This document is the author's final manuscript version of the journal article, incorporating any ... more This document is the author's final manuscript version of the journal article, incorporating any revisions agreed during the peer review process. There may be differences between this and the publisher's version. You are advised to consult the publisher's version if you wish to cite from this article.
Study focus: Groundwater is of strategic importance. The accurate estimation of groundwater recha... more Study focus: Groundwater is of strategic importance. The accurate estimation of groundwater recharge and assessing the fundamental controlling factors are therefore of utmost importance to protect groundwater systems. We used the spatially-distributed waterbalance model WetSpass to estimate long-term average recharge in Flanders. We validated recharge rates with base flow estimates of 67 daily stream flow records using the hydrograph analyses. To this end we performed principal component analysis, multiple linear regression analysis and relative importance analysis to assess the controlling factors of the spatial variation of recharge and base flow with the influencing watershed characteristics. New hydrological insights for the region: The average resulting recharge is 235 mm/year and occurs mainly in winter. The overall moderate correlation between base flow estimates and modeled recharge rates indicates that base flow is a reasonable proxy of recharge. Groundwater recharge variation was explained in order of importance by precipitation, soil texture and vegetation cover; while base flow variation was strongly controlled by vegetation cover and groundwater depth. The results of this study highlight the important role of spatial variables in estimation of recharge and base flow. In addition, the prominent role of vegetation makes clear the potential importance of land-use changes on recharge and hence the need to include a proper strategy for land-use change in sustainable management of groundwater resources.
Drought is a recurrent natural hazard affecting arid/semi-arid, as well as temperate regions. Num... more Drought is a recurrent natural hazard affecting arid/semi-arid, as well as temperate regions. Numerous research efforts have been made for all types of drought (e.g. meteorological, hydrological and agricultural) in arid/semi-arid regions, whereas only a small number of studies have been performed in temperate regions. Moreover, in these regions, the type of hydrological drought which is related to groundwater is largely left unstudied. The GRoWaDRISK project is aimed to contribute to covering this gap. This paper summarises the aims, scope and methodology of the project. A large part of the Belgian territory was chosen as the study area. The project encompasses three groups of research tasks. First, knowledge regarding influencing factors of groundwater drought will be increased through using the best available spatial information on related variables (groundwater level, recharge and discharge). Second, the socio-economic and environmental impacts of droughts will be assessed for t...
A recently concluded research project called Measuring and Modelling Urban Dynamics (MAMUD), fund... more A recently concluded research project called Measuring and Modelling Urban Dynamics (MAMUD), funded by Belspo, investigated how high and moderate resolution satellite imagery can be used for mapping and modeling urban growth and its impact on the hydrology of the urban and suburban environment. In this paper, some of the research methods and major findings of this project are briefly discussed with a focus on work that was carried out on the Greater Dublin Area in Ireland.
International Journal of Applied Earth Observation and Geoinformation, 2013
This paper aims at developing a methodology for assessing urban dynamics in urban catchments and ... more This paper aims at developing a methodology for assessing urban dynamics in urban catchments and the related impact on hydrology. Using a multi-temporal remote sensing supported hydrological modelling approach an improved simulation of runoff for urban areas is targeted. A time-series of five medium resolution urban masks and corresponding sub-pixel sealed surface proportions maps was generated from Landsat and SPOT imagery. The consistency of the urban mask and sealed surface proportion timeseries was imposed through an urban change trajectory analysis. The physically based rainfall-runoff model WetSpa was successfully adapted for integration of remote sensing derived information of detailed urban land use and sealed surface characteristics. A first scenario compares the original land-use class based approach for hydrological parameterisation with a remote sensing sub-pixel based approach. A second scenario assesses the impact of urban growth on hydrology. Study area is the Tolka River basin in Dublin, Ireland. The grid-based approach of WetSpa enables an optimal use of the spatially distributed properties of remote sensing derived input. Though change trajectory analysis remains little used in urban studies it is shown to be of utmost importance in case of time series analysis. The analysis enabled to assign a rational trajectory to 99% of all pixels. The study showed that consistent remote sensing derived land-use maps are preferred over alternative sources (such as CORINE) to avoid over-estimation errors, interpretation inconsistencies and assure enough spatial detail for urban studies. Scenario 1 reveals that both the class and remote sensing sub-pixel based approaches are able to simulate discharges at the catchment outlet in an equally satisfactory way, but the sub-pixel approach yields considerably higher peak discharges. The result confirms the importance of detailed information on the sealed surface proportion for hydrological simulations in urbanised catchments. In addition a major advantage with respect to hydrological parameterisation using remote sensing is the fact that it is site-and period-specific. Regarding the assessment of the impact of urbanisation (scenario 2) the hydrological simulations revealed that the steady urban growth in the Tolka basin between 1988 and 2006 had a considerable impact on peak discharges. Additionally, the hydrological response is quicker as a result of urbanisation. Spatially distributed surface runoff maps identify the zones with high runoff production. It is evident that this type of information is important for urban water management and decision makers. The results of the remote sensing supported modelling approach do not only indicate increased volumes due to urbanisation, but also identifies the locations where the most relevant impacts took place.
Remote Sensing for Agriculture, Ecosystems, and Hydrology V, 2004
Determination and description of groundwater systems is essential for the management and developm... more Determination and description of groundwater systems is essential for the management and development of ecological values, especially in the valley parts of river basins. At the land surface, groundwater systems appear as infiltration (relatively dry) and discharge zones (relatively wet). Groundwater discharge zones offer a high potential for nature values because of their constant moisture presence and their specific water quality. Current methods for the determination of discharge and infiltration zones use either detailed time-consuming fieldwork or data intensive numerical simulation models. Consequently, there is a direct need for repeatable, area covering, mapping possibilities for the determination of moisture gradients and more specifically discharge and infiltration zones. Within the framework of the CASI-SWIR campaign 2002, the Department of Hydrology and Hydraulic Engineering of the Vrije Universiteit Brussel (VUB) executed a combined airborne hyperspectral remote sensing and field campaign to analyze moisture gradients in the Doode Bemde, a riparian nature reserve. The main objective of the study is to test the best hyperspectral analysis method, using the hyperspectral CASI-SWIR data, for the known, based upon field and simulation data, moisture gradients in the Doode Bemde area. Simultaneously with the airborne hyperspectral campaign, field measurements of soil moisture, groundwater levels, vegetation temperature and spectral characteristics of some key vegetation species (phreatophytes) were performed. The method of analysis consists of statistical comparison of moisture gradients, obtained from measurements and simulations, with individual bands, a combination of bands and multivariate derivatives. The paper describes the setup of the field and airborne measurement campaign, the methodology of analysis as well as first analysis results.
International Journal of Applied Earth Observation and Geoinformation, 2012
The goal of this paper is to evaluate the DisTrad sharpening technique for deriving land surface ... more The goal of this paper is to evaluate the DisTrad sharpening technique for deriving land surface temperatures over urban areas. While the original DisTrad technique is based on the correlation between land surface temperature and NDVI, this study evaluates the performance of DisTrad over different land covers by analysing the correlation between land surface temperature and 15 different indices: BASVI, R, B, NDWI, NDBaI, SVI, SAVI, NDBI, NDSI, UI, FC, VC, V, IBI, NDVI. In addition, we have analysed the correlation between land surface temperature and impervious percentage. These indices and land surface temperature were derived from a Landsat 7 ETM+ image of 2001 covering the city of Dublin. It is concluded that for most indices selecting 25% of the pixels with the lowest coefficient of variance increases the correlation between the index and the land surface temperature. Results show that the DisTrad technique in combination with impervious percentage sharpens urban areas at 30 m resolution most successfully. Although vegetation cover was high during acquisition of the image, the use of impervious percentage showed improved results compared to NDVI. This allows an improved estimation of spatial patterns of urban heat islands.
Ariel Rapid #: —4712814 IP: 132.177 228 62 #: https://0~www.sciencedirect.com.ilsurod.lib.neu. edu... more Ariel Rapid #: —4712814 IP: 132.177 228 62 #: https://0~www.sciencedirect.com.ilsurod.lib.neu. edu/science/1 LOCATION: NED :: Snell Library ... Further, the leaf reflectance of maize was measured in situ around the cleared plots, using an ASD contact probe with leafclip, that ...
Determination of groundwater systems is essential for the management and development of ecologica... more Determination of groundwater systems is essential for the management and development of ecological values of valleys and wetlands. At the land surface, groundwater systems appear as infiltration and discharge zones; the latter are relatively wet because of the upward groundwater seepage, while the former are relatively dry. Groundwater discharge zones offer a high potential for nature values because of their
In general groundwater models need readily available data of measured heads for calibration. In s... more 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.
For the emerging field of ecohydrology it is essential to be able to estimate spatially distribut... more For the emerging field of ecohydrology it is essential to be able to estimate spatially distributed water and energy balances in different types of ecosystems. This information is a prerequisite for predicting the occurrence of vegetation species in dependence of site specific conditions. In this contribution the results of a field and airborne imaging spectroscopy campaign in the Doode Bemde
The knowledge of mechanisms of interaction of surface and groundwater in the hyporheic zone in ri... more The knowledge of mechanisms of interaction of surface and groundwater in the hyporheic zone in rivers is essential for conserving, managing and restoring river adjacent wetlands and its habitats. Reliable estimation of groundwater-surface water exchange challenges hydrological sciences. A promising approach, overcoming limitations of individual methods, is the combination of different methodologies including flux estimates based on thermal measurements, piezometer nests, slug tests and seepage meters. In this contribution such a multi-methodology approach is tested for the Upper Biebrza River, Poland. Time series of thermal profiles are obtained for a period of 9 months. The thermal and physical soil properties show strong spatial and vertical heterogeneities typical for the peat soils of the area. Transient simulations with the numerical 1D heat transport model STRIVE were used to quantify the vertical advective fluxes in the riverbed allowing a first level investigation of groundwater-surface water exchange. The net exchange along the examined section during the 9 month is estimated as a 10.4 mm/d upward flux, which is evaluated as a relatively low intensity of groundwater seepage. Time series of both temperature and hydraulic head gradients were used to calculate hydraulic conductivities and to quantify transient groundwater-surface water exchanges for three locations. They indicated an exchange flux relatively relative stable in time only interrupted by peak values during flood events. Seepage meter measurements provided independent verification results. Interpolating calculated fluxes along the river with GIS techniques resulted in spatially distributed interaction maps. Sections of higher fluxes are statistically correlated to the proximity of the river to the morainic plateaus, which border the river alluvium. In sections where the river is central in the alluvium and relatively far away from the upland low or infiltrating conditions are obtained. This geomorphological configuration of the position of the river and the morainic plateau might allow groundwater seepage to occur at the foot of the valley flank and to induce lateral flow into the peat filled valley and hereby providing an explanation for the occurrence of groundwater dependent vegetation at locations relatively far from the seepage zone (van Loon et al., 2009).
This document is the author's final manuscript version of the journal article, incorporating any ... more This document is the author's final manuscript version of the journal article, incorporating any revisions agreed during the peer review process. There may be differences between this and the publisher's version. You are advised to consult the publisher's version if you wish to cite from this article.
Study focus: Groundwater is of strategic importance. The accurate estimation of groundwater recha... more Study focus: Groundwater is of strategic importance. The accurate estimation of groundwater recharge and assessing the fundamental controlling factors are therefore of utmost importance to protect groundwater systems. We used the spatially-distributed waterbalance model WetSpass to estimate long-term average recharge in Flanders. We validated recharge rates with base flow estimates of 67 daily stream flow records using the hydrograph analyses. To this end we performed principal component analysis, multiple linear regression analysis and relative importance analysis to assess the controlling factors of the spatial variation of recharge and base flow with the influencing watershed characteristics. New hydrological insights for the region: The average resulting recharge is 235 mm/year and occurs mainly in winter. The overall moderate correlation between base flow estimates and modeled recharge rates indicates that base flow is a reasonable proxy of recharge. Groundwater recharge variation was explained in order of importance by precipitation, soil texture and vegetation cover; while base flow variation was strongly controlled by vegetation cover and groundwater depth. The results of this study highlight the important role of spatial variables in estimation of recharge and base flow. In addition, the prominent role of vegetation makes clear the potential importance of land-use changes on recharge and hence the need to include a proper strategy for land-use change in sustainable management of groundwater resources.
Drought is a recurrent natural hazard affecting arid/semi-arid, as well as temperate regions. Num... more Drought is a recurrent natural hazard affecting arid/semi-arid, as well as temperate regions. Numerous research efforts have been made for all types of drought (e.g. meteorological, hydrological and agricultural) in arid/semi-arid regions, whereas only a small number of studies have been performed in temperate regions. Moreover, in these regions, the type of hydrological drought which is related to groundwater is largely left unstudied. The GRoWaDRISK project is aimed to contribute to covering this gap. This paper summarises the aims, scope and methodology of the project. A large part of the Belgian territory was chosen as the study area. The project encompasses three groups of research tasks. First, knowledge regarding influencing factors of groundwater drought will be increased through using the best available spatial information on related variables (groundwater level, recharge and discharge). Second, the socio-economic and environmental impacts of droughts will be assessed for t...
A recently concluded research project called Measuring and Modelling Urban Dynamics (MAMUD), fund... more A recently concluded research project called Measuring and Modelling Urban Dynamics (MAMUD), funded by Belspo, investigated how high and moderate resolution satellite imagery can be used for mapping and modeling urban growth and its impact on the hydrology of the urban and suburban environment. In this paper, some of the research methods and major findings of this project are briefly discussed with a focus on work that was carried out on the Greater Dublin Area in Ireland.
International Journal of Applied Earth Observation and Geoinformation, 2013
This paper aims at developing a methodology for assessing urban dynamics in urban catchments and ... more This paper aims at developing a methodology for assessing urban dynamics in urban catchments and the related impact on hydrology. Using a multi-temporal remote sensing supported hydrological modelling approach an improved simulation of runoff for urban areas is targeted. A time-series of five medium resolution urban masks and corresponding sub-pixel sealed surface proportions maps was generated from Landsat and SPOT imagery. The consistency of the urban mask and sealed surface proportion timeseries was imposed through an urban change trajectory analysis. The physically based rainfall-runoff model WetSpa was successfully adapted for integration of remote sensing derived information of detailed urban land use and sealed surface characteristics. A first scenario compares the original land-use class based approach for hydrological parameterisation with a remote sensing sub-pixel based approach. A second scenario assesses the impact of urban growth on hydrology. Study area is the Tolka River basin in Dublin, Ireland. The grid-based approach of WetSpa enables an optimal use of the spatially distributed properties of remote sensing derived input. Though change trajectory analysis remains little used in urban studies it is shown to be of utmost importance in case of time series analysis. The analysis enabled to assign a rational trajectory to 99% of all pixels. The study showed that consistent remote sensing derived land-use maps are preferred over alternative sources (such as CORINE) to avoid over-estimation errors, interpretation inconsistencies and assure enough spatial detail for urban studies. Scenario 1 reveals that both the class and remote sensing sub-pixel based approaches are able to simulate discharges at the catchment outlet in an equally satisfactory way, but the sub-pixel approach yields considerably higher peak discharges. The result confirms the importance of detailed information on the sealed surface proportion for hydrological simulations in urbanised catchments. In addition a major advantage with respect to hydrological parameterisation using remote sensing is the fact that it is site-and period-specific. Regarding the assessment of the impact of urbanisation (scenario 2) the hydrological simulations revealed that the steady urban growth in the Tolka basin between 1988 and 2006 had a considerable impact on peak discharges. Additionally, the hydrological response is quicker as a result of urbanisation. Spatially distributed surface runoff maps identify the zones with high runoff production. It is evident that this type of information is important for urban water management and decision makers. The results of the remote sensing supported modelling approach do not only indicate increased volumes due to urbanisation, but also identifies the locations where the most relevant impacts took place.
Remote Sensing for Agriculture, Ecosystems, and Hydrology V, 2004
Determination and description of groundwater systems is essential for the management and developm... more Determination and description of groundwater systems is essential for the management and development of ecological values, especially in the valley parts of river basins. At the land surface, groundwater systems appear as infiltration (relatively dry) and discharge zones (relatively wet). Groundwater discharge zones offer a high potential for nature values because of their constant moisture presence and their specific water quality. Current methods for the determination of discharge and infiltration zones use either detailed time-consuming fieldwork or data intensive numerical simulation models. Consequently, there is a direct need for repeatable, area covering, mapping possibilities for the determination of moisture gradients and more specifically discharge and infiltration zones. Within the framework of the CASI-SWIR campaign 2002, the Department of Hydrology and Hydraulic Engineering of the Vrije Universiteit Brussel (VUB) executed a combined airborne hyperspectral remote sensing and field campaign to analyze moisture gradients in the Doode Bemde, a riparian nature reserve. The main objective of the study is to test the best hyperspectral analysis method, using the hyperspectral CASI-SWIR data, for the known, based upon field and simulation data, moisture gradients in the Doode Bemde area. Simultaneously with the airborne hyperspectral campaign, field measurements of soil moisture, groundwater levels, vegetation temperature and spectral characteristics of some key vegetation species (phreatophytes) were performed. The method of analysis consists of statistical comparison of moisture gradients, obtained from measurements and simulations, with individual bands, a combination of bands and multivariate derivatives. The paper describes the setup of the field and airborne measurement campaign, the methodology of analysis as well as first analysis results.
International Journal of Applied Earth Observation and Geoinformation, 2012
The goal of this paper is to evaluate the DisTrad sharpening technique for deriving land surface ... more The goal of this paper is to evaluate the DisTrad sharpening technique for deriving land surface temperatures over urban areas. While the original DisTrad technique is based on the correlation between land surface temperature and NDVI, this study evaluates the performance of DisTrad over different land covers by analysing the correlation between land surface temperature and 15 different indices: BASVI, R, B, NDWI, NDBaI, SVI, SAVI, NDBI, NDSI, UI, FC, VC, V, IBI, NDVI. In addition, we have analysed the correlation between land surface temperature and impervious percentage. These indices and land surface temperature were derived from a Landsat 7 ETM+ image of 2001 covering the city of Dublin. It is concluded that for most indices selecting 25% of the pixels with the lowest coefficient of variance increases the correlation between the index and the land surface temperature. Results show that the DisTrad technique in combination with impervious percentage sharpens urban areas at 30 m resolution most successfully. Although vegetation cover was high during acquisition of the image, the use of impervious percentage showed improved results compared to NDVI. This allows an improved estimation of spatial patterns of urban heat islands.
Ariel Rapid #: —4712814 IP: 132.177 228 62 #: https://0~www.sciencedirect.com.ilsurod.lib.neu. edu... more Ariel Rapid #: —4712814 IP: 132.177 228 62 #: https://0~www.sciencedirect.com.ilsurod.lib.neu. edu/science/1 LOCATION: NED :: Snell Library ... Further, the leaf reflectance of maize was measured in situ around the cleared plots, using an ASD contact probe with leafclip, that ...
Determination of groundwater systems is essential for the management and development of ecologica... more Determination of groundwater systems is essential for the management and development of ecological values of valleys and wetlands. At the land surface, groundwater systems appear as infiltration and discharge zones; the latter are relatively wet because of the upward groundwater seepage, while the former are relatively dry. Groundwater discharge zones offer a high potential for nature values because of their
In general groundwater models need readily available data of measured heads for calibration. In s... more 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.
For the emerging field of ecohydrology it is essential to be able to estimate spatially distribut... more For the emerging field of ecohydrology it is essential to be able to estimate spatially distributed water and energy balances in different types of ecosystems. This information is a prerequisite for predicting the occurrence of vegetation species in dependence of site specific conditions. In this contribution the results of a field and airborne imaging spectroscopy campaign in the Doode Bemde
The knowledge of mechanisms of interaction of surface and groundwater in the hyporheic zone in ri... more The knowledge of mechanisms of interaction of surface and groundwater in the hyporheic zone in rivers is essential for conserving, managing and restoring river adjacent wetlands and its habitats. Reliable estimation of groundwater-surface water exchange challenges hydrological sciences. A promising approach, overcoming limitations of individual methods, is the combination of different methodologies including flux estimates based on thermal measurements, piezometer nests, slug tests and seepage meters. In this contribution such a multi-methodology approach is tested for the Upper Biebrza River, Poland. Time series of thermal profiles are obtained for a period of 9 months. The thermal and physical soil properties show strong spatial and vertical heterogeneities typical for the peat soils of the area. Transient simulations with the numerical 1D heat transport model STRIVE were used to quantify the vertical advective fluxes in the riverbed allowing a first level investigation of groundwater-surface water exchange. The net exchange along the examined section during the 9 month is estimated as a 10.4 mm/d upward flux, which is evaluated as a relatively low intensity of groundwater seepage. Time series of both temperature and hydraulic head gradients were used to calculate hydraulic conductivities and to quantify transient groundwater-surface water exchanges for three locations. They indicated an exchange flux relatively relative stable in time only interrupted by peak values during flood events. Seepage meter measurements provided independent verification results. Interpolating calculated fluxes along the river with GIS techniques resulted in spatially distributed interaction maps. Sections of higher fluxes are statistically correlated to the proximity of the river to the morainic plateaus, which border the river alluvium. In sections where the river is central in the alluvium and relatively far away from the upland low or infiltrating conditions are obtained. This geomorphological configuration of the position of the river and the morainic plateau might allow groundwater seepage to occur at the foot of the valley flank and to induce lateral flow into the peat filled valley and hereby providing an explanation for the occurrence of groundwater dependent vegetation at locations relatively far from the seepage zone (van Loon et al., 2009).
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