A contribuição dos solos originados sobre granitos e rochas alcalinas na condutividade hidráulica, na recarga do lençol freático e na suscetibilidade erosiva: um estudo de caso na alta bacia hidrográfica do Rio dos Bois em Iporá-GO

Abstract

A part of the study was the analysis of soils which refers to texture, moisture, density, porosity and penetration resistance, as these soils properties influence the infiltration capacity and erosive susceptibility. The study evaluated the variation in water table using two monitoring wells. Other items were evaluated and analyzed, such as the climatological water balance, which required temperature and precipitation data from 2010 to 2012; assessment of soil erodibility by Universal Soil Loss by Laminar Erosion Equation (USLE); evaluation and some morphometric analysis factors of the basin, such as maximum and minimum height, massiveness orographic coefficient, superficial extension length, drainage density, level of rugosity, maintenance coefficient and average declivity. Other physical parameters were evaluated to integrate and comprehend the dynamic of water in the basin; among them the declivity classes in the area, the type of relief and the use and occupation of land can be mentioned. The hydrographic basin used in this study has an area of 10 km2 and is situated in the Northern area of Iporá which borders with the municipality of Diorama on the West of Goiás State. In the basin predominates soft wavy relief, the predominant declivity is between 0 and 6%. The loss of soil by erosion is less than 2 ton.ha.year in most part of the basin. Rainfall is concentrated between the months of September and March, with a dry season from April to August. The rainfall erosive capacity is of 997 ton.ha.Mj.mm. The average hydraulic conductivity of the soil is 10-5 m/s both in surface and in depth. The texture of soils used for the infiltration varied from loamy to very loamy, the density in the soils on granite was superior lightly the one of the soils on alkaline rocks. The total porosity is lightly larger in the soils developed in alkaline rocks, but when statisticment analyzed, both are same, happening the same with the resistance of the soil to the penetration, that was below 2500 kPa, that is the strip limits for impediment to the growth of the roots. The capacity of medium infiltration for all the analyzed soils was of 10-5 m/s, in other words, high value the moderate so much for the superficial infiltration, as for the infiltration in depth. The contribution area for recharge of the water table is 26% of the basin where soils prevail well developed, of texture predominantly loamy. It prevails in the basin an water table with good storage capacity and supply.