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Enhanced TOPMODEL for Spatially Distributed Water Balance Simulation in Small Watersheds

This study presents an enhanced version of TOPMODEL applied to small watersheds to simulate hydrological processes. Utilizing DEM data alongside vegetation, soil, and land cover information, we estimate model parameters essential for effective water balance representation. The model incorporates snowpack dynamics, interception, evapotranspiration, and critical flow paths, including infiltration excess and saturated overland flow. Detailed results illustrate the model's robustness in providing hourly streamflow simulations and insights into watershed processes, demonstrating its utility in various topographic and climatic conditions.

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Enhanced TOPMODEL for Spatially Distributed Water Balance Simulation in Small Watersheds

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

  2. Overview • 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

  3. Stream line Contour line Upslope contributing area a Hydrologic Model • 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.

  4. Input precip and temperature • Direct and diffuse solar radiation • Day of year and latitude • Scaled by temp range as proxy of cloud clover • Scaled by radiation plane • Temperature • Apply lapse rate • Interception • Throughfall • Evaporation • Rain/Snow • - Snow pack • Melt/ablation • Potential Evapotranspiration • Season, Radiation, • Saturated water-vapor Density • 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

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

  6. 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.

  7. AREA 2 3 AREA 1 12 Are there any questions ?

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