Application of the climatic water balance method for recharge evaluation and extreme climate indices analysis in the northern region of Rio de Janeiro state BR at the present climate

The increasing use of groundwater as an alternative source to meet the water demand leads to the necessity of availability studies and the influence of climate variations to aquifer recharge. Assessment of aquifer behavior in face of climate change scenarios may provide invaluable information and can assist in the planning and management of these resources. The objective of this work is to use climate data (precipitation and temperature) to estimate recharge using Thornthwaite- Mather (1955) method through simulations with groundwater budget software and extreme climate indices analysis using the software RClimDex elaborated by the Meteorological Service of Canada. The climatological analysis of Campos dos Goytacazes municipality, loca ed in the northern region of Rio de Janeiro state Brazil to the period of 1961-1990 indicates an annual rainfall relatively low (1055 mm) with 64% of the total (672 mm) concentrated in the rainy period that goes from October to January. The number of rainy days (days which total rainfall exceeds 1 mm) fluctuates between 4 and 12 in June and December, respectively. With respect to consecutive dry days, the average is around 30 and 35 days/year, which probably occurs in the winter period. The compensated temperature oscillates between 20.7 ° C in July and 26.6 ° C in February. The recharge estimate was elaborated through the Hydrometeorological Balance using temperature and precipitation data obtained from the meteorological station of the Brazilian Institute of Meteorology (INMET) located in the city of Campos dos Goytacazes RJ for the period of 1961/01/01 to 2016/12/31 using as tool the software Easybal 4.0 (Vazquéz-Suñe and Castro, 2002), provided average annual precipitation results of 958.2 mm and average annual recharge of 232.32 mm, so approximately 22% of the water that precipitates in the form of rain percolates and arrives at the aquifer recharging it. The obtained results show a high correlation (0.93) between the recharge and precipitation values in the study area, so that the precipitation variations are directly related to the variations of the recharge to the aquifer. Results also indicate an increase trend in temperature and a decrease in rainfall in the study area, which is becoming hotter and dryer through time. As rainfall and recharge trends are strong related, it is possible to conclude that a decrease in rainfall leads to a decrease in the recharge. This process is certainly accelerated by climate change and affects the water availability in the aquifer, reducing its water potential.