SPDSS_Task44-3_LowerSPlatteAlluviumRegionAquiferWaterLevels

• Title: SPDSS Task 44.3 - Lower South Platte Alluvium Region Aquifer Levels - Phase 3
• Description: This Technical Memorandum was undertaken under Task 44.3 of Phase 2 of the SPDSS, and summarizes the compilation, analysis and mapping of water level data of the South Platte Alluvial Aquifer.
• Decision Support - Doc Type: Task Memorandum
• Date: 11/29/2006
• DSS Category: Groundwater
• DSS: South Platte
• Basin: South Platte
• Contract/PO #: C153953
• Grant Type: Non-Reimbursable
• Bill Number: SB01-157, HB02-1152, SB03-110, HB04-1221, SB05-084, HB06-1313, SB07-122
• Prepared By: CDM

^ Data collected in Task 39 using automated data loggers provides high-resolution water
level data in 37 dedicated monitoring wells. This previously unavailable data is
necessary for understanding water level fluctuations throughout the year that are
caused by pumping, changes in stream stage, precipitation, irrigation and managed
recharge sources.
Water level measurements in the South Platte Alluvium Region were abundant in the
late 1960s (approximately 3,000 measurements per year), but by the 1990s the number of
measurements had declined to about one-third of that amount. Recent programs such
as the enhanced 2003 spring water level measurement effort (denoted by "Colorado
State University' in Table 1) represent a substantial improvement in the number and
distribution of measurements in the South Platte Alluvium Region. The primary source
of water level data in the South Platte Alluvium Region since 1986 has been the DWR.
5.0 Recommendations
The following additional data needs were identified based upon this analysis:
^ The alluvial water level data presented in this TM and in HydroBase are the most
comprehensive currently available and should be utilized by members of government
agencies, water management groups and the public in water resources-related activities
for the alluvial aquifer of the South Platte River downstream of Chatfield Reservoir and
its tributaries.
^ Continue alluvial aquifer water level data collection efforts in the spring and autumn
from the existing DWR monitoring network and from the SPDSS monitoring wells with
automated data loggers, as is planned for Task 39 in Phase 4.
^ Collect spring alluvial water level measurements consistently in the month of April to
minimize the year-to-year variability and reduce the influence of spring and early
summer pumping on the water level data collected.
Continue programs such as the enhanced 2003 spring water level measurement effort
(denoted by "Colorado State University" in Table 1) on a periodic basis. This water level
data represents a substantial improvement in the number and distribution of
measurements in the South Plate Alluvium Region and helps reduce uncertainties in
groundwater modeling by providing a good data set for model calibration purposes.
^ Expand the current water level collection program to include additional alluvial wells in
areas with data gaps. This includes areas in the Cache la Poudre River and in Box Elder,
Beaver and Badger Creeks. A greater density of water level measurements will allow for
a greater understanding of local water level trends from year to year.
^ HydroBase should include a field in its water level measurement tables to indicate if the
water level measurement was collected under pumping conditions. For data solicited
SPDSS Phase 3 Task 44.3 TM -Final 16
11/29/2006