Grantee Research Project Results
2013 Progress Report: Consequences of Global Climate and Emissions Changes on U.S. Water Quality: An Integrated Modeling Assessment
EPA Grant Number: R834189Title: Consequences of Global Climate and Emissions Changes on U.S. Water Quality: An Integrated Modeling Assessment
Investigators: Liang, Xin-Zhong , Wuebbles, Donald J. , Arnold, Jeff , Daggupati, Prasad , Srinivasan, Raghavan , He, Yuxiang
Current Investigators: Liang, Xin-Zhong , Wuebbles, Donald J. , Srinivasan, Raghavan , Tuppad, Pushpa , Arnold, Jeff
Institution: University of Maryland - College Park
EPA Project Officer: Packard, Benjamin H
Project Period: August 1, 2009 through July 31, 2012 (Extended to July 31, 2014)
Project Period Covered by this Report: August 1, 2012 through July 31,2013
Project Amount: $723,559
RFA: Consequences of Global Change for Water Quality (2008) RFA Text | Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Climate Change , Watersheds , Aquatic Ecosystems , Water
Objective:
The objective of this project is to quantify and better understand the impacts and uncertainties of global climate and emission changes from the present to 2050 on U.S. water quality, focusing on the nitrogen cycle and accounting for potential agricultural land conversion to alternative food and biofuel crops, to enable decision makers to design effective management plans and regional adaptive strategies to reduce the risk of harmful impacts. State-of-the-art modeling systems (GCM: CCSM4 for CMIP5, RCM: CWRF, and hydrology and water quality model: PSWAT) are used to quantify the impacts on future U.S. water quality by a suite of climate changes projected from the present to 2050, including mean and variability (especially extremes). The system integrates climate dynamics, atmospheric physics and chemistry, terrestrial hydrology, agroecology and biogeochemistry, surface emissions, and their nonlinear interactions across a full range of spatial and temporal scales. It consists of one general circulation model (GCM), which is from the National Center for Atmospheric Research (NCAR), NCAR community atmosphere model coupled with the model for ozone and related chemical tracers (MOZART) chemistry (CAM-Chem) to project global changes in climate and chemical transport under the 5th Intergovernmental Panel on Climate Change (IPCC), accounting for dynamic land use changes. They represent the likely range of future projections of climatic and chemical lateral boundary conditions (LBCs) that force ESSIC/UMD Climate extension of the Weather Research and Forecasting model (CWRF) to downscale regional climate and air quality in North America. They then provide climatic and hydrologic conditions and atmospheric NO3- and NH4+ depositions that drive the Soil and Water Assessment Tool (SWAT) to predict water quantity and quality over the entire continental United States. Such a predictive SWAT (PSWAT) incorporates the most comprehensive pollutant sources (natural and anthropogenic, point and nonpoint), surface and subsurface watershed processes (upland, soil, plant and crop, channel and flood plain, urban, lake and reservoir), agricultural practices (cropping, fertilizer and pesticide use, irrigation, tillage), and other human managements (dam control, sewage discharge, land use alteration). It determines water yield and supply, streamflow, surface runoff, groundwater recharge, nutrients (N, P), pathogens, bacteria, and sediments, and also feeds the changing hydrology and canopy back to CWRF. To enhance result credibility, PSWAT must be objectively calibrated to derive unknown parameters and then validated against surface observations, including precipitation, snow cover, air temperature, vegetation, crop yield, ozone, nitrogen wet deposition, and in-stream nitrogen loading. To this end, the main achievements during this reporting period are given below.
Progress Summary:
The PSWAT system has been further improved in the following aspects: 1) updated PSWAT core code from version SWAT2009 to version SWAT2012; and 2) developed an interface to cope with changing point source, manure, and atmospheric deposition into PSWAT for application under the different climate change scenarios. This year’s efforts focus mainly on new representative concentration pathways (RCPs) downscaling by the CWRF. We collected, distributed, and projected the point source, manure, according to the population growth projections. Our major achievements during this reporting period are as follows:
- We have reproduced the observed climate during 1979-2005 based on the CWRF downscaled from the CMIP5 GCM simulations for the present-day condition, as well as the corresponding water quality such as nitrogen and phosphorus variations during this period. This effort established the baseline for our next work—evaluating the individual and combined impacts of global climate and emissions changes on future U.S. water quality.
- We have completed the CWRF downscaling of the CCSM4 simulations for IPCC CMIP5 under the new representative concentration pathway (RCP) mitigation scenarios from 2006 to 2100 and also finished the PSWAT runs as driven by the CWRF results to illustrate how climate and anthropogenic changes cause the degradation of environment, nutrient (such as nitrogen and phosphorus) changes, and trends in the surface runoff. In particular, we presented in this report the initial analysis of these runs, focusing on the effects of the climate change alone.
- We have constructed all the necessary datasets of pollutant point sources from sewage treatment and other sources, fertilizer, and livestock. We then geographically allocated them onto PSWAT 8-digital HUCs watersheds over the entire United States. These pollutant distributions also were projected onto year 2050, including the point sources, fertilizer, and the manure from livestock changes based on the IPCC scenarios RCP4.5 and RCP8.5. This projection included several key factors such as those related to population growth and land use changes. The outcome will allow us to understand the contributing factors and their relative importance for the projected differences from the current to the future by PSWAT. Our next task is to finish such experiments and subsequent diagnostic analyses that will determine the individual and combined impacts of climate and emissions changes, natural and anthropogenic changes, and atmospheric depositions and regional-local sources, on the future U.S. water quality distributions.
- We have projected the changes of nitrogen loadings under climate change only, where all water pollutant sources are kept unchanged from the present-day condition. The outcome provides the first-order estimate of the U.S. water quality response to climate change if all pollutant emissions remain the same as the present-day level. Our main finding is that the future nitrogen loading in the major watersheds has strong seasonal and spatial variations. Over the upper Mississippi River basin, the nitrogen loading is projected (by climate change only) to increase significantly in late winter to spring, with a distinct peak in April, but to decrease in summer, with the peak in June. For this basin, the water quality problem in the future will occur earlier in season. The total nitrogen loading will increase largely over much of the Upper Mississippi River basin, the Ohio River basin and the Mid-Atlantic watershed. Medium-level increases also are projected over the coastal regions, including the Texas-Gulf and South Atlantic-Gulf watersheds. More detailed analyses are in progress and will elaborate the seasonal variations and geographic distributions of water quantity and quality trends over the entire United States, and explain why these trends occur.
- We have calculated some preliminary statistics for the increase in nitrogen at eight digital basins; 45% of U.S. streams have medium to high levels of nitrogen—the trend increasing from the current levels by the middle of this century. The increasing trend will result in deteriorating coastal waters and will exacerbate most of the eutrophication in coastal areas; and potential streamflow volume decreases in the Rockies and interior southwest, and increases in the east and southeast coasts. Many watersheds likely are to experience significant changes in the timing of streamflow and pollutant delivery. In particular, the system tends to shift from the spring snowmelt-dominated runoff to greater winter runoff.
- We have developed a 12-digit basin scale (HUC12) SWAT model, which can meet the requirement of future climate assessment at the finer scale. A critical task was its calibration, which affects the credibility of the model projection. Developing a physical-based distributed hydrologic model must integrate a huge amount of physical and statistical information and calibrate a large set of unknown parameters on each basin. To this end, we carefully calibrated SWAT at finer resolution (HUC12 scale) over a large-scale basin WLEB (West Lake Erie Basin), including Indiana, Michigan and Ohio with an area of ~28,330 km2, as well as over the MRB (Missouri River Basin). The traditional approach of calibrating the model only at the catchment outlet cannot account for hydrological and land management differences across the basin. Therefore, we developed a new calibration strategy to capture the spatial and temporal variability of hydrologic and land management patterns across the basin. The calibration ensures that gauged and ungauged subunits within the watersheds are represented reasonably well by incorporating wide variations in hydrology and crop management systems produced in different subunits of the large river watersheds due to variations in rainfall, soils, land use and vegetation. We plan to conduct a sensitivity experiment to determine how the new calibration approach affects the PSWAT projections of future U.S. water quality change.
Future Activities:
- We will further analyze the nutrient (nitrogen and phosphorus) distribution and changing spatial and temporal distribution patterns, and their relationship with climate-driving variables (e.g., temperature, precipitation, humidity, wind speed, radiation) from current to 2100 under the RCP8.5 and RCP4.5.
- We will identify the vulnerability regions for the U.S. future water quality.
- We will conduct sensitivity studies of the major factors that were incorporated into this investigation: a) atmospheric deposition; b) plant fixation; c) point sources; d) synthetic fertilizer; e) livestock manure; and f) climate change. We will quantify the individual and combined impacts of these factors.
- We will determine the sensitive factors that affect the U.S. future water quality over the vulnerable regions and their relative contributions.
- We will design an experiment to test to what extent the higher population release of nutrients affects aquatic health (e.g., eutrophication due to eating habits with an associated increased industrial production will release increased amounts of nutrients in the lower water volume resulting in both higher nutrient loads but also point source discharges in the future).
- We will test different agricultural farming practices to find out how they impact nitrogen using efficiency to affect the water quality and soil health.
- We will test the effect of the newly developed HUC12-scale calibration on the U.S. water quality projection.
- We will publish several papers to document our major findings, especially on the projected future U.S. water quality changes and their contributing factors from climate change and emission changes, including both natural and anthropogenic factors.
Journal Articles on this Report : 3 Displayed | Download in RIS Format
Other project views: | All 8 publications | 6 publications in selected types | All 6 journal articles |
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Type | Citation | ||
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Liang X-Z, Xu M, Yuan X, Ling T, Choi HI, Zhang F, Chen L, Liu S, Su S, Qiao F, He Y, Wang JXL, Kunkel KE, Gao W, Joseph E, Morris V, Yu T-W, Dudhia J, Michalakes J. Regional Climate–Weather Research and Forecasting model. Bulletin of the American Meteorological Society 2012;93(9):1363-1387. |
R834189 (2012) R834189 (2013) R834189 (Final) R833373 (Final) |
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Srinivasan R, Zhang X, Arnold J. SWAT ungauged:hydrological budget and crop yield predictions in the Upper Mississippi River Basin. Transactions of the ASABE 2010;53(5):1533-1546. |
R834189 (2010) R834189 (2011) R834189 (2012) R834189 (2013) R834189 (Final) |
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Wang X, White M, Tuppad P, Lee T, Srinivasan R, Zhai T, Andrews D, Narasimhan B. Simulating sediment loading into the major reservoirs in Trinity River Basin. Journal of Soil and Water Conservation 2013;68(5):372-383. |
R834189 (2013) R834189 (Final) |
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Supplemental Keywords:
climate change, hydrologic processes, coupled model, nutrient, pathogen, bacteria, sediment, water yield, water supply, streamflow, surface runoff, soil moisture, groundwater recharge, discharge, fertilizer, pesticide, irrigation, drainage, tillage, dam control, urbanization, livestock, manure, GCM, RCM, AQM, WQM, water quality, modeling, land use, agriculture;, RFA, Air, climate change, Air Pollution Effects, AtmosphereRelevant Websites:
Development of predictive SWAT to assess global change impacts on U.S. water quality (PDF) Exit
Simulating sediment loading into the major reservoirs in Trinity River Basin Exit
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.