Investigation of Hydrological Response of Three Identical Artificial Hillslopes at the Landscape Evolution Observatory

Katarena Matos1, Antonio Alves Meira Neto1, Peter Troch1,2, Till Volkmann2

1Department of Hydrology and Atmosheric Sciences

2Biosphere 2

The University of Arizona

Hydrological processes at the hillslope scale are complex and monitoring hillslopes with a large number of sensors or replicate experimental designs is rarely feasible. The Landscape Evolution Observatory at Biosphere 2 consists of three, large (330 m2) artificial hillslopes packed with 1-m depth of initially homogeneous, basaltic soil. Each landscape contains a spatially dense network of sensors capable of resolving meter-scale lateral heterogeneity and sub-meter scale vertical heterogeneity in moisture content and water potential, as well as the hillslope-integrated water balance components. The three hillslopes are thought to be nearly identical, however recent data showed significant differences in discharge and storage behavior. A 45-day periodic-steady-state tracer experiment was conducted in November and December of 2016, where a 3.5-day long, identical irrigation sequence was repeated 15 times.  Each sequence’s rainfall, runoff, and storage dynamics were recorded, and distributed moisture characteristics were derived using paired moisture content and matric potential data from 496 positions in each hillslope. In order to understand why the three hillslopes behave hydrologically different, we analyzed soil water retention characteristics at various scales ranging from individually paired moisture and matric potential to whole-hillslope soil water retention characteristics. The results confirm the distinct hydrological behavior between the three hillslopes.