2000 Progress Report: PULSES - The Importance of Pulsed Physical Events for Watershed Sustainability in Coastal Louisiana

EPA Grant Number: R828009
Title: PULSES - The Importance of Pulsed Physical Events for Watershed Sustainability in Coastal Louisiana
Investigators: Day, John , Cable, Jaye , Fry, Brian , Justic, Dubravko , Kemp, Paul , Reyes, Enrique , Templet, Paul , Twilley, Robert
Institution: Louisiana State University - Baton Rouge , University of Louisiana at Lafayette
Current Institution: Louisiana State University - Baton Rouge , University of Southwestern Louisiana
EPA Project Officer: Hiscock, Michael
Project Period: February 28, 2000 through February 27, 2003 (Extended to August 27, 2004)
Project Period Covered by this Report: February 28, 2000 through February 27, 2001
Project Amount: $899,995
RFA: Water and Watersheds (1999) RFA Text |  Recipients Lists
Research Category: Water and Watersheds , Water


The overall objective of this project is to evaluate multiple effects of different scales of river inputs in one coastal watershed, the Caernarvon watershed, just south of New Orleans, where river inputs have been ongoing since the 1991 opening of a gated river diversion structure. Specifically, the physical science objective is to evaluate hydrodynamic and marsh accretion responses to different levels of river inputs. Ecological science objectives are to: (1) evaluate marsh plant growth responses; (2) monitor water quality changes across the watershed; (3) evaluate the function of wetland soils and benthic sediments as nutrient sinks in response to repeated flooding events with river water; (4) assay effects of river inputs on fish, shrimp, and oysters using stable isotopes; and (5) monitor phytoplankton production and possible eutrophication. Subsequently, we will develop an integrated physical/biological water quality model and a regional level simulation model to understand freshwater discharge and nutrient interactions. The objective of the social science subproject is to provide an interface between the natural and human systems of the region within the context of sustainable development through a conceptual model building, cost/benefit analysis, energy analysis, and multicriteria/stakeholder analysis.

Progress Summary:

The first high flow (6,500 cubic-feet-per-second [cfs]) pulsed discharge was from March 7-21, 2001. We monitored physical and ecological responses of the watershed area before, during, and after the discharge.

Water quality of the watershed area was monitored weekly during various discharges for 7 weeks using a flow-through system. Total suspended sediments during the high flow appeared to be channeled over 10 km down the western route, but rapidly dispersed within 5 km along the eastern route. The western route tended to have high chlorophyll values, reaching as high as 60 ppb, compared with the eastern route that never had chlorophyll values above 35 ppb. Salinities were markedly lowered during high river discharge, but there seemed to be a lag of several weeks for this effect to reach the outermost estuary. The temperature initially decreased adjacent to the diversion structure, but it warmed to near-ambient conditions within a few kilometers.

Two field investigations for benthic nutrient fluxes in the Breton Sound watershed were conducted in 2001. An initial flux experiment was conducted during low flow (500 cfs) of river water through the diversion structure at Caernarvon. A second study took place during a high flow event. Initial nutrient values of the water at all field stations during the high pulse in March showed a clear pattern of decreasing nitrate (142-0.6 M), nitrite (2.4-0 M), silicate (111-28 M), and phosphate (1.5-0 M) in the water with increasing distance from the diversion structure. Ammonium concentrations (1.1-0.4 M) did not follow a clear pattern.

Initial results showed strong spatial gradients in C, N, and S isotope distributions, with low C and S isotope values normally associated with river discharges. However, particulate organic material in the March flooding PULSE had surprisingly high 13C values, perhaps reflecting eroding ancient marine deposits in upper Mississippi watersheds.

A simple eutrophication model was developed to include N, Si, and P uptakes of the Michaelis-Menten type, and multiple algal assemblages, whose productivity is simultaneously dependent on nutrient concentrations, nutrient ratios, and ambient light intensity. This model is designed to run either as a stand-alone module or linked to a larger two-dimensional hydrodynamic model.

As a first step for a regional level simulation model to understand freshwater discharge and nutrient dynamic interactions, we prepared a model that consists of three unit cells representing the whole basin. Our intention was to test these new unit models for water exchanges and associated dissolved and suspended materials (e.g., salt, total suspended sediments, nutrients) across model boundaries and with the atmosphere (precipitation, denitrification, etc.). Results indicated that any further increases in salinity for any of the sites create deleterious conditions for the communities. Only a continuous effort via freshwater discharge seems to contribute to maintaining the present conditions for the ecosystems.

For the social science segment, work done thus far has demonstrated that the externalizing of environmental costs?as demonstrated by pollution and destruction of habitat and other public resources?leads to subsidies for those responsible for the externalization, but it also leads to costs and losses for the public. It seems clear that externalities are one way to appropriate natural capital and establish de facto property rights, which result in subsidies for those doing the externalization and costs for those bearing the externality. Public policy increasingly embraces externalization as a means to satisfy the demands of industry, and subsidies continue to rise. The combination of effects results in a spiral of public decline and, ultimately, private decline, which is not easily reversed. The loss of wetlands in the Caernarvon watershed under study represents such a cost; re-establishing the wetlands through pulsed diversions will likely improve social and natural capital.

Future Activities:

We will continue to investigate the hydrologic implications of various forcing functions on sediment and nutrient delivery to marshes, effects of pulsed versus normal diversion flow on the basin, and temporal and spatial variability of stage and flow in the basin. We will continuously study the variability of benthic fluxes within one site and water column-based processes with a modified experimental approach in an upcoming third flux study, scheduled for June 2001. Isotopic compositions of grass shrimp and commercial brown shrimp are being assayed to determine if this riverine particulate material is incorporated into spring food webs at Caernarvon. We also are using N isotopes to track the fate of river nitrogen added to this system. We will calibrate the two-dimensional hydrodynamic model using available data records collected during the first project year.

An energy flow analysis will be conducted to investigate how the river diversion operation has been changing the energy flow (e.g., in carbon) in the Brenton Sound watershed through marsh plant production and fishery output. We will carry out two forms of cost/benefit analysis: conventional cost/benefit analysis and embodied energy analysis to provide implications that will be based on willingness to pay and energy consumed and captured. For the stakeholder analysis, we will conduct a survey of members of the Caernarvon Interagency Advisory Committee, environmental groups in Louisiana, and other stakeholders (e.g., shrimpers, oyster fishers, local people) in the parishes of St. Bernard and Plaquemine around the Caernarvon facility, after completion of internal review of the questionnaire. Along with the survey work, multicriteria analysis will be conducted.

Journal Articles on this Report : 3 Displayed | Download in RIS Format

Other project views: All 109 publications 18 publications in selected types All 17 journal articles
Type Citation Project Document Sources
Journal Article Templet PH. Energy flow diversity and economic development. International Journal of Energy, Environment and Economics 2000;10(1):23-38. R828009 (2000)
R828009 (Final)
not available
Journal Article Templet PH. Externalities, subsidies and the ecological footprint:an empirical analysis. Ecological Economics 2000;32(3):381-383. R828009 (2000)
R828009 (Final)
not available
Journal Article Templet PH. Energy price disparity and public welfare. Ecological Economics 2001;36(3):443-460. R828009 (2000)
R828009 (Final)
  • Full-text: Science Direct
  • Abstract: Science Direct
  • Other: Science Direct PDF
  • Supplemental Keywords:

    environmental image, green economics, sustainable management., RFA, Scientific Discipline, Geographic Area, Water, Ecosystem Protection/Environmental Exposure & Risk, Nutrients, Water & Watershed, Ecosystem/Assessment/Indicators, Ecosystem Protection, State, Ecological Effects - Environmental Exposure & Risk, Southeast, Environmental Monitoring, Ecological Risk Assessment, Watersheds, nutrient transport, coastal ecosystem, eutrophication, ecological exposure, flood plains, coastal watershed, economics, marsh plant growth, river inputs, watershed sustainablity, sediment transport, fisheries, conservation, Louisiana (LA), Louisiana, pulsed physical events, tropical storms, aquatic ecosystems, watershed sustainablility, riverine ecosystems , water quality

    Relevant Websites: Exit

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    Progress and Final Reports:

    Original Abstract
  • 2001 Progress Report
  • 2002 Progress Report
  • 2003
  • Final Report