Tuesday, 11 July 2006

A Hydropedologic Study of Subsurface Water Flow in a Forested Catchment.

Xiaobo Zhou, Penn State University, 116 ASI Bld., University Park, PA 16802, Henry Lin, Penn State Universtiy, 415 Agricultural Sciences and Industries Building, University Park, PA 16802, Charles Walker, The Pennsylvania State University, 420 ASI Building, University Park, PA 16802, and Qing Zhu, Department of Crop and Soil Science, The Pennsylvania State University, 116 ASI Building, State College, PA 16802.

Soil moisture is a key component for understanding hydrological processes. The subsurface water flow (lateral and vertical) plays a critical role on areal soil moisture redistribution. Systematic and dynamic soil moisture observations are needed to monitor soil moisture status and model water flow pathways in spatial and temporal scales. The objective of this study is to characterize the soil moisture distribution and subsurface water flow at the Shale Hills Catchment in central Pennsylvania. Hydropedologic approaches integrating soil information with hydrological processes were used to guide experimental design, monitoring device installation, and soil moisture modeling. Soil moisture content and water movement at different landforms and soil profiles at this forested catchment were investigated over two years using Time Domain Reflectometry (TDR) probes and Tensiometers. The dynamic soil moisture status at two selected sites were also monitored using automatic system using an array of soil matric potential probes (229-L and Decagon matric potential probes), soil water content probes (ECH2O-10), and temperature probes. Probes were inserted at different soil profiles as well as their interfaces to study subsurface water flow. A “bottleneck” phenomenon was observed at certain soil layers, of which the hydraulic conductivity is very low, and as a result determines the water movement and distribution within entire soil profiles. The soil moisture responses to different rainfall intensity patterns at different soil layers were also investigated. The characteristic curves of soil moisture change during dry down period were established for soil layers. Soil texture and other ancillary data (bulk density, hydraulic conductivity) were used to understand the soil moisture spatial distribution and water subsurface movement.

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