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.