Summary Analysis Of The North American (US Portion) OCED Eutrophication Project: Nutrient Loading - Lake Response Relationships And Trophic State Indices
Date
1978-01
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Abstract
The US participation in the OECD Eutrophication Program of having 20 investigators prepare reports on the
nutrient load-lake and impoundment response relationships for
their respective water bodies. This report presents a critical
review of these overall relationships with particular emphasis
given to evaluation of the Vollenweider nutrient load-trophic
state formulations. This review includes consideration of the
nutrient load response relationships for 38 water bodies, or
parts of water bodies, located throughout the US, with the preponderance
located in the northern half of the US. It has been
found that the Vollenweider nutrient load relationship involving
water body mean depth, hydraulic residence time and phosphorus
load correlates well with the trophic states assigned by the US
OECD eutrophication study investigators.
A good correlation has also been found between phosphorus
loading, normalized as to hydraulic residence time and mean
depth, and the average chlorophyll and water clarity (as measured
by Secchi depth) for the US OECD water bodies. In general,
phosphorus and nitrogen loads to US OECD water bodies were within
a factor of + two of the loads predicted on the basis of average
nutrient concentrations within the water bodies and on the land
use patterns within the water body watersheds. Generalized nutrient export coefficients have been developed
in this study,
enabling estimates of nutrient loads to be made on the basis
of land use patterns within the watershed.
The relationships developed in this study can be used to predict
the improvement in water quality that will result from a
change in the phosphorus load to a water body for which phosphorus
is the key chemical element limiting planktonic algal
growth. The US OECD water bodies all show approximately the
same trophic status when evaluated by several recently-proposed
trophic state index systems. A new trophic state index system
has been developed in this study which is based on the relationship
between the actual phosphorus loading and permissible phosphorus
loading as defined in the Vollenweider phosphorus loading
and mean depth/hydraulic residence time relationship. This
relationship has been modified to enable water quality managers
to determine the appropriate phosphorus load for a particular
water body in order to yield a certain chlorophyll content from
planktonic algae and its corresponding water clarity. It is
recommended that these relationships be used as a basis for establishing critical phosphorus loads to lakes and impoundments.
This report was submitted in fulfillment of Contract No.
R-803356-01-0 and Contract No. R-803356-01-3 under the sponsorship
of the U.S. Environmental Protection Agency. Work was
completed as of August, 1977.
Description
Keywords
OCED Eutrophication Project, Nutrient Loading, Lake Response