Wyoming State Water Plan, Wyoming Water Development Office
Rafting on Snake River Lake Marie, Snowy Mountains Wyoming Wind River Range picture

Hydrologic Modeling Description

Green River Basin Water Plan

Comparison of Spreadsheet Model to Deterministic Model

Characteristic Spreadsheet Deterministic
Uses Existing USGS Gaging Data Yes Yes
Uses Existing Diversion Records Yes Yes
Uses Research Estimates for Return Flow Patterns Yes Yes
Uses Published Crop Consumptive Use Estimates Yes Yes
Uses Reservoir Storage Information Yes Yes
Tracks Water in Major System Diversions Yes Yes
Applies Prior Appropriation Doctrine to Diversions No Yes
Uses Historic Diversion Amounts Yes Can
Uses Hydrologic Equations to Calculate Parameters No Yes
Produces Monthly Data for a Period of Record No Yes
Produces Monthly Data for Average, Wet and Dry Years Yes Can
Calibrated to Observed Data, usually within +/- 10% Yes Yes
Degree of Difficulty in Setup and Calibration Moderate High
Degree of Flexibility in Output Presentation High Fixed
Designed to Optimize Operations of Irrigators No Yes
Designed to Assess Available Water Resources Yes Yes
Designed to Mimic Historic Operations Yes Can

Primary Differences:

  1. Spreadsheet Model provides monthly flows at points of interest for average, wet and dry years. Wet and Dry years are typically defined as those years for which the period of record shows 10 percent have more flow (Wet) and 90 percent have more flow (Dry). Spreadsheet models are suitable for planning studies.

  2. Deterministic Model provides flows at points of interest for every year in the period of record used. These models can be used for planning, but are more often used for project-specific studies. For example, for a 30-year period, a deterministic model will provide 30 years of output. A spreadsheet model will have three years of results.