The Impact of Future Climate Variability on the Hydrology of the Delaware River Basin

Transcription

1 The Impact of Future Climate Variability on the Hydrology of the Delaware River Basin Timothy W. Hawkins Shippensburg University 2018 AWRA Annual Meeting

2 Outline Delaware River Watershed Model description Climate projections Model assessment Hydrologic projections

3 Delaware Bay and Watershed Watershed: 35,066 km 2 Bay: 2,025 km 2 Main Stem: 330 miles (undammed) Tributaries: 216; 14,057 miles States: NY, PA, NJ, DE Counties: 42; Municipalities: 838 Water supply: 15 million people Watershed: $22.5 billion/year Port: $19 billion/ year

4 Temperature ( C) Climate Change and the Watershed rcp2.6 rcp4.5 rcp6.0 rcp

5 Modeling the Watershed 864 grid cells 1/8 (~12 km x 12 km) 141 water cells 225 watershed cells Monthly time step Development: Projections:

6 Gridded Parameters and Constants Lat, Lon, area Average monthly day length Elevation Subsurface storage Land use land cover

7 Inputs Outputs Monthly average temperature (T; C) Monthly total precipitation (P; mm) Rainfall (P rain ) Snowfall (P snow ) Snowmelt (Melt) Snowcover (Snow) Available water (P avail ) Potential ET (PE) Actual ET (AE) Subsurface Moisture (SM) Surplus water (S) Runoff (RO) All outputs in mm

8 Monthly Gridded Inputs 231 CMIP5 projections 1/8 (~12 km x 12 km) statistically downscaled T & P Monthly models; 4 RCP; several runs Observed T and P for validation Used for hydrologic model development

9 Model Workflow 1. Differentiate rainfall/snowfall f (T)

10 Model Workflow 1. Differentiate rainfall/snowfall f (T) 2. Snowmelt based on f (T)

11 Model Workflow 1. Differentiate rainfall/snowfall f (T) 2. Snowmelt based on f (T) 3. Accumulate snow water storage

12 Model Workflow 1. Differentiate rainfall/snowfall f (T) 2. Snowmelt based on f (T) 3. Accumulate snow water storage 4. Available water from melt and rainfall

13 Model Workflow 1. Differentiate rainfall/snowfall f (T) 2. Snowmelt based on f (T) 3. Accumulate snow water storage 4. Available water from melt and rainfall 5. Hamon PE constrained

14 Model Workflow 1. Differentiate rainfall/snowfall f (T) 2. Snowmelt based on f (T) 3. Accumulate snow water storage 4. Available water from melt and rainfall 5. Hamon PE constrained 6. Subsurface moisture f (PE, P avail, capacity, LULC)

15 Model Workflow 1. Differentiate rainfall/snowfall f (T) 2. Snowmelt based on f (T) 3. Accumulate snow water storage 4. Available water from melt and rainfall 5. Hamon PE constrained 6. Subsurface moisture f (PE, P avail, capacity, LULC) 7. Surplus water

16 Model Workflow 1. Differentiate rainfall/snowfall f (T) 2. Snowmelt based on f (T) 3. Accumulate snow water storage 4. Available water from melt and rainfall 5. Hamon PE constrained 6. Subsurface moisture f (PE, P avail, capacity, LULC) 7. Surplus water 8. AE f (PE, P avail, SM)

17 Model Workflow 1. Differentiate rainfall/snowfall f (T) 2. Snowmelt based on f (T) 3. Accumulate snow water storage 4. Available water from melt and rainfall 5. Hamon PE constrained 6. Subsurface moisture f (PE, P avail, capacity, LULC) 7. Surplus water 8. AE f (PE, P avail, SM) 9. Runoff f (surplus, LULC)

18 Model Workflow 1. Differentiate rainfall/snowfall f (T) 2. Snowmelt based on f (T) 3. Accumulate snow water storage 4. Available water from melt and rainfall 5. Hamon PE constrained 6. Subsurface moisture f (PE, P avail, capacity, LULC) 7. Surplus water 8. AE f (PE, P avail, SM) 9. Runoff f (surplus, LULC) 10. Aggregate RO for subwatersheds

19 Model Evaluation 8 10 Gage 8 Gage 10 Whole Basin

20 Gage 8 Gage gage avg Model Evaluation Monthly r r sig NS Annual r r sig NS

21 Model Results

22 Model Results

23 Model Results

24 Model Results

25 Model Results

26 Model Results

27 Model Results

28 Percent Change between Future and Baseline Trends per Century RCP 2.6 RCP 4.5 RCP 6.0 RCP 8.5 T ( C) PE (mm) AE (mm) SM (%) RO (mm) P (mm) Pr (mm) Ps (mm) SWE (mm) Melt (mm)

29 Percent Change between Future and Baseline Trends per Century RCP 2.6 RCP 4.5 RCP 6.0 RCP 8.5 T ( C) PE (mm) AE (mm) SM (%) RO (mm) P (mm) Pr (mm) Ps (mm) SWE (mm) Melt (mm)

30 Percent Change between Future and Baseline Trends per Century RCP 2.6 RCP 4.5 RCP 6.0 RCP 8.5 T ( C) PE (mm) AE (mm) SM (%) RO (mm) P (mm) Pr (mm) Ps (mm) SWE (mm) Melt (mm)

31 Percent Change between Future and Baseline Trends per Century RCP 2.6 RCP 4.5 RCP 6.0 RCP 8.5 T ( C) PE (mm) AE (mm) SM (%) RO (mm) P (mm) Pr (mm) Ps (mm) SWE (mm) Melt (mm)

32 Percent Change between Future and Baseline Trends per Century RCP 2.6 RCP 4.5 RCP 6.0 RCP 8.5 T ( C) PE (mm) AE (mm) SM (%) RO (mm) P (mm) Pr (mm) Ps (mm) SWE (mm) Melt (mm)

33 Percent Change between Future and Baseline Trends per Century RCP 2.6 RCP 4.5 RCP 6.0 RCP 8.5 T ( C) PE (mm) AE (mm) SM (%) RO (mm) P (mm) Pr (mm) Ps (mm) SWE (mm) Melt (mm)

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44 Modeled DJF Snow Cover

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46 Distribution of Modeled Runoff

47 Basin-wide increases T, P, P r, PE, AE, RO Basin-wide decreases P s, SWE, melt, SM High spatial variability Runoff as an integrator Increasing % most under rcp 8.5 Increasing in winter Range in projections PE calculation matters Conclusions

48 Future Work Impact on flood hydrology Impact on tree species Repeat analysis at 800 m resolution Examine drought and surplus conditions

49 Questions? Acknowledgements Alfonso Yáñez, Jonathon Chester, Troy Pomeroy, Antonia Price, Claire Jantz, Christopher Woltemade, Scott Drzyzga, Patrick Jantz Tim Hawkins projects/drb/

50 Impact of Constraining PE Energy Only Simple proportion based on LE and H 7 traditional ET s ET calculations reasonable ET future changes not reasonable except for energy only Milly and Dunne (2017)

51 Impact of Constraining PE Calculate Hamon and Energy only for GCM s 1 cell for DRB, monthly Calculate Hamon diff between future downscaled and historic GCM If Hamon difference > GCM Energy Only: PE = Historic Hamon + Energy Only diff + diff btw downscaled PE and running mean Take home message: Statistically constrained runaway PE Accounts for increased stomatal resistance w/ warmer temperatures.

52 Impact of Constraining PE