Hydraulic characterization from porous aquifers of the Brazilian Federal District

Hydraulic conductivity (K) in unsaturated soil is a key input parameter for modeling subsurface water and solute movements. K-values are also important to better define the potential of aquifers and to optimize water resources management activities. Since K-values are usually not readily available, different techniques are applied to estimate them. This study aimed to estimate unsaturated K-values from porous aquifers found in the Federal District of Brazil. Infiltration tests were conducted in different soil types using the open-end-hole approach and the permeability test using shallow boreholes with specific depths, as reported by Heitfeld in 1979. Soil structure was taken into consideration in such estimations. In order to consider important soil properties such as soil texture and bulk density, K-values were also estimated by means of pedotransfer functions (PTFs). Soil texture was determined in the laboratory and used as input parameter for PTFs. Results from open-end-hole method and permeability test compared to those obtained from pedotransfer functions. K-values from four different shallow porous aquifers systems encountered in the Federal District varied from 10-8 ms-1 to 10-6ms-1. Highest K-values were found in Oxisols while the lowest rates were found in Inceptisols. Decreasing conductivity trend was found with increasing depth due to the increase of loamy soils. Variations in the rate of hydraulic conductivity indicated heterogeneity of porous aquifers due to differences in textural and structural characteristics of the soils.

非饱和土壤中的导水率（Hydraulic Conductivity，简称K）是模拟地下水与溶质运移过程的核心输入参数。K值对于明确含水层潜能、优化水资源管理活动同样具有重要意义。由于K值通常难以直接获取，学界常采用多种技术手段开展估算。本研究旨在估算巴西联邦特区境内多孔含水层的非饱和K值。研究针对不同土壤类型，采用Heitfeld于1979年报道的方法，实施开口钻孔法入渗试验与特定深度浅钻孔渗透试验。此类估算过程中纳入了土壤结构因素。为纳入土壤质地、容重等关键土壤属性，本研究同时借助土壤传递函数（Pedotransfer Functions，简称PTFs）进行K值估算。研究人员在实验室测定土壤质地，并将其作为PTFs的输入参数。对开口钻孔法与渗透试验得到的K值结果，与土壤传递函数的估算结果开展对比。巴西联邦特区境内四类不同的浅层多孔含水层系统的K值范围为10^-8 m·s^-1至10^-6 m·s^-1。氧化土（Oxisols）的K值最高，而始成土（Inceptisols）的K值最低。随土层深度增加，黏壤土占比提升，导水率呈下降趋势。导水率的数值差异表明，多孔含水层的非均质性源于土壤质地与结构特征的差异。