Variability Climatic of Water Availability in the Semiarid of the State of Rio Grande do Norte

The semiarid of state Rio Grande do Norte has great seasonal and interannual climatic variability, being frequently punished by long periods of drought. Region that has as predominant biome the caatinga, recognized for being well adapted to the lack of water and high temperatures. Through the Water Balance (WB) of Thornthwaite and Mather, we evaluated the variability of water availability to the region of potiguar semiarid region predominantly the caatinga biome. For that purpose, were used the historical data recorded at the meteorological station installed in the city of Cruzeta (Rio Grande do Norte) for three different periods: (i) WB with data of 30 years between 1961 and 1990 (henceforth, climatology); (ii) average WB for the period 2000 to 2016 (hereinafter, the present climate); and (iii) scenario estimates for possible climate changes, in which a mean temperature increase for the caatinga biome of 2 °C between 2041 - 2070 and an average forecast of -20% for rainfall (hereafter, future climate) was adopted. For calculations of the WB estimates, the Available Water Capacity (AWC) of 100 mm was considered. The results of the present climate, showed that the temperatures were elevated in 0.6 °C in comparison to the climatology of the region. The rainfall volumes were on average 10% below the climatology in most of the years and consumed integrally by the actual evapotranspiration rate, increasing the rate of water deficiency by 213 mm per year. With regard to the future climate, with the increase of 2 oC in average temperature until the end of the 21st century, the water deficit increases considerably, reaching four times higher than the precipitated volumes, placing the region in an increasingly critical situation in relation to demand and water supply. Given the results present here, it is increasingly important to adopt adequate planning and management of water resources and thus maintain the supply of water for regional demand.