Given the great variability of the precipitation in the Brazilian Northeast, it is necessary to use climate indexes for its monitoring. In this sense, this work aims to present a study of the space-time variation in the rainfall precipitation at the Salgado Basin, located in the state of Ceará, using the Rainfall Anomaly Index (RAI) as a tool. In order to do so, daily precipitation data from seven meteorological stations were used for the period between 1974 and 2015. From the data obtained, the RAI was calculated and plotted in spatial distribution maps. It was possible to observe that the rainy season at the basin lasts from January to April, and the driest period of the year lasts from July to October. The historical series presented drier years than rainy ones. A variation in the RAI within the basin was evidenced, and the region corresponding to Chapada do Araripe was more humid. The years with the most extreme anomalies were related to SSTA events, which favored its occurrence.

The potential effects of climatic changes on water resources are crucial to be assessed, particularly in dry regions such as north-east Brazil (1 million km²), where water supply is highly reliant on open-water reservoirs. This study analyses the impact of evaporation (by the Penman method) on water availability for four scenarios based on two regional climatic models (Eta-CanESM2 and Eta-MIROC5) using the Representative Concentration Pathways (RCPs) 4.5 and 8.5. We compared the water availability in the period of 2071–2100 with that of the historical period (1961–2005). The scenarios derived from the Eta-CanESM2 model indicate an increase in the dry-season evaporative rate (2 % and 6 %, respectively) by the end of the century. Unlike the above scenarios, the ones derived from the Eta-MIROC5 model both show a change in the dry-season evaporative rate of −2 %. Consequently, for a 90 % reliability level, the expected reservoir capacity to supply water with high reliability is reduced by 80 %. It is reasonable to state that both patterns of future evaporation in the reservoirs may prove to be plausible. Because model-based projections of climate impact on water resources can be quite divergent, it is necessary to develop adaptations that do not need quantitative projections of changes in hydrological variables but rather ranges of projected values. Our analysis shows how open-water reservoirs might be impacted by climate change in dry regions. These findings complement a body of knowledge on the estimation of water availability in a changing climate and provide new data on and insights into water management in reservoir-dependent drylands.

A evapotranspiração de referência tem papel importante no manejo de irrigação, e sua estimativa deve ser realizada pelo método que melhor se adeque as condições climáticas locais. Dessa forma objetivou-se neste trabalho comparar métodos empíricos de estimativa da evapotranspiração de referência (Radiação Solar, Blaney-Criddle, Hargreaves-Samani e Makkink) ao método de Penman-Monteith (FAO 56) no estado de Alagoas. Para tanto utilizou-se de dados meteorológicos referentes à temperatura máxima e mínima do ar (°C), insolação (horas/dia), umidade relativa do ar (%) e velocidade do vento (m.s-1), obtidos por meio do Instituto Nacional de Meteorologia (INMET) para o período de 1995 a 2015. Os municípios estudados foram: Areia Branca, Maceió, Palmeira dos Índios, Pão de açúcar e Porto de Pedras. Os dados foram processados por meio do software REF-ET, onde se obteve os dados de ET0 pelos cinco métodos acima descritos. Para a comparação dos métodos com o método padrão utilizou-se as seguintes estatísticas: coeficiente de determinação (R²), coeficiente de correlação (r), erro absoluto médio (EAM), raiz do erro quadrado médio (REQM), índice de concordância (d) e índice de desempenho (c). Dentre os métodos avaliados verificou-se que o melhor desempenho foi obtido pelo método de Blaney Criddle-FAO, com base em todos os indicadores utilizados, e, juntamente com o método de Hargreaves Samani, apresentaram um comportamento bastante semelhante ao método padrão na estimativa anual da evapotranspiração de referência.

Comportamento de chuvas intensas para bacia em região semiárida de Caatinga preservada - DOI:10.5039/agraria.v14i3a6138