Miriam Mine

Monthly rainfall–runoff modelling using artificial neural networks

Abstract Rainfall–runoff models usually present good results, but parameter calibration sometimes is tedious and subjective, and in many cases it depends on additional data surveys in the field. An alternative to the conceptual models is provided by empirical models, which relate input and output by means of an arbitrary mathematical function that bears no direct relationship to the physical characteristics of the rainfall–runoff process. This category includes the artificial neural networks (ANNs), whose implementation is the main focus of this paper. This study evaluated the capacity of ANNs to model with accuracy the monthly rainfall–runoff process. The case study was performed in the Jangada River basin, Paraná, Brazil. The results of the three ANNs that produced the best results were compared to those of a conceptual model at monthly time scale, IPHMEN. The ANNs presented the best results with highest correlation coefficients and Nash-Sutcliffe statistics and the smallest difference of volume. Citation Machado, F., Mine, M., Kaviski, E. & Fill, H. (2011) Monthly rainfall–runoff modelling using artificial neural networks. Hydrol. Sci. J. 56(3), 349–361.

Nonstationarity in determining flow-duration curves aiming water resources permits

Anthropogenic activities in the watersheds are responsible for land use changes, thus interfering in its rivers flows regimes. Consequently, changes occur in the hydrological series statistical moments, a condition known as nonstationarity. The use of a nonstationary time series can cause relevant errors, misleading and biasing the ongoing analyses. In this manner, this paper evaluates the possible effects of nonstationarity over water availability for water resources permits in six Brazilian gauges, considering the Q95% as reference. Median and seasonal flow-duration curves are employed in two distinct periods, before and after 1969, for all the series. Results suggested that Q95% increased in four gauges and reduced in the remainder two. Moreover, important changes were observed in intermediate flow-durations, suggesting that the variations are not limited to the series extreme values

Não Estacionariedade na Construção de Curvas de Permanência com Vistas à Outorga de Recursos Hídricos

Anthropogenic activities in the watersheds are responsible for land use changes, thus interfering in its rivers flows regimes. Consequently, changes occur in the hydrological series statistical moments, a condition known as nonstationarity. The use of a nonstationary time series can cause relevant errors, misleading and biasing the ongoing analyses. In this manner, this paper evaluates the possible effects of nonstationarity over water availability for water resources permits in six Brazilian gauges, considering the Q95% as reference. Median and seasonal flow-duration curves are employed in two distinct periods, before and after 1969, for all the series. Results suggested that Q95% increased in four gauges and reduced in the remainder two. Moreover, important changes were observed in intermediate flow-durations, suggesting that the variations are not limited to the series extreme values

Nonstationarity in building flow duration curves aiming at obtaining water resource permits

Anthropogenic activities in the watersheds are responsible for land use changes, thus interfering in its rivers flows regimes. Consequently, changes occur in the hydrological series statistical moments, a condition known as nonstationarity. The use of a nonstationary time series can cause relevant errors, misleading and biasing the ongoing analyses. In this manner, this paper evaluates the possible effects of nonstationarity over water availability for water resources permits in six Brazilian gauges, considering the Q95% as reference. Median and seasonal flow-duration curves are employed in two distinct periods, before and after 1969, for all the series. Results suggested that Q95% increased in four gauges and reduced in the remainder two. Moreover, important changes were observed in intermediate flow-durations, suggesting that the variations are not limited to the series extreme values

Rainfall Trend Analysis in the Region of Curitiba Using Regional Climate Model Scenarios

This paper analyses precipitation trends in the metropolitan region of Curitiba in the context of climate changes, through the regional climate models (RCM) analysis and statistical tests using, developing tools that provide safety-measure criteria to be taken and measures to predict future impacts related to climate changes. Trend analysis has been performed using the Curitiba station hydrological data and the scenarios generated by three RCM (ETA, PROMES, and RCA1). Exploratory Data Analysis (EDA), statistical tests (Mann Kendall, Seasonal Mann Kendall and others), linear regression, and the Rescaled Adjusted Partial Sums (RAPS) method, were applied. The results have identified the ETA model is the most representative of the region, besides trends in historical and simulated data series. Assuming the RCM’s uncertainties and the results, rainfall tends to increase in 2056 for the future period of precipitations.

Comparison between Deseasonalized Models for Monthly Streamflow Generation in a Hurst–Kolmogorov Process Framework

AbstractThe Hurst–Kolmogorov (HK) behavior in geophysical series is the product of fluctuations occurring simultaneously at several time scales. In streamflow time series, the clustering of similar events characterizes this behavior and brings forth the peculiarly persistent structure of such series. Because the Hurst exponent expresses the intensity of the HK behavior in time series, it is essential to preserve it in modeling hydrological series. This paper addresses an approach for multisite monthly streamflow generation in a HK framework. A deseasonalized symmetric moving average (SMAD) model is proposed, in which the seasonal components are removed from the streamflow series prior to their submission to the model. A case study applied at six gauging stations in the Iguazu River Basin, southern Brazil, is presented. SMAD synthetic series are compared with a multisite contemporaneous autoregressive integrated moving average (CARIMA) model. The results show that both models exhibited similar performance ...

Impact of climate change on hydropower production within the La Plata Basin

ABSTRACT This paper aims to estimate the variation of the combined dependable energy output of the set of major hydropower plants within the Brazilian part of the La Plata Basin due to possible climate changes during the twenty-first century. It uses and compares the predictions of two regional climate models, namely PROMES [Castro, M., Fernández, C., and Gaertner, M.A., 1993. Description of a mesoscale atmospheric numerical model. In: J.I. Díaz and J.L. Lions, eds. Mathematics, climate and environment. Rech. Math. Appl. Ser. Mason, 230–253; Gallardo, A., Galvan, C., and Mermejo, R., 2012. PROMES-MOSLEF: An atmosphere-ocean coupled regional model. Coupling and preliminary results over the Mediterranean basin. 4th HYMEX Workshop 2 2010] and RCA models [Rummukainem, M., 2010. State-of-the-art with regional climate models. WIREs Climate Change, 1, 82–96]. Rainfall and temperature predictions are converted into streamflow at key gauge stations using Variable Infiltration Capacity Model [Liang, X., Lettenmaier, D.P., Wood, E.F., and Burges, E.F., 1994. A simple hydrologically based model of land surface water and energy fluxes for general circulation models. Journal of Geophysical Research, 99, n. D7, 14,451–14,428]. The evaluation of the dependable energy output used the natural energy hydrograph method engineering consultants (Canambra Engineering Consultants, 1969. Power study of South Brazil. 13 v. Appendice XVII Final Report. Rio de Janeiro: Canambra Engineering Consultants), combined with the Monte Carlo simulation of synthetic series of natural energy. The main contribution of this paper is the consolidation of a methodology that provides estimates of the systems dependable energy as a function of the return period for both observed and future predicted streamflows. As a conclusion, a reduction of the dependable energy output of the hydropower plants within the La Plata Basin could be expected during the twenty-first century