Geoscience Reference
In-Depth Information
6.1
Introduction
Pollutants from agriculture, contaminated sediments, urban runoff and combined
sewer overflows (CSOs) are the primary impairment contributors of Great Lakes
shoreline waters and their tributaries, causing increased levels of nitrogen, phos-
phorus, and toxic substances in both surface water and groundwater, eutrophica-
tion in receiving lakes, and harmful algal blooms (HABs) and beach closings due
to viral and bacterial and/or toxin delivery to affected sites (U. S. Environmental
Protection Agency, U.S. EPA
2002
;HeandHe
2008
). Management of these
problems and rehabilitation of the impaired waters to a fishable and swimmable
state require identifying the impaired waters and tracking both point and nonpoint
source material through a watershed by hydrologic processes. During the past
decades, a number of simulation models have also been developed to track the
production and transport of both point and nonpoint source materials through a
watershed by hydrologic processes. Examples of the models include ANSWERS
(Areal Nonpoint Source Watershed Environment Simulation), CREAMS (Chemicals,
Runoff and Erosion from Agricultural Management Systems), GLEAMS (Ground-
water Loading Effects of Agricultural Management Systems), AGNPS (Agricultural
Nonpoint Source Pollution Model), EPIC (Erosion Productivity Impact Calcu-
lator), BASINS (Better Assessment Science Integrating point and Nonpoint
Sources), HSPF (Hydrologic Simulation Program in FORTRAN), and SWAT
(Soil and Water Assessment Tool) , to name a few (He and DeMarchi
2010
).
While models like these have been quite useful in addressing some watershed
issues, however, there are still some key unanswered science questions that are
bottleneck problems for an effective restoration of the Great Lakes and prevention
of water pollutions. For example, where does the sediment or nutrient come from
and how is it being transported downstream to the watershed outlet and nearshore
waters of Great Lakes? What and where should best management practices (BMPs)
be implemented to produce the maximum effects in the restoration of watersheds?
Answering these questions requires an integrated, spatially distributed, physically-
based watershed-scale hydrologic water quality modeling system to link the land
use and management practices to the movement of materials (sediments, animal
and human manures, agricultural chemicals, nutrients, etc.) in both surface and
subsurface waters within a watershed (Bouraoui and Grizzetti
2007
; Croley and He
2006
,
2008
; He and Croley
2007a
,
b
,
2008
; He and DeMarchi
2010
). To meet this
need, the National Oceanic and Atmospheric Administration (NOAA) Great Lakes
Environmental Research Laboratory (GLERL), Western Michigan University, and
Case Western Reserve University are jointly developing a spatially distributed,
physically based watershed-scale water quality model to estimate movement of
materials through both point and nonpoint sources in both surface and subsurface
waters to the Great Lakes watersheds (Croley and He
2005
,
2006
; He and Croley
2007a
,
b
; He and DeMarchi
2010
).
This paper describes procedures for estimating potential loadings of nutrients
from fertilizers and livestock manure and combined sewer overflows (CSOs) into
surface water and groundwater from multiple databases of land use/cover, animal
production, fertilizers, and CSOs. It first gives a brief description of the distributed
