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Détails du magazine
Format
Magazine
eISSN
1338-4333
Première publication
28 Mar 2009
Période de publication
4 fois par an
Langues
Anglais

Chercher

Volume 68 (2020): Edition 2 (June 2020)

Détails du magazine
Format
Magazine
eISSN
1338-4333
Première publication
28 Mar 2009
Période de publication
4 fois par an
Langues
Anglais

Chercher

11 Articles
access type Accès libre

Response of the parameters of excess infiltration and excess storage model to land use cover change

Publié en ligne: 26 May 2020
Pages: 99 - 110

Résumé

Abstract

The Loess Plateau is the main source of water in Yellow River, China. After 1980s, the Yellow river water presented a significant reduction, what caused the decrease of the Yellow river discharge had been debated in academic circles. We proceeded with runoff generation mechanisms to explain this phenomenon. We built saturation excess runoff and infiltration excess runoff generation mechanisms for rainfall–runoff simulation in Jingle sub-basin of Fen River basin on the Loess Plateau, to reveal the influence of land use change on flood processes and studied the changes of model parameters under different underlying conditions. The results showed that the runoff generation mechanism was mainly infiltration-excess overland flow, but the flood events of saturation-excess overland flow had an increasing trend because of land use cover change (the increase of forestland and grassland areas and the reduction of cultivated land). Some of the model parameters had physical significances,such as water storage capacity (WM), infiltration capacity (f), evapotranspiration (CKE), soil permeability coefficient (k) and index of storage capacity distribution curve (n) showed increasing trends, and index of infiltration capacity distribution curve (m) showed a decreasing trend. The above results proved the changes of runoff generation mechanism from the perspective of model parameters in Jingle sub-basin, which can provide a new perspective for understanding the discharge reduction in the Yellow River basin.

Mots clés

  • Land use
  • Saturation excess and infiltration excess model
  • Model parameters
  • Fen River
access type Accès libre

Simultaneous determination of wettability and shrinkage in an organic residue amended loamy topsoil

Publié en ligne: 26 May 2020
Pages: 111 - 118

Résumé

Abstract

In agricultural land use, organic residues such as compost, digestate, and sewage sludge are discussed as costeffective soil conditioner that may improve the water holding capacity and crop available soil moisture. The objective of this study is to determine the effect of application of digestates with different compositions in maize, sugar beet and winter wheat, compost of shrub debris and sewage sludge on shrinkage behaviour and contact angle of till-derived loamy topsoil of a Haplic Luvisol under agricultural use. Novelty is the simultaneous determination of contact angle and shrinkage of soils amended with digestates composed of different composition in maize, sugar beet and winter wheat, compost of shrub debris and sewage sludge. The results suggest that the application of organic residues impacts the air capacity, while the contact angles remained in the subcritical range between > 0° and < 90°. The relationship between CA values and moisture ratios, ϑ, during proportional shrinkage was positive and linear (r2 of 0.98) and negative during residual- and zero-shrinkage (r2 of 0.93).

Mots clés

  • Luvisol
  • Organic residues
  • Contact angle
  • Wettability
  • Shrinkage
access type Accès libre

Validation of friction factor predictions in vertical slurry flows with coarse particles

Publié en ligne: 26 May 2020
Pages: 119 - 127

Résumé

Abstract

The paper presents validation of a mathematical model describing the friction factor by comparing the predicted and measured results in a broad range of solid concentrations and mean particle diameters. Three different types of solids, surrounded by water as a carrier liquid, namely Canasphere, PVC, and Sand were used with solids density from 1045 to 2650 kg/m3, and in the range of solid concentrations by volume from 0.10 to 0.45. All solid particles were narrowly sized with mean particle diameters between 1.5 and 3.4 mm. It is presented that the model predicts the friction factor fairly well. The paper demonstrates that solid particle diameter plays a crucial role for the friction factor in a vertical slurry flow with coarse solid particles. The mathematical model is discussed in reference to damping of turbulence in such flows. As the friction factor is below the friction for water it is concluded that it is possible that the effect of damping of turbulence is included in the KB function, which depends on the Reynolds number.

Mots clés

  • Flow with coarse particles
  • Particle-wall stress
  • Modelling of vertical flow
access type Accès libre

Hydrology of the Carpathian Basin: interactions of climatic drivers and hydrological processes on local and regional scales – HydroCarpath Research

Publié en ligne: 26 May 2020
Pages: 128 - 133

Résumé

Abstract

The paper introduces the Special Section on the Hydrology of the Carpathians in this issue. It is the result of an initiative of the Department of Land and Water Resources Management of the Slovak University of Technology in Bratislava, the Institute of Hydraulic Engineering and Water Resources Management of the TU Vienna and the Institute of Geomatics and Civil Engineering of the University of Sopron to allow young hydrologists in the Carpathian Basin (and from outside) to present their research and re-network on the emerging topics of the hydrology of the Carpathians at the HydroCarpath Conferences since 2012.

Mots clés

  • Carpathian Basin
  • Evapotranspiration
  • Runoff coefficient
  • Hydrological regime
  • CN number
  • Climate change
access type Accès libre

Partitioning evapotranspiration using stable isotopes and Lagrangian dispersion analysis in a small agricultural catchment

Publié en ligne: 26 May 2020
Pages: 134 - 143

Résumé

Abstract

Measuring evaporation and transpiration at the field scale is complicated due to the heterogeneity of the environment, with point measurements requiring upscaling and field measurements such as eddy covariance measuring only the evapotranspiration. During the summer of 2014 an eddy covariance device was used to measure the evapotranspiration of a growing maize field at the HOAL catchment. The stable isotope technique and a Lagrangian near field theory (LNF) were then utilized to partition the evapotranspiration into evaporation and transpiration, using the concentration and isotopic ratio of water vapour within the canopy. The stable isotope estimates of the daily averages of the fraction of evapotranspiration (Ft) ranged from 43.0–88.5%, with an average value of 67.5%, while with the LNF method, Ft was found to range from 52.3–91.5% with an average value of 73.5%. Two different parameterizations for the turbulent statistics were used, with both giving similar R2 values, 0.65 and 0.63 for the Raupach and Leuning parameterizations, with the Raupach version performing slightly better. The stable isotope method demonstrated itself to be a more robust method, returning larger amounts of useable data, however this is limited by the requirement of much more additional data.

Mots clés

  • Evapotranspiration partitioning
  • Stable isotopes
  • Lagrangian dispersion theory
access type Accès libre

The role of stony soils in hillslope and catchment runoff formation

Publié en ligne: 26 May 2020
Pages: 144 - 154

Résumé

Abstract

The role of stony soils in runoff response of mountain catchments is rarely studied. We have compared simulated response of stony soils with measured catchment runoff for events caused by rains of small and high intensities in the mountain catchment of the Jalovecký Creek, Slovakia. The soil water response was simulated for three sites with stoniness 10–65% using the Hydrus-2D single porosity model. Soil hydraulic parameters employed in the modelling, i. e. the saturated hydraulic conductivity and parameters of the soil water retention curves, were obtained by two approaches, namely by the Representative Elementary Volume approach (REVa) and by the inverse modelling with Hydrus-1D model (IMa). The soil water outflow hydrographs simulated by Hydrus-2D were compared to catchment runoff hydrographs by analysing their skewness and peak times. Measured catchment runoff hydrographs were similar to simulated soil water outflow hydrographs for about a half of rainfall events. Interestingly, most of them were caused by rainfalls with small intensity (below 2.5 mm/10 min). The REV approach to derive soil hydraulic parameters for soil water outflow modelling provided more realistic shapes of soil water outflow hydrographs and peak times than the IMa approach.

Mots clés

  • Lateral subsurface flow
  • Mountain catchment
  • Soil water flow modelling
access type Accès libre

Controls on event runoff coefficients and recession coefficients for different runoff generation mechanisms identified by three regression methods

Publié en ligne: 26 May 2020
Pages: 155 - 169

Résumé

Abstract

The event runoff coefficient (Rc) and the recession coefficient (tc) are of theoretical importance for understanding catchment response and of practical importance in hydrological design. We analyse 57 event periods in the period 2013 to 2015 in the 66 ha Austrian Hydrological Open Air Laboratory (HOAL), where the seven subcatchments are stratified by runoff generation types into wetlands, tile drainage and natural drainage. Three machine learning algorithms (Random forest (RF), Gradient Boost Decision Tree (GBDT) and Support vector machine (SVM)) are used to estimate Rc and tc from 22 event based explanatory variables representing precipitation, soil moisture, groundwater level and season. The model performance of the SVM algorithm in estimating Rc and tc is generally higher than that of the other two methods, measured by the coefficient of determination R2, and the performance for Rc is higher than that for tc. The relative importance of the explanatory variables for the predictions, assessed by a heatmap, suggests that Rc of the tile drainage systems is more strongly controlled by the weather conditions than by the catchment state, while the opposite is true for natural drainage systems. Overall, model performance strongly depends on the runoff generation type.

Mots clés

  • Machine learning
  • Event runoff analyses
  • Event runoff coefficient
  • Recession coefficient
  • Runoff generation
access type Accès libre

The L-moment based regional approach to curve numbers for Slovak and Polish Carpathian catchments

Publié en ligne: 26 May 2020
Pages: 170 - 179

Résumé

Abstract

The main objective of the paper was to propose and evaluate the performance of a regional approach to estimate CN values and to test the impact of different initial abstraction ratios. The curve number (CN) was analyzed for five Slovak and five Polish catchments situated in the Carpathian Mountains. The L-moment based method of Hosking and Wallis and the ANOVA test were combined to delineate the area in two homogenous regions of catchments with similar CN values. The optimization condition enabled the choice of the initial abstraction ratio, which provided the smallest discrepancy between the tabulated and estimated CNs and the antecedent runoff conditions. The homogeneity in the CN within the regions of four Slovak and four Polish catchments was revealed. Finally, the regional CN was proposed to be at the 50% quantile of the regional theoretical distribution function estimated from all the CNs in the region.

The approach is applied in a group of Slovak and Polish catchments with physiographic conditions representative for the Carpathian region. The main benefit of introducing a common regional CN is the opportunity to apply this procedure in catchments of similar soil-physiographic characteristics and to verify the existing tabulated CN. The paper could give rise to an alternative way of estimating the CN values in forested catchments and catchments with a lack of data or without observations.

Mots clés

  • Catchment curve number
  • Homogeneity
  • Regional frequency analysis
access type Accès libre

Analysis of changes in hydrological cycle of a pristine mountain catchment. 1. Water balance components and snow cover

Publié en ligne: 26 May 2020
Pages: 180 - 191

Résumé

Abstract

We analyse water balance, hydrological response, runoff and snow cover characteristics in the Jalovecký Creek catchment (area 22 km2, mean elevation 1500 m a.s.l.), Slovakia, in hydrological years 1989–2018 to search for changes in hydrological cycle of a mountain catchment representing hydrology of the highest part of the Western Carpathians. Daily air temperature data from two meteorological stations located in the studied mountain range (the Tatra Mountains) at higher elevations show that the study period is 0.1°C to 2.4°C warmer than the climatic standard period 1951–1980. Precipitation and snow depth data from the same stations do not allow to conclude if the study period is wetter/drier or has a decreasing snow cover. Clear trends or abrupt changes in the analysed multivariate hydrometric data time series are not obvious and the oscillations found in catchment runoff are not coherent to those found in catchment precipitation and air temperature. Several time series (flashiness index, number of flow reversals, annual and seasonal discharge maxima, runoff coefficients) indicate that hydrological cycle is more dynamic in the last years of the study period and more precipitation runs off since 2014. The snow cover characteristics and climatic conditions during the snow accumulation and melting period do not indicate pronounced changes (except the number of days with snowfall at the Kasprowy Wierch station since 2011). However, some data series (e.g. flow characteristics in March and June, annual versus summer runoff coefficients since 2014) suggest the changes in the cold period of the year.

Mots clés

  • Mountain catchment
  • Hydrological cycle
  • Time series
access type Accès libre

Analysis of changes in hydrological cycle of a pristine mountain catchment. 2. Isotopic data, trend and attribution analyses

Publié en ligne: 26 May 2020
Pages: 192 - 199

Résumé

Abstract

δ18O in precipitation at station Liptovský Mikuláš (about 8.5 km south from the outlet of the Jalovecký Creek catchment) remains constantly higher since 2014 that might be related to greater evaporation in the region of origin of the air masses bringing precipitation to the studied part of central Europe. Increased δ18O values are reflected also in the Jalovecký Creek catchment runoff. Seasonality of δ18O in the Jalovecký Creek became less pronounced since 2014. The most significant trends found in annual hydrological data series from the catchment in the study period 1989–2018 have the correlation coefficients 0.4 to 0.7. These trends are found in the number of flow reversals (change from increasing to decreasing discharge and vice versa), June low flow, number of simple runoff events in summer months (June to September) and the flashiness index. The attribution analysis suggests that drivers responsible for the changes in these data series include the number of periods with precipitation six and more days long, total precipitation amount in February to June, number of days with precipitation in June to September and total precipitation in May on days with daily totals 10 mm and more, respectively. The coefficients of determination show that linear regressions between the drivers and supposedly changed data series explain only about 31% to 36% of the variability. Most of the change points detected in the time series by the Wild Binary Segmentation method occur in the second and third decades of the study period. Both hydrometric and isotopic data indicate that hydrological cycle in the catchment after 2014 became different than before.

Mots clés

  • Oxygen isotope in precipitation and runoff
  • Time series
  • Trends and break points
access type Accès libre

Multi-model climatic water balance prediction in the Zala River Basin (Hungary) based on a modified Budyko framework

Publié en ligne: 26 May 2020
Pages: 200 - 210

Résumé

Abstract

Providing information on the impacts of climate change on hydrological processes is becoming ever more critical. Modelling and evaluating the expected changes of the water resources over different spatial and time scales can be useful in several fields, e.g. agriculture, forestry and water management. Previously a Budyko-type spatially distributed long-term climate-runoff model was developed for Hungary. This research includes the validation of the model using historical precipitation and streamflow measurements for three nested sub-catchments of the Zala River Basin (Hungary), an essential runoff contributing region to Lake Balaton (the largest shallow lake in Central Europe). The differences between the calculated (from water balance) and the estimated (by the model) mean annual evapotranspiration varied between 0.4% and 3.6% in the validation periods in the sub-catchments examined. Predictions of the main components of the water balance (evapotranspiration and runoff) for the Zala Basin are also presented in this study using precipitation and temperature results of 12 regional climate model simulations (A1B scenario) as input data. According to the projections, the mean annual temperature will be higher from period to period (2011–2040, 2041–2070, 2071–2100), while the change of the annual precipitation sum is not significant. The mean annual evapotranspiration rate is expected to increase slightly during the 21st century, while for runoff a substantial decrease can be anticipated which may exceed 40% by 2071–2100 relative to the reference period (1981–2010). As a result of this predicted reduction, the runoff from the Zala Basin may not be enough to balance the increased evaporation rate of Lake Balaton, transforming it into a closed lake without outflow.

Mots clés

  • Evapotranspiration
  • Runoff
  • Budyko-model
  • Water balance
  • Climate change
11 Articles
access type Accès libre

Response of the parameters of excess infiltration and excess storage model to land use cover change

Publié en ligne: 26 May 2020
Pages: 99 - 110

Résumé

Abstract

The Loess Plateau is the main source of water in Yellow River, China. After 1980s, the Yellow river water presented a significant reduction, what caused the decrease of the Yellow river discharge had been debated in academic circles. We proceeded with runoff generation mechanisms to explain this phenomenon. We built saturation excess runoff and infiltration excess runoff generation mechanisms for rainfall–runoff simulation in Jingle sub-basin of Fen River basin on the Loess Plateau, to reveal the influence of land use change on flood processes and studied the changes of model parameters under different underlying conditions. The results showed that the runoff generation mechanism was mainly infiltration-excess overland flow, but the flood events of saturation-excess overland flow had an increasing trend because of land use cover change (the increase of forestland and grassland areas and the reduction of cultivated land). Some of the model parameters had physical significances,such as water storage capacity (WM), infiltration capacity (f), evapotranspiration (CKE), soil permeability coefficient (k) and index of storage capacity distribution curve (n) showed increasing trends, and index of infiltration capacity distribution curve (m) showed a decreasing trend. The above results proved the changes of runoff generation mechanism from the perspective of model parameters in Jingle sub-basin, which can provide a new perspective for understanding the discharge reduction in the Yellow River basin.

Mots clés

  • Land use
  • Saturation excess and infiltration excess model
  • Model parameters
  • Fen River
access type Accès libre

Simultaneous determination of wettability and shrinkage in an organic residue amended loamy topsoil

Publié en ligne: 26 May 2020
Pages: 111 - 118

Résumé

Abstract

In agricultural land use, organic residues such as compost, digestate, and sewage sludge are discussed as costeffective soil conditioner that may improve the water holding capacity and crop available soil moisture. The objective of this study is to determine the effect of application of digestates with different compositions in maize, sugar beet and winter wheat, compost of shrub debris and sewage sludge on shrinkage behaviour and contact angle of till-derived loamy topsoil of a Haplic Luvisol under agricultural use. Novelty is the simultaneous determination of contact angle and shrinkage of soils amended with digestates composed of different composition in maize, sugar beet and winter wheat, compost of shrub debris and sewage sludge. The results suggest that the application of organic residues impacts the air capacity, while the contact angles remained in the subcritical range between > 0° and < 90°. The relationship between CA values and moisture ratios, ϑ, during proportional shrinkage was positive and linear (r2 of 0.98) and negative during residual- and zero-shrinkage (r2 of 0.93).

Mots clés

  • Luvisol
  • Organic residues
  • Contact angle
  • Wettability
  • Shrinkage
access type Accès libre

Validation of friction factor predictions in vertical slurry flows with coarse particles

Publié en ligne: 26 May 2020
Pages: 119 - 127

Résumé

Abstract

The paper presents validation of a mathematical model describing the friction factor by comparing the predicted and measured results in a broad range of solid concentrations and mean particle diameters. Three different types of solids, surrounded by water as a carrier liquid, namely Canasphere, PVC, and Sand were used with solids density from 1045 to 2650 kg/m3, and in the range of solid concentrations by volume from 0.10 to 0.45. All solid particles were narrowly sized with mean particle diameters between 1.5 and 3.4 mm. It is presented that the model predicts the friction factor fairly well. The paper demonstrates that solid particle diameter plays a crucial role for the friction factor in a vertical slurry flow with coarse solid particles. The mathematical model is discussed in reference to damping of turbulence in such flows. As the friction factor is below the friction for water it is concluded that it is possible that the effect of damping of turbulence is included in the KB function, which depends on the Reynolds number.

Mots clés

  • Flow with coarse particles
  • Particle-wall stress
  • Modelling of vertical flow
access type Accès libre

Hydrology of the Carpathian Basin: interactions of climatic drivers and hydrological processes on local and regional scales – HydroCarpath Research

Publié en ligne: 26 May 2020
Pages: 128 - 133

Résumé

Abstract

The paper introduces the Special Section on the Hydrology of the Carpathians in this issue. It is the result of an initiative of the Department of Land and Water Resources Management of the Slovak University of Technology in Bratislava, the Institute of Hydraulic Engineering and Water Resources Management of the TU Vienna and the Institute of Geomatics and Civil Engineering of the University of Sopron to allow young hydrologists in the Carpathian Basin (and from outside) to present their research and re-network on the emerging topics of the hydrology of the Carpathians at the HydroCarpath Conferences since 2012.

Mots clés

  • Carpathian Basin
  • Evapotranspiration
  • Runoff coefficient
  • Hydrological regime
  • CN number
  • Climate change
access type Accès libre

Partitioning evapotranspiration using stable isotopes and Lagrangian dispersion analysis in a small agricultural catchment

Publié en ligne: 26 May 2020
Pages: 134 - 143

Résumé

Abstract

Measuring evaporation and transpiration at the field scale is complicated due to the heterogeneity of the environment, with point measurements requiring upscaling and field measurements such as eddy covariance measuring only the evapotranspiration. During the summer of 2014 an eddy covariance device was used to measure the evapotranspiration of a growing maize field at the HOAL catchment. The stable isotope technique and a Lagrangian near field theory (LNF) were then utilized to partition the evapotranspiration into evaporation and transpiration, using the concentration and isotopic ratio of water vapour within the canopy. The stable isotope estimates of the daily averages of the fraction of evapotranspiration (Ft) ranged from 43.0–88.5%, with an average value of 67.5%, while with the LNF method, Ft was found to range from 52.3–91.5% with an average value of 73.5%. Two different parameterizations for the turbulent statistics were used, with both giving similar R2 values, 0.65 and 0.63 for the Raupach and Leuning parameterizations, with the Raupach version performing slightly better. The stable isotope method demonstrated itself to be a more robust method, returning larger amounts of useable data, however this is limited by the requirement of much more additional data.

Mots clés

  • Evapotranspiration partitioning
  • Stable isotopes
  • Lagrangian dispersion theory
access type Accès libre

The role of stony soils in hillslope and catchment runoff formation

Publié en ligne: 26 May 2020
Pages: 144 - 154

Résumé

Abstract

The role of stony soils in runoff response of mountain catchments is rarely studied. We have compared simulated response of stony soils with measured catchment runoff for events caused by rains of small and high intensities in the mountain catchment of the Jalovecký Creek, Slovakia. The soil water response was simulated for three sites with stoniness 10–65% using the Hydrus-2D single porosity model. Soil hydraulic parameters employed in the modelling, i. e. the saturated hydraulic conductivity and parameters of the soil water retention curves, were obtained by two approaches, namely by the Representative Elementary Volume approach (REVa) and by the inverse modelling with Hydrus-1D model (IMa). The soil water outflow hydrographs simulated by Hydrus-2D were compared to catchment runoff hydrographs by analysing their skewness and peak times. Measured catchment runoff hydrographs were similar to simulated soil water outflow hydrographs for about a half of rainfall events. Interestingly, most of them were caused by rainfalls with small intensity (below 2.5 mm/10 min). The REV approach to derive soil hydraulic parameters for soil water outflow modelling provided more realistic shapes of soil water outflow hydrographs and peak times than the IMa approach.

Mots clés

  • Lateral subsurface flow
  • Mountain catchment
  • Soil water flow modelling
access type Accès libre

Controls on event runoff coefficients and recession coefficients for different runoff generation mechanisms identified by three regression methods

Publié en ligne: 26 May 2020
Pages: 155 - 169

Résumé

Abstract

The event runoff coefficient (Rc) and the recession coefficient (tc) are of theoretical importance for understanding catchment response and of practical importance in hydrological design. We analyse 57 event periods in the period 2013 to 2015 in the 66 ha Austrian Hydrological Open Air Laboratory (HOAL), where the seven subcatchments are stratified by runoff generation types into wetlands, tile drainage and natural drainage. Three machine learning algorithms (Random forest (RF), Gradient Boost Decision Tree (GBDT) and Support vector machine (SVM)) are used to estimate Rc and tc from 22 event based explanatory variables representing precipitation, soil moisture, groundwater level and season. The model performance of the SVM algorithm in estimating Rc and tc is generally higher than that of the other two methods, measured by the coefficient of determination R2, and the performance for Rc is higher than that for tc. The relative importance of the explanatory variables for the predictions, assessed by a heatmap, suggests that Rc of the tile drainage systems is more strongly controlled by the weather conditions than by the catchment state, while the opposite is true for natural drainage systems. Overall, model performance strongly depends on the runoff generation type.

Mots clés

  • Machine learning
  • Event runoff analyses
  • Event runoff coefficient
  • Recession coefficient
  • Runoff generation
access type Accès libre

The L-moment based regional approach to curve numbers for Slovak and Polish Carpathian catchments

Publié en ligne: 26 May 2020
Pages: 170 - 179

Résumé

Abstract

The main objective of the paper was to propose and evaluate the performance of a regional approach to estimate CN values and to test the impact of different initial abstraction ratios. The curve number (CN) was analyzed for five Slovak and five Polish catchments situated in the Carpathian Mountains. The L-moment based method of Hosking and Wallis and the ANOVA test were combined to delineate the area in two homogenous regions of catchments with similar CN values. The optimization condition enabled the choice of the initial abstraction ratio, which provided the smallest discrepancy between the tabulated and estimated CNs and the antecedent runoff conditions. The homogeneity in the CN within the regions of four Slovak and four Polish catchments was revealed. Finally, the regional CN was proposed to be at the 50% quantile of the regional theoretical distribution function estimated from all the CNs in the region.

The approach is applied in a group of Slovak and Polish catchments with physiographic conditions representative for the Carpathian region. The main benefit of introducing a common regional CN is the opportunity to apply this procedure in catchments of similar soil-physiographic characteristics and to verify the existing tabulated CN. The paper could give rise to an alternative way of estimating the CN values in forested catchments and catchments with a lack of data or without observations.

Mots clés

  • Catchment curve number
  • Homogeneity
  • Regional frequency analysis
access type Accès libre

Analysis of changes in hydrological cycle of a pristine mountain catchment. 1. Water balance components and snow cover

Publié en ligne: 26 May 2020
Pages: 180 - 191

Résumé

Abstract

We analyse water balance, hydrological response, runoff and snow cover characteristics in the Jalovecký Creek catchment (area 22 km2, mean elevation 1500 m a.s.l.), Slovakia, in hydrological years 1989–2018 to search for changes in hydrological cycle of a mountain catchment representing hydrology of the highest part of the Western Carpathians. Daily air temperature data from two meteorological stations located in the studied mountain range (the Tatra Mountains) at higher elevations show that the study period is 0.1°C to 2.4°C warmer than the climatic standard period 1951–1980. Precipitation and snow depth data from the same stations do not allow to conclude if the study period is wetter/drier or has a decreasing snow cover. Clear trends or abrupt changes in the analysed multivariate hydrometric data time series are not obvious and the oscillations found in catchment runoff are not coherent to those found in catchment precipitation and air temperature. Several time series (flashiness index, number of flow reversals, annual and seasonal discharge maxima, runoff coefficients) indicate that hydrological cycle is more dynamic in the last years of the study period and more precipitation runs off since 2014. The snow cover characteristics and climatic conditions during the snow accumulation and melting period do not indicate pronounced changes (except the number of days with snowfall at the Kasprowy Wierch station since 2011). However, some data series (e.g. flow characteristics in March and June, annual versus summer runoff coefficients since 2014) suggest the changes in the cold period of the year.

Mots clés

  • Mountain catchment
  • Hydrological cycle
  • Time series
access type Accès libre

Analysis of changes in hydrological cycle of a pristine mountain catchment. 2. Isotopic data, trend and attribution analyses

Publié en ligne: 26 May 2020
Pages: 192 - 199

Résumé

Abstract

δ18O in precipitation at station Liptovský Mikuláš (about 8.5 km south from the outlet of the Jalovecký Creek catchment) remains constantly higher since 2014 that might be related to greater evaporation in the region of origin of the air masses bringing precipitation to the studied part of central Europe. Increased δ18O values are reflected also in the Jalovecký Creek catchment runoff. Seasonality of δ18O in the Jalovecký Creek became less pronounced since 2014. The most significant trends found in annual hydrological data series from the catchment in the study period 1989–2018 have the correlation coefficients 0.4 to 0.7. These trends are found in the number of flow reversals (change from increasing to decreasing discharge and vice versa), June low flow, number of simple runoff events in summer months (June to September) and the flashiness index. The attribution analysis suggests that drivers responsible for the changes in these data series include the number of periods with precipitation six and more days long, total precipitation amount in February to June, number of days with precipitation in June to September and total precipitation in May on days with daily totals 10 mm and more, respectively. The coefficients of determination show that linear regressions between the drivers and supposedly changed data series explain only about 31% to 36% of the variability. Most of the change points detected in the time series by the Wild Binary Segmentation method occur in the second and third decades of the study period. Both hydrometric and isotopic data indicate that hydrological cycle in the catchment after 2014 became different than before.

Mots clés

  • Oxygen isotope in precipitation and runoff
  • Time series
  • Trends and break points
access type Accès libre

Multi-model climatic water balance prediction in the Zala River Basin (Hungary) based on a modified Budyko framework

Publié en ligne: 26 May 2020
Pages: 200 - 210

Résumé

Abstract

Providing information on the impacts of climate change on hydrological processes is becoming ever more critical. Modelling and evaluating the expected changes of the water resources over different spatial and time scales can be useful in several fields, e.g. agriculture, forestry and water management. Previously a Budyko-type spatially distributed long-term climate-runoff model was developed for Hungary. This research includes the validation of the model using historical precipitation and streamflow measurements for three nested sub-catchments of the Zala River Basin (Hungary), an essential runoff contributing region to Lake Balaton (the largest shallow lake in Central Europe). The differences between the calculated (from water balance) and the estimated (by the model) mean annual evapotranspiration varied between 0.4% and 3.6% in the validation periods in the sub-catchments examined. Predictions of the main components of the water balance (evapotranspiration and runoff) for the Zala Basin are also presented in this study using precipitation and temperature results of 12 regional climate model simulations (A1B scenario) as input data. According to the projections, the mean annual temperature will be higher from period to period (2011–2040, 2041–2070, 2071–2100), while the change of the annual precipitation sum is not significant. The mean annual evapotranspiration rate is expected to increase slightly during the 21st century, while for runoff a substantial decrease can be anticipated which may exceed 40% by 2071–2100 relative to the reference period (1981–2010). As a result of this predicted reduction, the runoff from the Zala Basin may not be enough to balance the increased evaporation rate of Lake Balaton, transforming it into a closed lake without outflow.

Mots clés

  • Evapotranspiration
  • Runoff
  • Budyko-model
  • Water balance
  • Climate change

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