Streamflow, Sediment, and Nutrient Simulation of the Bitterroot Watershed using SWAT

Transcription

1 Streamflow, Sediment, and Nutrient Simulation of the Bitterroot Watershed using SWAT by Dr. Michael Van Liew Montana Department of Environmental Quality Helena, Montana, USA

2 Site Map of SWAT Watersheds in Montana, USA Clark Fork to Idaho Canada Montana Blackfoot Watershed (6 sq km) Upper Clark Fork/Little Blackfoot Watershed (485 sq km) Bitterroot Watershed (73 sq km) Idaho Yellowstone National Park Wyoming

3 Major impairments include: --sediment --nitrogen --phosphorus --flow alteration --thermal modification --metals (Cu, Pb, Hg) Bitterroot TMDL Development

4 Ravalli County 44% growth rate from 199 to 2 Greater Missoula area soon to become the most populated urban center in MT

5 Modeling Approach with SWAT NED, land cover, and soil GIS layers read in to define watershed features Land cover GIS layer modified to account for the following features: Unpaved roads Forest harvest On-site septic systems using continuous fertilization Hobby farm lawn area Hobby farm livestock area Watershed delineation consists of 85 subbasins and 188 HRUs based on 15 land cover and 38 soil types

6 Modeling Approach with SWAT Irrigation diversions based on data available for DEQ and the Bitterroot Irrigation District; adjustments made for losses due to consumptive use during the months from July to October Seasonal rotation of cattle for grazing on pasture, range and forest lands within a given subbasin Three types of irrigated crops (pasture, mixed crops and alfalfa) Monthly variations in point source loadings based on NPDES data Sediment losses from roads read in as point sources from WEPP as determined by Water & Environmental Technologies, PC SWAT revised to consider losses of organic nitrogen and phosphorus due to bank erosion Adjustments to Runoff Curve Number and USLS C factor for forest fire and forest harvest

7 Model Calibration and Validation with SWAT 4 year calibration period from 2 to 23 16% dryer than average; 4 year validation period from 1995 to % wetter than average; 5 year warm-up period from 1988 to 1992 Automated calibration based on streamflow record for Darby, Florence, and Missoula USGS gages; subsequent fine tuning manual calibration based on streamflow records from Darby, Florence, Missoula, East Fork, Laird, Skalkaho, Blodgett, and Lolo Manual calibration of sediment, total nitrogen and total phosphorus based on Darby, Florence, and Missoula gages Calibration includes fertilizer on pasture, mixed crops, alfalfa, and lawn cover types; riparian buffer strips on 1/3 rd of the agricultural areas

8 Total: Comparison of runoff curve number and USLE C factor among land use/management types SWAT AREA AREA Curve No. USLE Code Land Cover Type (km**2) (%) Range C Factor ALFA Irrigated Alfalfa AGRL Irrigated Mixed Crops BARN Hobby Farm Livestock FRHV Forest Harvest FRSE Forest PAST Irrigated Pasture LAWN Hobby Farm Lawn RNGB Range Brush RNGE Range Grass SEPT On Site Septic Systems ULOW Low Density Urban UMED Medium Density Urban UPAV Unpaved Roads BARE Barren/Ice WETF Wetland

9 Lolo Gage earlier record Florence Gage Missoula Airport Missoula Gage Location of Climate Stations Streamgages Stevensville Blodgett Gage earlier record Hamilton Twelve Mi. Cr Daly Cr Skalkaho Gage Darby Darby Gage East Fork Gage Laird Gage Nez Perce Camp Saddle Mt. Sula 33 Subbasin Number Climate Station Stream Gage

10 Seven Subbasin Groupings used for Calibrating Parameters that govern the Hydrologic Response on the Bitterroot Watershed

11 Measured versus Simulated Monthly Streamflow for the Calibration (2 to 23) and Validation (1995 to 1998) Periods for the Bitterroot River at Missoula 45 Monthly Streamflow (cms) measured simulated Jan-95 Jul-95 Jan-96 Jul-96 Jan-97 Jul-97 Jan-98 Jul-98 Jan-99 Jul-99 Jan- Jul- Jan-1 Jul-1 Jan-2 Jul-2 Jan-3 Jul-3

12 Measured versus Simulated Average Monthly Streamflow during the Calibration Period (2 to 23) for the Bitterroot River at Missoula 2 Average Monthly Streamflow (cms) measured simulated jan feb mar apr may jun jul aug sep oct nov dec

13 Measured versus Simulated Average Monthly Streamflow during the Validation Period (1995 to 1998) for the Bitterroot River at Missoula 35 Average Monthly Streamflow (cms) measured simulated jan feb mar apr may jun jul aug sep oct nov dec

14 Percent Bias and Nash Sutcliffe Coefficient of Efficiency Streamflow Statistics during the Calibration (C) and Validation (V) Periods for the Main Stem Bitterroot Gages Area Gage PBIAS Monthly Daily (sq km) Location (%) NSE NSE 2718 Darby C Darby V Florence C Florence V Missoula C Missoula V Laird C East Fork C Skalkaho C

15 Measured versus Simulated Average Monthly Sediment Load during the Calibration Period (2 to 23) for the Bitterroot River at Missoula 12 Average Monthly Sediment Load (Tonnes) measured simulated jan feb mar apr may jun jul aug sep oct nov dec

16 Measured versus Simulated Average Monthly Sediment Load during the Validation Period (1995 to 1998) for the Bitterroot River at Missoula 3 Average Monthly Sediment Load (Tonnes) measured simulated jan feb mar apr may jun jul aug sep oct nov dec

17 Measured versus Simulated Average Monthly Sediment Load from 1993 to 23 for the Bitterroot River at Missoula 9 Monthly Sediment Load (Tonnes) Jan-93 May-93 Sep-93 Jan-94 May-94 Sep-94 Jan-95 May-95 Sep-95 Jan-96 May-96 Sep-96 Jan-97 May-97 Sep-97 Jan-98 May-98 Sep-98 Jan-99 May-99 Sep-99 Jan- May- Sep- Jan-1 May-1 Sep-1 Jan-2 May-2 Sep-2 Jan-3 May-3 Sep-3 Measured Simulated

18 Measured versus Simulated Average Monthly Sediment Load from 2 to 23 for Skalkaho Creek 35 Monthly Sediment Load (Tonnes) Measured Simulated Oct- Dec- Feb-1 Apr-1 Jun-1 Aug-1 Oct-1 Dec-1 Feb-2 Apr-2 Jun-2 Aug-2 Oct-2 Dec-2 Feb-3 Apr-3 Jun-3 Aug-3

19 Measured versus Simulated Average Monthly Total Nitrogen Load from 1993 to 23 for the Bitterroot River at Missoula 16 Monthly Total Nitrogen Load (Kg) Jan-93 Jul-93 Jan-94 Jul-94 Jan-95 Jul-95 Jan-96 Jul-96 Jan-97 Jul-97 Jan-98 Jul-98 Jan-99 Jul-99 Jan- Jul- Jan-1 Jul-1 Jan-2 Jul-2 Jan-3 Jul-3 Measured Simulated

20 Measured versus Simulated Average Monthly Total Phosphorus Load from 1993 to 23 for the Bitterroot River at Missoula 25 Monthly Total Phosphorus Load (Kg) Jan-93 Jul-93 Jan-94 Jul-94 Jan-95 Jul-95 Jan-96 Jul-96 Jan-97 Jul-97 Jan-98 Jul-98 Jan-99 Jul-99 Jan- Jul- Jan-1 Jul-1 Jan-2 Jul-2 Jan-3 Jul-3 Measured Simulated

21 Measured versus Simulated Average Monthly Total Nitrogen Load for the Calibration Period (2 to 23) for the Bitterroot River at Missoula Average Monthly Total N Load (Kg) measured simulated jan feb mar apr may jun jul aug sep oct nov dec

22 Measured versus Simulated Average Monthly Total Nitrogen Load for the Validation Period (1995 to 1998) for the Bitterroot River at Missoula 3 Average Monthly Total N Load (Kg) measured simulated jan feb mar apr may jun jul aug sep oct nov dec

23 Measured versus Simulated Average Monthly Total Phosphorus Load for the Calibration Period (2 to 23) for the Bitterroot River at Missoula Average Monthly Total P Load (Kg) measured simulated jan feb mar apr may jun jul aug sep oct nov dec

24 Measured versus Simulated Average Monthly Total Phosphorus Load for the Validation Period (1995 to 1998) for the Bitterroot River at Missoula 4 35 Average Monthly Total P Load (Kg) measured simulated jan feb mar apr may jun jul aug sep oct nov dec

25 Percent Bias and Nash Sutcliffe Coefficient of Efficiency Sediment and Nutrient Statistics during the Calibration (C) and Validation (V) Periods for the Bitterroot River near Darby and at Missoula Gage PBIAS Monthly Constituent Location (%) NSE Sediment Darby C Sediment Darby V Sediment Missoula C Sediment Missoula V Total Nitrogen Missoula C Total Nitrogen Missoula V Total Phosphorus Missoula C Total Phosphorus Missoula V

26 Modeled Sources of Sediment Yield for the Bitterroot River at Missoula based on an 11 year average 5.% 45.% 44.2% 4.% 35.% 3.% 25.% 22.7% 2.% 15.% 1.% 16.2% 11.3% 5.%.% Bank erosion Range grass Range brush Forest Mixed crops 3.4%.9%.8%.2%.1%.%.%.%.%.%.%.%.% Hobby livestock Pasture Point sources Med urban dev Alfalfa Forest harvest Low urban dev Hobby lawn Wetlands Septic systems Barren/Ice Unpaved roads

27 25.% Modeled Sources of Total Nitrogen Yield for the Bitterroot River at Missoula based on an 11 year average 21.1%21.% 2.% 18.1% 15.% 1.% 1.1% 7.7% 6.1% 5.% 4.2% 3.2% 3.1% 2.8% 2.2%.%.3%.1%.1%.%.%.% Bank erosion Pasture Mixed crops Forest Septic systems Range grass Alfalfa Point sources Hobby lawn Range brush Hobby livestock Med urban dev Low urban dev Forest harvest Wetlands Barren/Ice Unpaved roads

28 Modeled Sources of Total Phosphorus Yield for the Bitterroot River at Missoula based on an 11 year average 35.% 3.% 29.6% 25.% 2.% 19.8% 15.% 1.% 14.6% 11.6% 1.3% 7.1% 5.%.% 2.5% 1.8% 1.6%.7%.1%.1%.1%.1%.%.%.% Bank erosion Mixed crops Range grass Range brush Forest Point sources Pasture Alfalfa Hobby livestock Med urban dev Low urban dev Septic systems Hobby lawn Forest harvest Wetlands Barren/Ice Unpaved roads

29 1.% 9.% 8.% Modeled Monthly Sources of Sediment Yield for the Bitterroot River at Missoula Point Source Bank Erosion Non Point Source 7.% 6.% 5.% 4.% 3.% 2.% 1.%.% jan feb mar apr may jun jul aug sep oct nov dec

30 Modeled Monthly Sources of Total Nitrogen Yield for the Bitterroot River at Missoula 1.% 9.% 8.% Point Source Bank Erosion Non Point Source 7.% 6.% 5.% 4.% 3.% 2.% 1.%.% jan feb mar apr may jun jul aug sep oct nov dec

31 1.% Modeled Monthly Sources of Total Phosphorus Yield for the Bitterroot River at Missoula 9.% 8.% Point Source Bank Erosion Non Point Source 7.% 6.% 5.% 4.% 3.% 2.% 1.%.% jan feb mar apr may jun jul aug sep oct nov dec

32 Percent Changes in Sediment, Total N, and Total P with Scenario Implementation (- decrease + increase) Percent Change in Constituent No No 11 meter Bank Stability Watershed Constituent Fertilizer Grazing buffer on Tribs Ambrose Cr sediment 12% 2% -7% -14% Subbasin total N -27% -12% -9% -19% 31 total P -1% -7% -8% -27% Miller Cr sediment 3% 8% -3% -54% Subbasin total N -9% -4% -4% -52% 37 total P % -1% -2% -62% Bitterroot R sediment 5% 3% -6% -14% All total N -35% -18% -5% -8% Subbasins total P -7% -8% -4% -16%

33 Average Monthly Total Nitrogen Load for the Target, Baseline, and No Fertilizer/Grazing Conditions for Ambrose Creek 4 Average Monthly Total N Load (Tonnes) target baseline simulation no fertilizer or grazing jan feb mar apr may jun jul aug sep oct nov dec

34 Average Monthly Total Phosphorus Load for the Target, Baseline, and No Fertilizer/Grazing Conditions for Ambrose Creek 4 Average Monthly Total P Load (Tonnes) target baseline simulation no fertilizer or grazing jan feb mar apr may jun jul aug sep oct nov dec

35 Average Monthly Total Nitrogen Load for the Target, Baseline, and No Fertilizer/Grazing Conditions for the Bitterroot River at Missoula 12 Average Monthly Total N Load (Tonnes) target baseline simulation no fertilizer or grazing jan feb mar apr may jun jul aug sep oct nov dec

36 Average Monthly Total Phosphorus Load for the Target, Baseline, and No Fertilizer Conditions for the Bitterroot River at Missoula 1 Average Monthly Total P Load (Tonnes) target baseline simulation no fertilizer or grazing jan feb mar apr may jun jul aug sep oct nov dec

37 Conclusions Inclusion of septic, hobby farms, unpaved roads, and forest harvest areas as delineated land cover types may be important sources of sediment and nutrients for certain subbasins within the Bitterroot The model exhibited an element of robustness in that it performed as well under wetter than average conditions (validation period) as compared to dryer than average conditions (calibration period) SWAT performed well in predicting sediment, total nitrogen, and total phosphorus Model simulations suggest that bank erosion accounts for 44%, 21%, and 3% of the total sediment, total N, and total P yields from the watershed: these nutrient yields are appreciably different from previous SWAT simulations in Montana that have not considered the impact of bank erosion on nutrient transport. To substantiate nutrient loadings simulated in this study, field investigations need to be implemented to measure losses of N and P associated with bank erosion

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39 Average Monthly Total Phosphorus Load for the Target, Baseline, and No Fertilizer/Grazing Conditions for Ambrose Creek 3 Average Monthly Total P Load (Tonnes) target baseline simulation no fertilizer or grazing jan feb mar apr may jun jul aug sep oct nov dec

40 Measured versus Simulated Average Monthly Total Nitrogen Concentration for the Calibration Period (2 to 23) for the Bitterroot River at Missoula 5 Average Monthly Total N Load (Tonnes) measured simulated jan feb mar apr may jun jul aug sep oct nov dec

41 Measured versus Simulated Average Monthly Total Nitrogen Concentration for the Validation Period (1995 to 1998) for the Bitterroot River at Missoula 9 Average Monthly Total N Load (Tonnes) measured simulated jan feb mar apr may jun jul aug sep oct nov dec

42 Measured versus Simulated Average Monthly Total Phosphorus Concentration for the Calibration Period (2 to 23) for the Bitterroot River at Missoula 6 Average Monthly Total P Load (Tonnes) measured simulated jan feb mar apr may jun jul aug sep oct nov dec

43 Measured versus Simulated Average Monthly Total Phosphorus Concentration for the Validation Period (1995 to 1998) for the Bitterroot River at Missoula 14 Average Monthly Total P Load (Tonnes) measured simulated jan feb mar apr may jun jul aug sep oct nov dec

44 Measured versus Simulated Average Monthly Total Nitrogen Concentration for the Calibration Period (2 to 23) for the Bitterroot River at Missoula 5 Average Monthly Total N Load (Tonnes) measured simulated jan feb mar apr may jun jul aug sep oct nov dec

45 Measured versus Simulated Average Monthly Total Nitrogen Concentration for the Validation Period (1995 to 1998) for the Bitterroot River at Missoula 1 Average Monthly Total N Load (Tonnes) measured simulated jan feb mar apr may jun jul aug sep oct nov dec

46 6 Measured versus Simulated Average Monthly Total Phosphorus Concentration for the Calibration Period (2 to 23) for the Bitterroot River at Missoula Average Monthly Total P Load (Tonnes) measured simulated jan feb mar apr may jun jul aug sep oct nov dec

47 Measured versus Simulated Average Monthly Total Phosphorus Concentration for the Validation Period (1995 to 1998) for the Bitterroot River at Missoula 14 Average Monthly Total P Load (Tonnes) measured simulated jan feb mar apr may jun jul aug sep oct nov dec

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