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A. Nanou-giannarou - One of the best experts on this subject based on the ideXlab platform.
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Development and verification of a 3-D integrated surface water-Groundwater Model
Journal of Hydrology, 2009Co-Authors: Katerina Spanoudaki, Anastasios I. Stamou, A. Nanou-giannarouAbstract:Summary Coupled Modelling of surface and subsurface systems is a valuable tool for quantifying surface water–Groundwater interactions. In the present paper, the 3-D non-steady state Navier–Stokes equations, after Reynolds averaging and with the assumption of a hydrostatic pressure distribution, are for the first time coupled to the 3-D saturated Groundwater flow equations in an Integrated suRface watEr–Groundwater Model (IRENE). A finite-difference method is used for the solution of the governing equations of IRENE. A semi-implicit scheme is used for the discretisation of the surface water flow equations and a fully implicit scheme for the discretisation of the Groundwater flow equations. The two sets of equations are coupled at the common interface of the surface water and Groundwater bodies, where water exchange takes place, using Darcy’s law. A new approach is proposed for the solution of the coupled surface water and Groundwater equations in a simultaneous manner, in such a fashion that gives computational efficiency at low computational cost. IRENE is verified against three analytical solutions of surface water–Groundwater interaction, which are chosen so that different components of the Model can be tested. The Model closely reproduces the results of the analytical solutions and can therefore be used for analysing and predicting surface water–Groundwater interactions in real-world cases.
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Development and verification of a 3-D integrated surface water–Groundwater Model
Journal of Hydrology, 2009Co-Authors: Katerina Spanoudaki, Anastasios I. Stamou, A. Nanou-giannarouAbstract:Coupled Modelling of surface and subsurface systems is a valuable tool for quantifying surface water-Groundwater interactions. In the present paper, the 3-D non-steady state Navier-Stokes equations, after Reynolds averaging and with the assumption of a hydrostatic pressure distribution, are for the first time coupled to the 3-D saturated Groundwater flow equations in an Integrated suRface watEr-Groundwater Model (IRENE). A finite-difference method is used for the solution of the governing equations of IRENE. A semi-implicit scheme is used for the discretisation of the surface water flow equations and a fully implicit scheme for the discretisation of the Groundwater flow equations. The two sets of equations are coupled at the common interface of the surface water and Groundwater bodies, where water exchange takes place, using Darcy's law. A new approach is proposed for the solution of the coupled surface water and Groundwater equations in a simultaneous manner, in such a fashion that gives computational efficiency at low computational cost. IRENE is verified against three analytical solutions of surface water-Groundwater interaction, which are chosen so that different components of the Model can be tested. The Model closely reproduces the results of the analytical solutions and can therefore be used for analysing and predicting surface water-Groundwater interactions in real-world cases. (C) 2009 Elsevier B.V. All rights reserved
M F P Bierkens - One of the best experts on this subject based on the ideXlab platform.
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a global scale two layer transient Groundwater Model development and application to Groundwater depletion
Advances in Water Resources, 2017Co-Authors: Inge De Graaf, Rens Van Beek, Tom Gleeson, Nils Moosdorf, Oliver Schmitz, Edwin Sutanudjaja, M F P BierkensAbstract:Abstract Groundwater is the world’s largest accessible source of freshwater to satisfy human water needs. Moreover, Groundwater buffers variable precipitation rates over time, thereby effectively sustaining river flows in times of droughts and evaporation in areas with shallow water tables. In this study, building on previous work, we simulate Groundwater head fluctuations and Groundwater storage changes in both confined and unconfined aquifer systems using a global-scale high-resolution (5′) Groundwater Model by deriving new estimates of the distribution and thickness of confining layers. Inclusion of confined aquifer systems (estimated 6–20% of the total aquifer area) improves estimates of timing and amplitude of Groundwater head fluctuations and changes Groundwater flow paths and Groundwater-surface water interaction rates. Groundwater flow paths within confining layers are shorter than paths in the underlying aquifer, while flows within the confined aquifer can get disconnected from the local drainage system due to the low conductivity of the confining layer. Lateral Groundwater flows between basins are significant in the Model, especially for areas with (partially) confined aquifers were long flow paths crossing catchment boundaries are simulated, thereby supporting water budgets of neighboring catchments or aquifer systems. The developed two-layer transient Groundwater Model is used to identify hot-spots of Groundwater depletion. Global Groundwater depletion is estimated as 7013 km3 (137 km3y − 1 ) over 1960–2010, which is consistent with estimates of previous studies.
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a global scale two layer transient Groundwater Model development and application to Groundwater depletion
Hydrology and Earth System Sciences Discussions, 2016Co-Authors: Inge De Graaf, Rens Van Beek, Tom Gleeson, Nils Moosdorf, Oliver Schmitz, Edwin Sutanudjaja, M F P BierkensAbstract:Abstract. Groundwater is the world's largest accessible source of freshwater to satisfy human water needs. Moreover, Groundwater buffers variable precipitation rates over time, thereby effectively sustaining river flows in times of droughts as well as evaporation in areas with shallow water tables. Lateral flows between basins can be a significant part of the basins water budget, but most global-scale hydrological Models do not consider surface water-Groundwater interactions and do not include a lateral Groundwater flow component. In this study we simulate Groundwater head fluctuation and Groundwater storage changes in both confined and unconfined aquifer systems using a global-scale high-resolution (5 arc-minutes) Groundwater Model by deriving new estimates of the distribution and thickness of confining layers. Inclusion of confined aquifer systems (estimated 6 % to 20 % of the total aquifer area) changes timing and amplitude of head fluctuations, as well as flow paths and Groundwater-surface water interactions rates. Also, timing and magnitude of Groundwater head fluctuations are better estimated when confining layers are included. Groundwater flow paths within confining layers are shorter then paths in the underlying aquifer, while flows within the confined aquifer can get disconnected from the local drainage system due to the low conductivity of the confining layer. Lateral Groundwater flows between basins are significant in the Model, especially for areas with (partially) confined aquifers were long flow paths are simulated crossing catchment boundaries, thereby supporting water budgets of neighboring catchments or aquifer systems. The two-layer transient Groundwater Model is used to identify hotspots of Groundwater depletion resulting in an estimated global Groundwater depletion of 6700 km3 over the 1960–2010, consistent with estimates of previous studies.
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a high resolution global scale Groundwater Model
Hydrology and Earth System Sciences, 2015Co-Authors: I E M De Graaf, Edwin Sutanudjaja, L P H Van Beek, M F P BierkensAbstract:Groundwater is the world's largest accessible source of fresh water. It plays a vital role in satisfying basic needs for drinking water, agriculture and industrial activities. During times of drought Groundwater sustains baseflow to rivers and wetlands, thereby supporting ecosystems. Most global-scale hydrological Models (GHMs) do not include a Groundwater flow component, mainly due to lack of geohydrological data at the global scale. For the simulation of lateral flow and Groundwater head dynamics, a realistic physical representation of the Groundwater system is needed, especially for GHMs that run at finer resolutions. In this study we present a global-scale Groundwater Model (run at 6' resolution) using MODFLOW to construct an equilibrium water table at its natural state as the result of long-term climatic forcing. The used aquifer schematization and properties are based on available global data sets of lithology and transmissivities combined with the estimated thickness of an upper, unconfined aquifer. This Model is forced with outputs from the land-surface PCRaster Global Water Balance (PCR-GLOBWB) Model, specifically net recharge and surface water levels. A sensitivity analysis, in which the Model was run with various parameter settings, showed that variation in saturated conductivity has the largest impact on the Groundwater levels simulated. Validation with observed Groundwater heads showed that Groundwater heads are reasonably well simulated for many regions of the world, especially for sediment basins ( R 2 = 0.95). The simulated regional-scale Groundwater patterns and flow paths demonstrate the relevance of lateral Groundwater flow in GHMs. Inter-basin Groundwater flows can be a significant part of a basin's water budget and help to sustain river baseflows, especially during droughts. Also, water availability of larger aquifer systems can be positively affected by additional recharge from inter-basin Groundwater flows.
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Large-scale Groundwater Modeling using global datasets: a test case for the Rhine-Meuse basin
2011Co-Authors: E. H. Sutanudjaja, F.c. Van Geer, L P H Van Beek, S. M. De Jong, M F P BierkensAbstract:Abstract. Large-scale Groundwater Models involving aquifers and basins of multiple countries are still rare due to a lack of hydrogeological data which are usually only available in developed countries. In this study, we propose a novel approach to construct large-scale Groundwater Models by using global datasets that are readily available. As the test-bed, we use the combined Rhine-Meuse basin that contains Groundwater head data used to verify the Model output. We start by building a distributed land surface Model (30 arc-second resolution) to estimate Groundwater recharge and river discharge. Subsequently, a MODFLOW transient Groundwater Model is built and forced by the recharge and surface water levels calculated by the land surface Model. Although the method that we used to couple the land surface and MODFLOW Groundwater Model is considered as an offline-coupling procedure (i.e. the simulations of both Models were performed separately), results are promising. The simulated river discharges compare well to the observations. Moreover, based on our sensitivity analysis, in which we run several Groundwater Model scenarios with various hydrogeological parameter settings, we observe that the Model can reproduce the observed Groundwater head time series reasonably well. However, we note that there are still some limitations in the current approach, specifically because the current offline-coupling technique simplifies dynamic feedbacks between surface water levels and Groundwater heads, and between soil moisture states and Groundwater heads. Also the current sensitivity analysis ignores the uncertainty of the land surface Model output. Despite these limitations, we argue that the results of the current Model show a promise for large-scale Groundwater Modeling practices, including for data-poor environments and at the global scale.
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Upscaling hydraulic conductivity: theory and examples from geohydrological studies
Nutrient Cycling in Agroecosystems, 1998Co-Authors: M F P Bierkens, J.w.j. Van Der GaastAbstract:This paper presents an overview of the theory of upscaling hydraulic conductivity and describes two case studies in which some of this theory has been applied. The representative hydraulic conductivity of a numerical Model block (‘block conductivity’ for short) is defined in terms of smaller scale hydraulic conductivities. Also, using elementary examples, some general properties of block conductivities are given. Analytical solutions for the block conductivity are presented that were derived by various authors for uniform flow conditions both in a deterministic and in a stochastic setting. Some results of the hydraulic upscaling theory are illustrated by two case studies from the Netherlands. The first case study deals with deriving the representative hydraulic conductivity tensor of a clay layer. Upscaling results are compared with traditional harmonic averaging. In the second case study the upscaling is used to derive the three-dimensional distribution of block conductivities for a numerical Groundwater Model of a confining layer of complex deposits. Here stochastic upscaling is used together with a geostatistical simulation approach. The simulated block conductivities are used in a numerical Groundwater Model and results are compared with pumping tests. When the upscaling is ignored Groundwater flow through the deposits is predicted wrongly.
Katerina Spanoudaki - One of the best experts on this subject based on the ideXlab platform.
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Development and verification of a 3-D integrated surface water-Groundwater Model
Journal of Hydrology, 2009Co-Authors: Katerina Spanoudaki, Anastasios I. Stamou, A. Nanou-giannarouAbstract:Summary Coupled Modelling of surface and subsurface systems is a valuable tool for quantifying surface water–Groundwater interactions. In the present paper, the 3-D non-steady state Navier–Stokes equations, after Reynolds averaging and with the assumption of a hydrostatic pressure distribution, are for the first time coupled to the 3-D saturated Groundwater flow equations in an Integrated suRface watEr–Groundwater Model (IRENE). A finite-difference method is used for the solution of the governing equations of IRENE. A semi-implicit scheme is used for the discretisation of the surface water flow equations and a fully implicit scheme for the discretisation of the Groundwater flow equations. The two sets of equations are coupled at the common interface of the surface water and Groundwater bodies, where water exchange takes place, using Darcy’s law. A new approach is proposed for the solution of the coupled surface water and Groundwater equations in a simultaneous manner, in such a fashion that gives computational efficiency at low computational cost. IRENE is verified against three analytical solutions of surface water–Groundwater interaction, which are chosen so that different components of the Model can be tested. The Model closely reproduces the results of the analytical solutions and can therefore be used for analysing and predicting surface water–Groundwater interactions in real-world cases.
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Development and verification of a 3-D integrated surface water–Groundwater Model
Journal of Hydrology, 2009Co-Authors: Katerina Spanoudaki, Anastasios I. Stamou, A. Nanou-giannarouAbstract:Coupled Modelling of surface and subsurface systems is a valuable tool for quantifying surface water-Groundwater interactions. In the present paper, the 3-D non-steady state Navier-Stokes equations, after Reynolds averaging and with the assumption of a hydrostatic pressure distribution, are for the first time coupled to the 3-D saturated Groundwater flow equations in an Integrated suRface watEr-Groundwater Model (IRENE). A finite-difference method is used for the solution of the governing equations of IRENE. A semi-implicit scheme is used for the discretisation of the surface water flow equations and a fully implicit scheme for the discretisation of the Groundwater flow equations. The two sets of equations are coupled at the common interface of the surface water and Groundwater bodies, where water exchange takes place, using Darcy's law. A new approach is proposed for the solution of the coupled surface water and Groundwater equations in a simultaneous manner, in such a fashion that gives computational efficiency at low computational cost. IRENE is verified against three analytical solutions of surface water-Groundwater interaction, which are chosen so that different components of the Model can be tested. The Model closely reproduces the results of the analytical solutions and can therefore be used for analysing and predicting surface water-Groundwater interactions in real-world cases. (C) 2009 Elsevier B.V. All rights reserved
Peter Bauer-gottwein - One of the best experts on this subject based on the ideXlab platform.
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Performance evaluation of Groundwater Model hydrostratigraphy from airborne electromagnetic data and lithological borehole logs
Hydrology and Earth System Sciences, 2015Co-Authors: Pernille Aabye Marker, Esben Auken, Anders Vest Christiansen, Nikolaj Foged, Jens Christian Refsgaard, Peter Bauer-gottweinAbstract:Large-scale hydrological Models are important de- cision support tools in water resources management. The largest source of uncertainty in such Models is the hydros- tratigraphic Model. Geometry and configuration of hydroge- ological units are often poorly determined from hydrogeo- logical data alone. Due to sparse sampling in space, litholog- ical borehole logs may overlook structures that are impor- tant for Groundwater flow at larger scales. Good spatial cov- erage along with high spatial resolution makes airborne elec- tromagnetic (AEM) data valuable for the structural input to large-scale Groundwater Models. We present a novel method to automatically integrate large AEM data sets and lithologi- cal information into large-scale hydrological Models. Clay- fraction maps are produced by translating geophysical re- sistivity into clay-fraction values using lithological borehole information. Voxel Models of electrical resistivity and clay fraction are classified into hydrostratigraphic zones usingk- means clustering. Hydraulic conductivity values of the zones are estimated by hydrological calibration using hydraulic head and stream discharge observations. The method is ap- plied to a Danish case study. Benchmarking hydrological per- formance by comparison of performance statistics from com- parable hydrological Models, the cluster Model performed competitively. Calibrations of 11 hydrostratigraphic cluster Models with 1-11 hydraulic conductivity zones showed im- proved hydrological performance with an increasing num- ber of clusters. Beyond the 5-cluster Model hydrological per- formance did not improve. Due to reproducibility and pos- sibility of method standardization and automation, we be- lieve that hydrostratigraphic Model generation with the pro- posed method has important prospects for Groundwater mod- els used in water resources management.
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Sequential and joint hydrogeophysical inversion using a field-scale Groundwater Model with ERT and TDEM data
Hydrology and Earth System Sciences, 2013Co-Authors: Daan Herckenrath, Gianluca Fiandaca, Esben Auken, Peter Bauer-gottweinAbstract:Increasingly, ground-based and airborne geophys- ical data sets are used to inform Groundwater Models. Re- cent research focuses on establishing coupling relationships between geophysical and Groundwater parameters. To fully exploit such information, this paper presents and compares different hydrogeophysical inversion approaches to inform a field-scale Groundwater Model with time domain electromag- netic (TDEM) and electrical resistivity tomography (ERT) data. In a sequential hydrogeophysical inversion (SHI) a Groundwater Model is calibrated with geophysical data by coupling Groundwater Model parameters with the inverted geophysical Models. We subsequently compare the SHI with a joint hydrogeophysical inversion (JHI). In the JHI, a geo- physical Model is simultaneously inverted with a groundwa- ter Model by coupling the Groundwater and geophysical pa- rameters to explicitly account for an established petrophysi- cal relationship and its accuracy. Simulations for a synthetic Groundwater Model and TDEM data showed improved esti- mates for Groundwater Model parameters that were coupled to relatively well-resolved geophysical parameters when em- ploying a high-quality petrophysical relationship. Compared to a SHI these improvements were insignificant and geophys- ical parameter estimates became slightly worse. When em- ploying a low-quality petrophysical relationship, groundwa- ter Model parameters improved less for both the SHI and JHI, where the SHI performed relatively better. When comparing a SHI and JHI for a real-world Groundwater Model and ERT data, differences in parameter estimates were small. For both
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Sequential and joint hydrogeophysical inversion using a field-scale Groundwater Model with ERT and TDEM data
2013Co-Authors: Daan Herckenrath, Gianluca Fiandaca, Esben Auken, Peter Bauer-gottweinAbstract:Abstract. Increasingly, ground-based and airborne geophysical datasets are used to inform Groundwater Models. Recent research focuses on establishing coupling relationships between geophysical and Groundwater parameters. To fully exploit such information, this paper presents and compares a joint hydrogeophysical inversion (JHI) approach and sequential hydrogeophysical inversion (SHI) approach to inform a field-scale Groundwater Model with Time Domain Electromagnetic (TDEM) and Electrical Resistivity Tomography (ERT) data. The implemented SHI coupled inverted geophysical Models with Groundwater parameters, where the strength of the coupling was based on geophysical parameter resolution. To test whether the implemented SHI over- or underestimated the coupling strength between Groundwater and geophysical Model, we compared its results with a JHI in which a geophysical Model is simultaneously inverted with a Groundwater Model using additional coupling constraints that explicitly account for an established petrophysical relationship and its accuracy. The first set of simulations for a synthetic Groundwater Model and TDEM data, employing a high-quality petrophysical and geometric relationship, showed improved estimates for Groundwater Model parameters that were coupled to relative well-resolved geophysical parameters. Compared to a SHI these improvements were insignificant and geophysical parameter estimates became slightly worse. In a second set of simulations, employing a low-quality petrophysical relationship, Groundwater parameter improved less for both the SHI and JHI, where the SHI performed slightly better. For a real-world Groundwater Model and ERT data, different parameter estimates were obtained with a JHI and SHI. Parameter uncertainty was reduced but was similar for the SHI and JHI. The geometric constraint showed little impact while the petrophysical constraint showed significant changes in geophysical and Groundwater parameters. For both cases investigated in this paper, the SHI seems favorable, taking in account parameter error, data fit and the complexity of implementing a JHI in combination with its larger computational burden.
Okke Batelaan - One of the best experts on this subject based on the ideXlab platform.
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Bayesian data fusion for water table interpolation: Incorporating a hydrogeological conceptual Model in kriging
Water Resources Research, 2010Co-Authors: Luk Peeters, Dominique Fasbender, Okke Batelaan, Alain DassarguesAbstract:The creation of a contour map of the water table in an unconfined aquifer based on head measurements is often the first step in any hydrogeological study. Geostatistical interpolation methods (e.g., kriging) may provide exact interpolated Groundwater levels at the measurement locations but often fail to represent the hydrogeological flow system. A physically based, numerical Groundwater Model with spatially variable parameters and inputs is more adequate in representing a flow system. Because of the difficulty in parameterization and solving the inverse problem, however, a considerable difference between calculated and observed heads will often remain. In this study the water‐table interpolation methodology presented by Fasbender et al. (2008), in which the results of a kriging interpolation are combined with information from a drainage network and a digital elevation Model (DEM), using the Bayesian data fusion framework, is extended to incorporate information from a tuned analytic element Groundwater Model. The resulting interpolation is exact at the measurement locations whereas the shape of the head contours is in accordance with the conceptual information incorporated in the Groundwater‐flow Model. The Bayesian data fusion methodology is applied to a regional, unconfined aquifer in central Belgium. A cross‐validation procedure shows that the predictive capability of the interpolation at unmeasured locations benefits from the Bayesian data fusion of the three data sources (kriging, DEM, and Groundwater Model), compared to the individual data sources or any combination of two data sources.
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gis based recharge estimation by coupling surface subsurface water balances
Journal of Hydrology, 2007Co-Authors: Okke Batelaan, F De SmedtAbstract:A spatially distributed water balance Model is developed to simulate long-term average recharge depending on land cover, soil texture, topography and hydrometeorological parameters. The Model simulates recharge iteratively connected to a Groundwater Model, such that the recharge estimate is also influenced by the Groundwater depth and vice versa. Parameter estimation for the Model is performed on the basis of literature values of water balance fluxes from mainly Belgium and The Netherlands. By graphical and non-linear baseflow separation for 17 catchments it is shown that recharge spatially varies considerably. The water balance Model coupled to a regional Groundwater Model is applied and successfully tested on the 17 catchments. The application shows that the resulting recharge has a spatial complex pattern, depending to a large extend on the soil texture and land cover. Moreover, shallow Groundwater levels in valleys cause negative recharge conditions as a result of evapotranspiration by abundant phreatophytic vegetation. GIS analysis shows how recharge strongly varies for different combinations of land cover and soil texture classes. The performed analysis provides a better insight into the sustenance and management of Groundwater resources.
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Integrating vegetation mapping in Groundwater Modelling for ecohydrological predictions within an ecosystem vision.
2004Co-Authors: Jan Corluy, Okke Batelaan, Boud Verbeiren, Florimond De SmedtAbstract:In general, Groundwater Models need readily available data of measured heads for calibration. In some cases timeseries of measured heads are not readily available, do not exist or are of insufficient quality in order to carry out a sound calibration. In this article, an alternative methodology for calibrating Groundwater Models is presented, based on a feedback from ecology towards hydrology. On the basis of the available vegetation survey and with the use of GIS, area-covering maps of different hydrological parameters were created and compared to the output of the Groundwater Model. A number of different evaluation criteria were established to facilitate this comparison. By adopting this methodology a successful calibration of the Model was obtained. The presented Groundwater Model was developed in the framework of an ecosystem vision for four brook valleys at the southern side of the Campine Plateau in Flanders in order to make ecohydrological predictions for hypothetical scenarios.
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Development of a Groundwater Model for some Small Sub-Catchments of the Dender Basin
Geologica Belgica, 2002Co-Authors: Boud Verbeiren, Okke Batelaan, Florimond De SmedtAbstract:To characterise the ecological condition of valleys hydrological variables such as Groundwater level, fluctuation, discharge zones, etc. are required. In this study a Groundwater Modelling approach is used for the estimation of these variables. Within the framework of the action plan “Development of ecosystem approaches for different valleys in Flanders” a MODFLOW Groundwater Model was developed, for three sub-catchments of the Dender River. GIS was used to prepare the input, to analyse the output and to present the results of the Groundwater Modelling. The results of the Groundwater Model, a set of hydrological variables, was used to analyse the relationship between vegetation and Groundwater. Both the present Groundwater system as well as a future optimal situation were simulated. The Model and its analyses serve, within this ecosystem approach, as a basis for the formulation of policy measures for nature conservation and (potential) nature management in the area.
