Geology topics

L. Rick Arnold

Publications and source records attributed to L. Rick Arnold.

10 recordsLinked to original sources

USGS2020

Hydrogeologic characterization, groundwater chemistry, and vulnerability assessment, Ute Mountain Ute Reservation, Colorado and Utah

The U.S. Geological Survey, in cooperation with the Ute Mountain Ute Tribe (UMUT), initiated a study in 2016 to increase understanding of the hydrogeology and chemistry of groundwater within select areas of the Ute Mountain Ute Reservation (UMUR) in Colorado and Utah, identify vulnerabilities to the system and other natural resources, and outline information needs to aid in the understanding and protection of groundwater resources. The results presented for this study can be used to support the UMUT’s goal of protecting their vital groundwater resources on the UMUR. Hydrogeologic conditions were characterized for the surficial aquifer contained in Quaternary-age unconsolidated surficial deposits and the Dakota aquifer contained in the Cretaceous-age Dakota Sandstone. In the surficial aquifer, median depth to water ranges from about 5.4 to 17.2 feet below land surface in the Farm and Ranch Enterprise area and 11 to 34 feet below land surface in the Towaoc area, and the water table slopes generally southwest or south. A map of depth to the top of the Dakota Sandstone was constructed from existing well data. Depths range from zero in outcrop areas to more than 3,000 feet below land surface on mesas in the southeastern part of the UMUR. Groundwater-chemistry data were collected by the UMUT from 13 springs and 31 wells from 1996 through 2017. Specific conductance was much lower for samples from springs than from wells; median values were 512 and 6,024 microsiemens per centimeter at 25 degrees Celsius, respectively. Spring samples were well oxygenated. A few well samples were anoxic (dissolved oxygen concentrations less than 0.5 milligrams per liter [mg/L]), indicating reducing conditions in the aquifer. About 75 percent of spring samples had fresh water (total dissolved solids concentrations less than 1,000 mg/L), and about 85 percent of well samples had brackish or highly saline water (total dissolved solids concentrations greater than 1,000 mg/L). Water type for springs on the Ute Mountains was calcium bicarbonate. Lower-altitude springs had a calcium-sulfate water type. Most well samples had sodium as the dominant cation, and sulfate, bicarbonate, and chloride as the dominant anions. Fluoride concentrations in about 45 percent of well samples were greater than an agricultural-use standard of 2 mg/L. Nitrate plus nitrite concentrations in most spring and well samples were less than about 1.6 mg/L per liter. Concentrations in samples from wells in the irrigated agricultural area were elevated; the maximum concentration was 78.5 mg/L. About one-half of the trace-element samples had concentrations that were less than laboratory reporting limits. Only aluminum, arsenic, and selenium in spring samples, and boron and selenium in well samples, were detected at concentrations greater than surface-water standards or water-quality standards for agricultural use of groundwater. Only three organic compounds, the pesticides alachlor and atrazine and the volatile organic compound di(2-ethylhexyl) phthalate, were detected in well samples. The Escherichia coli bacteria was detected in 47 and 23 percent of samples from wells and springs, respectively. The E. coli detections included samples from three culturally significant springs, which did not meet the UMUT cultural-use standard of total absence of E. coli. Tritium and carbon-14 were the primary environmental tracers used for interpreting groundwater ages for Lopez 2 Spring and five wells (AP–1, 5000 Block, Cottonwood Spring, Goodknight, and SE Toe). Water from the AP–1 well contained a mixture of pre- and post-1950s recharge. Tritium and carbon-14 recharge ages for Lopez 2 Spring (post-1950s in age), Goodknight and SE Toe wells (pre-1950s in age), and Cottonwood Spring well (primarily pre-1950s in age) are supported by helium-4 data. The helium-4 data for the 5000 Block well are inconsistent with the tritium and carbon-14 age of pre-1950s recharge because of interference caused by high methane concentrations in the water. Springs and surficial deposits are more vulnerable to contamination from anthropogenic chemicals than deeper bedrock wells. Bedrock aquifers are vulnerable in areas where the geologic formations containing the aquifers are exposed at the land surface. Groundwater in deep bedrock aquifers is likely thousands of years old and is not currently affected by present-day land uses. Both shallow and deep groundwater are vulnerable to naturally occurring salts and minerals, such as of total dissolved solids, major ions, nitrate, and trace elements. Effects of a changing climate on water resources and other ecological characteristics of the UMUR could include changes in evapotranspiration, a decrease in snowpack, decreased aquifer recharge and flow of springs, a decrease in soil moisture, and increased occurrence of wildfires and forest mortality. Of particular interest for the UMUT are possible effects of a changing climate on medicinal and culturally important plants and springs Several information needs were identified during this study that would aid in the understanding and protection of groundwater resources on the UMUR. These include well-completion information for bedrock wells, the collection of environmental tracer data at additional wells, the addition of methane and hydrocarbon analysis to well sampling plans, and the resampling of springs and wells that were last sampled in 2002 or earlier.

Colorado↗

USGS2016

Groundwater and surface-water interaction, water quality, and processes affecting loads of dissolved solids, selenium, and uranium in Fountain Creek, near Pueblo, Colorado, 2012–2014

In 2012, the U.S. Geological Survey, in cooperation with the Arkansas River Basin Regional Resource Planning Group, initiated a study of groundwater and surface-water interaction, water quality, and loading of dissolved solids, selenium, and uranium to Fountain Creek near Pueblo, Colorado, to improve understanding of sources and processes affecting loading of these constituents to streams in the Arkansas River Basin. Fourteen monitoring wells were installed in a series of three transects across Fountain Creek near Pueblo, and temporary streamgages were established at each transect to facilitate data collection for the study. Groundwater and surface-water interaction was characterized by using hydrogeologic mapping, groundwater and stream-surface levels, groundwater and stream temperatures, vertical hydraulic-head gradients and ratios of oxygen and hydrogen isotopes in the hyporheic zone, and streamflow mass-balance measurements. Water quality was characterized by collecting periodic samples from groundwater, surface water, and the hyporheic zone for analysis of dissolved solids, selenium, uranium, and other selected constituents and by evaluating the oxidation-reduction condition for each groundwater sample under different hydrologic conditions throughout the study period. Groundwater loads to Fountain Creek and in-stream loads were computed for the study area, and processes affecting loads of dissolved solids, selenium, and uranium were evaluated on the basis of geology, geochemical conditions, land and water use, and evapoconcentration. During the study period, the groundwater-flow system generally contributed flow to Fountain Creek and its hyporheic zone (as a single system) except for the reach between the north and middle transects. However, the direction of flow between the stream, the hyporheic zone, and the near-stream aquifer was variable in response to streamflow and stage. During periods of low streamflow, Fountain Creek generally gained flow from groundwater. However, during periods of high streamflow, the hydraulic gradient between groundwater and the stream temporarily reversed, causing the stream to lose flow to groundwater. Concentrations of dissolved solids, selenium, and uranium in groundwater generally had greater spatial variability than surface water or hyporheic-zone samples, and constituent concentrations in groundwater generally were greater than in surface water. Constituent concentrations in the hyporheic zone typically were similar to or intermediate between concentrations in groundwater and surface water. Concentrations of dissolved solids, selenium, uranium, and other constituents in groundwater samples collected from wells located on the east side of the north monitoring well transect were substantially greater than for other groundwater, surface-water, and hyporheic-zone samples. With one exception, groundwater samples collected from wells on the east side of the north transect exhibited oxic to mixed (oxic-anoxic) conditions, whereas most other groundwater samples exhibited anoxic to suboxic conditions. Concentrations of dissolved solids, selenium, and uranium in surface water generally increased in a downstream direction along Fountain Creek from the north transect to the south transect and exhibited an inverse relation to streamflow with highest concentration occurring during periods of low streamflow and lowest concentrations occurring during periods of high streamflow. Groundwater loads of dissolved solids, selenium, and uranium to Fountain Creek were small because of the small amount of groundwater flowing to the stream under typical low-streamflow conditions. In-stream loads of dissolved solids, selenium, and uranium in Fountain Creek varied by date, primarily in relation to streamflow at each transect and were much larger than computed constituent loads from groundwater. In-stream loads generally decreased with decreases in streamflow and increased as streamflow increased. In-stream loads of dissolved solids and selenium increased between the north and middle transects but generally decreased between the middle and south transects. By contrast, uranium loads generally decreased between the north and middle transects but increased between the middle and south transects. In-stream load differences between transects appear primarily to be related to differences in streamflow. However, because groundwater typically flows to Fountain Creek under low-flow conditions, and groundwater has greater concentrations of dissolved solids, selenium, and uranium than surface water in Fountain Creek, increases in loads between transects likely are affected by inflow of groundwater to the stream, which can account for a substantial proportion of the in-stream load difference between transects. When loads decreased between transects, the primary cause likely was decreased streamflow as a result of losses to groundwater and flow through the hyporheic zone. However, localized groundwater inflow likely attenuated the magnitude by which the in-stream loads decreased. The combination of localized soluble geologic sources and oxic conditions likely is the primary reason for the occurrence of high concentrations of dissolved solids, selenium, and uranium in groundwater on the east side of the north monitoring well transect. To evaluate conditions potentially responsible for differences in water quality and redox conditions, physical characteristics such as depth to water, saturated thickness, screen depth below the water table, screen height above bedrock, and aquifer hydraulic conductivity were compared by using Wilcoxon rank-sum tests. Results indicated no significant difference between depth to water, screen height above bedrock, and hydraulic conductivity for groundwater samples collected from wells on the east side of the north transect and groundwater samples from all other wells. However, saturated thickness and screen depth below the water table both were significantly smaller for groundwater samples collected from wells on the east side of the north transect than for groundwater samples from other wells, indicating that these characteristics might be related to the elevated constituent concentrations found at that location. Similarly, saturated thickness and screen depth below the water table were significantly smaller for groundwater samples under oxic or mixed (oxic-anoxic) conditions than for those under anoxic to suboxic conditions. The greater constituent concentrations at wells on the east side of the north transect also could, in part, be related to groundwater discharge from an unnamed alluvial drainage located directly upgradient from that location. Although the quantity and quality of water discharging from the drainage is not known, the drainage appears to collect water from a residential area located upgradient to the east of the wells, and groundwater could become concentrated in nitrate and other dissolved constituents before flowing through the drainage. High levels of nitrate, whether from anthropogenic or natural geologic sources, could promote more soluble forms of selenium and other constituents by affecting the redox condition of groundwater. Whether oxic conditions at wells on the east side of the north transect are the result of physical characteristics or of groundwater inflow from the alluvial drainage, the oxic conditions appear to cause increased dissolution of minerals from the shallow shale bedrock at that location. Because ratios of hydrogen and oxygen isotopes indicate evaporation likely has not had a substantial effect on groundwater, constituent concentrations at that location likely are not the result of evapoconcentration.

Colorado↗

USGS2012

Using hydrogeology to identify the source of groundwater to Montezuma Well, a natural spring in central Arizona: part 1

Montezuma Well is a natural spring located within a “sinkhole” in the desert environment of the Verde Valley in Central Arizona. It is managed by the National Park Service as part of Montezuma Castle National Monument. Because of increasing development of groundwater in the area, this research was undertaken to better understand the sources of groundwater to Montezuma Well. The use of well logs and geophysics provides details on the geology in the area around Montezuma Well. This includes characterizing the extent and position of a basalt dike that intruded a deep fracture zone. This low permeability barrier forces groundwater to the surface at the Montezuma Well “pool” with sufficient velocity to entrain sand-sized particles from underlying bedrock. Permeable fractures along and above the basalt dike provide conduits that carry deep sourced carbon dioxide to the surface, which can dissolve carbonate minerals along the transport path in response to the added carbon dioxide. At the ground surface, CO 2 degasses, depositing travertine. Geologic cross sections, rock geochemistry, and semi-quantitative groundwater flow modeling provide a hydrogeologic framework that indicates groundwater flow through a karstic limestone at depth (Redwall Limestone) as the most significant source of groundwater to Montezuma Well. Additional groundwater flow from the overlying formations (Verde Formation and Permian Sandstones) is a possibility, but significant flow from these units is not indicated.

Arizona↗

USGS2012

Comparison of two methods for estimating base flow in selected reaches of the South Platte River, Colorado

The U.S. Geological Survey, in cooperation with the Colorado Water Conservation Board, compared two methods for estimating base flow in three reaches of the South Platte River between Denver and Kersey, Colorado. The two methods compared in this study are the Mass Balance and the Pilot Point methods. Base-flow estimates made with the two methods were based upon a 54-year period of record (1950 to 2003). The Mass Balance method for estimating base flow is based on a mass balance of all known inflows to and outflows from a given stream reach, with the equation being solved for groundwater flow into or out of the reach. A positive mass balance indicates a gaining reach (base flow) and a negative balance indicates a losing reach. The mass balance was calculated using daily mean streamflow, wastewater treatment plant discharge, and stream diversion data. Monthly mean base flow was calculated as the average of all daily mean mass-balance results for a given month. The Pilot Point method is based on a daily mean mass balance of all inflows to and outflows from a stream reach. The Pilot Point differs from the Mass Balance method in that extreme daily mass-balance results are constrained utilizing two analytical solutions that represent the maximum possible streamflow gain or loss. Additionally, the Pilot Point method utilizes a smoothing function, based on a moving average of the daily constrained mass-balance results. The moving average for this study utilized a moving-average period, called the bin width, of 61 days. The maximum and minimum base-flow constraints and the smoothing function are utilized to provide base-flow estimates that exhibit reasonable maximum values and temporal variability consistent with the concept of groundwater flow being gradual and slow. Both the Mass Balance and Pilot Point results provided similar patterns in annual and monthly base flow. All three reaches were indicated to be gaining reaches, particularly after about 1970, with the magnitude of base flow increasing downstream. This degree of similarity between the two methods was expected because both methods are based on a streamflow mass balance. The magnitude of estimates provided by the two methods was measurably different. The stream gains and losses estimated using the Mass Balance method were consistently more variable and of greater magnitude than those estimated using the Pilot Point method. In the Denver to Henderson reach, the median estimated annual mean base flow was 34.0 cubic feet per second (ft 3 /s) using the Mass Balance method and was 39.1 ft 3 /s using the Pilot Point method. In the Henderson to Fort Lupton reach, the median estimated annual mean base flow was 50.0 ft 3 /s using the Mass Balance method and was 40.0 ft 3 /s using the Pilot Point method. In the Fort Lupton to Kersey reach, the median estimated annual mean base flow was 234 ft 3 /s using the Mass Balance method and was 214 ft 3 /s using the Pilot Point method. The Mass Balance results were quite variable over time such that they appeared suspect with respect to the concept of groundwater flow as being gradual and slow. The large degree of variability in the day-to-day and month-to-month Mass Balance results is likely the result of many factors. These factors could include ungaged stream inflows or outflows, short-term streamflow losses to and gains from temporary bank storage, and any lag in streamflow accounting owing to streamflow lag time of flow within a reach. The Pilot Point time series results were much less variable than the Mass Balance results and extreme values were effectively constrained. Less day-to-day variability, smaller magnitude extreme values, and smoother transitions in base-flow estimates provided by the Pilot Point method are more consistent with a conceptual model of groundwater flow being gradual and slow. The Pilot Point method provided a better fit to the conceptual model of groundwater flow and appeared to provide reasonable estimates of base flow.

Colorado↗

USGS2011

Well installation, single-well testing, and particle-size analysis for selected sites in and near the Lost Creek Designated Ground Water Basin, north-central Colorado, 2003-2004

This report describes results from a groundwater data-collection program completed in 2003-2004 by the U.S. Geological Survey in support of the South Platte Decision Support System and in cooperation with the Colorado Water Conservation Board. Two monitoring wells were installed adjacent to existing water-table monitoring wells. These wells were installed as well pairs with existing wells to characterize the hydraulic properties of the alluvial aquifer and shallow Denver Formation sandstone aquifer in and near the Lost Creek Designated Ground Water Basin. Single-well tests were performed in the 2 newly installed wells and 12 selected existing monitoring wells. Sediment particle size was analyzed for samples collected from the screened interval depths of each of the 14 wells. Hydraulic-conductivity and transmissivity values were calculated after the completion of single-well tests on each of the selected wells. Recovering water-level data from the single-well tests were analyzed using the Bouwer and Rice method because test data most closely resembled those obtained from traditional slug tests. Results from the single-well test analyses for the alluvial aquifer indicate a median hydraulic-conductivity value of 3.8 x 10-5 feet per second and geometric mean hydraulic-conductivity value of 3.4 x 10-5 feet per second. Median and geometric mean transmissivity values in the alluvial aquifer were 8.6 x 10-4 feet squared per second and 4.9 x 10-4 feet squared per second, respectively. Single-well test results for the shallow Denver Formation sandstone aquifer indicate a median hydraulic-conductivity value of 5.4 x 10-6 feet per second and geometric mean value of 4.9 x 10-6 feet per second. Median and geometric mean transmissivity values for the shallow Denver Formation sandstone aquifer were 4.0 x 10-5 feet squared per second and 5.9 x 10-5 feet squared per second, respectively. Hydraulic-conductivity values for the alluvial aquifer in and near the Lost Creek Designated Ground Water Basin generally were greater than hydraulic-conductivity values for the Denver Formation sandstone aquifer and less than hydraulic-conductivity values for the alluvial aquifer along the main stem of the South Platte River Basin reported by previous studies. Particle sizes were analyzed for a total of 14 samples of material representative of the screened interval in each of the 14 wells tested in this study. Of the 14 samples collected, 8 samples represent the alluvial aquifer and 6 samples represent the Denver Formation sandstone aquifer in and near the Lost Creek Designated Ground Water Basin. The sampled alluvial aquifer material generally contained a greater percentage of large particles (larger than 0.5 mm) than the sampled sandstone aquifer material. Alternatively, the sampled sandstone aquifer material generally contained a greater percentage of fine particles (smaller than 0.5 mm) than the sampled alluvial aquifer material consistent with the finding that the alluvial aquifer is more conductive than the sandstone aquifer in the vicinity of the Lost Creek Designated Ground Water Basin.

Open-File Report↗

USGS2011

Water and rock geochemistry, geologic cross sections, geochemical modeling, and groundwater flow modeling for identifying the source of groundwater to Montezuma Well, a natural spring in central Arizona

The National Park Service (NPS) seeks additional information to better understand the source(s) of groundwater and associated groundwater flow paths to Montezuma Well in Montezuma Castle National Monument, central Arizona. The source of water to Montezuma Well, a flowing sinkhole in a desert setting, is poorly understood. Water emerges from the middle limestone facies of the lacustrine Verde Formation, but the precise origin of the water and its travel path are largely unknown. Some have proposed artesian flow to Montezuma Well through the Supai Formation, which is exposed along the eastern margin of the Verde Valley and underlies the Verde Formation. The groundwater recharge zone likely lies above the floor of the Verde Valley somewhere to the north or east of Montezuma Well, where precipitation is more abundant. Additional data from groundwater, surface water, and bedrock geology are required for Montezuma Well and the surrounding region to test the current conceptual ideas, to provide new details on the groundwater flow in the area, and to assist in future management decisions. The results of this research will provide information for long-term water resource management and the protection of water rights.

Arizona↗

USGS2010

Geographic information system datasets of regolith-thickness data, regolith-thickness contours, raster-based regolith thickness, and aquifer-test and specific-capacity data for the Lost Creek Designated Ground Water Basin, Weld, Adams, and Arapahoe Counties, Colorado

These datasets were compiled in support of U.S. Geological Survey Scientific-Investigations Report 2010-5082-Hydrogeology and Steady-State Numerical Simulation of Groundwater Flow in the Lost Creek Designated Ground Water Basin, Weld, Adams, and Arapahoe Counties, Colorado. The datasets were developed by the U.S. Geological Survey in cooperation with the Lost Creek Ground Water Management District and the Colorado Geological Survey. The four datasets are described as follows and methods used to develop the datasets are further described in Scientific-Investigations Report 2010-5082: (1) ds507_regolith_data: This point dataset contains geologic information concerning regolith (unconsolidated sediment) thickness and top-of-bedrock altitude at selected well and test-hole locations in and near the Lost Creek Designated Ground Water Basin, Weld, Adams, and Arapahoe Counties, Colorado. Data were compiled from published reports, consultant reports, and from lithologic logs of wells and test holes on file with the U.S. Geological Survey Colorado Water Science Center and the Colorado Division of Water Resources. (2) ds507_regthick_contours: This dataset consists of contours showing generalized lines of equal regolith thickness overlying bedrock in the Lost Creek Designated Ground Water Basin, Weld, Adams, and Arapahoe Counties, Colorado. Regolith thickness was contoured manually on the basis of information provided in the dataset ds507_regolith_data. (3) ds507_regthick_grid: This dataset consists of raster-based generalized thickness of regolith overlying bedrock in the Lost Creek Designated Ground Water Basin, Weld, Adams, and Arapahoe Counties, Colorado. Regolith thickness in this dataset was derived from contours presented in the dataset ds507_regthick_contours. (4) ds507_welltest_data: This point dataset contains estimates of aquifer transmissivity and hydraulic conductivity at selected well locations in the Lost Creek Designated Ground Water Basin, Weld, Adams, and Arapahoe Counties, Colorado. This dataset also contains hydrologic information used to estimate transmissivity from specific capacity at selected well locations. Data were compiled from published reports, consultant reports, and from well-test records on file with the U.S. Geological Survey Colorado Water Science Center and the Colorado Division of Water Resources.

Data Series↗

USGS2009

Depth to water, saturated thickness, and other geospatial datasets used in the design and installation of a groundwater monitoring-well network in the High Plains Aquifer, Colorado

These datasets were compiled in support of U.S. Geological Survey Data Series 456, Design and Installation of a Groundwater Monitoring-Well Network in the High Plains Aquifer, Colorado. These datasets were developed as part of a cooperative project between the U.S. Geological Survey and the Colorado Department of Agriculture. The purpose of the project was to design a 30-well network and install 20 of the 30 wells to characterize water quality in the High Plains aquifer in areas of irrigated agriculture in Colorado. The five datasets are described as follows and are further described in Data Series 456: (1) ds472_dtw: This dataset represents the depth to groundwater in the High Plains Aquifer in Colorado in 2000. This grid was used to determine areas where the depth to water was less than 200 feet below land surface. (2) Ds472_sat: This dataset represents the saturated thickness of the High Plains aquifer within Colorado in 2000. This grid was used to determine areas where the saturated thickness was greater than 50 feet. (3) Ds472_equalareas: This dataset includes 30 equal-area polygons overlying the High Plains Aquifer in Colorado having a depth to water less than 200 feet, a saturated thickness greater than 50 feet, and underlying irrigated agricultural lands. (4) Ds472_randomsites: This dataset includes 90 randomly-generated potential groundwater sampling sites. This dataset provides a first, second, and third choice placed within the 30 equal area polygons of dataset dsXX_equalareas. (5) Ds472_welldata: This dataset includes point locations and well completion data for the 20 wells installed as part of this project. The datasets that pertain to this report can be found on the U.S. Geological Survey's NSDI (National Spatial Data Infrastructure) Node, the links are provided on the sidebar.

Colorado↗

USGS2006

Application of a stream-aquifer model to Monument Creek for development of a method to estimate transit losses for reusable water, El Paso County, Colorado

The U.S. Geological Survey, in cooperation with Colorado Springs Utilities, the Colorado Water Conservation Board, and the El Paso County Water Authority, began a study in 2004 to (1) apply a stream-aquifer model to Monument Creek, (2) use the results of the modeling to develop a transit-loss accounting program for Monument Creek, (3) revise the existing transit-loss accounting program for Fountain Creek to incorporate new water-management strategies and allow for incorporation of future changes in water-management strategies, and (4) integrate the two accounting programs into a single program with a Web-based user interface. The purpose of this report is to present the results of applying a stream-aquifer model to the Monument Creek study reach. Transit losses were estimated for reusable-water flows in Monument Creek that ranged from 1 to 200 cubic feet per second (ft 3 /s) and for native streamflows that ranged from 0 to 1,000 ft 3 /s. Transit losses were estimated for bank-storage, channel-storage, and evaporative losses. The same stream-aquifer model used in the previously completed (1988) Fountain Creek study was used in the Monument Creek study. Sixteen model nodes were established for the Monument Creek study reach, defining 15 subreaches. Channel length, aquifer length, and aquifer width for the subreaches were estimated from available topographic and geologic maps. Thickness of alluvial deposits and saturated thickness were estimated using lithologic and water-level data from about 100 wells and test holes in or near the Monument Creek study reach. Estimated average transmissivities for the subreaches ranged from 2,000 to 12,000 feet squared per day, and a uniform value of 0.20 was used for storage coefficient. Qualitative comparison of recorded and simulated streamflow at the downstream node for the calibration and verification simulations indicated that the two streamflows compared reasonably well. No adjustments were made to the model parameters. Differences between recorded and simulated streamflow volumes for all calibration and verification simulations ranged from about –8.8 to 7.5 percent; the total error for all simulations was about –0.7 percent. The model was used to estimate bank-storage losses for 10 to 15 native streamflows for each reusable-water flow of 1, 3, 5, 7, 10, 15, 20, 30, 40, 50, 100, and 200 ft 3 /s. Then the 10 to 15 bank-storage loss values were used in least-squares linear regression to estimate a relation between bank-storage loss and native streamflow for each of the 12 reusable-water flow rates. The 12 regression relations then were used to develop “look-up” tables of bank-storage loss for reusable-water flows ranging from 1 to 200 ft 3 /s (in 1-ft 3 /s increments). Additional model simulations indicated that (1) when the ratio of downstream native streamflow to upstream native streamflow was less than 1, bank-storage loss generally increased and (2) when the ratio of downstream native streamflow to upstream native streamflow was larger than 1, bank-storage loss generally decreased. These results were used to develop a bank-storage loss adjustment factor based on the ratio of native streamflow at the downstream node to native streamflow at the upstream node. The model also was used to estimate a recovery period, which is the length of time needed for the bank-storage loss to return to the stream. The recovery period was 1 day for six subreaches; 2 days for four subreaches; between 3 and 12 days for four subreaches; and 28 days for one subreach. Channel-storage losses are about 10 percent of the reusable-water flow for most of the subreaches, except for two subreaches, where the channel-storage losses are about 20 percent, and one subreach, where the losses are about 30 percent, owing to the greater channel lengths. Evaporative losses were estimated by the use of monthly pan-evaporation data and the incremental increase in stream width resulting from any reusable-water flows. Monthly pan-evaporation data were converted to a daily rate. The daily rate, when multiplied by the stream-width increase (in feet) that results from reusable-water flow and by the subreach length (in miles) gives the daily evaporative loss in cubic feet per second.

Colorado↗

USGS2003

Hydrogeology of a Biosolids-Application Site Near Deer Trail, Colorado, 1993-99

This report presents hydrogeology data and interpretations resulting from two studies related to biosolids applications at the Metro Wastewater Reclamation District property near Deer Trail, Colorado, done by the U.S. Geological Survey in cooperation with the Metro Wastewater Reclamation District: (1) a 1993-99 study of hydrology and water quality for the Metro Wastewater Reclamation District central property and (2) a 1999 study of regional bedrock-aquifer structure and local ground-water recharge. Biosolids were applied as a fertilizer during late 1993 through 1999. The 1993 Metro Wastewater Reclamation District property boundary constitutes the study area, but hydrogeologic structure maps for a much larger area are included in the report. The study area is located on the eastern margin of the Denver Basin, a bowl-shaped sequence of sedimentary rocks. The uppermost bedrock formations in the vicinity of the study area consist of the Pierre Shale, the Fox Hills Sandstone, and the Laramie Formation, parts of which comprise the Laramie-Fox Hills hydrostratigraphic unit and thus, where saturated, the Laramie-Fox Hills aquifer. In the vicinity of the study area, the Laramie-Fox Hills hydrostratigraphic unit dips gently to the northwest, crops out, and is partially eroded. The Laramie-Fox Hills aquifer is either absent or not fully saturated within the Metro Wastewater Reclamation District properties, although this aquifer is the principal aquifer used for domestic supply in the vicinity of the study area. Yield was small from two deep monitoring wells in the Laramie-Fox Hills aquifer within the study area. Depth to water in these wells was about 110 and 150 feet below land surface, and monthly water levels fluctuated 0.5 foot or less. Alluvial aquifers also are present in the unconsolidated sand and loess deposits in the valleys of the study area. Interactions of the deeper parts of the Laramie-Fox Hills aquifer with shallow ground water in the study area include a general close hydraulic connection between alluvial and bedrock aquifers, recharge of the Cottonwood Creek and much of the Muddy Creek alluvial aquifers by the bedrock aquifer, and possible recharge of the bedrock aquifer by a Rattlesnake Creek tributary. Some areas of shallow ground water were recharged by infiltration from rain or ponds, but other areas likely were recharged by other ground water. Data for shallow ground water indicate that ground-water recharge takes less than a day at some sites to about 40 years at another site. Depth to shallow ground water in the study area ranged from about 2 feet to about 37 feet below land surface. Shallow ground-water levels likely were affected by evapotranspiration. Ground water is present in shallow parts of the bedrock aquifer or in alluvial aquifers in four drainage basins: Badger Creek, Cottonwood Creek, Muddy Creek, and Rattlesnake Creek. These drainage basins generally contained only ephemeral streams, which flow only after intense rain.

Water-Resources Investigations Report↗