Intensity-duration-frequency (IDF) relationships are traditional tools in water infrastructure planning and design. IDFs are developed under a stationarity assumption which may not be realistic, neither in the present nor in the future, under a changing climatic condition. This paper introduces a framework for generating non-stationary IDFs under climate change, assuming that probability of occurrence of quantiles changes over time. Using Extreme Value Theory, eight trend combinations in Generalized Extreme Value (GEV) parameters using time as covariate are compared with a stationary GEV, to identify the best alternative. Additionally, a modified Equidistance Quantile Matching (EQM_NS) method is implemented to develop IDFs for future conditions, introducing non-stationarity where justified, based on the Global Climate Models (GCM). The methodology is applied for Moncton and Shearwater gauges in Northeast Canada. From the results, it is observed that EQM_NS is able to capture the trends in the present and to translate them to estimated future rainfall intensities. Comparison of present and future IDFs strongly suggest that return period can be reduced by more than 50 years in the estimates of future rainfall intensities (e.g., historical 100-yr return period extreme rainfall may have frequency smaller than 50-yr under future conditions), raising attention to emerging risks to water infrastructure systems.

In Brazil, little is known about climate change impacts on extreme events at local scale. Here, we explored ways of communicating it, in the form of intensity-duration-frequency (IDF) curves, using the nonstationary equidistant quantile matching (EQM_NS) method. EQM_NS was applied in two urbanized areas of Brazil: São Paulo and Porto Alegre. This research was conducted using recorded and modeled precipitation data, the latter using the Regional Climate Model Eta. Results indicated an increase in rainfall intensity for rare events, which were intensified under nonstationarity. The use of stationarity misrepresented the trends related to precipitation, being able to mask the direction of change in future conditions. Future IDFs with Eta’s 3-hourly resolution appeared to be intensified when compared with those from daily resolution. The increase in rainfall intensity was more significant for short durations than for daily ones, bringing concerns about associated hazards and their impacts on society and urban infrastructure.

Os eventos extremos, acentuados pelas mudanças climáticas, podem desencadear situações de secas prolongadas e chuvas intensas, impactando expressivamente o gerenciamento de recursos hídricos. Neste contexto, o presente estudo objetiva avaliar as consequências das mudanças climáticas sobre o regime pluviométrico na bacia hidrográfica do rio Verde Grande utilizando dados provenientes de quatro modelos de circulação global: BESM, HadGEM 2-ES e MIROC 5. A metodologia tem o intuito de projetar equações de intensidade-duração-frequência (IDF) para o futuro e compará-las com as equações IDF baseadas em dados observados. Para isso, foram considerados dois cenários: o RCP 4.5, caracterizado pela estabilização das emissões de gases de efeito estufa, e o RCP 8.5, marcado pelo aumento contínuo dessas emissões. Os resultados indicam reduções nos valores de precipitações máximas diárias e nos totais anuais para as projeções climáticas na bacia do rio Verde Grande. Dessa forma, recomenda-se a realização de estudos mais aprofundados para desenvolver ações adaptativas e mitigatórias em resposta às consequências das mudanças climáticas para a bacia do rio Verde Grande.