SPDSS_Task2_IDKeyStreamflowGages

• Title: SPDSS Task 2 - Identify Key Streamflow Gages and Estimate Streamflows for Missing Records
• Description: The objective of this task is to identify key streamflow gages to use in the SPDSS modeling efforts and to develop a method for filling missing data. Revised memo to account for new information regarding the Balzac Gage. Revised February 2007.
• Decision Support - Doc Type: Task Memorandum
• Date: 2/10/2007
• DSS Category: Surface Water
• DSS: South Platte
• Basin: South Platte
• Contract/PO #: C153954
• Grant Type: Non-Reimbursable
• Bill Number: SB01-157, HB02-1152, SB03-110, HB04-1221, SB05-084, HB06-1313, SB07-122
• Prepared By: Leonard Rice Engineering

SPDSS Memorandum
Final
To: Ray Alvarado and Ray Bennett
From: LRE -Erin Wilson, Beorn Courtney, and Kara Sobieski
Subject: Methods for Filling Missing Streamflow Records (In Support of Task 2 -Identify
Key Streamflow Gages and Estimate Streamflows for Missing Records)
Date: September 20, 2004
Introduction
Missing historical Streamflow records need to be filled on a monthly basis as outlined in Task 2.
One of the DSS Data Management Interfaces, Time Series Tool (TSTooI), was used under
RGDSS to fill monthly Streamflow data through regression with upstream, downstream, or
nearby gages. Another tool, the Mixed Station Model (MSM), was used under CRDSS to fill
monthly baseflows. MSM was originally developed by the USGS and enhanced under CRDSS.
MSM has not been used in previous DSS efforts to directly fill Streamflow data.
The purpose of this memo is to investigate the regression filling methods available with TSTooI
and MSM. Advantages and limitations of each tool are identified and a recommendation is made
for using these models to fill historical Streamflow data, as well as baseflows, and for developing
the average, wet, and dry patterns for filling diversions.
Approach
The regression filling methods in TSTooI and MSM require the following input data sets:
Dependent -data to be filled
Independent -data to be used as the basis for filling
TSTooI only allows the use of one independent data set to fill a specified missing period of a
dependent data set. Conversely, MSM uses multiple independent data sets to fill a given
dependent data set (i.e. MSM may select a different independent data set to fill each month
within a missing period).
With any filling routine, it is important to review the results graphically as well as statistically.
TSTooI allows the user to quickly view the results graphically, while MSM does not offer this
feature. TSTooI and MSM provide different statistical measurements. With TSTooI, the user
can compare two regressions or the "goodness of fit" through the correlation coefficient, r
(which can be used to calculate the coefficient of determination, r~). For a perfect fit, r = r~ = 1,
signifying the regression line explains 100 percent of the variability of the data. When r = r~ = 0,
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