Saturated Hydraulic Conductivity in a Southern Patagonian Peatland: Estimation Methods and Associated Properties

Abstract

Saturated hydraulic conductivity (K) is often used to characterise the hydrological dynamics of peatlands. There are several methods to determine hydraulic conductivity, both in the field and in the laboratory. In the field, the piezometer method is one of the most widely used, while in the laboratory, the modified cube method (MCM) is often used in peaty soils due to its practicality. It also allows the estimation of anisotropy as K can be measured vertically or horizontally. Patagonia hosts the largest concentration of peatlands in South America, which are recognised for their pristine conservation status. However, there are few studies that address the hydrological dynamics of peatlands in the region. In this work, we aimed to investigate the relationships of K with other properties in southern peatlands and relate it to peat type classification. We also evaluate the performance of a modified MCM method, using a variable falling head; finally, we compare the laboratory and field methods used. The study was carried out in a pristine raised bog in southern Tierra del Fuego (Argentina). K was a function of depth, bulk density, humification index, and root density. Peat type classification adequately summarised these ecohydrological properties. Anisotropy was observed, but no preferential flow direction was evident. Both methods were consistent, showing that high and low permeability sites were well represented both in the field and in the laboratory. The alternative MCM method using the falling head mode obtained low experimental error and high correlation with the traditional MCM method. This method proved to be an interestingalternative as its application is simpler, reliable and recommended especially for low permeability samples.