SIMULATION OF SUBSURFACE WATER, NUTRIENTS, AND CONTAMINATION DISCHARGE TO COAST - Advances in Geosciences - page 235

SIMULATION OF SUBSURFACE WATER, NUTRIENTS,
AND CONTAMINATION DISCHARGE TO COAST
A. GHOSH BOBBA
National Water Research Institute, Environment Canada
Burlington, ON, Canada L7R 4A6
[e-mail]
Ecosystems of the coastlines are receiving extraordinary amounts of nutrients
as a consequence of human activities such as fertilizers, industrial emissions to
the atmosphere, and disposal of waste water in coastal watersheds. The loadings
of nitrogen and phosphorous to coastal aquatic environments even exceed those
to fertilized agro-ecosystem. Increased nutrient loading from anthropogenic
sources is pervasive and function of shallow coastal ecosystems during com-
ing decades.
During the last decade, it has become apparent that subsurface water flow
and transport of nutrients into shallow coastal water are far more significant
and widespread than had been realized. The importance of subsurface water
is not so much because of the magnitude of flow rates, but rather because
of the high nutrient concentrations in subsurface water compared to those
in receiving sea/lake water. Although highly variable, the nutrient content of
subsurface water discharging onto coastal water may be up to five orders of
magnitude larger than concentrations in receiving sea/lake water.
Subsurface water discharge has shown to be a source of nitrogen, typically
as nitrate, in shallow sediments of lakes and coastlines. The response of primary
producers to nutrient loading within an estuary must be dependent on the bal-
ance between increased growth due to elevated inputs of the limiting nutrient
and losses related to the flushing rate, as per the model. This is the point of
the well-documented relation between phosphorous loading and phytoplankton
chlorophyll.
In this paper, some Canadian and Indian examples show the roles of geo-
hydrology and hydro-geochemical processes are investigated by the applica-
tion of numerical models for water quantity and quality modeling of receiving
waters. This model also predicts the movements of contaminants in subsurface
and surface waters and coastal sediments.
1. Introduction
Subsurface water discharge from watersheds to coastal and estuarine waters
has been a topic of theoretical and practical interest for at least a century. 1
Most work has stressed controls on saltwater intrusion to freshwater aquifers
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