Effect of Mitigation on U.S. Water Quality
Draft, July 31, 2017
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Climate Change Impacts and Greenhouse Gas Mitigation Effects
on US Water Quality
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Supplement 2: Demonstration of QUALIDAD Outputs
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Brent Boehlert1,2,*, Kenneth M. Strzepek3, Steven C. Chapra2, Charles Fant3, Yohannes
Gebretsadik3, Megan Lickley3, Richard Swanson4, Alyssa McCluskey4, James E. Neumann1,
Jeremy Martinich5
1. Industrial Economics, Inc., Cambridge, Massachusetts, USA
2. Tufts University, Medford, Massachusetts, USA
3. Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
4. University of Colorado, Boulder, Colorado, USA
5. U.S. Environmental Protection Agency (EPA), Washington, D.C., USA
* Corresponding author, phone: (617) 354-0074, fax: (617) 354-0463,
[email protected]
1.
INTRODUCTION
This supplement presents a set of graphics that demonstrate the responsiveness of the
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QUALIDAD parsimonious water quality model to (1) loading under constant flow and temperature
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conditions, and (2) loading of a single constituent at a time given constant flow and time-varying
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temperature conditions over a single year. Each graphic presents results for a single
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representative basin with a main channel that is 100 kilometers in length, where loadings occur as
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a distributed nonpoint source over the length of the river, and the presented concentrations of each
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constituent occur at the basin outlet. The constituents in each figure include river temperature,
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particulate organic carbon (Part org C), dissolved organic carbon (Dis org C), organic nitrogen (Org
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N), river flow, ammonia, nitrate, organic phosphorus (Org P), photosynthetically active radiation
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(PAR), inorganic phosphorus (Inorg P), phytoplankton (Phyto), and dissolved oxygen (DO). In
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Section 2, carbon and DO are measured in grams per cubic meter (g/m3), and all other constituents
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are measured in mg/m3. In Section 3, the carbon and DO are measured in mg/m3, whereas the
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others are measured in μg/m3.
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2.
RESULTS UNDER CONSTANT LOADINGS, FLOWS AND TEMPERATURES
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Figure S1 shows the set of constituents evaluated within QUALIDAD, and the effect of
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introducing a constant loading of each constituent under constant temperature and river flow conditions
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over a period of 10 days. This exercise simply demonstrates that under constant loading, temperature,
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and flow, each constituent reaches a steady state concentration within approximately four days. In the
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case of DO, there is an initial spike toward saturation as reaeration occurs, and then levels fall slightly as
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the concentration of dissolved organic carbon increases in the basin.
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Figure S1: Water quality constituent concentrations at steady state temperatures and
flows, and constant nonpoint source loadings
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3.
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RESULTS WITH ONE LOADING AT A TIME UNDER VARIED TEMPERATURES
Figures S2 through S6 present the effect of adding constant nonpoint source loading of one
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constituent to the representative basin under time-varying temperature and PAR conditions, while
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loadings of all other constituents remain at zero. Each graphic presents hourly constituent concentrations
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over a one-year period. Figure S2 shows loadings of particulate organic carbon transformed into
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dissolved organic carbon, which then causes slight reductions of DO from full saturation. Note that on
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the DO graphic, the gray line is DO saturation given river temperature, and the red line is the modeled
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DO level. Figure S3 shows the significant effect that a larger loading of dissolved organic carbon has on
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DO levels, and Figure S4 shows an organic nitrogen loading, its breakdown into ammonia, which is
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subsequently broken down into nitrate. Due to the low levels of organic nitrogen introduced (measured in
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μg/m3), the resulting effect on DO levels is minimal. The transformation of organic phosphorus loadings
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to dissolved phosphorus are shown in Figure S5; as with introduction of organic nitrogen, the too little
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phosphorus is introduced to have a significant effect on DO. Lastly, Figure S6 shows the complex effects
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of introducing constant levels of phytoplankton to the basin. As can be seen, phytoplankton death
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introduces organic carbon, nitrogen, and phosphorus to the system, but again at low enough
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concentrations to have a minimal effect on DO.
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Figure S2: Constituent concentrations when constant nonpoint source loadings of
particulate organic carbon are applied
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Figure S3: Constituent concentrations when constant nonpoint source loadings of dissolved
organic carbon are applied
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Figure S4: Constituent concentrations when constant nonpoint source loadings of organic
nitrogen are applied
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Figure S5: Constituent concentrations when constant nonpoint source loadings of organic
phosphorus are applied
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Figure S6: Constituent concentrations when constant nonpoint source loadings of
phytoplankton are applied
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