Martin Hanel
Czech University of Life Sciences Prague
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Featured researches published by Martin Hanel.
Journal of Hydrology and Hydromechanics | 2012
Martin Hanel; Adam Vizina; Petr Máca; Jiří Pavlásek
A Multi-Model Assessment of Climate Change Impact on Hydrological Regime in the Czech Republic In present paper we assess the climate change impact on mean runoff between the periods 1961-1990 (control period) and 2070-2099 (scenario period) in the Czech Republic. Hydrological balance is modelled with a conceptual hydrological model BILAN at 250 catchments of different sizes and climatic conditions. Climate change scenarios are derived using simple delta approach, i.e. observed series of precipitation, temperature and relative air humidity are perturbed in order to give the same changes between the control and scenario period as in the ensemble of 15 transient regional climate model (RCM) simulations. The parameters of the hydrological model are for each catchment estimated using observed data. These parameters are subsequently used to derive discharge series under climate change conditions for each RCM simulation. Although the differences in the absolute values of the changes in runoff are considerable, robust patterns of changes can be identified. The majority of the scenarios project an increase in winter runoff in the northern part of the Czech Republic, especially at catchments with high elevation. The scenarios also agree on a decrease in spring and summer runoff in most of the catchments. Dopady Klimatické Změny na Hydrologický Režim v České Republice Podle Souboru Klimatických Modelů V článku předkládáme výsledky modelování změn hydrologického režimu v důsledku změn klimatu mezi časovými obdobími 1961-1990 a 2070-2099 podle souboru patnácti regionálních klimatických modelů pro 250 povodí v České republice. Hydrologická bilance byla modelována pomocí konceptuálního hydrologického modelu BILAN. Časové řady ovlivněné změnou klimatu byly získány jednoduchou přírůstkovou metodou, tj. pozorované časové řady srážek, teplot a vlhkostí vzduchu (vstupy do modelu BILAN) byly opraveny pro každou simulaci pomocí přírůstkových faktorů tak, aby měsíční změny těchto veličin byly stejné jako podle uvažované simulace klimatického modelu. Hydrologický model je nakalibrován s využitím pozorovaných dat, identifikované parametry jsou následně využity pro simulaci hydrologické bilance pro řady ovlivněné klimatickou změnou. Základní podstata možných změn hydrologické bilance na území České republiky vyplývá z projekcí srážek a teplot pro Evropu, tj. postupné zvyšování teplot během celého roku a pokles letních, růst zimních a stagnace ročních srážek. V období od začátku podzimu do začátku léta dochází k růstu srážek, jenž je doprovázen řádově stejným růstem územního výparu způsobeným růstem teplot. V letním období dochází k poklesu srážek a v důsledku úbytku zásob vody v povodí nemůže docházet k výraznému zvyšování územního výparu. Důležitým faktorem ovlivňující změny odtoku je posun doby tání v důsledku vyšší teploty přibližně z dubna na leden-únor. Změny odtoku v období leden-květen jsou tedy dominantně určeny právě odlišnou dynamikou sněhové zásoby, změny v letním období zejména úbytkem srážek. Výsledné odhady změn odtoku jsou zatíženy značnou nejistotou, nicméně lze identifikovat robustní jevy společné pro řadu simulací. Jak ukazují výsledky, na většině modelovaných povodí je pokles odtoků v období od dubna do října společný valné většině modelů. Na druhé straně, růst odtoku v zimních měsících je značně nejistý. S tím souvisí i nejistota spojená se změnami roční bilance odtoků.
Water Resources Management | 2013
Martin Hanel; Magdalena Mrkvickova; Petr Máca; Adam Vizina; Pavel Pech
An ensemble of fifteen regional climate model (RCM) simulations has been used to estimate the climate change impacts on runoff and several drought characteristics for 250 basins in the Czech Republic. The scenario series of precipitation and temperature have been derived with four simple statistical downscaling methods (SDMs): the delta change and bias correction method, both in two alternatives considering the changes/biases in the mean, and in the mean and variance. Bootstrap resampling has been used to assess the effect of sampling variability and the differences in the estimated changes in runoff obtained by different SDMs were evaluated. Further simplification of the SDMs (spatial-average changes/biases and ensemble-average changes in precipitation and temperature) have been considered. It was shown, that given the spread between the projections of individual RCM simulations and the sampling variability, the differences in the estimated changes in mean runoff between the SDMs are not very large. The same partly holds also for the effect of spatial averaging. In general, the SDMs accounting for variability have led to smaller decrease (or larger increase) in runoff and the decrease was also smaller for bias correction methods than in the case of delta change methods. In contrast to changes in mean runoff, significant differences between the estimates based on different SDMs were found for the drought characteristics. In addition, the averaging of the changes in precipitation and temperature over the RCMs resulted in much stronger decrease in runoff than indicated by ensemble average changes in runoff.
Computing | 2013
Vojtěch Havlíček; Martin Hanel; Petr Máca; Michal Kuráž; Pavel Pech
This paper focuses on improving rainfall-runoff forecasts by a combination of genetic programming (GP) and basic hydrological modelling concepts. GP is a general optimisation technique for making an automated search of a computer program that solves some particular problem. The SORD! program was developed for the purposes of this study (in the R programming language). It is an implementation of canonical GP. Special functions are used for a combined approach of hydrological concepts and GP. The special functions are a reservoir model, a simple moving average model, and a cumulative sum and delay operator. The efficiency of the approach presented here is tested on runoff predictions for five catchments of various sizes. The input data consists of daily rainfall and runoff series. The forecast step is one day. The performance of the proposed approach is compared with the results of the artificial neural network model (ANN) and with the GP model without special functions. GP combined with these concepts provides satisfactory performance, and the simulations seem to be more accurate than the results of ANN and GP without these functions. An additional advantage of the proposed approach is that it is not necessary to determine the input lag, and there is better convergence. The SORD! program provides an easy-to-use alternative for data-oriented modelling combined with simple concepts used in hydrological modelling.
Environmental Modelling and Software | 2017
Martin Hanel; Roman Kožín; Martin Heřmanovský; Radek Roub
Abstract Due to inherent bias the climate model simulated precipitation and temperature cannot be used to drive a hydrological model without pre-processing – statistical downscaling. This often consists of reducing the bias in the climate model simulations (bias correction) and/or transformation of the observed data in order to match the projected changes (delta change). The validation of the statistical downscaling methods is typically limited to the scale for which the transformation was calibrated and the driving variables (precipitation and temperature) of the hydrological model. The paper introduces an R package ”musica” which provides ready to use tools for routine validation of statistical downscaling methods at multiple time scales as well as several advanced methods for statistical downscaling. The musica package is used to validate simulated runoff. It is shown that using conventional methods for downscaling of precipitation and temperature often leads to substantial biases in simulated runoff at all time scales.
Journal of Hydrology and Hydromechanics | 2016
Vojtěch Svoboda; Martin Hanel; Petr Máca; Jan Kyselý
Abstract Projected changes of warm season (May–September) rainfall events in an ensemble of 30 regional climate model (RCM) simulations are assessed for the Czech Republic. Individual rainfall events are identified using the concept of minimum inter-event time and only heavy events are considered. The changes of rainfall event characteristics are evaluated between the control (1981–2000) and two scenario (2020–2049 and 2070–2099) periods. Despite a consistent decrease in the number of heavy rainfall events, there is a large uncertainty in projected changes in seasonal precipitation total due to heavy events. Most considered characteristics (rainfall event depth, mean rainfall rate, maximum 60-min rainfall intensity and indicators of rainfall event erosivity) are projected to increase and larger increases appear for more extreme values. Only rainfall event duration slightly decreases in the more distant scenario period according to the RCM simulations. As a consequence, the number of less extreme heavy rainfall events as well as the number of long events decreases in majority of the RCM simulations. Changes in most event characteristics (and especially in characteristics related to the rainfall intensity) depend on changes in radiative forcing and temperature for the future periods. Only changes in the number of events and seasonal total due to heavy events depend significantly on altitude.
Advances in Meteorology | 2016
Marta Martinkova; Martin Hanel
The intensity of precipitation extremes is expected to increase as the climate warms and it may cause floods and increase erosion. From the Clausius-Clapeyron relation (CC) it follows that the maximum moisture content of the atmosphere increases by approximately 7% per degree as temperature rises. However, the increases in observed hourly precipitation extremes of approximately two times the CC relation were described recently. This super CC scaling is attributed to the increased prevalence of convective rainfall and decreased prevalence of stratiform rainfall as temperatures increase. We carried out the disaggregation of precipitation into prevailing stratiform and convective component on the observational data from the Czech Republic for 1966–2006. Then, we analyzed trends in characteristics of disaggregated events and assessed correlation of precipitation intensities with daily mean temperature. The results suggest the increasing trend of convective precipitation in summer. The scaling for total rain events is steeper than for the events with prevailing convective component and for the events with prevailing stratiform component. It is a result of mixing of the two storm types. At higher temperature the events with prevailing convective component prevail and vice versa.
Journal of Climate | 2015
Martin Hanel; T. Adri Buishand
AbstractA linear mixed-effects (LME) model is developed to discriminate the sources of variation in the changes of several precipitation characteristics over the Rhine basin as projected by an ensemble of 191 global climate model (GCM) simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5). The uncertainty in climate change projections originates from natural internal variability, imperfect climate models, and the unpredictability of future greenhouse gas forcing. The LME model allows for the quantification of the contribution of these sources of uncertainty as well as the interaction between greenhouse gas forcing and climate model. In addition, dependence between climate models can be accounted for by using a two-level LME model in which the GCMs are grouped according to their atmospheric circulation model. Statistical models of varied complexity are assessed by the Akaike information criterion. More than 60% of the variance of the changes in mean summer precipitation and various ...
Scientific Reports | 2018
Martin Hanel; Oldřich Rakovec; Yannis Markonis; Petr Máca; Luis Samaniego; Jan Kyselý; Rohini Kumar
Early 21st-century droughts in Europe have been broadly regarded as exceptionally severe, substantially affecting a wide range of socio-economic sectors. These extreme events were linked mainly to increases in temperature and record-breaking heatwaves that have been influencing Europe since 2000, in combination with a lack of precipitation during the summer months. Drought propagated through all respective compartments of the hydrological cycle, involving low runoff and prolonged soil moisture deficits. What if these recent droughts are not as extreme as previously thought? Using reconstructed droughts over the last 250 years, we show that although the 2003 and 2015 droughts may be regarded as the most extreme droughts driven by precipitation deficits during the vegetation period, their spatial extent and severity at a long-term European scale are less uncommon. This conclusion is evident in our concurrent investigation of three major drought types – meteorological (precipitation), agricultural (soil moisture) and hydrological (grid-scale runoff) droughts. Additionally, unprecedented drying trends for soil moisture and corresponding increases in the frequency of agricultural droughts are also observed, reflecting the recurring periods of high temperatures. Since intense and extended meteorological droughts may reemerge in the future, our study highlights concerns regarding the impacts of such extreme events when combined with persistent decrease in European soil moisture.
Open Geosciences | 2018
Marta Martinkova; Tomáš Hejduk; Petr Fučík; Jan Vymazal; Martin Hanel
Abstract Water quality in rural catchments is influenced by many societal and bio-physical factors (e.g. different pollution sources, land use and land cover changes). Good ecological status and surface water quality are currently challenged mainly due to different poorly identified pollution sources. The main objective of this study is to estimate the potential of different measures (land use changes and/or reduction in point sources) and their combinations in decreasing the nitrate-nitrogen load from Jankovský stream catchment. The eco-hydrological model SWIM, which simulates dynamics of nutrients in a catchment was used in the study. The simulations for scenario measures showed that nitrate-nitrogen loads at the outlet can be decreased more by reduction of municipal nitrate-nitrogen sources rather than by agricultural land-use change. Overall, the modeling results demonstrated that the most effective scenario was the combination of total reduction of municipal nitrate-nitrogen sources and agricultural land-use change.
Nature Communications | 2018
Yannis Markonis; Martin Hanel; Petr Máca; Jan Kyselý; Edward R. Cook
In recent years, there has been growing concern about the effect of global warming on water resources, especially at regional and continental scales. The last IPCC report on extremes states that there is medium confidence about an increase on European drought frequency during twentieth century. Here we use the Old World Drought Atlas palaeoclimatic reconstruction to show that when Europe’s hydroclimate is examined under a millennial, multi-scale perspective, a significant decrease in dryness can be observed since 1920 over most of central and northern Europe. On the contrary, in the south, drying conditions have prevailed, creating an intense north-to-south dipole. In both cases, hydroclimatic conditions have shifted to, and in some regions exceeded, their millennial boundaries, remaining at these extreme levels for the longest period of the 1000-year-long record.In recent years, there has been an ongoing discussion about the hydroclimatic changes over Europe. Here, the authors show that since the beginning of the 20th century, hydroclimatic conditions have shifted to their millennial boundaries, remaining at these extreme levels for a period of unprecedented duration.