Identifier

etd-11122007-143256

Degree

Master of Science (MS)

Department

Renewable Natural Resources

Document Type

Thesis

Abstract

Understanding stream hydrology of headwater regions is critical in effective land management for downstream water quantity and quality. Although extensive research has been performed on headwater streams in topographically variable areas, fewer studies examine low-gradient headwater stream systems, such as those existing on much of the southeastern coastal plain. This study aims to investigate spatial and temporal variation of headwater stream hydrology in a low-gradient forested watershed, quantify mass loading of suspended and dissolved solids in the watershed, and assess the applicability of a spatially distributed model in predicting hydrologic responses of a flat terrain landscape. Stream discharge and sediments were monitored for 17 months (Dec 2005 – Apr 2007) throughout the Flat Creek Watershed, a 369 km2 basin located in north central Louisiana. Containing 1st, 2nd, and 3rd order streams, land slopes average 3.9% and channel slopes are less than 1%. Results show that streamflow variability throughout the study period was highest in the 1st order streams, but ranged from intermittent conditions to water levels exceeding bankfull height throughout the watershed. Evapotranspiration in the watershed was high, exceeding 80% of the precipitation in most areas, and was partly due to low levels of rainfall. Suspended and dissolved solid loading was mainly controlled by discharge levels, as concentrations of solids did not vary extensively throughout the study period. Sediment yields in the Flat Creek Watershed were also lower than many other regions in the United States. Additionally, hydrologic simulation of streamflow using the Soil and Water Assessment Tool (SWAT) did not perform well, suggesting this type of model may not be applicable to the complex runoff processes created by the flat terrain. Representation of the water budget for the 17 months was reasonably close, but streamflow timing was off with consistent overestimation of storm peaks and underestimation of baseflow discharge. Physical watershed characteristics including the low slopes, elevated water table, beaver/debris dams, and stream geomorphology combine to increase water storage and residence time, reduce peak stormflows, sustain higher baseflows, and influence sediment loading rates in the low-gradient forested watershed.

Date

2007

Document Availability at the Time of Submission

Secure the entire work for patent and/or proprietary purposes for a period of one year. Student has submitted appropriate documentation which states: During this period the copyright owner also agrees not to exercise her/his ownership rights, including public use in works, without prior authorization from LSU. At the end of the one year period, either we or LSU may request an automatic extension for one additional year. At the end of the one year secure period (or its extension, if such is requested), the work will be released for access worldwide.

Committee Chair

Y. Jun Xu

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