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Hydrologic/Watershed Modeling. Glenn Tootle, P.E. Department of Civil and Environmental Engineering University of Nevada, Las Vegas tootleg@unlv.nevada.edu. , Ph.D. Department of Civil and Architectural Engineering University of Wyoming tootleg@uwyo.edu. Questions?.

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Hydrologic/Watershed Modeling

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Hydrologic watershed modeling

Hydrologic/Watershed Modeling

Glenn Tootle, P.E.

Department of Civil and Environmental Engineering

University of Nevada, Las Vegas


, Ph.D.

Department of Civil and Architectural Engineering

University of Wyoming




  • Who has used / developed a hydrologic model?

  • What model(s) did you use?

  • Examples

Conceptual model of watershed modeling

Conceptual Model of Watershed Modeling

  • Typical Input

  • Topography

  • Soil Characteristics

  • Land cover

  • Land use

  • Meteorological data

  • Typical Output

  • Streamflow

  • Subsurface Flow

  • Depth to water table

Steps to hydrologic modeling

Steps to Hydrologic Modeling

  • Delineate watershed

  • Obtain hydrologic and geographic data

  • Select modeling approach

  • Calibrate/Verify model

  • Use model for assessment/prediction/design

What is a watershed

What is a Watershed?

  • Area that topographically contributes to the drainage to a point of interest

Natural Watershed

  • Points of Interest

  • Road crossing

  • Stream gage

  • Reservoir inlet

  • Wastewater treatment plant

  • Location of stream restoration

Urban watershed

Urban Watershed

Usgs quad map

USGS Quad Map

Digital elevation model dem

Digital Elevation Model (DEM)

  • Digital file that stores the elevation of the land surface a specified grid cell size (e.g., 30 meters)

Geographic data

Geographic Data

  • Land use

  • Land cover

Geographic data1

Geographic Data

  • Soil type/classification

Hydrologic data

Hydrologic Data

  • Meteorological Data

    • Temperature

    • Precipitation

    • Wind speed

    • Humidity

  • Extrapolation of point measurements

    • Theissen Polygons

    • Inverse distance weighting

Hydrologic data1

Hydrologic Data


  • Hydrologic Data

    • Streamflow

      • Peak discharge

      • Daily flow volume

      • Annual flow volume

    • Soil moisture

    • Groundwater level

Modeling approaches examples

Modeling Approaches (examples)

Basis for many hydrologic models

Basis for Many Hydrologic Models

  • Hydrologic Budget (In – Out = ΔStorage)

Transpiration (T)

Streamflow (Q)

Evaporation (E)

Groundwater out (GWout)


Precipitation (P)

Groundwater in (GWin)

Infiltration (I)


(P + GWin) – (E + T + I + GWout + Q) = ΔStoragereservoir

Which model should be used

Which Model Should be Used?

  • It Depends on:

    • What time scale are you working at?

    • What hydrologic quantity are you trying to obtain?

    • What data do you have for your watershed?

    • How fast of a computer do you have?

Spatial scaling of models

Spatial Scaling of Models


Parameters assigned to each grid cell, but cells with same parameters are grouped


Parameters assigned to each grid cell


Parameters assigned to each subbasin




Stanford watershed model hspf

Stanford Watershed Model(HSPF)

  • Physically-based and continuous simulation

Variable infiltration capacity vic 3l

Variable Infiltration Capacity (VIC-3L)

  • Continuous simulation and physically-based

  • Macroscale hydrologic model that solves full water and energy balances

Vic 3l example

VIC-3L Example

Calibrating a model

Calibrating a Model

  • Typically the model is calibrated against observed streamflow data

  • Depending on the model complexity, parameters are adjusted until observed streamflow equals model streamflow

  • Which observed value to use:

    • Qpeak

    • Qvolume

    • tpeak



  • tpeak

  • Qvolume


Sensitive parameters

Sensitive Parameters

  • Precipitation

  • Soil parameters

    • Hydraulic conductivity

    • Soil water holding capacity

  • Evaporation (for continuous simulation)

  • Flow routing parameters (for event-based)



  • Precipitation

    • Extrapolation of point to other areas

    • Temporal resolution of data

  • Soils information

    • Surveys are based on site visits and then extrapolated

  • Routing parameters

    • Usually assigned based on empirical studies

Use of models

Use of Models

  • Assessment

    • What happens if land use/land cover is changed?

  • Prediction

    • Flood forecasting

  • Design

    • How much flow will occur in a 100 year storm?



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