Meteorological droughts and water resources: Historical and future perspectives for Rio Grande do Norte state, Northeast Brazil

The objective of this study was to relate the meteorological droughts in the present climate (1991–2016) and their projections for near future (2025–2050) under the RCP2.6 and RCP8.5 with the water resources of the Rio Grande do Norte (RN) state, located in the Northeast Brazil. For this, we proposed a relationship between the categories of the Standardized Precipitation Evapotranspiration Index (SPEI) and the water variation of four reservoirs. The SPEI was calculated using the regional climate models (RCM) and its ensemble (obtained through the principal component analysis – RCM_Ens_PCA) from the CORDEX‐CORE project for the South America domain (SAM‐22). The results indicated that approximately 70% of the times when the SPEI was classified in drought categories (SPEI ≤ −0.50), there was a decrease in the stored volume of the reservoirs, being this impact more evident in years in which the SPEI values were more intense. For wet years (SPEI > 0.50), we found that in 80.0% of the times there was an increase in the stored volume. For the near‐future climate, the analyses indicated higher spread between simulations, indicating greater uncertainties. However, the RCM members and the ensemble projected a predominance of more wet (dry) years during the 2025–2033 (2042–2047) periods, especially in the RCP2.6. Thus, it is expected that the RN state would not face water scarcity from 2025 to 2033 but would probably face water deficit from 2042 to 2047. Therefore, our results show information that can be useful for decision‐makers to plan strategic actions for water security. We showed that the SPEI can be used as a predictor variable to make association with the water variation of the Rio Grande do Norte state reservoirs. For the near‐future climate, the analyses indicated higher spread between simulations, indicating greater uncertainties. However, the RCM members and the ensemble projected a predominance of more wet (dry) years during the 2025–2033 (2042–2047) periods, especially in the RCP2.6. Thus, it is expected that the RN state would not face water scarcity from 2025 to 2033, but would probably face water deficit from 2042 to 2047.