Grantee Research Project Results
2012 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 , Texas A & M University , University of Illinois Urbana-Champaign
Current 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, 2011 through July 31,2012
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 ISWS/UIUC 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. A state-of-the-art modeling system is 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 two general circulation models (GCMs), with low (National Center for Atmospheric Research – NCAR) and high (Geophysical Fluid Dynamics Laboratory – GFDL) climate sensitivity, and 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 three intergovernmental panels on climate change (IPCC) special report on emissions scenarios (SRES) (low, medium, high) accounting for dynamic landuse changes; they represent the likely range of future projections of climatic and chemical lateral boundary conditions (LBCs) that force ISWS climate extension of the weather research and forecasting model (CWRF) and Environmental Protection Agency (EPA) community multiscale air quality model (CMAQ) to downscale regional climate and air quality in North America; these 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, landuse 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.
Progress Summary:
The Predictive Soil and Water Assessment Tool (PSWAT) system has been further improved on the basis of previous 2 years' achievements. This year’s effort mainly focus on analyzing variation and distribution characteristics of RCM downscaled results from GCMs for present and future, and linking the predicted climate change such as increasing atmospheric water vapor content, changing precipations patterns, intensity and extremes, reduced snow cover and widespread melting of ice, to hydrological variability through PSWAT model. Our major achievements during this reporting period are as follows.
- We have investigated the effects of projected global changes in climate and human‐related emissions on precipitation and temperature from current to 2100s using regional climate models. The future changes in climate due to increasing atmospheric concentrations of carbon dioxide and other trace gases are likely to result in a shortage of precipitation on the western United States; the decreasing trend of future precipitation is most significant for the Rio Grande, Upper Colorado, Lower Colorado, and Great Basin watersheds across the United States. In particular, the Lower Colorado watershed is projected with a substantial decrease of more than 20.33% for B1, 34.22% for A1B, and 63.93% for A1FI, comparing with the present‐day precipitation. Meanwhile, large temperature increases are projected, ranging from the highest 6.77 (A1FI) for Upper Colorado to the lowest 1.49 (B1) for Texas‐Gulf, with regional distribution characteristics strongly depending on complex geology and varied topography. All of those changes with large uncertainties under different scenarios impose challenges for the national responses to future water resource management. As a contribution to addressing the issues, we further evaluated runoff distribution for decision‐makers in the long‐term management of water resources using PSWAT results driven by the RCM simulation.
- We have investigated the runoff distribution changes from current to 2100s over different basins of the United States based on the latest developed CWRF‐SWAT coupling system (PSWAT) with the intent of better understanding to what extent the global warming modulates or exacerbates regional‐scale water resources. We found that the projected runoff changes differ considerably over the United States. In particularly, the western United States has obviously decreasing trends. Previous studies have mostly used precipitation and temperature changes to roughly explain the runoff results. Here, we calculated the runoff elasticity of precipitation, radiation, wind, and humidity, and runoff sensitivity to temperature based on annual mean climatic variables and PSWAT outputs. The results indicate that all 18 U.S. basins can be classified into three subcategories as evidenced by large variations of the n index, which represents the effect of catchment characteristics. This index was calculated from total precipitation and potential evapotranspiration in each basin. The first category has the largest n, greater than 2.0, the second category has the smallest n around 1.0, and the third category falls between. Different categories are identified with distinctly different ranges of elasticity for all four climatic variables. The largest elasticity is from precipitation that plays the central role on runoff responses to climate change. This is followed by that from radiation, and the temperature sensitivity is the least among other climatic variables affecting runoff. The three n‐categories happen to divide the U.S. basins into three broad bands. The first category (n > 2.0) consists of the basins in the eastern United States, where abundant precipitation prevails and runoff changes are determined more strongly by changes in precipitation and radiation than other basins. The second category (n~1.0) contains the basins in the western United States, where precipitation amounts are relatively small, the precipitation and radiation impacts on runoff changes are reduced noticeably, and the humidity effect is the smallest among all basins. The third category includes the basins in the central United States, where the sensitivity of runoff responses to climate change is between the eastern and western bands. These three categories well represent three climate regimes in the United States, each with a distinct hydrologic cycle (precipitation, evaporation, runoff, soil moisture) variation that is mainly determined by the geographic, terrestrial ecologic and physiographic characteristics.
- We have analyzed the ratio of annual mean snowmelt to annual mean runoff. This ratio can be considered as an index to quantify the relative fraction of runoff that is contributed by snowmelt. Snow has important climatic consequences: snowmelt directly contributes to soil moisture storage and runoff; snow cover is very effective at cutting off heat and moisture transfer from the ground surface to the overlying atmosphere; snow-albedo feedback and latent heat to melt snow may amplify or retard warming. These processes emphasized the critical role of snow on hydrology, especially in the western United States. In the western mountainous region and to a more limited extent, in the northern tier of states, the fraction of snowfall in total precipitation decrease greatly in 2100s compared with that of 2000s (A1B). The pattern of the annual mean snowmelt to precipitation ratio pushes northward, and narrows the total areal extension. Climate warming impacts on snow cover has far‐reaching effects on not only runoff as part of the natural system, but also human systems associated with irrigation, hydro‐electrical generation, and management of natural river ecosystems such as the Colorado River basin.
- We have found that the geographic pattern of annual mean runoff is surprisingly similar to the physiographic regimes, which depict the distinct regions that are grouped in terms of similar rock and soil types, as well as geographic features like mountains, plateaus, valleys, etc. This close relationship will be beneficial to analyze the complex mechanism of essential regulations on soil, vegetation, and atmosphere transfer processes in PSWAT. The major effect of surface physiographic characteristics on annual runoff is through their control on evapotranspiration under prevailing climate conditions. Over the basins with low water absorptivity, rainfall goes rapidly to runoff, and little is stored in soil moisture for subsequent transpiration. On the other hand, high absorptive basins have large soil‐moisture capacity and allow a large portion of rainfall to be stored in soil moisture, that in turn is available for subsequent transpiration, and hence acts to reduce runoff. We therefore plan to incorporate such physiographic dependence into an analysis of runoff responses to climate change.
- We have investigated improved/higher spatial and temporal resolution (HUC 12 levels) watersheds and atmospheric depositions on global emissions. We defined 13437, 5729, 5229 and 1073 12‐digit sub‐watersheds in the Missouri River Basin (MRB), Upper Mississippi River Basin (UMRB), Ohio River Basin (ORB) and Trinity River Basin (TRB) respectively, which represents a major part of the United States to develop higher resolution data, and developed a set of high accuracy initial data for PSWAT in those regions, including land use/cover, soils, management practices, fertilizer and manure application.
- Given the above, we are well positioned to address the fundamental issues we originally proposed to study (i.e., to quantify and understand the impacts of global climate and emission changes from the present to 2050 on U.S. water quality, focusing on the nitrogen cycle). This will be our major goal in the next phase of the research.
Future Activities:
- Simulate future projections for 2050 to quantify the individual and combined impacts of global climate and emissions changes on U.S. water quality using CWRF output scenarios.
- On the basis of established PSWAT coupling system, further develop the online version, investigate effects of SWAT feedback information on CWRF, and further improve the prediction capacity and accuracy of climate model by making full use of SWAT detailed hydrological information to refine land surface processes.
- Modify relating processes to ameliorate the above-mentioned problems.
- Project future water quality change with potential agricultural adaptation for 2050 and 2010.
Journal Articles on this Report : 2 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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Supplemental Keywords:
Climate change, hydrological 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, GCM, RCM, AQM, WQM, RFA, Air, climate change, Air Pollution Effects, Atmosphere
Relevant Websites:
http://www.isws.illinois.edu/atmos/modeling/caqims/compparts.asp?prt=rcm Exit
http://www.wcrp-climate.org/conference2011/abstracts/C43/Liang_C43_TH220A.pdf 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.