2. TOP_PRMS George Leavesley, Dave Wolock, and Rick Webb

3. The Data –Weaseled DEM in conjunction with ancillary data describing vegetation, soils, and land cover used to estimate model parameters –Required data limited to precipitation and minimum and maximum temperatures. Observed discharge at basin outlet needed if model is to be calibrated. The Model –Enhanced TOPMODEL Snowpack accumulation, ablation, and melt Interception and throughfall Evapotranspiration Distribution of solar radiation Root zone above unsaturated zone Flow paths: infiltration excess, saturated overland flow, direct flow (macropore), and base flow Results –Simple and robust model capable of yielding insight into many small watershed processes Overview

4. Hydrologic Model Upslope contributing area a Stream line Contour line TOPMODEL (Beven and Kirkby, 1979 and later) applied to each subwatershed. Temperature and radiation based potential (reference) evapotranspiration. Vegetation based interception component. Modified soil zone –Adjust ET based on soil moisture availability in root zone –Infiltration excess runoff generation capability –unsaturated storage and drainage Parameters scaled by GIS average properties over each subwatershed.

5. Input precip and temperature Interception Throughfall Evaporation Potential Evapotranspiration Season, Radiation, Saturated water-vapor Density Direct and diffuse solar radiation Day of year and latitude Scaled by temp range as proxy of cloud clover Scaled by radiation plane Flow generation Infiltration Excess (Hortonian flow) Saturated Overland Flow (Dunnian flow) Root Zone ET (scaled by SD), storage, and drainage Direct Flow (fraction of QUZ) Base flow Rain/Snow - Snow pack Melt/ablation Temperature Apply lapse rate

6. SD(SBAR) SUZ snowmelt (basin_snowmelt) hru_rain hru_snow intcp_evap (basin_intcp_evap) Water Balance for XTOP_PRMS net_rain net_snow intcp_stor (basin_intcp_stor) basin_obs_ppt (basin_ppt) snow_evap (basin_snowevap) pkwater_equiv (basin_pweqv) psoilhru (psoilbasin) SAE quz qdf SRZ qb rex qofs qof qscm (qbasinm) BAL = BAL + SBAR +SUMP - SUMAE - SUMQ + SUMRZ - SUMUZ EVAPO- TRANSPIRATION EXPLANATION RAINSNOW STORAGE DEFICIT FLOWPATH subcatchment, or topo index variable (basin_variable) All units are meters unless otherwise indicated qscfs (qbasincfs) (basin_net_ppt) runoff (cfs) observed variable basin_potet (coverbasin) acm precip(in) tmin/tmax (degrees) Summary variables: qtot, sumqrex, sumqofs, sumuz, sumqdf, sumqb solrad (langleys)

7. Summary and Conclusions Modeling system centered on TOPMODEL for representation of spatially distributed water balance based upon topography and GIS data (vegetation, soils, and land cover). Capability to automatically set up and run at different model element scales. Results provide hourly simulations of streamflow over the entire watershed.

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