Top PDF EVALUATION OF RAINFALL-RUNOFF MODELS FOR MEDITERRANEAN SUBCATCHMENTS

EVALUATION OF RAINFALL-RUNOFF MODELS FOR MEDITERRANEAN SUBCATCHMENTS

EVALUATION OF RAINFALL-RUNOFF MODELS FOR MEDITERRANEAN SUBCATCHMENTS

The development and the application of rainfall-runoff models have been a corner-stone of hydrological research for many decades. The amount of rainfall and its intensity and variability control the generation of runoff and the erosional processes operating at different scales. These interactions can be greatly variable in Mediterranean catchments with marked hydrological fluctuations. The aim of the study was to evaluate the performance of rainfall-runoff model, for rainfall-runoff simulation in a Mediterranean subcatchment. The Pan-European Soil Erosion Risk Assessment (PESERA), a simplified hydrological process-based approach, was used in this study to combine hydrological surface runoff factors. In total 128 input layers derived from data set includes; climate, topography, land use, crop type, planting date, and soil characteristics, are required to run the model. Initial ground cover was estimated from the Landsat ETM data provided by ESA.
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Mapping dominant runoff processes: an evaluation of different approaches
using similarity measures and synthetic runoff simulations

Mapping dominant runoff processes: an evaluation of different approaches using similarity measures and synthetic runoff simulations

To assess how the differences between the automatic DRP maps affect a hydrograph, synthetic runoff simulations were carried out. This approach was inspired by Weiler and Mc- Donnell (2004), who suggested using numerical experiments to isolate hypotheses and investigate their influence on the model output. In a recent review paper, Fatichi et al. (2016) acknowledge these studies to be different from the ones aim- ing at comparing performances of different models or val- idating model results. The word “synthetic” implies there- fore that the focus is exclusively on how the different DRP maps influence the simulated runoff, and not on how well the model reproduces a measured discharge. The model used for this study is an adapted version of the runoff generation mod- ule of the PREVAH model (Viviroli et al., 2009a). It is dis- tributed (500 m grid resolution) to take into account the spa- tial variability of the input data, which consists of a combina- tion of radar and traditionally measured rainfall data (Sideris et al., 2014). For each cell, the percentage of each RT is taken into account to avoid losing information because of the grid resolution.
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A space-time rainfall generator for highly convective Mediterranean rainstorms

A space-time rainfall generator for highly convective Mediterranean rainstorms

resolution data obtained from either denser land- networks or from meteorological radar rainfall estimates will improve model operation and reliability as a numerical simulator of realistic space-time rainfall intensity fields. More applied nu- merical experiments with the model are required to evaluate the practical benefits that can be expected from its used in applied hydrology, being clear to the authors that the greatest potentials are oriented towards watershed management and modeling with the aid of hydrological distributed simulation models that incorporate rainfall generators of this kind, ade- quately adapted to the characteristic rainfall events and their features occurring in the geographical region under study. In particular, the model reported herein with gamma-type raincells, in connection with a rainfall-runoff model, has al- ready been used for reservoir management purposes in Spain, by means of synthetic generation of inflow hydrographs of large return period, assessing the evaluation of flood con- trol operational criteria in the Beniarr´es dam (South East of Spain). (Garcia-Bartual and Serra, 2001; Garcia-Bartual et al., 2002).
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Forest cover influence on regional flood frequency assessment in Mediterranean catchments

Forest cover influence on regional flood frequency assessment in Mediterranean catchments

for estimating the index flood at ungauged sites. Many in- direct methods are based on multiregression models linking the index flood to a selected set of catchment descriptors (e.g. Kjeldsen and Jones, 2010), representing morphologi- cal, climatic and land use catchment features. These regres- sion methods take generally little consideration of the phys- ical phenomena underlying the transformation of rainfall in runoff and of the dominant flood generating mechanisms, al- though more recent studies evidenced that flood generating mechanisms can be relevant in flood regional analysis (Iaco- bellis and Fiorentino, 2000; Mertz and Bl¨oschl, 2003). Other indirect methods provide an estimate of the flood index based on a conceptual description of the hydrological response of the basin to intense rainfall events. Within the flood assess- ment procedures employed in Italy, an indirect estimation method largely applied is based on a conceptual model struc- tured according to the well-known rational formula (Rossi and Villani, 1992). Other conceptual approaches have been also proposed, based on an analytical derivation of the prob- ability distribution of floods (e.g. Becciu et al., 1993; Brath et al., 2001; Bocchiola et al., 2003). The index flood esti- mation method based on the rational formula implicitly as- sumes that the average value of the annual maximum peak discharges is related to the average value of the annual max- imum rainfall depth within a critical time interval, which is assumed equal to a characteristic time scale of the catchment response. A key parameter is the runoff coefficient, which conceptually represents the fraction of the total rainfall con- tributing to the flood peak response. Runoff coefficient val- ues are derived by regional models with respect to selected catchment descriptors that can be easily distinguished at re- gional scale. A general tendency is to employ the catchment lithology as principal catchment descriptor of the runoff co- efficient, while assuming negligible the additional informa- tion attached to the land-cover patterns for the assessment of flood extreme values, at least in rural catchments (e.g. Iaco- bellis and Fiorentino, 2000; Brath et al., 2001).
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The HYDROMED model and its application to semi-arid Mediterranean catchments with hill reservoirs 2: Rainfall-runoff model applications to three Mediterranean hill reservoirs

The HYDROMED model and its application to semi-arid Mediterranean catchments with hill reservoirs 2: Rainfall-runoff model applications to three Mediterranean hill reservoirs

In semi-arid regions, the major problem that will always face modellers is the quality of the inflow data. At present, unless the reservoir spillway is spilling, the only way of estimating the reservoir inflow is by looking at the change in the reservoir level. Because of wind, lag and resolution of the depth recorder, the inflow cannot be quantified accurately enough to calibrate rainfall-runoff models. Subsequently, hydrographs deduced from changes in the volume are not expected to give very accurate simulation results. In a heavy rainfall event there is likely to be some associated wind reservoir surging, which makes the estimation of the inflow more difficult. Moreover, most of the reservoirs are equipped with only one raingauge.
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Estimating RUSLE’s rainfall factor in the part of Italy with a Mediterranean rainfall regime

Estimating RUSLE’s rainfall factor in the part of Italy with a Mediterranean rainfall regime

The Mediterranean environment is known not only for its limited water availability but also for flood events and for rainfall erosion under several land usages (Kosmas et al., 1997). Empirical and process-based soil erosion models use rain as the rainfall–runoff erosivity index. In modelling sheet and rill erosion with RUSLE (Renard et al., 1997), the rainfall–runoff erosivity factor (R) quantifies the effect of raindrop impact and reflects the amount and rate of runoff likely to be associated with rain. To obtain an R-value by the RUSLE methodology, high resolution rainfall measurements at a small time step are required as well as accurate computation of the rainfall erosivity (EI 30 ) of each storm. Where such data are not available, alternative procedures are suggested in the USLE and RUSLE handbooks. The present study, therefore, seeks to estimate the R-factor from more readily available types of precipitation data such as mean monthly or annual totals. In Hawaii, for example, Lo et al. (1985) found a correlation between mean annual rainfall and R. In the USA, Renard and Freimund, (1994), used both mean annual precipitation and the Modified Fournier Index (Arnoldus, 1977) to estimate the R-factor. Similar approaches have been proposed for Belgium (Bollinne et al., 1979), Bavaria
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Rainfall-Runoff Modelling using Modified NRCS-CN,RS and GIS -A Case Study

Rainfall-Runoff Modelling using Modified NRCS-CN,RS and GIS -A Case Study

The USDA Soil Conservation Service curve number (SCS-CN) method has been widely accepted world over for its simplicity in application for rainfall and runoff modelling. It was reported that the concept of curve number has originated from the unit hydrograph theory. The unit hydrograph approach always requires a method for predicting rainfall contribution to the storm runoff. The SCS-CN method arose out of the empirical analysis of runoff particularly from small catchments and also suitable for hilly slope areas as per observations monitored by the USDA [9]. Geographic Information Systems (GIS) has been applied widely in hydrologic modeling in recent studies. The runoff estimated when compared with that of GIS tool indicated that the GIS method is providing satisfactory results and also as an alternative to the manual method of computation. Stuebe, Johnston [8] and Grove et al[3]. Runoff depth estimates using distributed CN are reported to be giving better result when compared with that of composite CN. It was reported that underestimation of runoff depth by CN method may be primarily due to nonlinear relationship between
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Mapping rainfall erosivity at a regional scale: a comparison of interpolation methods in the Ebro Basin (NE Spain)

Mapping rainfall erosivity at a regional scale: a comparison of interpolation methods in the Ebro Basin (NE Spain)

The global method used was generalized least squares (GLS) multiple regression. Regression is a global approach to spa- tial interpolation, and it is based on finding empirical rela- tionships between the variable of interest and other spatial variables. Regression-based techniques adapt to almost any space and usually generate adequate maps (Goodale et al., 1998; Vogt et al., 1997; Ninyerola et al., 2000). The relation- ships between climatic data and topographic and geographic variables have been extensively analyzed throughout the sci- entific literature, and regression-based models allow exploit- ing this relationship to produce maps of the climatic param- eters. Some authors have shown the advantages of incorpo- rating the information provided by ancillary data on mapping extreme rainfall probabilities (Beguer´ıa and Vicente-Serrano, 2006; Casas et al., 2007). Regression methods can be es- pecially adequate in large regions with complex atmospheric influences, such as the Ebro Valley (Daly et al., 2002; Weisse and Bois, 2002; Vicente-Serrano et al., 2003), or if the sam- ple network is not dense enough for local interpolation meth- ods (Dirks et al., 1998).
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An ensemble approach to assess hydrological models' contribution to uncertainties in the analysis of climate change impact on water resources

An ensemble approach to assess hydrological models' contribution to uncertainties in the analysis of climate change impact on water resources

Abstract. Over the recent years, several research efforts in- vestigated the impact of climate change on water resources for different regions of the world. The projection of future river flows is affected by different sources of uncertainty in the hydro-climatic modelling chain. One of the aims of the QBic 3 project (Qu´ebec-Bavarian International Collaboration on Climate Change) is to assess the contribution to uncer- tainty of hydrological models by using an ensemble of hy- drological models presenting a diversity of structural com- plexity (i.e., lumped, semi distributed and distributed mod- els). The study investigates two humid, mid-latitude catch- ments with natural flow conditions; one located in Southern Qu´ebec (Canada) and one in Southern Bavaria (Germany). Daily flow is simulated with four different hydrological mod- els, forced by outputs from regional climate models driven by global climate models over a reference (1971–2000) and a future (2041–2070) period. The results show that, for our hydrological model ensemble, the choice of model strongly affects the climate change response of selected hydrological indicators, especially those related to low flows. Indicators related to high flows seem less sensitive on the choice of the hydrological model.
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J. Braz. Chem. Soc.  vol.17 número1

J. Braz. Chem. Soc. vol.17 número1

The results obtained in this work confirm that urban stormwater runoff represents an important source of heavy metals to receiving surface waters. During the monitored period we collected information that revealed significant concentrations of lead, copper, and cadmium as well as considerable amounts of suspended solids in runoff waters. The loadings estimates of Pb, Cu, and Cd were compatible to previous works reported in the literature, despite the fact that pollutant loads are frequently broad due to the complexity of the conta- minant sources. A first flush effect was observed during a storm event for particulate Pb and Cd as well as for dissolved Cu. During the sampling period lead and cadmium were primarily particulate-bound whereas copper was mainly dissolved. The knowledge of metal partitioning is an important aspect for the management of urban stormwater runoff. High amounts of suspended solids and consequently particulate metals can be removed through some simple treatment techniques such as streets sweeping as well as through the employment of sustainable urban drainage systems (SUDS) such as wet detention ponds and filters. These practices would strongly reduce the loadings of metallic species that could reach natural waters. Finally, we consider that our findings provide reliable information concerning the necessity of public policies devoted to the protection of aquatic ecosystems.
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Development and testing of a large, transportable rainfall simulator for plot-scale runoff and parameter estimation

Development and testing of a large, transportable rainfall simulator for plot-scale runoff and parameter estimation

Abstract. There is increased interest in the interplay between vegetation conditions and overland flow generation. The lit- erature is unclear on this relationship, and there is little quan- titative guidance for modeling efforts. Therefore, experimen- tal efforts are needed, and these call for a lightweight trans- portable plot-scale (> 10 m 2 ) rainfall simulator that can be deployed quickly and quickly redeployed over various veg- etation cover conditions. Accordingly, a variable-intensity rainfall simulator and collection system was designed and tested in the laboratory and in the field. The system was tested with three configurations of common pressure wash- ing nozzles producing rainfall intensities of 62, 43, and 32 mm h −1 with uniformity coefficients of 76, 65, and 62 %, respectively, over a plot of 15.12 m 2 . Field tests were car- ried out on a grassy field with silt–loam soil in Orroli, Sar- dinia, in July and August 2010, and rainfall, soil moisture, and runoff data were collected. The two-term Philip infiltra- tion model was used to find optimal values for the saturated hydraulic conductivity of the soil surface and bulk soil, soil water retention curve slope, and air entry suction head. Op- timized hydraulic conductivity values were similar to both the measured final infiltration rate and literature values for saturated hydraulic conductivity. This inexpensive (less than USD 1000) rainfall simulator can therefore be used to iden- tify field parameters needed for hydrologic modeling.
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Hydrological model performance and parameter estimation in the wavelet-domain

Hydrological model performance and parameter estimation in the wavelet-domain

Abstract. This paper proposes a method for rainfall-runoff model calibration and performance analysis in the wavelet- domain by fitting the estimated wavelet-power spectrum (a representation of the time-varying frequency content of a time series) of a simulated discharge series to the one of the corresponding observed time series. As discussed in this pa- per, calibrating hydrological models so as to reproduce the time-varying frequency content of the observed signal can lead to different results than parameter estimation in the time- domain. Therefore, wavelet-domain parameter estimation has the potential to give new insights into model performance and to reveal model structural deficiencies. We apply the pro- posed method to synthetic case studies and a real-world dis- charge modeling case study and discuss how model diagnosis can benefit from an analysis in the wavelet-domain. The re- sults show that for the real-world case study of precipitation – runoff modeling for a high alpine catchment, the calibrated discharge simulation captures the dynamics of the observed time series better than the results obtained through calibra- tion in the time-domain. In addition, the wavelet-domain performance assessment of this case study highlights the fre- quencies that are not well reproduced by the model, which gives specific indications about how to improve the model structure.
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Comparison of different multi-objective calibration criteria of a conceptual rainfall-runoff model of flood events

Comparison of different multi-objective calibration criteria of a conceptual rainfall-runoff model of flood events

habitants encounter yearly. The objective functions used in this study can be divided in two broad categories: global and relative. Given the diversity of the flood events to be modelled such an approach was deemed necessary as the first type of criteria gives more weight to strong events whereas the second considers all events to be of equal weight. For each category, three different objective functions are considered:

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Estimation of synthetic flood design hydrographs using a distributed rainfall–runoff model coupled with a copula-based single storm rainfall generator

Estimation of synthetic flood design hydrographs using a distributed rainfall–runoff model coupled with a copula-based single storm rainfall generator

The flood frequency analysis (FFA) estimates how often a specified event will occur and aims to evaluate the flood event in terms of a maximum discharge value corresponding to a given return period and/or relative volume. The proba- bility of future events can be predicted by fitting the past ob- servations to selected probability distributions. Flood event estimation (hydrograph design) requires the use of different methods depending on whether it is enough to know the max- imum discharge value or whether it is necessary to know the full hydrograph. In both cases, the problem can be solved directly, starting from flow measurements available for the catchment, or indirectly using rainfall data recorded as input for a rainfallrunoff model. This latter approach is the basis of the derived distributed approach methods (DDA methods) that allow one to derive flood hydrographs using rainfallrunoff models. Analytical difficulties associated with this ap- proach are, often, overcome by adopting numerical Monte Carlo methods. In these cases, a stochastic rainfall genera- tor is used in order to generate rainfall data for a single event or continuously (Blöschl and Sivapalan, 1997; Loukas, 2002; Rahman et al., 2002; Aronica and Candela, 2007).
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Relationships between rainfall and throughfall in a secondary forest in southeastern Brazil: an evaluation of different statistical models

Relationships between rainfall and throughfall in a secondary forest in southeastern Brazil: an evaluation of different statistical models

and power model indicate that the relationship of these variables presents a high degree of linearity (CARIBONI et al., 2007), as shown in Figure 9. In addition, it is also possible to obtain parameters for the modelling of other hydrological processes from linear models (PYPKER et al., 2005; ZOU et al., 2015), such as canopy water storage capacity, the fraction of direct TF, amongst others. For example, the inverse value of the parameter a obtained by the linear model in the present study (Table 2) represents the canopy water storage capacity, indicating the RF depth needed to saturate the canopy and promote TF (LORENZON; DIAS; LEITE, 2013; STAELENS et al., 2008; TONELLO et al., 2014). Although the linear and power models have similar capabilities to explain the variation of TF mm , the use of linear models is recommended, since the parameters of these models can be used in more detailed analyzes of hydrological modelling, and allow comparison among the results obtained at different locations.
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On the role of the runoff coefficient in the mapping of rainfall to flood return periods

On the role of the runoff coefficient in the mapping of rainfall to flood return periods

than in the real world. In Viglione and Bl ¨oschl (2008) we have considered the basic case where only the storm durations play a relevant role. It was shown that, even in this very simple situation, the mapping of return periods is not trivial: unless for very particular cases, the return period of the flood peak is always smaller than the return period of the generating rainfall. This is in contrast with the observations in the real

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 Glimpses for Effective implementation of  Virtual Trainer

Glimpses for Effective implementation of Virtual Trainer

All learners require a flexible approach to the course. In addition, communication between the learners and lectures was limited to face-to-face meetings during specified periods. In virtual classroom, content was used to help learners acquire the life-long learning skills vital for Employees on the brink of finding jobs in the IT industry. The learning skills are Information literacy skills, Research skills, communication skills, and presentation skills. In virtual environment, the examination-based assessment is being replaced by continuous assessment. This will motivate the learners continuously demonstrate competence by doing research and developing and presenting individually as well as collaboratively.
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RBRH  vol.21 número4

RBRH vol.21 número4

In this paper, we proposed studying a small urban drainage catchment, named Pilot Basin of Mirassol (PBM) in Natal, RN - Brazil whose outlet is a detention and iniltration reservoir (DIR). The rainfall-runoff transformation processes, water accumulation in DIR and the process of iniltration and percolation in the soil proile until the free aquifer were modeled; and, from rainfall event observations, water levels in DIR, free aquifer water level measurements, and also, parameter values determination, it was able to calibrate and modeling these combined processes. The mathematical modeling was carried out from the use of a distributed rainfall-runoff model, and besides, we developed a model to simulate the soil percolation in an unsaturated porous media. Continuous simulation was run over a period of eighteen months in time intervals of one minute. The generated hydrographs were transformed into inlet volumes to the DIR and then, it was carried out water balance in these time intervals, considering iniltration and percolation of water in the soil proile. As a result, we obtain an evaluation on the storage water process in DIR as well as the iniltration of water, redistribution into the soil and the groundwater aquifer recharge, in continuous temporal simulation. We found that the DIR has good performance in order to storage storm water (loods) and contributing to the local aquifer recharge process.
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Sediment transport in runoff on rugous soil surface submitted to simulated rainfall

Sediment transport in runoff on rugous soil surface submitted to simulated rainfall

The treatments, with two replicates, consisted of four soil management systems conducted for 5.5 years as following - i) bare soil with one plowing (0.2 m depth) + two disking (0.15 m depth) up-and-down the slope, twice a year with additional manual weeding and chis- eling, in order to maintain soil surface weed free and with no crust throughout time, without crop (BS); ii) one plowing (0.2 m) + two disking (0.15 m) twice a year; the residues were incorporated into the soil and oat resi- dues were maintained on the soil surface for the last 6 months (CT); iii) no-till on natural grassland area culti- vated without soil till; residues were burned (NTB); and iv) continuous no-till after one conventional till at the establishment of the area named traditional no till; resi- dues were maintained on the soil surface (TNT). Crop sequences of oat (Avena sativa), soybean (Glycine max), vetch (Vicia sativa), maize (Zea mays), oat, bean (Phaseollus vulgaris), fodder radish (Raphanus sativus), soybean, vetch, maize and oats were cultivated in CT, NTB and TNT treatments for 5.5 years. Oat residues
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Sediment delivery ratio in a small semi-arid watershed under conditions of low connectivity

Sediment delivery ratio in a small semi-arid watershed under conditions of low connectivity

SDR values for individual runoff-generating events ranged from 0.08% to 1.67%, with an average of 0.68% (Table 2). These low values demonstrate the high capacity of the watershed for the retention of disaggregated sediment. Analysing the two events that generated runoff in 2013 (9 May and 10 May), it can be seen that the first event, even with precipitation and erosivity at 238% and 581% higher than the second event respectively, displayed a lower SDR, with a value of 0.53% (Table 2). This behaviour can be explained by the break in hydrological connectivity (BRACKEN et al., 2013; FRYIRS et al., 2007; FRYIRS, 2013) with the event of 9 May. In this first event, the soil had low antecedent moisture, and small surface reservoirs were dry, causing breaks in the connectivity of the system (FRYIRS et al., 2007) and generating sediment deposition throughout the watershed. The event of 9 May 2013, with 162 mm, a 70-year return period (using an historical series of 39 years, with the annual maximum values adjusted for the Gumbel distribution), and large erosivity, was able to break down large amounts of sediment, forming banks throughout the watershed, but due to poor connectivity was not able to transport them downstream from the watershed (BRACKEN et al., 2013; FRYIRS et al., 2007). Subsequent events, such
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