Volume 34, Issue 25 pp. 5043-5069
RESEARCH ARTICLE

Assessing plot-scale impacts of land use on overland flow generation in Central Panama

Sidney A. Bush

Corresponding Author

Sidney A. Bush

Department of Geography/ Institute of Arctic and Alpine Research, University of Colorado Boulder, Boulder, Colorado, USA

Correspondence

Sidney A. Bush, Department of Geography/Institute of Arctic and Alpine Research, University of Colorado Boulder, Boulder, CO.

Email: [email protected]

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Robert F. Stallard

Robert F. Stallard

U.S. Geological Survey, Water Mission Area, Hydro-ecological Interactions Branch, Boulder, Colorado, USA

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Brian A. Ebel

Brian A. Ebel

U.S. Geological Survey, Water Mission Area, Water Cycle Branch, Lakewood, Colorado, USA

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Holly R. Barnard

Holly R. Barnard

Department of Geography/ Institute of Arctic and Alpine Research, University of Colorado Boulder, Boulder, Colorado, USA

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First published: 30 September 2020
Citations: 5

This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Funding information: National Science Foundation, Grant/Award Number: EAR-1360384; Smithsonian Tropical Research Institute

Abstract

Land use in Panama has changed dramatically with ongoing deforestation and conversion to cropland and cattle pastures, potentially altering the soil properties that drive the hydrological processes of infiltration and overland flow. We compared plot-scale overland flow generation between hillslopes in forested and actively cattle-grazed watersheds in Central Panama. Soil physical and hydraulic properties, soil moisture and overland flow data were measured along hillslopes of each land-use type. Soil characteristics and rainfall data were input into a simple, 1-D representative model, HYDRUS-1D, to simulate overland flow that we used to make inferences about overland flow response at forest and pasture sites. Runoff ratios (overland flow/rainfall) were generally higher at the pasture site, although no overall trends were observed between rainfall characteristics and runoff ratios across the two land uses at the plot scale. Saturated hydraulic conductivity (Ks) and bulk density were different between the forest and pasture sites (p < 10−4). Simulating overland flow in HYDRUS-1D produced more outputs similar to the overland flow recorded at the pasture site than the forest site. Results from our study indicate that, at the plot scale, Hortonian overland flow is the main driver for overland flow generation at the pasture site during storms with high-rainfall totals. We infer that the combination of a leaf litter layer and the activation of shallow preferential flow paths resulting in shallow saturation-excess overland flow are likely the main drivers for plot scale overland flow generation at the forest site. Results from this study contribute to the broader understanding of the delivery of freshwater to streams, which will become increasingly important in the tropics considering freshwater resource scarcity and changing storm intensities.

DATA AVAILABILITY STATEMENT

The data that support the findings of this study have been made available at the following web address: https://doi.org/10.4211/hs.86c58dfe5067486aa014ea814e3e79ff.

The full text of this article hosted at iucr.org is unavailable due to technical difficulties.