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North Shore Lake Pontchartrain Nutrient Study - Acadian-Pontchartrain NAWQA
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North Shore Lake Pontchartrain Nutrient Study

An investigation of nutrient inputs to Lake Pontchartrain via North Shore streams

Study Description

The North Shore Lake Pontchartrain study investigates nutrient loading in streams draining into Lake Pontchartrain. The North Shore is rapidly expanding in population and urban development. Nutrient inputs into the lake from this rapidly-expanding urban and suburban area have been implicated in contributing to eutrophication. However, estimates of nutrient loading remain highly speculative. Initial samples have focused on one-time, seasonal water-chemistry and algae surveys. However, seasonal, even monthly, collections of water are not sufficient to characterize nutrient levels in these urbanizing streams, which are subject to swift, flashy drainage during rainstorms.

As the Nation develops nutrient criteria for evaluating water quality in the next few years, real- or near-real-time nitrate data will be invaluable to researchers and those responsible for making water-resource management decisions. Nitrates are an important component of nutrient enrichment of waterbodies, encouraging the growth of algae and aquatic plants, leading to algae blooms and clogging of waterways with nuisance plant species. In order to better characterize nutrient levels, we are currently field-testing an instrument for the continuous measurement of nitrate concentrations on the Tchefuncte River near Covington. The instrument, installed on a bridge, is capable of continuously sensing and recording nitrate in the low concentrations commonly encountered in the environment. Our lead technician, Van Bergeron, and chief, Dennis Demcheck, completed the first series of tests comparing the monitor's data to samples collected manually during a rainstorm. It is planned that the monitor will be linked to a satellite, enabling direct transfer of data to the Louisiana District office. The goal of this project is to display real-time nitrate data through the Internet.

Sites

Sites for this study were selected from previously sampled sites from our Bed Sediment and Fish Tissue Study and our monthly-sampled Fixed Sites, as well as small urbanizing streams sampled by other USGS studies.

Small graphic map of North Shore Lake Pontchartrain sites, cities, roads, and the hightide line.
Click on image to view a larger version in GIF format.
You may also view a large PNG version of the above graphic.


The following sites have been sampled in December of 1998, and March of 1999:
Site NameStation ID
Bayou Lacombe near Lacombe at US-19007374587
Tchefuncte River near Covington at US-19007375050
Bogue Falaya at Covington at US-19007375170
Tchefuncte River at Madisonville at LA-Hwy 2207375230
Tangipahoa River at Robert at US-19007375500
Pass Manchac at Manchac at I-5507380230
Bayou Liberty at Bonfouca at LA-Hwy 433301604089504700
Cane Bayou near Mandeville at US-190302015090001800
Bayou Castine near Mandeville at US-190302105090022100
Bayou Chinchouba near Mandeville at Causeway Access Rd.302238090053900

Methods and Analysis

Water was sampled twice in the winter of 1998-1999, according to methods published in the "Field Guide for Collecting and Processing Stream-water Samples for the National Water-Quality Assessment Program, Open File Report 94-455". We also sampled the algae community once that winter, characterizing both phytoplankton, and woody-debris periphyton. Methods are described in the "Methods for Collecting Algal Samples as Part of the National Water-Quality Asssessment Program, Open File Report 93-409".

Constituents analyzed:
  • Dissolved Major Ions
  • Dissolved Nutrients
  • Phytoplankton, Chlorophyll a and b
  • Dissolved and Suspended Organic Carbon

For questions about our North Shore Nutrient Study, please contact Dennis Demcheck [ddemchec@usgs.gov], 225-298-5481.



U.S. Department of the Interior, U.S. Geological Survey, Baton Rouge, Louisiana, USA
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