Hydrological Regulation on Dissolved Organic Carbon Transport from Agricultural and Forest Soils to Streams
Mei, Yi
:
2013-06-28
Abstract
Riparian top soil layer, rich in organic carbon, act as a source provider of dissolved organic carbon (DOC) to its adjacent stream, but the hydrological factors that control the dynamics of DOC from terrestrial sources to the stream are not well characterized so far. The purpose of this study is to answer the questions and test the hypotheses regarding the control of hydrology on DOC transport and delivery from the terrestrial sources to the stream. The study site is White Clay Creek watershed, located in southeastern Pennsylvania.
A field experiment, observation and mathematical model in a combined approach was used in this dissertation work to achieve our goal. Three physically-based hydrological models were developed. These models were integrated dual-permeability one dimensional soil core model; Two dimensional hillslope finite element model and a physically-based, distributed catchment model. Various numerical schemes were used to solve the related partial differential equations and ordinary differential equations, including finite different method, finite-element method and finite volume method. Models were calibrated against the data collected in the field after been built. Model uncertainties were evaluated using standard inverse modeling techniques. Monte Carlo simulation was used to explore the control of the hydrological factors on the discharge-DOC concentration relationship of the watershed.
The results suggest that the subsurface contribution of DOC accounts for about 72% of the total annual export from the watershed, and the riparian zone contributes more than 90% of total DOC in groundwater. Our results also suggest that the duration of the flood wave and hydraulic property of the riparian soil play an important role in controlling the lag time between peak stream stage and peak DOC concentration from the hillslope to the adjacent stream.