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

Abstract

There is an increasing need in quantifying the available water resources and how their availability will change over time in response to human-induced and natural changes. Earth surface processes are complex and interlinked and looking for the patterns that emerge as the system coevolves can lead to improved understanding of fundamental and underlying principles that link these observed patterns to the watershed functions. The three (East, Center and West) hillslopes that make up the Landscape Evolution Observatory (LEO) at Biosphere 2 can help us gain insight into overarching patterns that arise during the coevolution of a landscape. On November 2016 the first simultaneous, rainfall-runoff experiment was performed on the LEO hillslopes. The PERTH (PERiodic Tracer Hierarchy) experiment revealed fundamental differences in the hydrologic response of the hillslopes with respect to storage-discharge dynamics. The objective of this paper is to understand how and why three nearly identically built hillslopes behave significantly different from or similar to each other when exposed to the same atmospheric forcing. To do this, we take advantage of the spatially dense network of sensors embedded within the hillslope measuring data at a high temporal resolution. The East hillslope exhibits a higher water holding capacity compared to the Center and West hillslopes. The Center hillslope is characterized by a shallower water table near the seepage face and a significantly different discharge behavior. The West hillslope is characterized by a region of higher water holding capacity along the trough of the landscape. Based on our observations and data analysis, we develop hypotheses that can be tested using a hydrologic model in order to gain a deeper understanding of the processes that led the three identically built LEO landscapes to display different hydrologic behaviors