Freshwater and Nutrient Inputs to a Mississippi River Deltaic Estuary with River Re-Introduction

Description

In this study, I quantified freshwater and nutrient inputs in the Breton Sound estuary which is receiving freshwater reintroduction in an effort to restore deteriorating wetlands. Almost all wetlands of the Mississippi deltaic plain are isolated from riverine input due to flood control levees along the Mississippi River. This has altered water and nutrient budgets and is a primary cause of the massive wetland loss in the delta. Maintenance of the delta depends on a healthy, functioning ecosystem which includes riverine input.
The Breton Sound estuary is located southeast of New Orleans and until recently was hydrologically isolated from direct riverine input. In 1992, a freshwater diversion became operational at Caernarvon, LA that re-introduces freshwater, nutrients, and sediments from the Mississippi River into the estuary. Several inputs and losses were calculated for three annual (2000, 2001, and 2002) water budgets including precipitation (PPN), potential evapotranspiration (PET), the diversion, stormwater pumps, and groundwater. The inputs of ammonium (NH₄-N), nitrate (NO₃-N), total nitrogen (TN) and total phosphorus (TP) were determined for each of the water sources.
There was a different precipitation pattern for each of the years for which water and nutrient budgets were calculated. Precipitation contributed 48-57% of freshwater input while the diversion structure accounted for 33-48%. The net input of fresh groundwater was 3 to 4 orders of magnitude less than diversion input and precipitation. Atmospheric deposition was the largest contributor of NH₄-N accounting for 62-72% of the total NH₄ input followed by the diversion (total annual NH₄-N input was 1.39x10⁵ to 1.96x10⁵ kg). NO₃-N input to the estuary was an order of magnitude greater than NH₄-N input. The diversion was the greatest source of nitrate to the study area (7.78x10⁵ to 1.64x10⁶ kg) contributing 77-88% of total nitrate input. The diversion contributed 1.26x10⁶ to 2.10x10⁶ kg of TN, representing 77-79% of TN input. The diversion contributed 81-98% of TP input and was an order of magnitude greater than precipitation and stormwater pumps combined. Annual loading rates of NH₄-N and NO₃-N were 0.16-0.22 and 1.6-2.2 gNm^-2y^-1, respectively. TN ranged from 1.9-3.2 gNm^-2y^-1 and TP ranged from 0.17-0.29 gPm^-2y^-1.

Links & Downloads

1. http://etd.lsu.edu/docs/available/etd-11012004-115333/

Tags

Oceanography & Coastal Sciences

Additional Fields

Identifer	oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-11012004-115333
Date	02 November 2004
Creators	Hyfield, Emily Christina Grace
Contributors	Dubravko Justic, John W. Day, Jr., Enrique Reyes, Robert Gambrell
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-11012004-115333/
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.