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Learn about the features, variations, and hydrologic response units of PRMS modeling system, including HRU delineation, precipitation modeling, and solar radiation calculations. Explore the soil zone structure, flow computation, and hydrologic response units cascading flow.
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PRECIPITATION-RUNOFF MODELING SYSTEM(PRMS) MODELING OVERVIEW & DAILY MODE COMPONENTS
PRMS Features • Modular Design • Deterministic • Distributed Parameter • Daily and Storm Mode • Variable Time Step • User Modifiable • Optimization and Sensitivity Analysis
PRMS Variations PRMS_WET PRMS_ISO PRMS_Yakima PRMS_Jena PRMS-MODFLOW
Distributed Parameter Approach Hydrologic Response Units - HRUs HRU Delineation Based on: - Slope - Aspect - Elevation - Vegetation - Soil - Precip Distribution
HRU DELINEATION AND CHARACTERIZATION Grid Cell Hydrologic Response Units (HRUs) Polygon Hydrologic Response Units (HRUs)
Dill Basin, Germany Topography 750 km2 Sub-basins Land Use
PRMS -- HRU Delineation Pixelated Topographic
Relation of HRUs and Subsurface and GW Reservoirs Surface ( 6 hrus ) Subsurface ( 2 reservoirs ) Ground water (1 reservoir)
HRU resolution PRMS SSR resolution GWR resolution
MODEL DRIVING VARIABLES - TEMPERATURE - max and min daily - lapse rate varied monthly or daily - PRECIPITATION - spatial and elevation adjustment - form estimation
MODEL DRIVING VARIABLES - SOLAR RADIATION - measured data extrapolated to slope-aspect of each HRU - when no measured data, then estimated using temperature, precip, and potential solar radiation - max daily temperature procedure - daily temperature range procedure
Precipitation Gage Catch Error vs Wind Speed (Larsen and Peck, 1972) Rain (shield makes little difference) Snow (shielded) Snow (unshielded)
PRECIPITATION For each HRU - DEPTH hru_precip(hru) = precip(hru_psta) * mo_corr_precip(mo) mo_corr_snow(mo) = Snow_correction mo_corr_rain(mo) = Rain_correction
PRECIPITATION For each HRU - FORM (rain, snow, mixture of both) RAIN tmin(hru) > tmax_allsnow tmax(hru) > tmax_allrain(mo) SNOW tmax(hru) <= tmax_allsnow
[ ] tmax(hru) - tmax_allsnow prmx = * adjmix_rain(mo) (tmax(hru) - tmin(hru) PRECIPITATION For each HRU - FORM (rain, snow, mixture of both) MIXTURE OTHER Precipitation Form Variable Snowpack Adjustment
Precip and Temp Distribution Methods • Manual • Auto Elevation Lapse Rate • XYZ • Inverse Distance … PRMS_USGS PRMS_NWCC • Detrended Kriging
SOLAR RADIATION For each HRU daily_potsw(hru) = ( drad(hru) / horad ) * ------------------orad /cos_slp(hru) - drad and horad computed daily for each HRU and a horizontal surface - Missing data computed by obs_tmax - SolarRad relation [obs_tmax - obs_tmin] --> sky cover --> SolarRad relation
DRIVING VARIABLE INPUT SOURCES • Point measurement data • Radar data • Satellite data • Atmospheric model data
INTERCEPTION Net precipitation net_precip = [ hru_precip * (1. - covden)] + (PTF * covden) Throughfall PTF = hru_precip - (max_stor - intcp_stor)----- if [hru_precip > (max_stor - intcp_stor)] PTF = 0.if [hru_precip <= (max_stor - intcp_stor)] Losses from intcp_stor Rain - Free water surface evaporation rate Snow - % of potet rate for sublimation
Transpiration vs Soil Moisture Content and Weather Conditions
Potential Evapotranspiration (potet) - Pan Evaporation potet(hru) = epan_coef(mo) * pan_evap - Hamon potet(hru) = hamon_coef(mo) * dyl2 * vdsat - Jensen - Haise potet(hru) = jh_coef(mo) * --------------- (tavf(hru) - jh_coef_hru) * rin
Computed ET (AET) as function of PET and Soil Texture PRMS to PRMS/MMS SMAV = soil_moist SMAX = soil_moist_max RECHR = soil_rechr REMX = soil_rechr_max
Actual Evapotranspiration (actet) - f ( antecedent conditions, soil type) - Taken first from Recharge Zone & then Lower Zone - actet period ( months transp_beg to transp_end) transp_beg - start actet on HRU when S tmax_sum(hru) > transp_tmax(hru) transp_end - end actet
Point Evapotranspiration Comparison Aspen Park, CO Eddy correlation Jensen-Haise ET, inches
Basin Evapotranspiration Comparison Jensen-Haise RegCM2 Animas River Basin, Colarado WORKSHOP ON REGIONAL CLIMATE PREDICTION AND DOWNSCALING TECHNIQUES FOR SOUTH AMERICA
GW - ET Relations Mirror Lake, NH
SOIL ZONE(Original Version) sroff Recharge Zone (soil_rechr_max) soil_moist_max (rooting depth) Lower Zone excs (soil_moist > soil zone field capacity) excs - soil_to_gw soil_to_gw to subsurface reservoir to ground-water reservoir
Infiltration - DAILY MODE infil(hru) = net_precip(hru) - sroff(hru) - STORM MODE Point Infil (fr) fr = dI/dt = ksat * [1. + (ps / S fr)] Areal Infil (fin) qrp = ( .5 * net_precip2 / fr ) net_precip < fr qrp = net_precip - (.5 * fr) Otherwise fin = net_precip - qrp