2001 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, 2001 through February 27, 2002
Project Amount: $899,995
RFA: Water and Watersheds (1999) RFA Text |  Recipients Lists
Research Category: Water and Watersheds , Water


The overall objective of this research 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. The ecological science objectives are to: (1) evaluate marsh plant growth responses to river inputs; (2) monitor water quality changes across the watershed; (3) evaluate the function of wetland soils and benthic sediments in response to flooding events; (4) assay effects of river inputs on fish, shrimp, and oysters using stable isotopes; and (5) monitor phytoplankton production and possible eutrophication. Subsequently, an integrated physical/biological water quality model and a regional level simulation model will be developed 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 high flow pulsed discharges (6,500 cubic-feet-per-second - cfs) occurred for two 2-week periods: January 28-February 10, and March 4-March 17, 2002, for the second annual high pulse experiment. Physical and ecological trends of the watershed area have been monitored before, during, and after the discharges.

As a part of the physical study to assess the effects of the freshwater diversion on the Breton Sound Basin, sediment accumulation has been assessed using sediment filter pads in conjunction with other techniques. Results from the first pulse event in spring 2001, indicate little to no significant variation in accretion within each site; however, significant differences in accretion due to the diversion are seen with increasing distance from major diversion flow paths.

End of season live biomass was measured from September to October 2001. Plant samples for N-stable isotope analysis also were taken at the same locations. Water quality transects were conducted, using a flow-through system and discrete water samples throughout the report period. Based on salinity responses in the basin, water residence time in the estuary was between 1 to 2 weeks. Total suspended sediments (TSSs) were rapidly deposited in the estuary within the first several km of the diversion structure. The estuary was an effective sink for nitrogen and phosphorus, with a 47 percent decrease in NO3+NO2; a 44 percent decrease in total nitrogen; a 16 percent decrease in phosphate; and a 48 percent decrease in total phosphorus in the upper half of the estuary. Chlorophyll a consistently peaked in the mid estuary, and was negatively correlated to TSS and inorganic nitrogen concentrations. These results imply that river diversions may be used to process Mississippi River water prior to reaching offshore waters where eutrophication has become a recent concern, as well as enhancing marsh formation and stability, and preventing salt water intrusion from degrading Louisiana's remaining coastal wetlands.

Estuary cores were taken for incubation in continuous flow-through systems to track the nutrient cycling at the sediment-water interface during last summer and winter/spring 2002 to track the effects of temperature and high flow discharge on benthos organism. Marsh cores also were collected in fall 2001, and spring 2002. The marsh cores were monitored in the greenhouse for nutrient processing in a batch setting. Preliminary data show that the estuary cores have the potential to induce high nitrate/nitrite fluxes (400-600 µmol m-2h-1) from the water column to the sediments, which indicates that these estuarine sediments can function, at least temporarily, as nutrient sinks. Repeated experiments indicate a strong temporal variability of fluxes, which are a combination of active biological and passive sorptive processes that can strongly be influenced by the concentration and specification of ambient particulate and dissolved organic matter in the water at the respective study sites.

The C, N, and S cyclings have been examined to determine how they change in food webs, due to the freshwater inflow, through stable isotope analysis of shrimp, barnacles, and particulate organic matter in the water column from September 2000, through December 2001. Very strong gradients were found in C, N, and S isotope distributions; with low S and C and high N isotope values associated with the upper estuary. Although S isotopes are strongly related to salinity, C and N are mainly reflecting the signal from the Mississippi River water. With a time delay of about 1 to 2 months, the riverine related isotope signals appear in shrimp and barnacles. These primary consumers are common prey for higher trophic levels and, hence, the riverine signal will be transmitted to higher trophic levels. An analysis of phytoplankton community structure indicates that the plankton community of the Breton Sound estuary is a typical estuarine community with little evidence of algal blooms or harmful algal species. The community was dominated by diatoms during the spring 2002, pulsed diversion.

An integrated physical-biological water quality model is being developed to describe the coupling between river borne nutrient loads, nutrient ratios, and eutrophication in coastal watersheds. During the first project year, a simple eutrophication model was implemented that included dynamics of dissolved inorganic nitrogen (DIN) and a single algal group that was representative of coastal phytoplankton. During the 2001-2002 project year, a more complicated eutrophication model was developed. This model includes multiple N, Si, and P uptake 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 as a component of a larger 2-dimensional hydrodynamic model.

An environmental dataset was developed that includes precipitation, air temperature, solar irradiance, water temperature, river stage, diversion discharge, nutrient loading, and uptake from 1956 to 1998 for the regional simulation model for the Caernarvon Watershed. Another spatially distributed dataset includes topological and vegetation maps for the area. The spatial data comprised three habitat maps for the years 1956, 1978, and 1988, and a thematic satellite image for 1993. A bathymetric map for the coastal areas was obtained and merged with topographic elevations surveyed. This topological map, in combination with the respective habitat map, forms the basis for the spatial initial conditions in which the landscape model is run. Using the spatially descriptive model, a series of scenarios were prepared: (1) normal discharg; (2) no discharge; (3) increased (double the current conditions which match a prior level of operation); and (4) pulsing. After the model calibration, results indicated that any further increases in salinity for any of the sites creates deleterious conditions for the communities.

The purpose of a conceptual model of the interaction of the natural and economic systems is to provide decisionmakers and ecosystem managers with system level models that conceptually illustrate the interactions between natural and human systems. A study of how economies partition energy, both commercial energy and natural energy, into goods and services or waste, showed that those economies that partition more to goods are more efficient, with higher social and financial capital (Templet 2002a). Putting more natural energy, like the energy generated by the Caernarvon diversion, into an economic system will create more goods. On a relation of natural capital pollution and social welfare, pollution is found as only one of many costs that are passed on, or externalized, by the economic sector to the public and to the environment (i.e., to our common natural capital [Templet 2002b]).

The fishery production changes have been analyzed due to the freshwater input in the Breton Sound using the fishery data collected by the Louisiana Department of Wildlife and Fisheries. A preliminary time-series analysis showed that the population of gulf menhaden has increased statistically significantly after the diversion. The increased nutrient inputs in incoming riverine water presumably increased production of phytoplankton, zooplankton, and detritus, which leads to the increased population of gulf menhaden, followed by overall population increases of finfish, including spotted seatrout and red drum.

A questionnaire-based survey is being conducted with multiple groups of stakeholders around the Caernarvon diverson (e.g., state employees, land owners, fishermen, environmental groups, leasure sportmen, scientists) to comprehend diverse opinions and to measure the degrees of conflicts over the diversion, which will be completed by the end of May 2002.

Future Activities:

Data collected from feldspar horizon markers, Pb-210 dating, and sediment elevation tables (SETs) will help to resolve the short-term sediment pad data and will be completed by mid-summer. Quantitative analysis of sediment accretion will be completed by the same period. The hydrology data analysis will be completed by spring 2004.

The marsh mesocosms in a greenhouse environment will be maintained throughout the next several months, and various treatments will be applied to study biogeochemical cycling of nutrients in this type of long-term setup. Estuary field sampling and short-term incubation experiment will be continued. Data analysis and evaluation of the results will be another important focus for the future months.

In 2002, the isotope analysis will include fish samples from the area in the analysis to test the previous assumption. Besides uptake into the aquatic food web, the riverine N isotope signal will be traced into marsh grass, predominantly in the upper part of the estuary.

A general framework is being developed for the implementation of TABS model in the Caernarvon diversion area for an integrated physical-biological water quality modeling. Future activities will concentrate on developing the interface between the TABS hydrodynamic outputs and the biological sub model.

After completing the questionnaire-based survey, a face-to-face interview will be conducted with the members of Caernarvon Interagency Advisory Committee (CIAC), who are decisionmakers in controlling the discharge level as a component of the stakeholder analysis. Based on the result of stakeholder analysis, a multicriteria analysis will be conducted as an effort to define optimum level of discharge over conflicting physical, ecological, and socio-economic interests.

For a continuous study of fishery output analysis, its impacts on local economy will be measured by analyzing fishery-related economic data of Plaquemines and St. Bernard Parishes surrounding the Breton Sound, and overall Louisiana state.

Based on the field data of biomass growth, fishery output data, and other associated data available, an energy flow analysis will be conducted of the Breton Sound Basin, as a way to assess holistic impacts of the diversion. Additionally, the cost-effectiveness of the diversion facility in terms of money and embodied energy will be assessed during the fall of 2002. Money-based, cost-benefit analysis will show realized impacts through market price, while the embodied energy based cost-benefit analysis will include not-realized impacts (e.g., net primary production). Finally, the two results will be compared as a way to find a conservative way in designing sustainable environmental management.

The information will be provided to stakeholders in this region for a better understanding of the Breton Sound watershed and for better decisionmaking of sustainable environmental management.

Journal Articles on this Report : 4 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 Day JW, Ko J-Y. Some results from monitoring multiple aspects of the Caernarvon river diversion for spring 2001. CoastWise 2002;11(2):10-11. R828009 (2001)
R828009 (Final)
not available
Journal Article Justic D, Turner RE, Rabalais NN. Climatic influences on riverine nitrate flux: implications for coastal marine eutrophication and hypoxia. Estuaries 2003;26(1):1-11. R828009 (2001)
R828009 (2002)
R828009 (Final)
R827785E02 (Final)
  • Abstract: Springer - Abstract
  • Journal Article Templet PH. Partitioning of resources in production: an empirical analysis. Journal of Cleaner Production 2004;12(8-10):855-863. R828009 (2001)
    R828009 (2002)
  • Full-text: Science Direct
  • Abstract: Science Direct
  • Other: Science Direct PDF
  • Journal Article Xu Z, Cheng G, Chen D, Templet PH. Economic diversity, development capacity and sustainable development of China. Ecological Economics 2002;40(3):369-378. R828009 (2001)
    R828009 (2002)
    R828009 (Final)
  • Full-text: Science Direct
  • Abstract: Science Direct
  • Other: Science Direct PDF
  • Supplemental Keywords:

    watershed, estuary, restoration, ecosystem, integrated assessment, decision making, survey, ecology, modeling, monitoring, gulf coast, sustainable management, EPA region 6, 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

    http://www.ucs.louisiana.edu/~rrt4630/pulses.html Exit

    Progress and Final Reports:

    Original Abstract
  • 2000 Progress Report
  • 2002 Progress Report
  • 2003
  • Final Report