Comportamento hidrodinâmico do solo e da recarga potencial do aquífero a partir de poços de infiltração de águas pluviais

Abstract

The objective of this work was to analyze the hydrodynamic behavior of soil e potential groundwater recharge trough stormwater infiltration wells, built in real and pilot scale at the Federal University of São Carlos using monitoring and modeling. Therefore, it will be performed physical and hydraulic analyzes of the soil, monitoring of volumetric soil moisture, hydrological data and water level inside the wells, and rainfall simulations with 2000 L and 10000 L reservoirs. The modeling were developed by the Soil Water Balance Method and numerically using Hydrus 1D version 4.16 and 2D/3D version 2.5 softwares. The soil of the study area was heterogeneous in relation to pore size and distribution, which caused the saturated hydraulic conductivity of the soil (Ksat) to vary from 1.58 10-4 to 9.52 x 10-3 cm / s, values that assure the adequacy of the area for the implantation of stormwater infiltration wells. Among the methods used to determine Ksat employed in well desing, those proposed by Cauduro and Dorfman (s / d) and Pratt and Powel (1992) were more adequate. Soil moisture monitoring showed that the wetting front reach does not depend on the well diameter, but yes of the water level height inside well and that the surfaces that effectively contribute to infiltration is below half of this height. The localized and large distribution of runoff promoted by the well made the wetting and drying cycle effect were striking in the first operations of the structure. The increase in the well diameter decreased the soil water infiltration rate, it is consequence of its increased reservoir capacity and decreased resistant energy of water flow in the soil. In the estimation of groundwater potential recharge by the Water Balance Method, when considering rainwater management using infiltration wells, the average recharge value found for 2017 and 2018 was 2,72 times higher than for the grassland scenario, therefore, the wells contribute effectively to groundwater recharge. Two-dimensional numerical modeling of groundwater dynamics was inconclusive by Hydrus 2D/3D and Hydrus 1D simulation showed that the average potential recharges for 2017 and 2018 were 86, 84, 82 and 80% of total precipitated in the period, when the water table level was 1, 2, 5 and 8 m from the bottom of PGHidro, respectively, and the inicial recharge time is directly influenced by table level and rainfall distribution. In conclusion, the results showed the importance of considering infiltration wells in urban management, not only for direct runoff control but also as a source of groundwater recharge.