Template Crane

Hydrology Modeling in Alaska: Model Documentation Template (please fill out as much as possible)

Your name: Crane Johnson, USACE Alaska District

Model name: Streamflow Synthesis and Reservoir Regulation (SSARR) Model

HEC-HMS -HEC Hydrological Modeling System

Authors: SSARR U.S. Army Corps of Engineers Columbia Basin Water Management Division HEC-HMS US Army Corps of Engineers Hydrologic Engineering Center

Source code location (if public):

SSARR - http://www.nwd-wc.usace.army.mil/ftppub/SSARR_program

HEC-HMS – http://www.hec.usace.army.mil/software/hec-hms/

Citations and URLs for basic documentation:

Source code language: SSARR – Fortran HEC-HMS - Java

For the following section, you may wish to use appropriate keywords such as: Physically-based, statistical, lumped parameter, spatially distributed, transitive model, equilibrium model, implicit, semi-implicit, explicit, TOPMODEL based, finite element, finite differences, routing, bottom boundary condition, parallel code, Richardson equation, optimization, forecast, etc

Model type and/or conceptual framework: Both models are lumped parameter hydrologic models.

Data needed to run the model (inputs): Spring Snowpack (SWE) Air Temperature Precipitation Discharge Parameters and how they are derived: Empirically derived parameters

Spatial element used to lump inputs and outputs: Sub-basins and elevations bands (SSARR) Sub-basins and aspects (HEC-HMS)

Sub-models (i.e. snow or ground thermodynamics):

Rainfall/runoff transformation mechanism:

Empirical method based on calculated soil moisture and rainfall intensity (SSARR)

Runoff routing within spatial elements and to basin outlet: Cascade if reservoirs for all model routing.(SSARR).

Method for including sub-grid scale processes: N/A

Resolution (possible & prudent):

Method of deriving topography: USGS topographic maps to determine elevation bands for SSARR model and northern and southern aspect watersheds for HEC- HMS model

Calibration approaches: Overall model calibrated using historical peak flows (magnitude/volume). Operational model runs are calibrated to match observed antecedent hydrographs by adjusting initial conditions (primarily soil moisture). Treatment of frozen ground: No explicit treatment. Implicitly included in empirical parameters.

Strengths and Weaknesses in Alaska applications: Strengths – Robust models that are well documented and generally used for water control. Weaknesses – Individual parameters are often difficult to determine (typically empirically derived) with little in the way or regional guidance. No explicit treatment of permafrost.