Evaluation of the ground-water flow model for northern Utah Valley, Utah, updated to conditions through 2002 (original) (raw)
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Open-File Report, 1986
u.S. Geological Survey ABSTAACI' 'Ihis report was pre:flared in cooperation with several organizations in the Salt Lake Valley and with the Central Utah Water Conservancy District to present results of a study to determine changes in the groundwater conditions in Salt Lake Valley, Utah, from 1969 to 1983, and to predict the aquifer resPJnse to projected withdrawals. The average annual recharge and discharge from the groundwater reservoir in Salt Lake Valley, Utah, during 1969-82 were estimated to be about 352,000 and 353,000 acre-feet per year. Withdrawals from wells increased from 107,000 acre-feet per year during 1964-68 to 117,000 acre-feet per year during 1969-82. The greatest increase in use was for public supply and institutions which increased from 35,000 acre-feet per year during 1964-68 to 46,700 acre-feet per year during 1969-82. From 1969 to 1983 water levels declined from 5 to 15 feet in the southeast pa.rt of the valley where pumpa.ge fran large plblic-supply wells was greater during 1969-82 than during previous years. From February-March 1969 to February-March 1983 the quantity of ground water in storage in salt Lake Valley increased by about 33,000 acre-feet. A digital-computer model was calibrated to simulate, in threedimensions, the groundwater flow in the principal and shallow-unconfined aquifers in Salt Lake Valley. Simulations were made to project the resp:mse to a:mtinuing withdrawals through 2020. Alternative pumping rates used were (1) the 1982 rate of pumpage and (2) increasing the 1982 rate of pumpage by 65,000 acre-feet. The simulation at the increased rate of p.1IIIpa.ge indicated that drawdowns would reach 40-60 feet in the area east of Sandy. About 75 percent of the increased withdrawal was salvaged from water that otherwise would have been discharged to the Jordan River and its tributaries.
Simulating Water-Quality Trends in Public-Supply Wells in Transient Flow Systems
Groundwater, 2014
Models need not be complex to be useful. An existing groundwater-flow model of Salt Lake Valley, Utah, was adapted for use with convolution-based advective particle tracking to explain broad spatial trends in dissolved solids. This model supports the hypothesis that water produced from wells is increasingly younger with higher proportions of surface sources as pumping changes in the basin over time. At individual wells, however, predicting specific water-quality changes remains challenging. The influence of pumping-induced transient groundwater flow on changes in mean age and source areas is significant. Mean age and source areas were mapped across the model domain to extend the results from observation wells to the entire aquifer to see where changes in concentrations of dissolved solids are expected to occur. The timing of these changes depends on accurate estimates of groundwater velocity. Calibration to tritium concentrations was used to estimate effective porosity and improve correlation between source area changes, age changes, and measured dissolved solids trends. Uncertainty in the model is due in part to spatial and temporal variations in tracer inputs, estimated tracer transport parameters, and in pumping stresses at sampling points. For tracers such as tritium, the presence of two-limbed input curves can be problematic because a single concentration can be associated with multiple disparate travel times. These shortcomings can be ameliorated by adding hydrologic and geologic detail to the model and by adding additional calibration data. However, the Salt Lake Valley model is useful even without such small-scale detail.
Scientific Investigations Report, 2013
The Equus Beds aquifer is a primary water-supply source for Wichita, Kansas and the surrounding area because of shallow depth to water, large saturated thickness, and generally good water quality. Substantial water-level declines in the Equus Beds aquifer have resulted from pumping groundwater for agricultural and municipal needs, as well as periodic drought conditions. In March 2006, the city of Wichita began construction of the Equus Beds Aquifer Storage and Recovery project to store and later recover groundwater, and to form a hydraulic barrier to the known chloride-brine plume near Burrton, Kansas. In October 2009, the U.S. Geological Survey, in cooperation with the city of Wichita, began a study to determine groundwater flow in the area of the Wichita well field, and chloride transport from the Arkansas River and Burrton oilfield to the Wichita well field. Groundwater flow was simulated for the Equus Beds aquifer using the three-dimensional finite-difference groundwater-flow model MODFLOW-2000. The model simulates steady-state and transient conditions. The groundwater-flow model was calibrated by adjusting model input data and model geometry until model results matched field observations within an acceptable level of accuracy. The root mean square (RMS) error for water-level observations for the steady-state calibration simulation is 9.82 feet. The ratio of the RMS error to the total head loss in the model area is 0.049 and the mean error for water-level observations is 3.86 feet. The difference between flow into the model and flow out of the model across all model boundaries is-0.08 percent of total flow for the steady-state calibration. The RMS error for water-level observations for the transient calibration simulation is 2.48 feet, the ratio of the RMS error to the total head loss in the model area is 0.0124, and the mean error for water-level observations is 0.03 feet. The RMS error calculated for observed and simulated base flow gains or losses for the Arkansas River for the transient simulation is 7,916,564 cubic feet per day (91.6 cubic feet per second) and the RMS error divided by (/) the total
The North Platte Natural Resources District (NPNRD) has been actively collecting data and studying groundwater resources because of concerns about the future availability of the highly inter-connected surface-water and groundwater resources. This report, prepared by the U.S. Geological Survey in cooperation with the North Platte Natural Resources Dis¬trict, describes a groundwater-flow model of the North Platte River valley from Bridgeport, Nebraska, extending west to 6 miles into Wyoming. The model was built to improve the understanding of the interaction of surface-water and ground¬water resources, and as an optimization tool, the model is able to analyze the effects of water-management options on the simulated stream base flow of the North Platte River. The groundwater system and related sources and sinks of water were simulated using a newton formulation of the U.S. Geo¬logical Survey modular three-dimensional groundwater model, referred to as MODFLOW–NWT, which provided an improved ability to solve nonlinear unconfined aquifer simulations with wetting and drying of cells. Using previously published aquifer-base-altitude contours in conjunction with newer test-hole and geophysical data, a new base-of-aquifer altitude map was generated because of the strong effect of the aquifer-base topography on groundwater-flow direction and magnitude. The largest inflow to groundwater is recharge originating from water leaking from canals, which is much larger than recharge originating from infiltration of precipita¬tion. The largest component of groundwater discharge from the study area is to the North Platte River and its tributar¬ies, with smaller amounts of discharge to evapotranspiration and groundwater withdrawals for irrigation. Recharge from infiltration of precipitation was estimated with a daily soil-water-balance model. Annual recharge from canal seepage was estimated using available records from the Bureau of Reclamation and then modified with canal-seepage potentials estimated using geophysical data. Groundwater withdraw¬als were estimated using land-cover data, precipitation data, and published crop water-use data. For fields irrigated with surface water and groundwater, surface-water deliveries were subtracted from the estimated net irrigation requirement, and groundwater withdrawal was assumed to be equal to any demand unmet by surface water. The groundwater-flow model was calibrated to measured groundwater levels and stream base flows estimated using the base-flow index method. The model was calibrated through automated adjustments using statistical techniques through parameter estimation using the parameter estimation suite of software (PEST). PEST was used to adjust 273 parameters, grouped as hydraulic conductivity of the aquifer, spatial multipliers to recharge, temporal multipliers to recharge, and two specific recharge parameters. Base flow of the North Platte River at Bridgeport, Nebraska, streamgage near the eastern, downstream end of the model was one of the primary calibration targets. Simulated base flow reasonably matched estimated base flow for this streamgage during 1950–2008, with an average difference of 15 percent. Overall, 1950–2008 simulated base flow followed the trend of the estimated base flow reasonably well, in cases with generally increasing or decreasing base flow from the start of the simulation to the end. Simulated base flow also matched estimated base flow reasonably well for most of the North Platte River tributar¬ies with estimated base flow. Average simulated groundwater budgets during 1989–2008 were nearly three times larger for irrigation seasons than for non-irrigation seasons. The calibrated groundwater-flow model was used with the Groundwater-Management Process for the 2005 version of the U.S. Geological Survey modular three-dimensional groundwater model, MODFLOW–2005, to provide a tool for the NPNRD to better understand how water-management deci¬sions could affect stream base flows of the North Platte River at Bridgeport, Nebr., streamgage in a future period from 2008 to 2019 under varying climatic conditions. The simulation-optimization model was constructed to analyze the maximum increase in simulated stream base flow that could be obtained with the minimum amount of reductions in groundwater withdrawals for irrigation. A second analysis extended the first to analyze the simulated base-flow benefit of groundwater withdrawals along with application of intentional recharge, that is, water from canals being released into rangeland areas with sandy soils. With optimized groundwater withdrawals and intentional recharge, the maximum simulated stream base flow was 15–23 cubic feet per second (ft3/s) greater than with no management at all, or 10–15 ft3/s larger than with managed groundwater withdrawals only. These results indicate not only the amount that simulated stream base flow can be increased by these management options, but also the locations where the management options provide the most or least benefit to the simulated stream base flow. For the analyses in this report, simulated base flow was best optimized by reductions in groundwater withdrawals north of the North Platte River and in the western half of the area. Intentional recharge sites selected by the optimization had a complex distribution but were more likely to be closer to the North Platte River or its tributaries. Future users of the simulation-optimization model will be able to modify the input files as to type, location, and timing of constraints, decision variables of groundwater withdrawals by zone, and other variables to explore other feasible management scenarios that may yield different increases in simulated future base flow of the North Platte River.
2015
Groundwater modeling has been used since the 1970's as a way to analyze complex groundwater systems and to provide scientific evidence for management and policy determinations. The fundamental objective of this research was to develop a digital groundwater-flow model of the Rush Springs aquifer to assist in these determinations. The Rush Springs aquifer covers approximately 10,360 km 2 in westcentral Oklahoma and is the state's second most developed aquifer. This model will be used by government agencies to inform management decisions as well as gain insight about the aquifer's response to different scenarios such as policy determinations, changes in climate, or groundwater use. A steady-state simulation was first generated from the model. Hydraulic conductivity and recharge parameters were adjusted during calibration of the model to the 1956 head observations. The relationship between observed and simulated heads had a R 2 value of 0.97 and a mean residual of-11 m. A transient model was constructed for 1956 to 2013 with monthly time steps. Specific yield, recharge, and specific storage were adjusted for this simulation. The average residuals for the analyzed years ranged from-8 to-13 m. The second objective of this research was to utilize these models to analyze how groundwater use affects stream baseflow throughout the aquifer. Three different groundwater use scenarios from 2013-2023 were generated to compare how various management practices affect baseflow conditions including current groundwater use rates, assigning a 6093 m 3 /ha pumping rate out of every well in the model, as well as allowing for maximum irrigation use in the aquifer. Groundwater discharge to streams decreased for all three while recharge to the aquifer from the streams stayed relatively the same at approximately 1.5 m 3 /s. Recharge was also found to be a contributing factor in baseflow. Like the groundwater use scenarios, stream leakage out of the aquifer was larger than flow into the aquifer for all of these recharge scenarios. Unlike the groundwater use scenarios, stream leakage from the streams to the aquifer changed during the simulation period. This indicates that recharge has a greater effect on losing streams within this groundwater system than groundwater use. v
2017
An efficient water budget is necessary to develop sustainable practices in irrigated lands and determine future trends. Despite a lack of detailed knowledge, climate change is found to profoundly influence groundwater resources through changes in groundwater recharge, groundwater elevation, and groundwater flow processes. Prediction of the groundwater level (GWL) under a changing climate is essential to improve agricultural management. The goal of this research is to predict the GWL from 2056 to 2060 in the surrounding area of the MSEA. In order to achieve the target, the first research task is to develop a groundwater flow model and then simulate the model to match the historical GWL from 1991 to 2014. The School of Natural Resources (SNR) and the Nebraska Department of Natural Resources (DRN) provided historical groundwater level, soil lithology, and irrigation well data of the site. Visual MODFLOW Flex (version 2015.1) was used to develop the groundwater flow model. Results show that groundwater modeling fairly matched the historical groundwater pattern. The calibrated groundwater model was then applied to predict GWL in the area from 2057 to 2060 using future climate data. In this study, future climate data were obtained from a downscaled climate change predictions from the Community Climate System Model (CCSM4) that represents the worst climate scenario with a high greenhouse gas emission pathway. Future predictions