Lake Pontchartrain and the drainage basin have experienced environmental degradation because of human settlement, land use and climate changes. A thorough understanding of hydrologic trends and variability associated with the changes is critical for sustainable water resources management and ecosystem restoration in the region. This study examined freshwater inflow (1940-2002) and suspended solids loadings (1978-2001) from three upper Lake Pontchartrain watersheds that contribute to the lake estuary: the Amite, Tickfaw, and Tangipahoa river watersheds. The relationships of freshwater inflow and suspended solids loadings with climate variables and population growth were investigated. Using observed daily discharge, a spatially-distributed hydrologic model (SWAT) was evaluated, and the model then was employed to assess hydrologic responses of the coastal watersheds to potential climate change. The study showed an annual freshwater inflow of 5 km3 yr-1 and average suspended solids inputs of 210,360 tons yr-1 entering Lake Pontchartrain. More than 69% of annual water yield and 66% of suspended solids occurred from December to May and from January to April, respectively. Over 80% of the variation in annual freshwater inflow could be explained by annual precipitation. A significant increase in freshwater inflow was found in the Amite River watershed over the past sixty years, coinciding with both climatic variation and population growth. The hydrologic modeling showed a good agreement between the simulated and observed daily discharge, with a relatively high Nash-Sutcliffe model efficiency (> 0.811) and low mean error (< 5.6%). The simulation further indicated that, unlike upland watersheds, calibration of the surface and channel routing parameters in the SWAT model became most critical for lowland coastal watersheds with gentle relief. The climate change assessment showed a significant influence of precipitation on annual freshwater yield with an increase of 19.3%-40.1% in response to a 10%-20% increase in annual precipitation. Potential air temperature increase would have only a marginal effect on freshwater yield as shown by a 1.4%-2.9% decrease in the annual freshwater yield for a 1.6 oC-3.3 oC increase in temperature. Warming, however, may pose risks of drought during spring and summer in this humid subtropical region.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-03312005-162802 |
| Date | 08 April 2005 |
| Creators | Wu, Kangsheng |
| Contributors | Paul LaRock, Yi-Jun Xu, William E. Kelso, Vijay P. Singh, Jim L. Chambers |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-03312005-162802/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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