1. K I M B E R L Y L Y O N S , M A S T E R ’ S S T U D E N T
U N I V E R S I T Y O F S O U T H F L O R I D A S T .
P E T E R S B U R G
Evaluating the effects of precipitation
extremes on watershed hydrology under
current and projected future climate
conditions using SWAT

2. Introduction
 “Water, water everywhere,
but not a drop to drink.” -
The Rime of the Ancient Mariner, Samuel
Taylor Coleridge
Figure 1: Diagram of earth’s waters.
http://water.usgs.gov/edu/watercyclehi.html
Figure 2: Safelight view of Earth
Figure 3: Image of CA water crisis http://www.latinoreport.com/dam-our-
childrens-future-full-stadiums-ahead/

3. Introduction
 High demand for this
limited resource
 Demand will continue to
increase
Figure 4: Map of projected water scarcity. http://www.unep.org/dewa/vitalwater/article141.html
Figure 5: Diagram of the effects of population growth on water resources.
http://na.unep.net/geas/getuneppagewitharticleidscript.php?article_id=76

4. Introduction
 Managing current water resources and planning for future
generations is critical
Geoscience
Figure 6: Image of the ideology behind IWRM.
http://www.watercentre.org/news/integrated-water-management-2013-
the-way-of-the-future

5. Introduction
 Catchment Process: Precipitation
 Spatially and Temporally Variable
 High Intensity
 Infiltration Runoff  Discharge
Figure 7: Image of the framework for utilizing all precipitation
sources. http://wcel.org/integrated-stormwater-management
Figure 8 and 9: Images illustrating differences of precipitation
intensity and quantity on water supplies.
 Water Supply
 Quantity and Quality
 GW Recharge
 Capture/Storage
 Treatment
 Alternative
Management

6. Introduction
 Climate Change
 Frequency of high intensity precipitation has and will
continue to increase
 Global: Increase frequency of the upper 0.3% of daily precipitation
 US: 40% increases in the frequency >6in/day [5]
 Future Projected: The intensity of precipitation events will likely
increase on average [4]
Figure 10: Image of the frequency, distribution and magnitude of projected extreme events. https://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch10s10-3-6-1.html

7. Introduction
 Therefore, planners and managers should
consider the effects of precipitation quantity
and intensity under current and future
climate projections
 Current climate surface water quantity
estimations could facilitate best management
practices (BMPs)
 Future climate surface water quantity projections
should result in more sustainable planning and
development
Extensive research on
watershed scale
hydrology using GIS ,
Historical Date and
Hydrologic Models
Far less research using
Future Projected
Climate Data and
Hydrologic Models

8. Introduction
Figure 11: Illustration of the steps required to
complete a climate impact
study.http://climate4im/impactportal/help/faq.jsp?q=scenarios
Figure 12: Illustration of the downscaling
processes that is required to for local watershed scale
hydrologic modeling.

9. Research Objectives
 This research utilizes the Soil and Water Assessment
Tool (SWAT) to evaluate the effects of precipitation
extremes on watershed hydrology in the Cobb Creek
Watershed, GA, USA under current and future
climate conditions projected by the Canadian Centre
for Climate Modeling and Analysis Coupled General
Circulation Model, CCCMA CGCM3.1, and the
Geophysical Fluids Dynamic Laboratory Coupled
Model, GFDL CM2.1.

10. Methodology: Research Area
 Cobb Creek
 Southeastern Georgia
 Headwaters of the Altahmaha
 Oconee and Ocmulgee
 HUC 10 Sub-basin
 892 km2
 Land use
 Forested: 50.7 %
 Row crops: 21.7%
 Wooded wetlands: 10.1%
 Pasture: 6.1%
 Soils
 Loam and Alluvium
 Elevation
 Minimum: 19m
 Maximum: 103m
 Impairments
 USEPA 305(b) and 303(d) lists
 Fecal Coliform
 Dissolved oxygen
Figure 13: Real-estate
photos showing land
uses in Cobb Creek
http://www.ghland.com/listing
/toombs-county-ga
Figure 14; The Cobb
Creek Watershed

11. Methodology:
SWAT Model
 USDA Model
 Two tiered
desegregation
scheme
 Semi distributed
 Continuous time
step
 Physical/ Physics
based
Figure 15: Conceptual Framework of SWAT Model
Figure 16:SWAT Model Calibration and Validation
Results

12. Methodology: Precipitation Inputs
 Current
 2010-2014
 NOAA Climatic Database
 Site/ Point Data
 Future
 2060- 2064
 Models
 CCCMA CGCM3.1
 GFDL CM2.1
 A1B Scenario
 Grid to Site Data
 Reduce natural variably 5yrs was used to represent each
time interval [5]
 High intensity: Top 10% of daily watershed precipitation
events
Figure 17: IPCC emissions
scenarios [4}

13. Results: The Big Picture

14. Results: The Big Picture

15. Results: The Top 10%
 Discharge Increases
 Total Flow
 CCMA: 38%
 GFDL: 47%
 Max Flows
 CCMA: 26%
 GFDL: 20%
 Precipitation
 Current: 8.6mm/day-
99.6mm/day
 CCMA: 12.1mm/day-
92.5mm/day
 GFDL: 11.6mm/day-
86.8mm/day

16. Results: The Top 10%
 Changes in
Temporal
Distribution

17. Conclusion
 The amount of watershed discharge from the top
10% of daily precipitation event could increase by
nearly 50% in the next 50 years
 Max flows increasing by almost 30%
 Consecutive high flow days and temperature could have also
had a large influence on flow magnitude
 Decrease in summer high flows could be detrimental
to agriculture and aquatic habits
 Slight shifts in the timing of seasonal rain could be indicative
of future large scale seasonal shifts
 Obvious differences in climate model projections
 Grain of salt
 Objective eye

18. References
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19. Acknowledgements
 USF
Environmental
Science and Policy
Program
 Dr. Barnali Dixon
and the Geospatial
Analytics Lab
 My loving family
and dear friends