TOWARD A WATERSHED MODEL FOR CLEAR LAKE S. Geoffrey Schladow UC - - PowerPoint PPT Presentation

TOWARD A WATERSHED MODEL FOR CLEAR LAKE

• S. Geoffrey Schladow

UC Davis

Blue Ribbon Committee Meeting

• Sept. 26, 2019

A distributed watershed model is a computer model that uses sets of mathematical equations to:

• 1. Simulate hydrologic processes (movement of water) across and

through the landscape

• 2. The accompanying erosion and sediment transport that may occur

due to steepness, lack of cover, imperviousness, type of land use etc.

• 3. The accompanying nutrient transport, uptake and release that is
• ccurring due to different activities, soils, reactions etc.

STEP 1 - Subwatershed Delineation

• Subdivision of the watershed into discrete components
• Delineation based on:
• elevation (topographic data)
• stream connectivity
• location of flow and water quality monitoring stations
• Each subwatershed is modeled with 1 representative stream
• Each subwatershed is modeled with 1 representative

meteorological time series

Lake Tahoe

Elevation 1889 - 2044 2045 - 2200 2201 - 2356 2357 - 2512 2513 - 2667 2668 - 2823 2824 - 2979 2980 - 3135 3136 - 3291 No Data Lake Tahoe Subwatersheds

Sub-watershed Delineation

This is provided by the Lidar data from which a Digital Elevation Model (DEM) has likely been produced already

1 2 3 4 5 Kilometers

Subwatersheds Streams Lake Tahoe

N

184

Watersheds

The Use of Sub- Watersheds is What Makes it a Distributed Watershed Model

Lake Tahoe

N

Lake Tahoe Final Composite Land Use Residential_SFP Residential_MFP CICU-Pervious Ski Runs-Pervious Vegetation-Unimpacted Vegetation-Recreational Vegetation-Turf Waterbody Roads-Unpaved Residential_SFI Residential-MFI CICU-Impervious Roads-Primary Roads-Secondary Subwatersheds

10 20 Miles

Step 2 - Land Use Classifications

This is provided by existing GIS layers, high resolution satellite data, Lidar data etc.

LiDAR is a remote sensing technology that measures distance by illuminating a target with a laser and analyzing the reflected light.

LIDAR

LiDAR Point Cloud (all LiDAR points) Bare Earth (LiDAR ground points)

“Satellite Survey”

Countless uses of satellite data

• Weather (from past data) – for watershed model?
• Water temperature - - climate change, lake water

movement etc.

• Algal blooms (cyano and general)

• 10

5 kilometers

Erodibility classes 1 2 3 4 5

Step 3 – Determining erosion potential

This is based on GIS layers of soil types, ground slope, coverage etc. Produces erodibility classes

Step 4 - Watershed Model Land-use Categories

Landuse Category

Pervious/Impervious Subcategory Name

Pervious SFR - Pervious Impervious SFR - Impervious Pervious MFR - Pervious Impervious MFR - Impervious Pervious CICU - Pervious Impervious CICU - Impervious Impervious Primary Roads Impervious Secondary Roads Pervious Unpaved Roads Pervious Ski Runs Pervious Recreation Pervious Burned Pervious Harvest Pervious Turf Areas Pervious Erosion Potential - 1 Pervious Erosion Potential - 2 Pervious Erosion Potential - 3 Pervious Erosion Potential - 4 Pervious Erosion Potential - 5

Transportation Vegetated Single Family Residential Multi Family Residential Commercial/Institutional/ Communications/Utilities

Step 5 - Meteorology – this is what “drives” the model

10 20 30 40 50 60 70 80 1/1/1995 7/1/1995 1/1/1996 7/1/1996 1/1/1997 7/1/1997 1/1/1998 7/1/1998 1/1/1999 7/1/1999 1/1/2000 7/1/2000 1/1/2001 7/1/2001 1/1/2002 7/1/2002 1/1/2003 7/1/2003 1/1/2004 7/1/2004 1/1/2005 Average Temperature (Deg F) 3 6 9 12 15 18 21 24 Data Quality (Impaired Hours) Number of Impaired Hours per Day Original Hourly SNOTEL Temperature (Fallen Leaf) Corrected Temperature * Historical average monthly reference crop evapotranspiration for Tahoe City, California UC Davis Division of Agriculture and Natural Resources, Publication 21454 1 2 3 4 5 6 7 8 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Inches/Month Tahoe City Reference ET * Reference ET adjusted for Evergreen Forest LSPC Modeled Total ET (10/1996-9/2003)

% U % U % U % U % U % U % U % U % U ( X ( X ( X

Lake Tahoe

• MT. ROSE

SKI AREA TAHOE CITY CROSS WARD CREEK MARLETTE LAKE RUBICON FALLEN LEAF ECHO PEAK HAGAN'S MEADOW HEAVENLY VALLEY GLENBROOK DAGGET PASS SOUTH LAKE TAHOE AP N

Subwatersheds Lake Tahoe

% U

NRCS SNOTEL Stations

( X

NCDC Weather Stations

10 20 Miles

% U % U % U % U % U % U % U % U % U % U % U % U % U

# Y # Y # Y # Y # Y # Y # Y # Y # Y # Y

Lake Tahoe Third Creek Incline Creek Ward Creek Blackwood Creek General Creek Marlette Creek Glenbrook Creek Logan House Creek Edgewood Creek Upper Truckee River at South Lake Tahoe Trout Creek Upper Truckee River at Hwy 50 Upper Truckee River at S. Upper Truckee Road

N

Subwatersheds Streams Lake Tahoe

% U

USGS Flow Gages

# Y

LTIMP Water Quality Stations

10 20 Miles

Step 6 - Calibration and Validation

• This is the hard part.
• Need at least 1 year of meteorological data to

“input” to the model for “calibration”, and at least 1 year to ”validate” the model performance.

• Calibration - adjust individual

coefficients for erosion, nutrient release etc. so that data from gauging stations match the measured values. TOC

• Validation – change nothing, confirm that model

can represent a different set of data

• If insufficient or poor stream data, the results are
• f dubious value - GIGO

1,000 2,000 3,000 4,000 5,000 6,000 7,000 R e s i d e n t i a l _ S F P R e s i d e n t i a l _ M F P C I C U

• P

e r v i

• u

s S k i _ R u n s

• P

e r v i

• u

s V e g _ e p 1 V e g _ e p 2 V e g _ e p 3 V e g _ e p 4 V e g _ e p 5 V e g _ R e c r e a t i

• n

a l V e g _ B u r n e d V e g _ H a r v e s t V e g _ T u r f W a t e r _ B

• d

y R e s i d e n t i a l _ S F I R e s i d e n t i a l _ M F I C I C U

• I

m p e r v i

• u

s R

• a

d s _ P r i m a r y R

• a

d s _ S e c

• n

d a r y R

• a

d s _ U n p a v e d Load, MT/yr Upland Fines, metric tons Upland TSS, metric tons

Output - Fine Sediment Loads

1,000 2,000 3,000 4,000 5,000 6,000 Residential_SFP Residential_MFP CICU-Pervious Ski_Runs-Pervious Veg_ep1 Veg_ep2 Veg_ep3 Veg_ep4 Veg_ep5 Veg_Recreational Veg_Burned Veg_Harvest Veg_Turf Water_Body Residential_SFI Residential_MFI CICU-Impervious Roads_Primary Roads_Secondary Roads_Unpaved Load, kg/yr

Surface TP, kg/yr Baseflow TP, kg/yr

Output - Phosphorus Loads

5,000 10,000 15,000 20,000 25,000 30,000 R e s i d e n t i a l _ S F P R e s i d e n t i a l _ M F P C I C U

• P

e r v i

• u

s S k i _ R u n s

• P

e r v i

• u

s V e g _ e p 1 V e g _ e p 2 V e g _ e p 3 V e g _ e p 4 V e g _ e p 5 V e g _ R e c r e a t i

• n

a l V e g _ B u r n e d V e g _ H a r v e s t V e g _ T u r f W a t e r _ B

• d

y R e s i d e n t i a l _ S F I R e s i d e n t i a l _ M F I C I C U

• I

m p e r v i

• u

s R

• a

d s _ P r i m a r y R

• a

d s _ S e c

• n

d a r y R

• a

d s _ U n p a v e d Load, kg/yr

Surface TN, kg/yr Baseflow TN, kg/yr

Output - Nitrogen Loads