Abstract

Abstract. The objective of this study was to analyze the changes and uncertainties related to water availability in the future (for the purposes of this study, the period between 2011 and 2040 was adopted), using a stochastic approach, taking as reference a climate projection from climate model Eta CPTEC/HadCM3. The study was applied to the Ijuí River basin in the south of Brazil. The set of methods adopted involved, among others, correcting the climatic variables projected for the future, hydrological simulation using artificial neural networks (ANNs) to define a number of monthly flows and stochastic modeling to generate 1000 hydrological series with equal probability of occurrence. A multiplicative type stochastic model was developed in which monthly flow is the result of the product of four components: (i) long-term trend component; (ii) cyclic or seasonal component; (iii) time-dependency component; and (iv) random component. In general, the results showed a trend to increased flows. The mean flow for a long period, for instance, presented an alteration from 141.6 m3 s−1 (1961–1990) to 200.3 m3 s−1 (2011–2040). An increment in mean flow and in the monthly standard deviation was also observed between the months of January and October. Between the months of February and June, the percentage of mean monthly flow increase was more marked, surpassing the 100 % index. Considering the confidence intervals in the flow estimates for the future, it can be concluded that there is a tendency to increase the hydrological variability during the period between 2011 and 2040, which indicates the possibility of occurrence of time series with more marked periods of droughts and floods.

Highlights

  • The objective of this study is to analyze the possible scenarios and uncertainties related to water availability in future, using a stochastic approach based on a climatic change scenario originating in the Eta CPTEC/HadCM3 climate model

  • Considering the mean of the 25 1000 series generated for the future period, the long period mean flow (LPMF) was Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

  • This study analyzed the possible changes and uncertainties related to water availabil5 ity in the future using a stochastic approach, based on the climate change scenario originating in the LOW member of Eta CPTEC/HadCM3 climate model, for the period between 2011 and 2040

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Summary

Introduction

Many studies have proved significant alterations in the composition of the 25 atmosphere and, in the climate-related variables. On this topic the IPCC (Intergovernmental Panel on Climate Changes) should be highlighted. Lished in 1988 by the World Meteorological Organization (WMO) and by the United Nations Environment Program (UNEP) whose objective is to supply scientific information in order to gain a better understanding of changes in the global climate, so as to evaluate their impact on society and on nature, and propose alternatives for adaptation 5 and mitigation. Studies developed on a global scale have shown that several natural systems 10 are already under the impact of climate changes

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