Geoscience Reference
In-Depth Information
Kawkawlin-Pine, and Pigeon-Wiscoggin Rivers) had often exceeded the targeted
TP load for the period of 1997-2008 except the dries years (Tao et al.
2010
). Thus,
it is imperative that the BMPs be expanded not only in farmland but also in non-
farmland, particularly in the critical NPS areas. Currently, the loading potentials of
nutrients (N and P
2
O
5
from manure and fertilizers) have been assigned to each
1-km
2
cell of the watershed study area (the watersheds were divided into 1-km
2
grid
cells) by using the AVDLBRM interface (Croley and He
2005
,
2006
; He and
Croley
2006
,
2007b
; He et al.
2008
; He and DeMarchi
2010
). These data layers
will be used with other input variables to simulate transportation of the nutrients in
the storages of upper soil zone, lower soil zone, groundwater, and surface water.
Additionally, soil erosion and sedimentation will be estimated by adapting the
Revised Universal Soil Loss Equation methodology to daily simulation. Eventually,
the DLBRM will simulate loading potential and transport of nutrients, pesticides,
and soil erosion and sedimentation in the Saginaw Bay Basin and other watersheds.
6.8 Summary
The NOAA's Great Lakes Environmental Research Laboratory, Western Michigan
University, and Case Western Reserve University are developing a spatially
distributed, physically-based watershed-scale water quality model to estimate
movement of materials through point and nonpoint sources in both surface and
subsurface waters to the Great Lakes watersheds. This paper, through a case study
of the Saginaw Bay Basin, estimates loading potential of nutrients from animal
manure and fertilizers and point sources. Annually, about 140,000 tons of N are
applied in the Saginaw Bay Basin, with livestock manure and fertilizer applications
and atmospheric deposition accounting for about 20 %, 70 %, and 10 %, respec-
tively. Livestock manure and fertilizers contribute approximately 20 % and 80 % of
the total phosphate applications (53,000 tons) per year.
While total fertilizer applications declined during the period of 1987 and 2002,
fertilizer applications on non-farmland increased significantly during the same
period. Point sources contribute about 25 % of the TP load entering the bay,
indicating municipalities, industrial and business entities as a large contributor of
the TP loading. Thus expansion and enhancement of the current water quality
programs in both farmland and urban areas is essential for achieving the targeted
nutrient load in the bay. Current efforts are focusing on the refinement of the
distributed large basin runoff water quality model for simulating pollutant transport
in both surface and subsurface water in the Saginaw Bay Watersheds to help
management agencies and ecosystem researchers for identifying critical pollution
areas to target implementation of the water quality control programs.
Long term, comprehensive water quality databases with adequate spatial and
temporal coverage are critical for both modeling point and nonpoint source
pollutions and assessing the effectiveness of water quality programs. A coordinated
network should be established among governmental agencies, research institutions,
