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

been abandoned. TSTooI was used to query every streamflow gage within the SPDSS study area
containing monthly data during the SPDSS study period. Gage locations were plotted in GIS to
inspect spatial coverage.
The next step was to check the USGS ratings and the amount of complete data available for each
gage. The TSTooI "Data Limits Summary" report was used to identify gages with less than 30
percent missing (at least 70 percent complete) monthly records throughout the SPDSS study
period. These gages were highlighted in GIS.
The following special criteria were then used to identify key streamflow gages specifically for
the surface water, ground water, and water budget models.
Surface Water Model:
• All gages with at least 70 percent complete data.
• Gages with less than 70 percent complete data at key locations for developing and
checking the baseflow distribution factor analysis.
• Gages in close proximity to major reservoirs or located on major tributaries that are
likely to be included in the surface water model that contain less than 70 percent
complete data. These gages may be used in calibrating the surface water model but are
not intended to be used directly in the baseflow generation. The available historical
data will be used during calibration to check baseflow distributions.
Ground Water Model:
• The ground water model will include the Denver Basin Aquifers and the mainstem of
the South Platte River. With assistance from the Ground Water Contractor, important
gages representing tributary flow to the South Platte and gages along the South Platte
River mainstem were identified.
Water Budget Model:
• Only gages measuring outflows from the water budget model area were included.
These gages are located at the state lines with Wyoming (North Platte River, Laramie
River, and Sand Creek) and Nebraska (South Platte River).
Using these criteria, a total of 65 key streamflow gages were selected out of the 300 gages
identified in the FS. The gage names and associated data are summarized below in Table 1
(organized first by Water District and sorted alphabetically). The key streamflow gages
specifically identified for the surface water, ground water, and water budget models are
described as follows.
Surface Water Model -All of the gages in Table 1 may be included and, as discussed
previously, missing historical data do not necessarily need to be filled for the surface water
modeling effort. Note that some of these key gages will also be used for the ground water
and water budget modeling. Locations of the key streamflow gages for the surface water
model are shown in Figure 1. As depicted by the legend, the gages are color coded to
indicate the percent missing data for each gage from 1950 through 2002. The purpose of
Figure 1 is to provide overall perspective of key surface water model streamflow gage
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