Conceptual Water Balance Model Research Articles

Uncertainty in rainfall input data in a conceptual water balance model: effects on outputs and implications for predictability

<p>As hydrological models become more prevalent in water resources planning and management, increasing levels of detail and precision are needed. Currently, reliable models that simulate the hydrological behavior of a basin are indispensable; however, it is also necessary to know the limits of the predictability and reliability of the model outputs. The present study evaluates the influence of uncertainty in the main input variable of the model, rainfall, on the output uncertainty of a hydrological model. Using concepts of identifiability and sensitivity, the uncertainty in the model structure and parameters was estimated. Then, the output uncertainty caused by uncertainties in i) the rainfall amounts and ii) the periods of the rainfall was determined. The main conclusion is that uncertainty in rainfall estimation during rainy periods produces greater output uncertainty. However, in non-rainy periods, the output uncertainty is not very sensitive to the uncertainty in rainfall. Finally, uncertainties in rainfall during the basin filling and emptying periods (Apr. – Jun. and Sep. – Nov., respectively) alter the uncertainty in subsequent periods. Therefore, uncertainties in these periods could result in limited ranges of model predictability.</p><p> </p><p><strong>Resumen</strong></p><p>Los modelos hidrológicos se han vuelto cada vez más necesarios en la planificación y gestión de recursos hídricos, donde un aumento en los niveles de detalle y precisión es necesario. Actualmente disponer de modelos para simular el comportamiento hidrológico de una cuenca resulta indispensable, sin embargo, también es necesario conocer los límites de predictibilidad y de confiabilidad de las salidas de un modelo. En este estudio se evalúan la influencia de la incertidumbre en la principal entrada de un modelo, la precipitación, sobre la incertidumbre de las salidas de un modelo hidrológico. Utilizando conceptos de identificabilidad y sensibilidad se estima la incertidumbre de los parámetros y estructura de un modelo. Luego, la incertidumbre en las salidas causadas por incertidumbre en i) los montos de precipitación, ii) los períodos de precipitación fue calculada. Como conclusiones se obtuvo que la incertidumbre en la estimación de la precipitación en períodos de lluvia produce mayor incertidumbre sobre las salidas. En períodos no lluviosos, la incertidumbre de las salidas es poco sensible a incertidumbre sobre las precipitaciones. Finalmente, incertidumbres en periodos de llenado y vaciado (Abril-Junio y Septiembre-Noviembre respectivamente) afectan la incertidumbre en las salidas en los períodos subsecuentes. Por lo tanto incertidumbres en aquellos períodos pueden resultar en rangos limitados de predictibilidad de un modelo.</p>

Hydrologic modelling for Lake Basaka: development and application of a conceptual water budget model.

Quantification of fluxes of water into and out of terminal lakes like Basaka has fundamental challenges. This is due to the fact that accurate measurement and quantification of most of the parameters of a lake's hydrologic cycle are difficult. Furthermore, quantitative understanding of the hydrologic systems and hence, the data-intensive modelling is difficult in developing countries like Ethiopia due to limitation of sufficient recorded data. Therefore, formulation of a conceptual water balance model is extremely important as it presents a convenient analytical tool with simplified assumptions to simulate the magnitude of unknown fluxes. In the current study, a conceptual lake water balance model was systematically formulated, solved, calibrated, and validated successfully. Then, the surface water and groundwater interaction was quantified, and a mathematical relationship developed. The overall agreement between the observed and simulated lake stage at monthly time step was confirmed based on the standard performance parameters (R(2), MAE, RMSE, E(f)). The result showed that hydrological water balance of the lake is dominated by the groundwater (GW) component. The net GW flux in recent period (post-2000s) accounts about 56% of the total water inflow. Hence, GW plays a leading role in the hydrodynamics and existence of Lake Basaka and is mostly responsible for the expansion of the lake. Thus, identification of the potential sources/causes for the GW flux plays a leading role in order to limit the further expansion of the lake. Measurement of GW movement and exchange in the area is a high priority for future research.

Measures against climate change and its impacts on water resources in Greece

This paper examines the actions toward the reduction of greenhouse gas emissions to the atmosphere that Greece has implemented to comply with international conventions and the Kyoto Protocol. It also concerns the analysis and processing of climate variables and the assessment of the impact of climate change on water resources in Northern Greece and on some critical water management issues, such as reservoir storage and water supply for agriculture and domestic use. Initially, a monthly conceptual water balance model was applied to estimate runoff values in the entrance of the Polyfyto reservoir under the UKHI equilibrium scenario referring to the year 2100. It was found that the mean annual runoff, mean winter runoff and summer runoff values will be reduced. Increases of the risks associated with the annual quantities of water supply have been observed.

Uncertainty assessment of monthly water balance models based on Incremental Modified Fuzzy Extension Principle method

In this paper, a new method, namely Incremental Modified Fuzzy Extension Principle (IMFEP), is proposed for uncertainty assessment of conceptual water balance models. IMFEP is based on a new modification of fuzzy extension principle using fuzzy approximate. The most important feature of the IMFEP method lies in its realistic superposition of convex fuzzy membership functions of model inputs at different fuzzy α-cuts. To evaluate the IMFEP method, four other fuzzy-based approaches have been used to assess the uncertainties in simulating monthly water balance in basin scale and their results are compared with IMFEP. These approaches, one based on simple fuzzy mathematics, Vertex method, UNcertainty Estimation based on local Errors and Clustering (UNEEC) and Modified Fuzzy Extension Principle (MFEP) have been previously used for uncertainty estimation of water models. The nonlinear monthly water balance models calibrated for the two basins in Iran and France and their outputs with the five aforementioned methods have been compared. For both basins, IMFEP and MFEP methods have shown the best performance followed by UNEEC and Vertex methods (however, the differences in the underlying assumptions of the UNEEC method have to be taken into account). It can be concluded that the IMFEP method shows strong performance of uncertainty propagation in all evaluated fuzzy α-cuts.

WABOL: A conceptual water balance model for analyzing rainfall water use in olive orchards under different soil and cover crop management strategies

A water balance model developed to simulate the effect of different soil management alternatives, as for instance conventional tillage or cover crop, on soil water balance has been implemented in a user friendly interface in order to allow its use by technicians and other stakeholder in the olive sector. In spite of this simplified interface for the user, the model uses process-based methodologies to describe the key processes controlling water balance in rainfed olive orchards, such as runoff, deep percolation, cover crop growth, soil evaporation and olive and cover crop transpiration.Model predictions were evaluated using 3-year period of runoff and soil moisture data for different soil managements from an experimental field located in an olive orchard in Southern Spain. Comparison of simulated results with experimental data suggests that the model predicts satisfactorily runoff losses and soil moisture. Thus, annual runoff simulation provided a RMSE of 4.4mm and the model efficiency was in general higher than 0.5. This suggests that the described model could be a useful tool for stakeholders to carry out a complete evaluation of different soil management alternatives in olive orchards. Finally, an example of an application of the model is presented. In this example, the model is used to evaluate the impact of using a cover crop, including different mowing dates, on the different components of the soil water balance compared to conventional tillage for the conditions of Cordoba, Southern Spain, using a 50year long record. This exercise indicates that the use of a cover crop in these conditions have a negative impact on olive transpiration (25% average reduction), although this impact can be mitigated using an early date killing of the cover crop, March 15th for the conditions simulated in this exercise.

Modelling catchment inflows into Lake Victoria: regionalisation of the parameters of a conceptual water balance model

The goal of this study was to evaluate regionalisation methods that could be used for modelling catchment inflows into Lake Victoria. WASMOD, a conceptual water balance model, was applied to nine gauged sub-basins in Lake Victoria basin in order to test the transferability of model parameters between the basins using three regionalisation approaches. Model calibration was carried out within the GLUE (generalised likelihood uncertainty estimation) framework for uncertainty assessment. The analysis was carried out for the period 1967–2000. Parameter transferability was assessed by comparing the likelihood values of regionalised simulations with the values under calibration for each basin. WASMOD performed well for all study sub-basins with Nash–Sutcliffe values ranging between 0.70 and 0.82. Transferability results were mixed. For the proxy-basin method, the best performing parameter donor basin was Mara with four proxy basins giving acceptable results. Sio, Sondu, Gucha and Duma also performed well. The global mean method gave acceptable performance for seven of the nine study basins. The ensemble regionalisation method provides the possibility to consider parameter uncertainty in the regionalisation. Ensemble regionalisation method performed best with an average departure of 40% from the observed mean annual flows compared to 48 and 60% for proxy-basin and global mean methods, respectively.

Flood forecast errors and ensemble spread—A case study

Flood forecasts are generally associated with errors, which can be attributed to uncertainties in the meteorological forecasts and the hydrologic simulations, and ensemble spreads are usually considered capable of representing them. To quantify these two components of the total forecast errors and to compare these to ensemble spreads, an extended data set is used. Four years of operational flood forecasts at hourly time step with lead times up to 48 h are evaluated for 43 catchments in Austria and Germany. Catchment sizes range from 70 to 25,600 km2, elevations from 200 to 3800 m, and mean annual precipitation from 700 to 2000 mm. A combination of ECMWF and ALADIN ensemble forecasts are used as input in a semidistributed conceptual water balance model on an hourly time step. The results indicate that, for short lead times, the ratio of hydrological simulation error to precipitation forecast error is 1.2 to 2.7 with increasing catchment size from 100 to 10,000 km2. For long lead times the ratio of hydrological simulation error to precipitation forecast error decreases from 1.1 to 0.9 with increasing catchment size. Clear scaling relationships of the forecast error components with catchment area are found. A similar scaling is also found for ensemble spreads, which are shown to represent quantitatively the total forecast error when forecasting floods.

Evaluating the snow component of a flood forecasting model

The objective of this study is to evaluate the snow routine of a semi-distributed conceptual water balance model calibrated to streamflow data alone. The model is used for operational flood forecasting in 57 catchments in Austria and southern Germany with elevations ranging 200–3,800 m a.s.l. We compared snow water equivalents (SWE) simulated by the hydrologic model with snow covered area (SCA) derived from a combined product of MODIS (version 5) Terra and Aqua satellite data for the period 2003–2009 using efficiency measures and a spatial analysis. In the comparison, thresholds for percent catchment snow cover and a cut-off water equivalent need to be chosen with care as they affect the snow model efficiency. Results indicate that the model has a tendency to underestimate snow cover in prealpine areas and forested areas while it performs better in alpine catchments and open land. The spatial analysis shows that for 88% of the analysed model area snow cover is modelled correctly on more than 80% of the days. The space borne snow cover data proved to be very useful for evaluating the snow model. We therefore suggest that the snow data will be similarly useful for data assimilation in real time flood forecasting.

Uncertainty issues of a conceptual water balance model for a semi‐arid watershed in north‐west of China

AbstractHydrological models are useful tools for better understanding the hydrological processes and performing the hydrological prediction. However, the reliability of the prediction depends largely on its uncertainty range. This study mainly focuses on estimating model parameter uncertainty and quantifying the simulation uncertainties caused by sole model parameters and the co‐effects of model parameters and model structure in a lumped conceptual water balance model called WASMOD (Water And Snow balance MODeling system). The validity of statistical hypotheses on residuals made in the model formation is tested as well, as it is the base of parameter estimation and simulation uncertainty evaluation. The bootstrap method is employed to examine the parameter uncertainty in the selected model. The Yingluoxia watershed at the upper reaches of the Heihe River basin in north‐west of China is selected as the study area. Results show that all parameters in the model can be regarded as normally distributed based on their marginal distributions and the Kolmogorov–Smirnov test, although they appear slightly skewed for two parameters. Their uncertainty ranges are different from each other. The model residuals are tested to be independent, homoscedastic and normally distributed. Based on such valid hypotheses of model residuals, simulation uncertainties caused by co‐effects of model parameters and model structure can be evaluated effectively. It is found that the 95% and 99% confidence intervals (CIs) of simulated discharge cover 42.7% and 52.4% of the observations when only parameter uncertainty is considered, indicating that parameter uncertainty has a great effect on simulation uncertainty but still cannot be used to explain all the simulation uncertainty in this study. The 95% and 99% CIs become wider, and the percentages of observations falling inside such CIs become larger when co‐effects of parameters and model structure are considered, indicating that simultaneous consideration of both parameters and model structure uncertainties accounts sufficient contribution for model simulation uncertainty. Copyright © 2012 John Wiley & Sons, Ltd.

SAC-SMA a priori parameter differences and their impact on distributed hydrologic model simulations

Summary Deriving a priori gridded parameters is an important step in the development and deployment of an operational distributed hydrologic model. Accurate a priori parameters can reduce the manual calibration effort and/or speed up the automatic calibration process, reduce calibration uncertainty, and provide valuable information at ungauged locations. Underpinned by reasonable parameter data sets, distributed hydrologic modeling can help improve water resource and flood and flash flood forecasting capabilities. Initial efforts at the National Weather Service Office of Hydrologic Development (NWS OHD) to derive a priori gridded Sacramento Soil Moisture Accounting (SAC-SMA) model parameters for the conterminous United States (CONUS) were based on a relatively coarse resolution soils property database, the State Soil Geographic Database (STATSGO) (Soil Survey Staff, 2011) and on the assumption of uniform land use and land cover. In an effort to improve the parameters, subsequent work was performed to fully incorporate spatially variable land cover information into the parameter derivation process. Following that, finer-scale soils data (the county-level Soil Survey Geographic Database (SSURGO) ( Soil Survey Staff, 2011a , Soil Survey Staff, 2011b ), together with the use of variable land cover data, were used to derive a third set of CONUS, a priori gridded parameters. It is anticipated that the second and third parameter sets, which incorporate more physical data, will be more realistic and consistent. Here, we evaluate whether this is actually the case by intercomparing these three sets of a priori parameters along with their associated hydrologic simulations which were generated by applying the National Weather Service Hydrology Laboratory’s Research Distributed Hydrologic Model (HL-RDHM) ( Koren et al., 2004 ) in a continuous fashion with an hourly time step. This model adopts a well-tested conceptual water balance model, SAC-SMA, applied on a regular spatial grid, and links to physically-based kinematic hillslope and channel routing models. Discharge and soil moisture simulated using the different set of parameters are presented to show how the parameters affect the results and under what conditions one set of parameters works better than another. In total, 63 basins ranging in size from 30 km2 to 5224 km2 were selected for this study. Sixteen of them were used to study the effects of different a priori parameters on simulated flow. Simulated hourly flow time series from three cases were compared to hourly observed data to compute statistics. Although the overall statistics are similar for the three different sets of parameters, improvements in simulated flow are observed for small basins when SSURGO-based parameters are used. Fifty-seven basins covering different climate regimes were used to analyze differences in the modeled soil moisture. Results again showed that the use of SSURGO-based parameters generate better soil moisture results when compared to STATSGO-based results, especially for the upper soil layer of smaller basins and wet basins.

Climate and catchment controls on the performance of regional flood simulations

Flood runoff is simulated for 57 catchments in Austria and Southern Germany. Catchment sizes range from 70 to 25,600 km2, elevations from 200 to 3800 m and mean annual precipitation from 700 to 2000 mm. A semi-distributed conceptual water balance model on an hourly time step is used to examine how model performance (both calibration and validation) is related to the hydroclimatic characteristics of the catchments. Model performance of runoff is measured in terms of four indices, the Nash–Sutcliffe model efficiency, the volume error, the percent absolute peak errors and the error in the timing of the peaks. The simulation results indicate that the model performance in terms of the Nash–Sutcliffe model efficiency has a tendency to increase with mean annual precipitation, mean annual runoff, the long-term ratio of rainfall and total precipitation and catchment size. Peak errors have a tendency to decrease with climatological variables as well as with catchment size. Catchment size is the most important control on the model performance but also the ratio rain/precipitation is an important factor. The hydrograph shapes tend to improve with the spatial scale and magnitude of the precipitation events. Calibration and validation results are consistent in terms of these controls on model performance.

The associated risks on water resources in Western Macedonia under climate change

This paper assesses the impacts of climate change on water resources in the Western Macedonia water district, located in northern Greece. Some critical water management issues, such as reservoir storage and water supply for agriculture and domestic use, are investigated. A conceptual water balance model was calibrated using monthly historical hydrometeorological data. The proposed model was applied in the entrance of the Polyfyto reservoir in order to estimate runoff values under a transient scenario (UKTR) referring to years 2032 and 2080. The results show that the mean annual runoff, mean winter runoff and summer runoff values, annual maximum and minimum values, as well as monthly maximum and minimum, would be reduced. By using this transient scenario, the risk associated with the water supply for power production, agriculture and domestic use has been evaluated under conditions of altered runoff. Increases of the risks associated with the annual quantities of water supply have been observed.

A Water Balance Derived Drought Index for Pinios River Basin, Greece

This study estimates hydrological drought characteristics using a water balance derived drought index in Pinios river basin, Thessaly, Greece. The concept of hydrological management at subwatershed scale has been adopted because it encompasses the areal extent of a drought event. Fourteen (14) sub-watersheds of Pinios river basin were delineated according to the major tributaries of Pinios river using GIS. For the assessment of hydrological drought, because none of the sub-watersheds have flow gauge stations at their outlets, a six-parameter monthly conceptual water balance model (UTHBAL model), has been applied regionally to simulate runoff for the period October 1960–September 2002. The synthetic runoff was normalized through Box-Cox transformation and standardized to the mean runoff to produce the water balance derived drought index for hydrological drought assessment. The standardized precipitation index (SPI) at multiple time scales and four indices of the Palmer method (i.e. PDSI, WPLM, PHDI and the Palmer moisture anomaly Z-index) were also calculated to assess hydrological droughts. The results showed that the water balance derived drought index is a good indicator of hydrological drought in all sub-watersheds, since is capable to quantify drought severity and duration. Furthermore, the drought index provides guidance on the selection of an appropriate meteorological drought index for operational hydrological drought monitoring. Hence, SPI at 3- and 6-month timescales and the WPLM could be used along with the water balance derived drought index in risk and decision analyses at the study area.

Parameter and modeling uncertainty simulated by GLUE and a formal Bayesian method for a conceptual hydrological model

Quantification of uncertainty of hydrological models has attracted much attention in hydrologic research in recent years. Many methods for quantification of uncertainty have been reported in the literature, of which GLUE and formal Bayesian method are the two most popular methods. There have been many discussions in the literature concerning differences between these two methods in theory (mathematics) and results, and this paper focuses on the computational efficiency and differences in their results, but not on philosophies and mathematical rigor that both methods rely on. By assessing parameter and modeling uncertainty of a simple conceptual water balance model (WASMOD) with the use of GLUE and formal Bayesian method, the paper evaluates differences in the results of the two methods and discusses the reasons for these differences. The main findings of the study are that: (1) the parameter posterior distributions generated by the Bayesian method are slightly less scattered than those by the GLUE method; (2) using a higher threshold value (>0.8) GLUE results in very similar estimates of parameter and model uncertainty as does the Bayesian method; and (3) GLUE is sensitive to the threshold value used to select behavioral parameter sets and lower threshold values resulting in a wider uncertainty interval of the posterior distribution of parameters, and a wider confidence interval of model uncertainty. More study is needed to generalize the findings of the present study. (C) 2010 Elsevier B.V. All rights reserved.

Scenario-based assessment and management of water resources in mid-Himalayan micro-watersheds with limited data availability

A conceptual hydrological water balance model has been developed and employed to assess the water availability in a mid-Himalayan watershed and analyse the dynamics of water supply and its utilization under different scenarios arising out of present and future developments. The model was calibrated and validated using daily runoff and rainfall data at different locations in the watershed. The water availability in streams and springs to meet the human, animal and crop requirements was assessed, and was found to vary in different quarters of the year with inequalities existing in different parts of the watershed. The model was successfully applied to analyse the impact of land-use changes and weather aberrations on water availability in the present and future scenarios. The drought scenarios are more critical in causing water scarcity in a given location, compared to the impact of land-use changes. The findings can be applied for assessing, planning and allocation of water resources among different sectors of water use in hilly areas and to make informed decisions during critical periods of water scarcity.

On the effectiveness of dry drainage in soil salinity control

Dry drainage is thought to be a potential approach to control soil salinity. This study took the Hetao Irrigation District as an example and evaluated the effectiveness of dry drainage by using remote sensing, a conceptual model and a field experiment. Archived remote sensing images from 1973–2006 were used to delineate the temporal and spatial change of soil salinity. The conceptual water and salt balance model was used to evaluate the role of dry drainage in removing excess salt from the irrigated land. The field experiment was performed to get field validation and give more accurate estimation. The results show that dry drainage did contribute to remove excess salt from the irrigated land and succeed in controlling soil salinity in the Hetao Irrigation District. It can be taken as an alternative approach in (semi-)arid area where artificial drainage is not applicable.

River flow modelling in two large river basins with non‐stationary behaviour: the Paraná and the Niger

AbstractA conceptual water balance model is applied in a distributed structure to model monthly river flow in tributaries of two very large river systems which exhibit non‐stationary behaviour, the Paraná in South America and the Niger in West Africa. The approach utilises global data sets of rainfall and potential evaporation (PE) time series and soil available water capacity at 0·5 degree latitude and longitude resolution. River flow data for tributaries ranging in size from 631 to 71 510 km2 for the period 1931–1990 (Paraná) and 1950–1989 (Niger) are used to calibrate and validate the model. The results show varying degrees of model performance during both the calibration and validation procedure. The analysis highlights some interesting issues pertaining to the development and application of water balance models such as sensitivity of model performance and parameter values to input data sets, particularly the method chosen to estimate PE. The paper ends with an analysis of prolonged fluctuation in flow characteristics exhibited by both rivers after the early 1970s, associated with fluctuation in rainfall regime and possibly change in land use or land cover. Between 1931–1971 and 1972–1990 Paraná river flows increased by ∼28% (rainfall increase ∼5%) and between 1950–1969 and 1970–1989 Niger river flows decreased by ∼34% (rainfall decrease ∼14%). Copyright © 2009 John Wiley & Sons, Ltd.

Climate Change and Associated Implications for the Water Policy Framework in the Basin of Venetikos

The impact of climate change on the hydrological regime and water resources in the basin of Venetikos has been assessed in this paper. Venetikos is a sub-basin of the Aliakmon River Basin, located in northern Greece. A monthly conceptual water balance model was calibrated using historical hydrometeorological data to determine changes in stream-flow runoff under two different equilibrium scenarios (UKHI, CCC) for year 2020, 2050 and 2100. The application of the two scenarios resulted in reduction of the mean winter and summer runoff values, and increase in maximum annual and decrease in minimum annual runoff values. Additionally, an increase of potential and actual evapo-transpiration was noticed due to temperature increase. As a result, a reduction of snow accumulation, as well as a decrease in spring runoff values and soil moisture are expected. A shift of the wet period towards December is remarked, resulting in severe prolongation of the dry period. Consequently, the water policy should be revised in order to address the above possible future changes.

Hydrological response to meteorological drought using the Palmer drought indices in Thessaly, Greece

This study evaluates the efficacy of Palmer drought indices to monitor hydrological droughts in river discharges and soil moisture in selected watersheds with varying geomorphologic characteristics in region of Thessaly, Greece. The Palmer four indices (PDSI, Weighted PDSI, PHDI and the moisture anomaly Z-index) were used as indicators of meteorological drought severity. The hydrological drought severity was evaluated from the outputs of the monthly UTHBAL conceptual water balance model. The UTHBAL model was calibrated with the available observed runoff data to extend, reconstruct and produce runoff and soil moisture timeseries for the hydrologic period 1960–2002 at the study catchments. The produced hydrologic variables were normalized through Box-Cox transformation and standardized to normal distribution. The standardized hydrologic variables were used as an indicator of hydrological drought severity and were compared with the Palmer drought indices timeseries estimated by basin-wide meteorological data. The results showed that, in general, the Weighted PDSI and the moisture anomaly Z-index were found to better represent river discharges and soil moisture, respectively, for all study watersheds irrespectively to their area, geophysical, and hydroclimatic characteristics. However, the results were quite variable in the identification of specific historical drought periods. Although, the Palmer indices were successful in the identification of drought severity of historical events, they failed to identify the drought duration.

A spatio‐temporal comparison of water balance modelling in an Alpine catchment

AbstractTo determine the distribution of water balance components in space and time, models are applied with a wide range of spatio‐temporal discretizations—from lumped to distributed in the spatial scale and from annual to daily (or shorter) time‐steps in the temporal scale. We present a comparative case study where we compare the simulation results of two conceptual water balance models using different spatio‐temporal discretizations. Such a comparison enables to assess if different models with different discretizations may still yield similar results in space and time. The study focuses on the mountainous catchment of the river Gail (app. 1300 km2) in southern Austria for the period 1971–1990. The first model uses a semi‐distributed discretization and daily data, whereas the second model uses a spatially distributed discretization (1 × 1 km raster) and monthly data. Both models use precipitation and temperature data as input. Parameters of the daily model were calibrated with runoff data of several gauges as part of a study focusing specifically on the Gail catchment. The distributed parameters of the monthly model were estimated regionally for establishing the water balance of the Hydrological Atlas of Austria. Both models perform equally well for runoff simulations. For simulation of temporal dynamics the models agree well for the main inputs and outputs of the system, with slightly lower agreements for sub‐components—such as snowmelt for instance. In the spatial domain the correlation between the models is significantly lower. Differences are mainly related to different calibration approaches and are not dependent on the spatio‐temporal discretization. Overall, the two water balance models yield consistent results, suggesting that the usage of monthly data is not inferior to the usage of daily data. Copyright © 2008 John Wiley & Sons, Ltd.