PRECIPITATION-RUNOFF MODELING SYSTEM

(PRMS)

SNOW MODELING OVERVIEW

PRMS

PRMS Parameters

original version

PRMSParameters

MMS Version

SNOW PROPERTIES

• Porous media

• Undergoes metamorphosis

• Surface albedo changes with time

• Density increases with time

• Has a free-water holding capacity

Energy Balance Formulation

Hm = Hsn + Hln + Hc + He + Hg + Hp + Hq

Temperature-Index FormulationM = Cm * ( Ta - Tb)

Modifications

Seasonal adjustment to Cm

Vary Cm for forest and open

Use equation only for non rain days

Account for Hg and Hq

Snowpack Energy Balance Components

Energy Balance FormulationHm = Hsn + Hln + Hc + He + Hg + Hp + Hq

Model Formulation (on each HRU)

PRMS SNOW MODEL

Hsn = swrad * (1. - albedo) * rad_trncf

Hln = emis * sb_const * tavg4 ( T4)

Hc + He = cecn_coef(mo) * tavg (ppt days)

= 0 (dry days)

Hp = tavg * net_precip

Hg assumed 0 Hq is computed

Snow Surface Albedo vs Time

Solar Radiation Transmission Coefficient vs Cover Density

Net Longwave Radiation

Hlw = (1. - covden_win) * [(emis * air) -snow)]

emis = emis_noppt no precip

= 1.0 precip

air and snow = sb_const * tavg4 [ ( T4)

where tavg is temp of air and temp of snow surface

+ covden_win * (air -snow)

Energy Balance FormulationHm = Hsn + Hln + Hc + He + Hg + Hp + Hq

Model Formulation

PRMS SNOW MODEL

Hsn = SWRin * (1. - ALBEDO) * TRNCF

Hln = T4

Hc + He = Cce * Tavg (ppt days)

= 0 (dry days)

Hp = Tavg * PTN

Hg assumed 0 Hq is computed

SNOWPACK DYNAMICS• 2-layered system

• energy balance: 2 12-hour periods

• energy exchange between layers -- conduction and mass transfer

• Tsurface = min(tavg or 0o C)

• Tpack is computed

• density = f(time, settlement constant)

• albedo decay = f(time, melt)

• melt volume: use depth-area depletion curve

Areal Snow Depletion Curve

MELT SEQUENCEcal_net > 0

snowmelt = cal_net / 203.2

pk_temp < 0o C

refreeze to satisfy pk_def

pk_temp = 0o C

satisfy free water holding capacity(freeh2o_cap)

remaining snowmelt reaches the soil surface

Max Temperature-Elevation Relations

TEMPERATURE

tmax(hru) = obs_tmax(hru_tsta) - tcrx(mo)

tmin(hru) = obs_tmin(hru_tsta) - tcrx(mo)

tcrx(mo) = [ tmax_lapse(mo) * elfac(hru)] -

For each HRU

where

elfac(hru) = [hru_elev - tsta_elev(hru_tsta)] / 1000.

-------------tmax_adj(hru)

Precipitation-Elevation Relations

Schofield Pass and Crested Butte (1975-97)

0

0.05

0.1

0.15

0.2

0.25

0.3

1 2 3 4 5 6 7 8 9 10 11 12

M onth

Av

era

ge

da

ily

pre

cip

ita

tio

n,

in i

nc

he

s

Schofield Pass

Crested Butte

Mean Daily PrecipitationSchofield Pass (10,700 ft) vs Crested Butte (9031 ft)

MONTH

Mea

n da

ily

prec

ip, i

n.

Precipitation Gage Catch Error vs Wind Speed (Larsen and Peck, 1972)

Rain (shield makes little difference)

Snow (shielded)

Snow (unshielded)

Precipitation Gauge Intercomparison Rabbit Ears Pass, Colorado

PRECIPITATION

- DEPTH

hru_precip(hru) = precip(hru_psta) * pcor(mo)

pcor(mo) = Rain_correction or Snow_correction

For each HRU

Precipitation Distribution Methods(module)

• Manual (precip_prms.f)

• Auto Elevation Lapse Rate (precip_laps_prms.f)

• XYZ (xyz_dist.f)

PCOR Computation

• Auto Elevation Lapse Rate

PCOR Computation

For each HRU

hru_psta = precip station used to compute hru_precip

[ hru_precip = precip(hru_psta) * pcor ]

hru_plaps = precip station used with hru_psta to compute ------ -------precip lapse rate by month [pmo_rate(mo)]

hru_psta

hru_plaps

PCOR Computation

pmn_mo

padj_sn or padj_rn

elv_plaps

Auto Elevation Lapse Rate Parameters

adj_p = pmo_rate *

• Auto Elevation Lapse Rate

PCOR Computation

For each HRU

snow_adj(mo) = 1. + (padj_sn(mo) * adj_p)

if padj_sn(mo) < 0. then snow_adj(mo) = - padj_sn(mo)

pmo_rate(mo) =pmn_mo(hru_plaps) - pmn_mo(hru_psta)

elv_plaps(hru_plaps) - elv_plaps(hru_psta)

hru_elev - elv_plaps(hru_psta)

pmn_mo(hru_psta)

PRECIPITATION

- FORM (rain, snow, mixture of both)

For each HRU

RAIN

tmin(hru) > tmax_allsnow

tmax(hru) > tmax_allrain(mo)

SNOW

tmax(hru) <= tmax_allsnow

PRECIPITATION

- FORM (rain, snow, mixture of both)

prmx = [(tmax(hru) - tmax_allsnow) / -------------------------(tmax(hru) - tmin(hru)] * adjmix_rain(mo)

For each HRU

Precipitation Form Variable

Snowpack Adjustment

MIXTURE

OTHER

PARAMETER ESTIMATION

PRMS Parameters Estimated

• 9 topographic (slope, aspect, area, x,y,z, …)

• 3 soils (texture, water holding capacity)

• 8 vegetation (type, density, seasonal interception, radiation transmission)

• 2 evapotranspiration

• 5 indices to spatial relations among HRUs, gw and subsurface reservoirs, channel reaches, and point measurement stations

BASIN DELINEATION AND CHARACTERIZATION

Polygon Hydrologic Response Units (HRUs) (based on slope, aspect, elevation, vegetation)

Grid Cell Hydrologic Response Units (HRUs) (Equal to Image Grid Mesh)

Focus of operational modeling Focus of research modeling

Upper San Joaquin River, CAEl Nino Year

ANIMAS RIVER, CO

SURFACE GW

SUBSURFACE

PREDICTED

MEASURED

EAST FORK CARSON RIVER, CA

SURFACE

GW

SUBSURFACE

CLE ELUM RIVER, WA

SURFACE

GW

SUBSURFACE

REMOTELY SENSED SNOW-COVERED AREA AND SNOWPACK WATER

EQUIVALENT

Satellite Image for Snow-Covered Area Computation

NASA Regional Earth Science Applications Center

Objective - Integrate remotely sensed data into operational resource management applications

~ 1 km pixel resolution of NOAA snow-covered area product on 750 km2 basin

SW Center - U of AZ, U of CO, USGS, --------------Lawrence Berkeley Labs

East Fork Carson River, CA

1986

1986

1988

Observed and Simulated Basin Snow-Covered Area

SIMULATED vs SATELLITE-OBSERVED SNOW-COVERED AREA

SIMULATED vs SATELLITE-OBSERVED SNOW-COVERED AREA

GUNNISON RIVER BASIN LOCATION

Upper Colorado River Basin

Gunnison River Basin

SUBBASINS WITH CONCURRENT STREAMFLOW AND SATELLITE DATA

East River

Taylor River

Lake Fork

Cochetopa Creek

Tomichi Creek

Cochetopa Creek

East River

Lake Fork

Taylor River

Tomichi Creek

eastEast River

0

0.2

0.4

0.6

0.8

1

1/0 1/20 2/9 2/29 3/20 4/9 4/29 5/19 6/8 6/28 7/18

1996

Per

cen

t B

asin

Sn

ow

cove

r

MODELSATELLITE

East River

0

0.2

0.4

0.6

0.8

1

1/0 1/20 2/9 2/29 3/20 4/9 4/29 5/19 6/8 6/28 7/18

1992

Per

cen

t B

asin

Sn

ow

cove

r

MODEL

SATELLITE

Percent Basin in Snow Cover

eastEast River

0

0.2

0.4

0.6

0.8

1

1/0 1/20 2/9 2/29 3/20 4/9 4/29 5/19 6/8 6/28 7/18

1996

Per

cen

t B

asin

Sn

ow

cove

r

MODELSATELLITE

East River

0

0.2

0.4

0.6

0.8

1

1/0 1/20 2/9 2/29 3/20 4/9 4/29 5/19 6/8 6/28 7/18

1992

Per

cen

t B

asin

Sn

ow

cove

r

MODEL

SATELLITE

East River

0

0.2

0.4

0.6

0.8

1

1/0 2/19 4/9 5/29 7/18 9/6

1995

Per

cen

t B

asin

Sn

ow

cove

r

MODEL

SATELLITE

Percent Basin in Snow Cover

coch

Cochetopa Creek

0

0.2

0.4

0.6

0.8

1

1/0 1/20 2/9 2/29 3/20 4/9 4/29 5/19 6/8 6/28 7/18

1994

Per

cen

t B

asin

Sn

ow

cove

r

MODELSATELLITE

Cochetopa Creek

0

0.2

0.4

0.6

0.8

1

1/0 2/19 4/9 5/29 7/18 9/6

1995

Pe

rce

nt

Ba

sin

Sn

ow

co

ve

r

MODELSATELLITE

Percent Basin in Snow Cover

lake

Lake Fork

0

0.2

0.4

0.6

0.8

1

1/0 1/20 2/9 2/29 3/20 4/9 4/29 5/19 6/8 6/28 7/18

1991

Per

cen

t B

asin

Sn

ow

cove

r

MODEL

SATELLITE

Lake Fork

0

0.2

0.4

0.6

0.8

1

1/0 2/19 4/9 5/29 7/18 9/6

1995

Per

cen

t B

asin

Sn

ow

cove

r

MODELSATELLITE

Percent Basin in Snow Cover

STARKWEATHER COULEE, ND

DEPRESSION STORAGE

ESTIMATION (BY HRU)

USING THE GIS WEASEL

(AREA & VOLUME)

WETLANDS HYDROLOGYDEPRESSION STORES (flowing and closed)

HRU 1

HRU 2

STORAGE HRU

FL

OW

GW

P ET

FLOW

Snow-covered Area1997

April 17

March 20

April 22May 6

SNOW

NO SNOW

1997

April 12 April 22

Snowpack Water Equivalent

Snow-covered Area

Snow-covered Area 1999

March 25

April 1

April 8

April 13

SNOW

NO SNOW

1999

April 7 April 8

Snowpack Water Equivalent

Snow-covered Area