1. Andy Wood Univ. of Washington (Seattle) NRCS Sprague River Watershed Science Meeting November 14, 2006 Klamath Falls, OR DHSVM Modeling in the Sprague R. Basin

2. Motivation There is a widespread perception that juniper encroachment has reduced streamflow … “The area dominated by western juniper represents a three- to ten-fold increase since the late 1800s… Many juniper-dominated sites show clear evidence of watershed degradation, loss of site productivity, decrease in forage production, loss of wildlife habitat, and overall-reduction in biodiversity.” (Swan, 1998) "areas of [juniper] encroachment are quite capable of setting into motion most of the known processes of desertification within the next 50-75 years over a very large portion of eastern Oregon". (Rumpel, et al., 1991) As well as opposing views… “Although many ranchers and range managers believe that junipers dry up springs and reduce streamflow and that water suddenly reappears when the trees are removed …, there is little substantive evidence to support these beliefs” (Belsky, 1996)

3. Motivation Estimates of water loss due to Juniper vary, but are realistic: from Eddleman et al, 1994: 5 (Nov) – 137 (Oct) liters/tree/month for 10 m tree from Miller et al., 1992 (as reported in Eddleman…) 2-54 liters/tree/month for 4.5 m tree 1for juvenile trees converting to hydrologist’s terms: 1 liter/tree/month = 0.081 mm/tree/day Assume a tree covers about 15 square meters The range is thus:~0.25 to 7.2 mm/day/m 2

4. Outline  DHSVM Overview  Sprague River basin DHSVM implementation  Juniper Management Scenarios  Results  Conclusions DHSVM: Distributed Hydrology-Soil-Vegetation Model

5. Approach: DHSVM Developed in the UW Land Surface Hydrology Research Group at UW for over a decade a research tool, also is used operationally applied to small catchments DHSVM: Distributed Hydrology-Soil-Vegetation Model

6. Approach: DHSVM description

7. DHSVM Snow Accumulation and Melt Model Approach: DHSVM description

8. Outline  DHSVM Overview  Sprague River basin DHSVM implementation  Juniper Management Scenarios  Results  Conclusions DHSVM: Distributed Hydrology-Soil-Vegetation Model

9. Approach: Sprague R. application Elevation

10. Sprague DHSVM: soil / veg parameters

11. Veg. type Recently switched to more detailed vegetation classes provided by Terry Nelson (NRCS)

12. Calibration Parameters for SOIL Approach: Sprague R. application [SOILS] # Soil information Soil Map File= Soil Depth File= pixel-varying depths Number of Soil Types= ################ SOIL 1 ############################# Soil Description1 = SAND Lateral Conductivity1 = 0.01 Exponential Decrease1 = 3.0 Maximum Infiltration1 = 2.0e-4 Surface Albedo1 = 0.1 Number of Soil Layers1 = 3 Porosity1 =.43.43.43 Pore Size Distribution1 =.24.24.24 Bubbling Pressure1 =.07.07.07 Field Capacity1 =.08.08.08 Wilting Point 1 =.03.03.03 Bulk Density1 = 1492. 1492. 1492. Vertical Conductivity1 = 0.01 0.01 0.01 Thermal Conductivity1 = 7.114 6.923 6.923 Thermal Capacity1 = 1.4e6 1.4e6 1.4e6 SENSITIVE

13. Calibration Parameters for VEGETATION Vegetation Description 16 = Western Juniper Over 50 Percent Canopy Impervious Fraction 16 = 0.0 Overstory Present 16 = TRUE Understory Present 16 = TRUE Fractional Coverage 16 = 0.75 Hemi Fract Coverage 16 = Trunk Space 16 = 0.2 Aerodynamic Attenuation 16 = 1.0 Radiation Attenuation 16 = 0.2 Max Snow Int Capacity 16 = 0.003 Snow Interception Eff 16 = 0.5 Mass Release Drip Ratio 16 = 0.4 Height 16 = 7.0 0.4 Overstory Monthly LAI 16 = 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Understory Monthly LAI 16 = 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Maximum Resistance 16 = 5000. 600. Minimum Resistance 16 = 200. 200. Moisture Threshold 16 = 0.33 0.13 Vapor Pressure Deficit 16 = 4000 4000 Rpc 16 =.108.108 Overstory Monthly Alb 16 = 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 Understory Monthly Alb 16 = 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 Number of Root Zones 16 = 3 Root Zone Depths 16 = 0.10 0.25 0.40 Overstory Root Fraction 16 = 0.20 0.40 0.40 Understory Root Fraction 16 = 0.40 0.60 0.00

14. Calibration Parameters for VEGETATION Vegetation Description 14 = Sagebrush Steppe Impervious Fraction 14 = 0.0 Overstory Present 14 = FALSE Understory Present 14 = TRUE Height 14 = 1.0 Understory Monthly LAI 14 = 1.0 1.0 1.0 1.0 2.0 3.0 3.0 3.0 2.0 1.0 1.0 1.0 Maximum Resistance 14 = 600 Minimum Resistance 14 = 200 Moisture Threshold 14 = 0.33 Vapor Pressure Deficit 14 = 4000 Rpc 14 = 0.108 Understory Monthly Alb 14 = 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 0.12 Number of Root Zones 14 = 3 Root Zone Depths 14 = 0.10 0.25 0.40 Understory Root Fraction 14 = 0.40 0.40 0.20

15. Model Forcings

17. Streamflow Simulation Locations: USGS & FS gages

18. Streamflow Calibration: varied performance

21. Streamflow Calibration: at outlet, not bad

22. Outline  DHSVM Overview  Sprague River basin DHSVM implementation  Juniper Management Scenarios  Results  Conclusions DHSVM: Distributed Hydrology-Soil-Vegetation Model

23. Scenarios Goal:To explore the effects on the water balance of the removal of juniper Approach: Identify areas that have a high proportion of juniper coverage Replace juniper with surrounding vegetation Compare resulting simulations

24. Scenarios: Juniper Subarea NE

25. juniper Pixel Analysis

26. Scenarios: Juniper Subarea SE

27. juniper Pixel Analysis

28. Scenarios: Subarea Veg Class Fractions ClassArea-NEArea-SE Name 10 Grass shrub sapling 20 Lava Flow 30 Lodgepole Pine Forest and Woodland Over 50 Percent Canopy 40 Lodgepole Pine Forest and Woodland Under 50 Percent Canopy 50 Pasture/Hay 61.2 Ponderosa Pine Dominant Mixed Forest Over 50 Percent Canopy 71.4 Ponderosa Pine Dominant Mixed Forest Under 50 Percent Canopy 815.11.7 Ponderosa Pine Forest and Woodland Over 50 Percent Canopy 97.314.2 Ponderosa Pine Forest and Woodland Under 50 Percent Canopy 100.0 Ponderosa Pine Juniper Woodland Over 50 Percent Canopy 110.0 Ponderosa Pine Juniper Woodland Under 50 Percent Canopy 121.5 Ponderosa Lodgepole Pine Over 50 Percent Canopy 131.6 Ponderosa Lodgepole Pine Under 50 Percent Canopy 1428.838.1 Sagebrush Steppe 150.0 Urban 1622.316.5 Western Juniper Over 50 Percent Canopy 1719.226.9 Western Juniper Under 50 Percent Canopy 180.0 Wet Meadow 191.62.5 Wetland 200.0 Whitebark Lodgepole Pine Montane Forest

29. Scenarios: Basin Veg Class Fractions ClassJuniperNo Juniper Name 11.11.1 Grass shrub sapling 20.00.0 Lava Flow 30.80.8 Lodgepole Pine Forest and Woodland Over 50 Percent Canopy 40.80.8 Lodgepole Pine Forest and Woodland Under 50 Percent Canopy 55.05.0 Pasture/Hay 69.39.3 Ponderosa Pine Dominant Mixed Forest Over 50 Percent Canopy 72.72.7 Ponderosa Pine Dominant Mixed Forest Under 50 Percent Canopy 813.313.3 Ponderosa Pine Forest and Woodland Over 50 Percent Canopy 99.59.5 Ponderosa Pine Forest and Woodland Under 50 Percent Canopy 101.01.0 Ponderosa Pine Juniper Woodland Over 50 Percent Canopy 111.31.3 Ponderosa Pine Juniper Woodland Under 50 Percent Canopy 1212.712.7 Ponderosa Lodgepole Pine Over 50 Percent Canopy 137.87.8 Ponderosa Lodgepole Pine Under 50 Percent Canopy 1418.228.8 Sagebrush Steppe 150.10.1 Urban 164.70.0 Western Juniper Over 50 Percent Canopy 176.00.0 Western Juniper Under 50 Percent Canopy 180.40.4 Wet Meadow 195.45.4 Wetland 200.00.0 Whitebark Lodgepole Pine Montane Forest

30. Outline  DHSVM Overview  Sprague River basin DHSVM implementation  Juniper Management Scenarios  Results  Conclusions DHSVM: Distributed Hydrology-Soil-Vegetation Model

31. Results: Evaluated for 1 “average” year

32. Results: Juniper Subarea SE Pixel Analysis NO-JUN: Juniper Replaced with Sagebrush (LAI variable 1.0-3.0) BASEHI: Juniper parameters for higher flow (LAI 1.0 / Rad Atten 0.4) BASELO: Juniper parameters for lower flow (LAI 3.0 / Rad Atten 0.2)

33. Results: Juniper Subarea SE - PIXEL Pixel Analysis

34. Results: Juniper Subarea SE Pixel Analysis

35. Scenarios: Juniper Subarea NE NO-JUN: Juniper Replaced with Sagebrush (LAI variable 1.0-3.0) BASEHI: Juniper parameters for higher flow (LAI 1.0 / Rad Atten 0.4) BASELO: Juniper parameters for lower flow (LAI 3.0 / Rad Atten 0.2)

36. Scenarios: Juniper Subarea NE - PIXEL

37. Scenarios: Juniper Subarea NE

38. Scenarios: Entire Basin Moving downstream to areas with smaller fractional coverage of juniper…smaller change to hydrograph after removal

39. Scenarios: Entire Basin Some particular locations show very little change after juniper removal

40. Scenarios: Entire Basin Overall (at outlet of basin), the effects of juniper removal appear to be small earlier melt? earlier drying?

41. Outline  DHSVM Overview  Sprague River basin DHSVM implementation  Juniper Management Scenarios  Results  Conclusions DHSVM: Distributed Hydrology-Soil-Vegetation Model

42. General Conclusions  Change from juniper to sagebrush land cover may be significant at the pixel (100 m) level  may lead to earlier snowmelt due primarily to reduced radiation attenuation  earlier snowmelt would lead to flow increases before current melt and flow decreases afterward  evaporation differences between juniper and sagebrush play less of a role than overstory effects on snow accumulation and melt  The vegetation cover change is detectable in the streamflow response for small areas having a large fraction of juniper cover  The streamflow response is barely detectable in the flows from the entire basin, for which the juniper coverage is a small fraction.  In either case (small or large area), the streamflow timing shift is more dramatic than the change in annual volume

43. Caveats!  The modeled streamflows are not well calibrated for the entire basin.  The vegetation parameters are not precisely known, hence these results are based on a sensitivity analysis of ‘plausible values’  The model’s simulation of water balance components has not been well validated -- e.g., ET or snowpack for different vegetation types  snow ablation appears to be too strong early in winter  DHSVM does not simulate a deep groundwater layer, hence where juniper or sagebrush roots are tapping into layers deeper than ~1.2 meters, physics are not represented  Succession of vegetation (to sagebrush) too simplistic?

44. Recommendations  The modeling framework has potential for further analysis  allows spatial distribution & temporal extension of analysis  allows interaction of climate, vegetation and hydrologic variables  Further effort is needed to verify model performance for water balance variables (primarily flow, snow, ET – but also, where possible, water table depth & soil moisture)  Oversight of plant ecologists is needed to vet vegetation parameter assignments  Efforts at streamflow calibration should continue Bottom line: Results at this point are interesting, but in no way definitive. More work would be needed to increase confidence in the DHSVM-based analysis.

45. DHSVM-simulated Snow Depth, near Seattle, WA

46. END

48. Moisture threshold i soil moisture threshold (0-1) above which soil moisture does not restrict transpiration for each vegetation layer for vegetation type i (number of vegetation layers floats) Vapor pressure deficit i vapor pressure deficit threshold in Pa above which stomatal closure occurs for each vegetation layer for vegetation type i (number of vegetation layers floats) rpc i fraction of shortwave radiation that is photosynthetically active for each layer for each vegetation type i (number of vegetation layers floats)