In this work were realized the seasonal determination and analysis of Water Balance (WB) and the analysis of the Meteorological Systems (MS) impact in the hydric regime for the Rio Grande do Sul State (RS) in 2006. Air temperature and rainfall monthly data from 2006, distributed in 16 surface meteorological stations of the RS were used to calculate the WB. The methods proposed by Thornthwaite & Mather (1955) and Thornthwaite (1948) were used to calculate the WB and the evapotranspiration, respectively. The impact of MS in the hydric regime of the RS in 2006 was analyzed using data of occurrence of Frontal System (FS), Mesoscale Convective System (MCS) and Severe Events (SE). The 2006 RS rainfall distribution was uniform in the four periods of the year, with higher rainfall volume in the northern half of RS, where there was no lack of water in 2006. In the southern half of RS in 2006 there was lack of water in JFM and in OND in the coastal region. The factors that contributed to water availability during 2006 in the northern half and lack of water in the southern half of RS in JFM (Jan, Feb, Mar) and in OND (Oct, Nov, Dec) in the coastal region were: MCS and SE higher frequency in the northern half; FS lower frequency in this year in the southern half of RS in relation to the normal climatological data and the ENSO (El Niño South Oscillation) acting whose configuration in 2006 caused dry spell in the Brazil south region.
water balance; meteorological systems; rainfall
