The goal of this study is to diagnose the manner in which radar‐rainfall input affects peak flow simulation uncertainties across scales. We used the distributed physically based hydrological model ...CUENCAS with parameters that are estimated from available data and without fitting the model output to discharge observations. We evaluated the model's performance using (1) observed streamflow at the outlet of nested basins ranging in scale from 20 to 16,000 km2 and (2) streamflow simulated by a well‐established and extensively calibrated hydrological model used by the US National Weather Service (SAC‐SMA). To mimic radar‐rainfall uncertainty, we applied a recently proposed statistical model of radar‐rainfall error to produce rainfall ensembles based on different expected error scenarios. We used the generated ensembles as input for the hydrological model and summarized the effects on flow sensitivities using a relative measure of the ensemble peak flow dispersion for every link in the river network. Results show that peak flow simulation uncertainty is strongly dependent on the catchment scale. Uncertainty decreases with increasing catchment drainage area due to the aggregation effect of the river network that filters out small‐scale uncertainties. The rate at which uncertainty changes depends on the error structure of the input rainfall fields. We found that random errors that are uncorrelated in space produce high peak flow variability for small scale basins, but uncertainties decrease rapidly as scale increases. In contrast, spatially correlated errors produce less scatter in peak flows for small scales, but uncertainty decreases slowly with increasing catchment size. This study demonstrates the large impact of scale on uncertainty in hydrological simulations and demonstrates the need for a more robust characterization of the uncertainty structure in radar‐rainfall. Our results are diagnostic and illustrate the benefits of using the calibration‐free, multiscale framework to investigate uncertainty propagation with hydrological models.
Key Points
Calibration‐free, multi‐scale framework to investigate uncertainty propagation w
Empirical radar rainfall error model to produce input ensembles
Impact of scale on peak flow simulation uncertainty
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Abstract
The effect of introducing radar data assimilation into the WRF Model to improve high-resolution rainfall forecasts that are used for flash flood forecasting is analyzed. The authors selected ...12 heavy rainfall events and performed two WRF 24-h simulations that produced quantitative precipitation forecasts (QPFs) for each, one using the standard configuration in forecast mode (QPF-Cold) and one using radar data assimilated at initialization (QPF-Hot). Simulation outputs are compared with NWS stage IV QPEs for storm placement, area over threshold coverage, and equitable threat scores. The two QPF products and stage IV data are used to force the distributed hydrological model CUENCAS for the same 800 km × 800 km domain centered over Iowa (and to calculate peak flows across the river network). The hydrological model responses to the three products are compared in terms of spatial location and flood intensity. In general, QPF-Hot outperformed QPF-Cold in replicating stage IV QPE statistics. However, QPF-Hot was too wet in the first 2 h of the event, and storms created by the radar-assimilation techniques dissipated quickly, with rainfall forecasts resembling QPF-Cold after 12 h. Flash flooding predicted by CUENCAS using QPF-Hot was more consistent with stage IV in terms of placement and intensity; however, results were not consistent for all events evaluated. The most encouraging result is that expected flash flooding was indeed predicted in all 12 cases using QPF-Hot and not QPF-Cold even though placement and intensity were not a perfect match. The initial results of this study indicate that radar assimilation improves WRF’s ability to capture the character of storms, promising more accurate guidance for flash flood warnings.
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El consumo de alimentos ricos en antocianos como el arándano (Vaccinium corymbosum), puede ayudar a prevenir diversas enfermedades debido a su capacidad antioxidante y antiinflamatoria. Al tratarse ...de un fruto perecedero y con considerables excedentes no exportables, una alternativa de aprovechamiento y consumo sería mediante la elaboración de vino. No obstante, su bajo contenido de azúcares puede limitar su vinificación, teniendo que suplementarlo con azúcares exógenos, procedimiento conocido como chaptalización, con lo cual además se puede mejorar la extracción de antocianos debido a su alta solubilidad en el etanol. El objetivo del presente estudio fue evaluar el efecto de la chaptalización sobre los parámetros colorimétricos en vino de arándano. Se suplementó el jugo de arándano (10 °Brix, mosto control) con mosto de uva y sacarosa hasta alcanzar 17 °Brix (mosto AUS). Tras la fermentación se determinó el grado alcohólico, la intensidad colorante (IC) y tonalidad, los cuales además fueron comparados con un vino tinto comercial. La chaptalización permitió incrementar el grado alcohólico de 6,25 a 10,10% v/v, así como mejorar considerablemente la extracción de antocianos, con valores de IC de 5,11 y 5,70, y tonalidad de 0,78 y 0,83 para el vino control y AUS, respectivamente; acercándose incluso el vino AUS al vino tinto comercial utilizado como referencia (IC: 5,98; tonalidad: 0,83). Con lo cual, se mejora la extracción de antocianos en el vino de arándano, pudiendo así aprovechar los beneficios de estos pigmentos en la prevención de diversas enfermedades.
AbstractDams are ubiquitous in the United States, with more than 87,000 influencing streamflow across the nation. The significant majority of these dams are small and are often ignored in real-time ...flood forecasting operations and at-site and regional flood frequency estimations. Even though the impacts of individual small dams on floods is often limited, the combined flood attenuation effects of a system of such dams can be significant. In this study, the authors investigate how a system of spatially distributed small dams affect flood frequency across a range of drainage basin scales using the 660-km2 Soap Creek watershed in southeastern Iowa, which contains more than 144 small dams. Results from continuous simulation of the system of small dams indicate that peak discharges reduced between 20 and 70% with the effect decreasing as the drainage area increases. This means that neglecting the effects of the system of small dams may lead to an overestimation of flood risk, which has implications in both flood frequency estimation and real-time flood forecasting. Considering that more small dams are being built across watersheds in Iowa and elsewhere in the country, the results also highlight how the peak discharge attenuation effects of these dams is an additional factor that invalidates the stationarity assumption that is used in at-site and regional flood frequency analysis.
AbstractIn this paper, a simple hydrologic example is employed to illustrate the important features of reservoir regulated flood frequency. Despite its practical significance, the estimation of ...reservoir regulated flood frequency is largely dominated by empirical methodologies containing assumptions that could lead to incorrect results. The goal of this paper is to show by means of a continuous rainfall-runoff simulation how several reservoir variables, including the reservoir storage capacity, the size of release structures, operation rules, and the statistical variability of inflows to the reservoir, quantitatively control the regulated flood frequency. Although the example presented in this paper does not encompass the full complexity of the problem, it reveals important features of the regulated flood frequency. The study also highlights how specific assumptions in the traditional and widely used inflow volume-duration-frequency (VDF)–based methodology could lead to underestimation of flood risk for locations downstream from reservoirs. This paper, therefore, provides insight into the steps necessary to move away from the VDF-based empirical analysis towards a more realistic framework for estimating regulated flood frequencies. Simultaneously, the difficulties in fully addressing this problem are acknowledged and, consequently, continued examination of this important subject by the hydrological-science and engineering community is advocated.
AbstractThis study examines the effects that the spatial configuration of flood retention ponds have on the reduction of flood peaks across different spatial scales in the catchment. A continuous ...simulation approach is used to investigate how different spatial organizations, storage capacities, and release capacities of retention ponds alter the downstream flood frequency curve. The simulation experiment involves a small (∼30 km2) hypothetical catchment, a 1,000 year-long randomly generated rainfall time series and a distributed rainfall-runoff model that simulates the transport of water along the drainage network. Moreover, a hypothetical order four Mandelbrot-Viseck tree is used as a generic template of river network branching. Three important insights emerge from this study’s theoretical exercise. First, flood retention ponds that are placed in the upstream section of the catchment and that are configured in parallel offer better flood control than either ponds that are configured in series along the main stem or a single, bigger pond that is located near the catchment outlet. Second, for ponds that are configured in series and have different flood release or storage capacities, the maximum reduction of peak discharges of low exceedance probability at the catchment outlet is achieved when the upstream pond is emptied first or has a larger storage capacity than the downstream pond. Third, the effect that retention ponds have on flood frequency diminishes in the downstream direction as the proportion of unregulated subcatchments that contribute to the peak discharge at the outlet also increases. This means that the flood mitigation benefits of flood retention ponds are primarily local, which underscores the added value of distributed flood retention ponds in terms of their ability to disperse the flood control benefits across the catchment.
Using a qualitative and descriptive approach, the article shows the case study of the experiences that are characteristic of the use of the collaborative digital bibliographic manager (CDBM) for ...research. For this reason, a scale was built to show the different uses and educational levels of the CDBM and thus qualify the research and the academic production. Subsequently, trends in its use in master's degree theses were analyzed. One hundred and eleven students from the modules assigned to the area of applied research participated in this study. The results show that the CDBM is a means of collecting, organizing and sharing documents for collaborative work and, in addition, it is highly used for research. It can be concluded that in the master's program there is an open and flexible curricular design that includes information technologies and has a virtual learning network based on the socialization of valuable experiences.
Several authors have reported diel oscillations in streamflow records and have hypothesized that these oscillations are linked to evapotranspiration cycles in the watershed. The timing of ...oscillations in rivers, however, lags behind those of temperature and evapotranspiration in hillslopes. Two hypotheses have been put forth to explain the magnitude and timing of diel streamflow oscillations during low-flow conditions. The first suggests that delays between the peaks and troughs of streamflow and daily evapotranspiration are due to processes occurring in the soil as water moves toward the channels in the river network. The second posits that they are due to the propagation of the signal through the channels as water makes its way to the outlet of the basin. In this paper, we design and implement a theoretical model to test these hypotheses. We impose a baseflow signal entering the river network and use a linear transport equation to represent flow along the network. We develop analytic streamflow solutions for the case of uniform velocities in space over all river links. We then use our analytic solution to simulate streamflows along a self-similar river network for different flow velocities. Our results show that the amplitude and time delay of the streamflow solution are heavily influenced by transport in the river network. Moreover, our equations show that the geomorphology and topology of the river network play important roles in determining how amplitude and signal delay are reflected in streamflow signals. Finally, we have tested our theoretical formulation in the Dry Creek Experimental Watershed, where oscillations are clearly observed in streamflow records. We find that our solution produces streamflow values and fluctuations that are similar to those observed in the summer of 2011.
This study examines the role of rainfall variability on the spatial scaling structure of peak flows using the Whitewater River basin in Kansas as an illustration. Specifically, we investigate the ...effect of rainfall on the scatter, the scale break and the power law (peak flows vs. upstream areas) regression exponent. We illustrate why considering individual hydrographs at the outlet of a basin can lead to misleading interpretations of the effects of rainfall variability. We begin with the simple scenario of a basin receiving spatially uniform rainfall of varying intensities and durations and subsequently investigate the role of storm advection velocity, storm variability characterized by variance, spatial correlation and intermittency. Finally, we use a realistic space–time rainfall field obtained from a popular rainfall model that combines the aforementioned features. For each of these scenarios, we employ a recent formulation of flow velocity for a network of channels, assume idealized conditions of runoff generation and flow dynamics and calculate peak flow scaling exponents, which are then compared to the scaling exponent of the width function maxima. Our results show that the peak flow scaling exponent is always larger than the width function scaling exponent. The simulation scenarios are used to identify the smaller scale basins, whose response is dominated by the rainfall variability and the larger scale basins, which are driven by rainfall volume, river network aggregation and flow dynamics. The rainfall variability has a greater impact on peak flows at smaller scales. The effect of rainfall variability is reduced for larger scale basins as the river network aggregates and smoothes out the storm variability. The results obtained from simple scenarios are used to make rigorous interpretations of the peak flow scaling structure that is obtained from rainfall generated with the space–time rainfall model and realistic rainfall fields derived from NEXRAD radar data.
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