Geology topics

Research about Elbert County, Colorado

Source-linked reports with geographic coverage including Elbert County, Colorado.

3 recordsLinked to original sources

USGS2026

Groundwater-level elevations in the bedrock aquifers of the Denver Basin aquifer system, Elbert County, Colorado, 2015–23

Water users in Elbert County, Colorado, rely on groundwater from bedrock aquifers in the Denver Basin aquifer system (upper Dawson, lower Dawson, Denver, Arapahoe, and Laramie-Fox Hills aquifers) for approximately half of their water uses. Withdrawals from the bedrocks aquifers have increased to meet the water use needs of expanding regional population growth and development. The U.S. Geological Survey, in cooperation with the Elbert County Board of County Commissioners, began a study in 2015 to monitor groundwater levels within Elbert County. The primary purpose of this report is to present a summary of groundwater levels measured during the study period (2015–23) and present results from statistical analyses of changes in groundwater-level elevations through time. Discrete groundwater levels were measured at 36 wells within Elbert County. Seven of those wells contained equipment to make and record continuous groundwater-level measurements at hourly intervals. All aquifers, except the lower Dawson aquifer, had only declining groundwater-level elevations in discrete measurements for wells with statistically significant trends. Of the eight statistically significant trends in the lower Dawson aquifer, two wells indicated increasing groundwater-level elevation from discrete measurements. The groundwater-level elevation trend medians in the upper Dawson, lower Dawson, Denver, Arapahoe, and Laramie-Fox Hills aquifers were −0.23, −0.66, −0.64, −0.39, and −0.63 feet per year, respectively, for discrete groundwater-level elevation measurements. Trends in continuous groundwater-level elevations were in agreement with statistically significant trends in discrete groundwater-level elevations for all wells. The groundwater-level elevation trend medians in this study, compared to the overall trends in a 2015−2018 study, both indicated declining groundwater-level elevations except in the upper Dawson aquifer, where the trend direction was opposite, a positive trend from 2015 to 2018 and a negative trend (declining groundwater elevations) from 2015 to 2023. The change in trends within the upper Dawson aquifer may be affected by differences in the study period and the trend analysis applied. Trends during the 2015–23 study period were compared to departures from the median 2015 groundwater-level elevation for each site in each aquifer. In general, the departures from the 2015 median supported trends observed at each site and correlated spatially with greater departures near the western border of Elbert County. Additionally, 30-year precipitation data showing wet and dry periods were overlaid with the departure from the 2015 median to assess groundwater-level patterns in wells in the five aquifers. Departures from the 2015 median groundwater-level elevations appeared greatest during the dry period between 2020 and 2023. Potentiometric-surface maps of the upper and lower Dawson aquifers created from static April 2023 groundwater elevations indicated groundwater-flow direction is generally from the south to the north. Results of this study could be used to guide additional groundwater monitoring in Elbert County and could aid in long-term planning of water resources.

Colorado↗

USGS2019

Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers of Elbert County, Colorado, 2015–18

Public and domestic water supplies in Elbert County, Colorado, rely on groundwater withdrawals from five bedrock aquifers in the Denver Basin aquifer system (lower Dawson, upper Dawson, Denver, Arapahoe, and Laramie-Fox Hills) to meet water demands. Increased pumping in response to regional population growth and development has led to declining groundwater levels in neighboring Douglas County. The U.S. Geological Survey, in cooperation with the Elbert County Board of County Commissioners, began a study in 2015 to monitor groundwater levels within Elbert County. The purpose of this study is to report on groundwater levels measured between April 2015 and June 2018, and analyze trends and changes in groundwater-level elevations throughout the county. Discrete groundwater levels were measured at 42 wells within Elbert County. Six of those wells contained equipment to make and record continuous groundwater-level measurements at hourly intervals. All five aquifers had wells with a rise in groundwater-level elevation and wells with a decline in groundwater-level elevation, based on a relative change in groundwater-level elevation between the April 2015 and April 2018 measurements. All aquifers except the upper Dawson had more wells with significant negative trends in discrete groundwater-level elevations than significant positive trends; however, at least one well within the upper Dawson, lower Dawson, Arapahoe, and Laramie-Fox Hills aquifers had a significant positive trend. Wells screened in the lower Dawson aquifer consistently had the most significant negative trends, with an average trend of −1.96 feet per year (ft/year). The upper Dawson, Denver, Arapahoe, and Laramie-Fox Hills aquifers had average trends of 0.03 ft/year, −1.04 ft/year, −0.46 ft/year, and −0.65 ft/year, respectively. Trends in continuous groundwater-level elevations were in agreement with significant trends in discrete groundwater-level elevations. Potentiometric-surface maps of the upper and lower Dawson aquifers for April 2015 and April 2018 show that differences in hydraulic head from the two measurement periods were greatest along the western part of Elbert County. Results of this study could guide future groundwater monitoring in the county and aid in long-term planning of water resources.

Colorado↗

USGS2001

The Kiowa core, a continuous drill core through the Denver Basin bedrock aquifers at Kiowa, Elbert County, Colorado

The Kiowa core was obtained as a component of the Denver Basin Project, a cooperative research effort to study the evolution of the Denver Basin, Colorado. The Kiowa core provides a virtually continuous stratigraphic record of the Upper Cretaceous and lower Tertiary strata of the Denver Basin. The upper portion of the core recovered strata conventionally referred to as the Arapahoe and Denver Formations and the Dawson Arkose. A prominent unconformity marked by a mature paleosol breaks these strata into two unconformity-bounded sequences; the lower sequence is termed Dl and the upper sequence, D2. Beneath these units and also penetrated by the core occur the Laramie Formation, Fox Hills Sandstone, and Pierre Shale. The site for coring was selected in order to obtain fine-grained strata suitable for both palynological and paleomagnetic analyses. The coring effort recovered 93 percent of the 2,256 ft of rock penetrated, resulting in a nearly continuous record of the sedimentary rocks recording the retreat of the Cretaceous Interior Seaway and the subsequent uplift of the Front Range portion of the Rocky Mountains. Palynological data constrain the Cretaceous-Tertiary boundary to a depth between 878 and 880 ft in the core. The palynological data also serve to bracket the age of the paleosol marking the unconformity between the Dl and D2 sequences to between middle Paleocene and earliest Eocene. The paleomagnetic data are interpreted to represent polarity intervals ranging from polarity subchrons 31r to 28n and polarity subchron 24r. Hydrologic analyses indicate variable aquifer characteristics across the State-defined bedrock aquifers. Individual aquifer units exhibit generally lower water-yield potential than was identified to the west in a core drilled by the U.S. Geological Survey (USGS) in 1987 at Castle Pines, Colorado. Downhole temperature measurements indicate a normal geothermal gradient of 30°C/ km. Perturbations of the gradient may represent active fluid flow through the aquifers penetrated by the core. Petrographic examination of the cored sandstone and mudstone units document both the clay-rich character of the paleosol series marking the boundary between the Dl and D2 sequences, and variation in sandstone composition with depth. The lower sequence (Dl) is characterized by litharenites with a significant volcaniclastic component, while the upper sequence (D2) is more arkosic. Extensive lignite beds occur in Dl in the cored interval and these appear as strong reflectors on the seismic line that passes near the core hole. A set of electric logs, core descriptions, and derived data sets accompany this report.

Colorado↗