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: Task 2 -Identify Key Streamflow Gages and Estimate Streamflows for Missing
Records
Date: September 20, 2004 (Revised February 2, 2006 /July 13, 2006/ February 10, 2007)
Introduction
Streamflow data are an important component of the SPDSS surface water, ground water, and
water budget modeling input data. Following is a brief description of how each model uses
Streamflow data:
Surface Water Model -Historical Streamflow data are used to develop baseflows
(natural Streamflows absent any human impact) and for model calibration. Two
approaches have been used in prior DSS developments to fill missing Streamflow data.
For the western slope, missing baseflows, not historical Streamflows, were estimated by
regression. Through this process, missing historical Streamflow values are never
filled. For the Rio Grande DSS, historical Streamflows were filled by regression with
historical stream gages. The filled Streamflows were then used to develop baseflow
estimates. The approach recommended for potential future SPDSS surface water
modeling is that which was adopted for the western slope where missing baseflows are
filled rather than filling missing historical Streamflows.
In addition, historical Streamflow data have been used for all DSS developments to
estimate average, wet, and dry months in the "pattern fill" technique for filling diversion
records and to calibrate the model. Missing historical streamflows do not need to be
filled for this process.
Ground Water Model -Streamflow data are used as an inflow to the ground water
model, to characterize the connection between aquifers and streams, and to develop and
calibrate the location and timing of stream gains and losses from ground water.
Missing streamflow data must be filled so that boundary conditions and gain-loss
estimates can be developed for every month of the study period.
• Water Budget Model - Streamflow is one of the major outflows from the basin.
Missing streamflow data must be filled so that the basin water budget boundary
conditions can be developed for every month of the study period.
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