Rainfall variability in the Paraíba do Meio river (AL): influence on the flow rate and dissolved phosphorus charges

Abstract

Studies aimed to watersheds are indispensable. Thus, this study aims to analyze the precipitation variability and its influence on the flow rate and loads of dissolved phosphorus in the Paraíba do Meio river in the state of Alagoas during the year 2017. The watershead of this river is located between the states of Alagoas and Pernambuco. Due to the high financial costs for performing the physical-chemical analysis of water, the collection of samples was based on a single point, in the city of Atalaia (AL), monthly from January to December, 2017, calendar year considered atypical from the rainfall point of view. In its first three months, it was not possible to obtain flow rate data, because according to the National Water Agency (NWA) the limnimetric scales did not measure in this period, and monthly flux of dissolved phosphorus, because the values of flow rate are needed to perform your calculation. Flow rate and precipitation data were obtained from NWA HidroWeb portal. The precipitation total in 2017 was 1866.9 mm, high compared to the climatological average for the region (1116.13 mm). The average flow rate in 2017 was 58.9 m³ s^-1. June and July had the highest phosphorus flux values (21.09 ton/month and 18.70 ton/month, respectively). January, February and March did not show nutrient flux, as there were no flow data. Precipitation and flow rate had an important influence on the phosphorus flux, because in the months with higher precipitation and flow rate, the phosphorus fluxes increased.