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

pumping or that contained too few water level measurements to determine a trend were
omitted from the analysis. The goodness of fit of the regression line was assessed to identify
those locations where the correlation was statistically significant. The correlation coefficient for
this line was statistically tested using the Student's t test and only those regressions that had a
significance level of ten percent or lower were retained, i.e., the probability of random variation
accounting for the correlation was 10 percent or less.
After groundwater elevation trends were analyzed, the identified water level change per year
for each well was posted on a map. The posted trends were used to generate color gradated
symbols to display regional groundwater elevation changes per year in the alluvium. The
resulting water level trend map and associated discussion are presented in Section 3.2.
Temporal Anal
Hydrographs for selected wells located throughout the South Platte Alluvium Region were
created. Hydrographs provide a detailed record of water level changes over time. Wells for
which hydrographs were created were selected based upon the period of record available,
existence of recent data, and the spatial distribution. Hydrographs were created for twenty
wells.
To create a hydrograph, all historical water level measurements from a given well were queried
from the SPDSS database. Using this historical record, the data set was filtered to only include
the first late winter/early spring (February to April) water level measurement of a given year.
These water level measurements were used to generate a hydrograph for a given well. Spring
water level measurements were used to minimize water level fluctuations due to summer
pumping. Spring water level data will most accurately represent long-term trends in water
levels. Hydrographs for the 20 wells in the South Platte Alluvium Region are presented in
Section 3.3. To aid in comparison, the vertical axis of each hydrograph is presented with a
uniform 10-foot interval and a range of 50 feet.
2.0 Water Level Database
One of the objectives of Task 44 was to create aHydroBase-compatible database with water
level data from the South Platte Alluvium Region. The remainder of this section describes the
SPDSS database with HydroBase compatible tables that are used to store water level data.
2.1 Database Structure
HydroBase is the State of Colorado's database used to manage hydrological data. Appendix D
provides a detailed listing of the database and fields from HydroBase that contain water level
information.
Four data tables contain aquifer water level data. These named WELL, WELL_MEAS,
REF_LOC_ACCURACY and REF_ELEV_ACCURACY.
The WELLS table contains the location, well elevation, permit number, well depth, and many
other types of information about wells. The WELLS table is the core table that links well
information data with water level, geophysical log, and aquifer test data.
SPDSS Phase 3 Task 44.3 TM -Final 10
11/29/2006