The increasing importance of catchment-scale and basin-scale models of the hydrological cycle makes it desirable to have a simple, yet physically realistic model for lateral subsurface water flow. As a first building block towards such a model, analytical solutions are presented for horizontal groundwater flow to surface waters held at prescribed water levels for aquifers with parallel and radial flow. The solutions are valid for a wide array of initial and boundary conditions and additions or withdrawals of water, and can handle discharge into as well as lateral infiltration from the surface water. Expressions for the average hydraulic head, the flux to or from the surface water, and the aquifer-scale hydraulic conductivity are developed to provide output at the scale of the modelled system rather than just point-scale values. The upscaled conductivity is time-variant. It does not depend on the magnitude of the flux but is determined by medium properties as well as the external forcings that drive the flow. For the systems studied, with lateral travel distances not exceeding 10 m, the circular aquifers respond very differently from the infinite-strip aquifers. The modelled fluxes are sensitive to the magnitude of the storage coefficient. For phreatic aquifers a value of 0.2 is argued to be representative, but considerable variations are likely. The effect of varying distributions over the day of recharge damps out rapidly; a soil water model that can provide accurate daily totals is preferable over a less accurate model hat correctly estimates the timing of recharge peaks.

대도시 복합유역의 지표 및 지표하 유출해석기법 개발 (I)- 이론 및 모듈의 개발 -

Surface-subsurface interactions are an intrinsic component of the hydrologic response within a watershed. In general, these interactions are considered to be one of the most difficult areas of the discipline, particularly for the modeler who intends simulate the dynamic relations between these two major domains of the hydrological cycle. In essence, one major complexity is the spatial and temporal variations in the dynamically interacting system behavior. The proper simulation of these variations requires the need for providing an appropriate coupling mechanism between the surface and subsurface components of the system. In this study, an approach for modelling surface-subsurface flow and transport in a fully intergrated way is presented. The model uses the 2-dimensional diffusion wave equation for sheet surface water flow, and the Boussinesq equation with the Darcy`s law and Dupuit-Forchheimer`s assumption for variably saturated subsurface water flow. The coupled system of equations governing surface and subsurface flows is discretized using the finite volume method with central differencing in space and the Crank-Nicolson method in time. The interactions between surface and subsurface flows are considered mass balance based on the continuity conditions of pressure head and exchange flux. The major module consists of four sub-module (SUBFA, SFA, IA and NS module) is developed.

Integrated electrical resistivity tomography (ERT) and self-potential (SP) techniques for assessing hydrological processes within glacial lake moraine dams

AbstractMoraine dams can be inherently unstable, but effective assessment strategies remain poorly identified. We integrate electrical resistivity tomography (ERT) with electrical self-potential (SP) and lake-level measurements to investigate the structure of, and hydrological processes within, a moraine-dam complex adjacent to Miage glacier, Italy. This complex separates two meltwater lakes characterized by an efficient subterranean hydraulic connection. Our ERT data reveal a continuous free surface within the complex, whose morphology reflects the topography of the moraine complex akin to unconfined groundwater aquifers. SP data were corrected for spatial changes in the thickness of the upper unsaturated layer using principles of electrography. The residual streaming-potential map is consistent with Darcian flow of lake waters through the moraine complex, characterized by a negative-to-positive potential change from <-30 mV to >+70 mV. These electrical signatures are consistent with those generated by water seepage through earth dams in various non-glacial settings. Integrated electrical geophysical methods thus provided an inexpensive and unobtrusive evaluation of the hydrological properties of and processes within the moraine complex. Since spatio-temporal patterns of subsurface water flow critically affect the strengths of moraine sediments, such methods promise to be powerful in assessing the long-term stability of moraine-dammed glacial lakes.

Resistência à erosão em ravinas, em latossolo argiloarenoso

As ravinas consistem em uma das formas de erosão hídrica com escoamento superficial concentrado em encostas de áreas degradadas e, ainda, sem escoamentos de subsuperfície. Os objetivos deste trabalho foram estudar o comportamento hidráulico do escoamento superficial das ravinas e determinar a erodibilidade (Kr) e a tensão crítica de cisalhamento (τc) na superfície de ravinas e, também, a erodibilidade (Kr) ao longo do perfil de encostas degradadas do litoral do Estado de Pernambuco. O experimento foi realizado em 2005, em um Latossolo Amarelo de textura argilosa pertencente à Formação Barreiras no município do Cabo de Santo Agostinho, PE. As parcelas foram delimitadas por chapas metálicas cravadas no solo no sentido do declive (1,0 m de largura por 3,0 m de comprimento). Os testes consistiram na aplicação de quatro níveis de vazão, determinando-se o volume de descarga líquida e a massa de sedimentos desagregados. As taxas de desagregação de solo foram lineares em relação às tensões de cisalhamento. Na superfície das ravinas, a erodibilidade (Kr) foi de 0,0016 kg N-1 s-1 e a tensão crítica de cisalhamento, de τc = 4,37 Pa. O baixo valor de erodibilidade e o alto de tensão crítica de cisalhamento de τc obtidos na superfície das ravinas possivelmente decorreram da formação de uma crosta superficial originada por ciclos de umedecimento e secagem. A erodibilidade (Kr) em profundidade variou entre 0,012 e 0,070 kg N-1 s-1, em função do teor de argila. O regime do escoamento superficial nas ravinas foi turbulento supercrítico e, portanto, semelhante ao do escoamento superficial nos sulcos de erosão, como descrito na literatura.

Communication and ‘Forestructures’ at the Geological Intersection of Caves and Subsurface Water Flow: Hermeneutics and Parochialism

The direction of cave and karst science throughout its history has been partly determined by communication—or, more commonly, the lack of communication—between non-scientist cavers and non-caving physical geologists writing about karst. Within each community, advancement of ‘cave awareness’ occurred through a hermeneutic circle in which ‘forestructures’ guided progress. One result was regionalism of speleo-genetic theories developed within karst science because of the weight of evidence placed upon local or regional observations. Many speleogenetic theories of the mid-1900s suffer from this parochialism, failing to take into account findings from karst of different geologic settings. During the past half-century, the accumulated worldwide data on caves and karst suggest larger, more encompassing theories of speleogenesis. One such example of how speleogenetic theories have changed, partly explored in this essay, is the relation of cave formation to the position of the water-table. In many karst aquifers, including but not limited to alpine systems, one modern view envisions the enlargement of caves to proceed in a punctuated manner, driven by floods.

Simulation of 1D surface and 2D subsurface water flow and nitrate transport in alternate and conventional furrow fertigation

Increasing water and fertilizer productivity stands as a relevant challenge for sustainable agriculture. Alternate furrow irrigation and surface fertigation have long been identified as water and fertilizer conserving techniques in agricultural lands. The objective of this study was to simulate water flow and fertilizer transport in the soil surface and in the soil profile for variable and fixed alternate furrow fertigation and for conventional furrow fertigation. An experimental data set was used to calibrate and validate two simulation models: a 1D surface fertigation model and the 2D subsurface water and solute transfer model HYDRUS-2D. Both models were combined to simulate the fertigation process in furrow irrigation. The surface fertigation model could successfully simulate runoff discharge and nitrate concentration for all irrigation treatments. Six soil hydraulic and solute transport parameters were inversely estimated using the Levenberg–Marquardt optimization technique. The outcome of this process calibrated HYDRUS-2D to the observed field data. HYDRUS-2D was run in validation mode, simulating water content and nitrate concentration in the soil profiles of the wet furrows, ridges and dry furrows at the upstream, middle and downstream parts of the experimental field. This model produced adequate agreement between measured and predicted soil water content and nitrate concentration. The combined model stands as a valuable tool to better design and manage fertigation in alternate and conventional furrow irrigation.

On the relative role of upslope and downslope topography for describing water flow path and storage dynamics: a theoretical analysis

AbstractMany current conceptual rainfall‐runoff and shallow landslide stability models are based on the topographic index concept derived from the steady‐state assumption for subsurface water flow dynamics and the hypothesis that the surface gradient is a good approximation for the gradient of the total hydraulic head. However, increasing field evidence from sites around the world has shown poor correlations between the topographic index and the patterns of soil water storage. Here we present a new, smoothed, dynamic topographic index and test the ability of this index to reproduce spatial patterns of wetness areas and storage as provided by a distributed, physically based, Boussinesq equation (BEq) solver. Our results show that the new smoothed dynamic topographic index outperforms previous, locally computed indices in the estimation of storage dynamics, resulting in less fragmented and disconnected spatial patterns of storage. Our new dynamic index is able to capture both the upslope and downslope controls on water flow and approximates storage dynamics across scales. The new index is compatible with high‐resolution topographic data. We encourage the use of our smoothed dynamic topographic index to describe the lateral subsurface flow component in landslide generation models and conceptual rainfall‐runoff models, especially when high‐resolution digital elevation models are available. Copyright © 2011 John Wiley & Sons, Ltd.

Nitrogen removal by an irrigated wooded buffer area

To demonstrate the efficiency of the wooded riparian soil in removing the exceeding nitrogen from the river water, a pilot-scale experimental system (0,8 ha) was planned and built on an area previously used to grow arable crops. It was constructed to allow the precise management of the system hydrology, because the water is electrically pumped from the adjacent Zero River into the irrigation ditches (ridges). The particular structure, characterized by ridges and furrows, facilitates sub-surface water flow through the woodland area and the creation of a suspended artificial aquifer seldom in contact with the groundwater. A grid of 36 piezometers was used to collect water samples. The results indicated that the nitrates retention capacity increased strongly from about 40 to 85% from the first to the third year. Ammonia nitrogen showed the highest annual variability, with the outputs in some cases exceeding the inputs. Organic nitrogen outputs were always higher than the inputs, but with a progressive reduction from the first to the third year. Overall, total nitrogen retention increased from 26% in the first year, to 62% in the third year. A monitoring campaign conducted after 8 year confirmed the long term efficiency of the site in nitrate removal with an increase also in organic nitrogen reduction.

The hydrology of the proglacial zone of a high-Arctic glacier(Finsterwalderbreen, Svalbard): Sub-surface water fluxes and complete water budget

Summary Proglacial areas receive fluxes of glacial meltwater in addition to their own hydrological inputs and outputs, while in high latitudes the seasonal development of the active layer also affects their hydrology. This paper supplements a previous study of the surface and atmospheric water fluxes in the proglacial area of the Svalbard glacier Finsterwalderbreen (77° N), by focusing on the sub-surface water fluxes of the active layer, and bringing together all the components of the proglacial water balance over a complete annual cycle. Particular attention is given to the transitional zone between the moraine complex and the flat sandur. Sub-surface water in the moraine complex (sourced mainly from snowmelt, lake drainage and active-layer thawing), is exchanged with sub-surface water from the sandur (sourced mainly from glacier-derived snow- and ice-melt), across a largely distinct boundary. Hydraulic head and specific discharge were monitored in a transect of wells spanning this boundary. A hydraulic gradient from the moraine complex to the sandur is maintained throughout the melt season, although this is reversed first briefly when glacial runoff floods the sandur, and then diurnally from mid-melt-season, as peak daily flow in the proglacial channel network drives sub-surface water in the sandur towards the moraine complex. It is estimated that the active layer does not freeze up until mid-December at this location, so that sub-surface water flow may be maintained for months after the cessation of surface runoff. However, the magnitude of sub-surface flow is very small: the total, annual flux from the moraine complex to the sandur is 11 mm, compared with 1073 mm of total, annual runoff from the whole catchment (glacier included). Furthermore, when considering the water balance of the entire proglacial area, there are unlikely to be significant, seasonal storage changes in the active layer.