Surface soil moisture variability in a sector of a humid basin characterized by extremely flat relief

Abstract

Assessing the degree of spatial organization exhibited by soil moisture plays an important role since hydrological responses of a system are conditioned, to a large degree, by such pattern. This is more significant on plains, because water stays longer on the surface; therefore, it has more time to evaporate or infiltrate and these two processes are basically influenced by soil moisture condition. The aim was to describe surface soil moisture variability by means of a spatial and temporal dimension analysis. Four environments were considered: (A) close to temporary water bodies, poorly drained soils, and humid prairies; (B) extended lowlands, with a cemented horizon in the soil profile, and humid mesophytic meadows; (C) the flat matrix of the landscape, significant proportion of bare soil, and halophytic steppes; and (D) mounds and dunes, deep soils, and mesophytic meadows. Throughout the sampling period, some environments registered high and almost constant values (0.47–0.64 m3/m3); others recorded low and almost invariant values (0.13–0.28 m3/m3), and others showed intermediate values with broader spectrum of variation. In order to further understand surface soil moisture dynamics, multiple linear regression analyses considering soil water storage and water table depth as explanatory variables were applied. In some environments, both variables are significantly involved in the response variable explanation, and in others, soil water storage is the most predictive one. We showed that even though the study area has an extremely flat relief, a soil moisture pattern that underlies the system arises during wet periods and it becomes diffuse in dry ones.