Recarga do aquífero livre na Universidade Federal do Pará, campus Belém

Abstract

In Brazil urban supply, rural supply, industry, mining, thermoelectric, animal and irrigation consume approximately 61.46 billion m³/year of fresh water, with the greatest demand being urban supply (25%). In Belém, groundwater collection to feed the Water Supply System has been increasing. Despite this, the low quality of its distribution ends up stimulating the capitation of water without any criteria, contributing to the overexploitation of aquifers. In the field of scientific research, in the State of Pará, the amount of work to estimate underground recharge is incipient, making the development of new research urgent. Therefore, this work aims to estimate the recharge of the aquifer free of primary porosity located in an alluvial deposit, underlying the Federal University of Pará (UFPA), Belém campus. The recharge estimate was carried out using the Water-Table Fluctuation (WTF) method in 8 monitoring wells distributed in the so-called health and professional sectors of the Federal University of Pará. The mean water level variation in the study area was between 0.76 and 2.27 m (discrete and continuous monitoring). A specific yield (Sy) was determined through a pumping test, which provided data that were analyzed in the AQTESOLV Demo software, using the Tartakovsky-Neuman analytical solution. The Sy result of the pumping test was 0.1 (10%). The estimated recharge for discrete monitoring was between 101.40 mm and 371.60 mm (year 2020), between 75.50 mm and 552.60 mm (year 2021) and between 19.50 mm and 140.50 mm (year 2022), with an average of 583.51 mm, which represents 6.93% of the precipitation in the study period (8,419.14 mm) and for continuous monitoring, it was between 40.00 mm and 87.90 mm (year 2020) and between 19.30 mm and 218.80 mm (year 2021), with an average of 539.45 mm, which corresponds to 38.86% of the precipitation of the study period (1,338.10 mm). Thus, based on discrete and continuous monitoring data, the average recharge for the study area corresponds to approximately 22.89% of the total precipitation. The results referring to the correlation between water table fluctuation and rainfall showed an average determination coefficient of 22.49%. Both the recharge and the correlation proved to be consistent with the other surveys carried out in Brazil. As explained above, continuous assessment of aquifer recharge is recommended for the sustainable use of groundwater resources, in order to ensure their multiple uses.