Development of an Unsaturated Region Below a Perennial River

Open-File Report, 1989

ground water. The program limits the amount of groundwater recharge to the available streamflow. It permits two or more streams to merge into one with flow in the merged stream equal to the sum of the tributary flows. The program also permits diversions from streams. Streams are divided into segments and reaches. Each reach corresponds to individual cells in the finite-difference grid used to simulate groundwater flow. A segment consists of a group of reaches connected in downstream order. Leakage is calculated for each reach on the basis of the head difference between the stream and aquifer and a conductance term. It is subtracted or added to the amount of streamflow into the reach. The stage in each reach can be computed using the Manning formula under the assumption of a rectangular stream channel. The amount of leakage in each reach (either into or out of the aquifer) is incorporated into the groundwater flow model by adding terms to the finite-difference equations. Recharge to the aquifer in a reach ceases when all the streamflow in upstream reaches has leaked into the aquifer and the stream is dry. A stream is permitted to flow again in downstream reaches if the head in the aquifer is above the elevation of the streambed. Results from the program have been compared to results from two analytical solutions. One assumes time varying areal recharge to the aquifer and discharge only to a stream and the other assumes recharge to the aquifer from a change in stream stage. Results from the program reasonably duplicated the analytical solutions. Manuscript approved for publication December 13, 1988 The groundwater flow model with the Streamflow-Routing Package has an advantage over the analytical solution in simulating the interaction between aquifer and stream because it can be used to simulate complex systems that cannot be readily solved analytically. The Streamflow-Routing Package does not include a time function for streamflow but rather streamflow entering the modeled area is assumed to be instantly available to downstream reaches during each time period. This assumption is generally reasonable because of the relatively slow rate of groundwater flow. Another assumption is that leakage between streams and aquifers is instantaneous. This assumption may not be reasonable if the streams and aquifers are separated by a thick unsaturated zone. Documentation of the Streamflow-Routing Package includes data input instructions; flow charts, narratives, and listings of the computer program for each of four modules ; and input data sets and printed results for two test problems, and one example problem.

Hydrological Sciences Journal-journal Des Sciences Hydrologiques, 2004

A study was made to develop a model that can be used to predict the steady-state stream depletion rates caused by a continuous pumping well located in a water table aquifer. The effects of nonlinear variation of evaporation with the depth to water table on steady-state stream depletion rate were investigated using model results. Dimensional analysis was used to determine the relationship between the scaled steady-state stream depletion, the scaled pumping distance, the scaled hydraulic conductivity, and the scaled initial depth to the water table. A dimensionless graph was developed for a wide range of these parameters. Analysis of this graph showed that the steady-state stream depletion rate decreases as the pumping distance between the well and the stream increases. The dimensionless graph also showed that steady-state stream depletion rates strongly depended on the initial position of the water table. Analysis indicated that, as the saturated conductivity increased, the effect of the initial position of the water table on the magnitude of stream depletion rate was more influential. Analysis also showed that, as the value of saturated conductivity decreased, the relative error produced by the assumption that at steady state all the pumped water is captured from the evaporation, also decreased.

Open-File Report

Documentation is provided of model input and sample output used in a previous report for analysis of groundwater flow and simulated pumping scenarios in Paradise Valley, Humboldt County, Nevada. Documentation includes files containing input values and listings of sample output. The files, in American International Standard Code for Information Interchange (ASCII) or binary format, are compressed and put on a 3-1/2inch diskette. The decompressed files require approximately 8.4 megabytes of disk space on an International Business Machine (IBM)-compatible microcomputer using the Microsoft Disk Operating System (MS-DOS) operating system version 5.0 or greater.

Journal of Environmental Management, 2016

Analytical study of the influence of both the pumping well discharge rate and pumping time on contaminant transport and attenuation is significant for hydrological and environmental science applications. This article provides an analytical solution for investigating the influence of both pumping time and travelling time together for one-dimensional contaminant transport in riverbank filtration systems by using the Green's function approach. The basic aim of the model is to understand how the pumping time and pumping rate, which control the travelling time, can affect the contaminant concentration in riverbank filtration systems. Results of analytical solutions are compared with the results obtained using a MODFLOW numerical model. Graphically, it is found that both analytical and numerical solutions have almost the same behaviour. Additionally, the graphs indicate that any increase in the pumping rate or simulation pumping time should increase the contamination in groundwater. The results from the proposed analytical model are well matched with the data collected from a riverbank filtration site in France. After this validation, the model is then applied to the first pilot project of a riverbank filtration system conducted in Malaysia. Sensitivity analysis results highlight the importance of degradation rates of contaminants on groundwater quality, for which higher utilization rates lead to the faster consumption of pollutants.

2012

Water Resources Management, 2020

Coupling surface water and groundwater models dynamically based on a simultaneous simulation of saturated and unsaturated zones of soil is a useful method for determining the recharge rate and flow exchange between a river and an aquifer as well as simultaneous operation of water resources systems. Thus, the main objectives of this study are to investigate the effects of surface water and groundwater interactions through their systematic simulation and to create a dynamic coupling between surface water and groundwater resources of the area by relevant mathematical models. Accordingly, hydrologic soil moisture method and MODFLOW model were employed to simulate the unsaturated and saturated zones, respectively. The results revealed that simultaneous simulation of the saturated and unsaturated zones of the soil can illustrate the interaction between surface water and groundwater at any spatial and temporal intervals well through using complete hydroclimatological balance components in the form of a coupled model. The application of this method in the Loor-Andimeshk Plain, located in the southwest of Iran, showed that aquifer recharge through the plain area from November to March is due to precipitation. On the other hand, in the warm months (June to September), the plain is merely fed through irrigation water penetration. As the level of river water in both Dez and Balarood rivers is higher than the Loor-Andimeshk aquifer level, hence the exchange occurs as a leakage from the river to the aquifer. The highest and lowest values of average exchangeable water in Balarood River occur in March and April and in Dez River are from June to September.

2006

to observe the effect of abstraction on permeability and hydraulic gradient in a simulated unconfined aquifer using sand tank model. In this study discharge was measured by volumetric method and coefficient of permeability (K) was calculated using Darcy's law. For this experiment sand having particle size from 0.006 to 2.0 mm were used. Water elevation of different piezometers was recorded for five different discharge rates such as 0.040, 0.0396, 0.035, 0.0322 and 0.03118 litre per second for layered stratum (Cu=1.76). The average values of coefficient of permeability and hydraulic gradient were 5.00 mm/s and 0.1575 m/m, respectively. For homogeneous formation (Cu=1.5), the discharges were 0.03675, 0.03603, 0.0355, 0.03539 and 0.03318 litre per second, and the calculated average values of coefficient of permeability and hydraulic gradient were 6.276 mm/s and 0.1148 m/m, respectively. Hydraulic gradient for layered stratum was found higher than that of homogeneous formation. Very good linear relationship was found between water elevations and piezometric distances for both layered and homogeneous formations. The correlation coefficient (r) between water elevations and piezometric distances for higher and lower discharges in layered stratum were found to be 0.964 and 0.993 also for homogeneous formations this values were 0.972 and 0.987, respectively.

University of California Water Resources Center, 2001

The Kern Water Bank (KWB) is located in the Kern River alluvial fan at the southern end of the San Joaquin Valley, Kern County, California. In January and August 2000, shallow and deep monitoring wells were sampled at 10 or 13 locations, respectively. The samples were analyzed for chlorofluorocarbons (CFC-11 and CFC-12) and stable isotopes of water (18 O and D). Results indicate that relatively young groundwater (<20 yrs) is found in northern and central areas in the shallower wells near where water is actively recharged. An intermediate dated (20 to 40 yrs) groundwater component is encountered in the deeper wells of the central areas of the KWB. The oldest waters (>40 yrs) are found in the southern and western areas and in the deep northern wells. The stable isotope composition varied significantly within the KWB and correlated neither with location or CFC age. It suggests a Sierra Nevada water source. A numerical model of flow was developed using Visual Modflow Software. The model is composed of three layers (total thickness 226 m), representing the basic aquifer structure. Each layer is built on a 58 columns, 39 rows grid consisting of 1935 active and 327 inactive cells ranging in size from 0.16 to 0.65 km 2. The model is built with hydrogeological parameters compiled by the California Department of Water Resources, monitoring wells, production wells, and assumed boundary conditions. Other field data consisted of: (i) spring 1994 initial groundwater surface, (ii) KWB and Kern County Water Agency (1994-2000) artificial recharge rates, (iii) seven years of hydraulic heads records at 26 monitoring wells and (iv) pumping rates at productions wells. The calibrated model was run over a 7 years simulation period (1994-2000) in a transient mode, with twelve time steps for each stress period. The root mean squared error between simulated and measured hydraulic heads was calculated at 8 m. The best agreement between simulated and observed hydraulic heads was found in the deep wells located in the southern section of the KWB away from the active spreading ponds.

2000

Water Resources Research, 1991

Analytical solutions for computing drawdowns and streamflow depletion rates often neglect conditions that exist in typical stream-aquifer systems. These conditions can include (I) partial penetration of the aquifer by the stream, (2) presence of a streambed clogging layer, (3) aquifer storage available to the pumping well from areas beyond the stream, and (4) hydraulic disconnection between the stream and the well. A methodology is presented for estimating extended flow lengths and other parameters used to approximate the increased head losses created by partially penetrating streams and clogging layer resistance effects. The computed stream depletion rates and drawdown distributions from several analytical solutions were compared to those obtained using a two-dimensional groundwater flow model. The stream geometry was approximated as a semicircle. Numerical simulation results indicate that, because of the use of simplifying assumptions, the analytical solutions can misrepresent aquifer drawdown distributions and overestimate stream depletion rates. Assuming that a correct simulation of the stream depletion phenomenon is provided by the numerical model, the error associated with each of the simplifying assumptions was determined. At a time of 58.5 days after pumping began, errors in computed stream depletion rates due to neglect of partial penetration were 20%, those due to neglect of clogging layer resistance were 45%, and those due to neglect of storage in areas beyond the stream were 21%. Neglecting hydraulic disconnection had only a minor effect (i.e., an error of 1% only at a time of 58.5 days after pumping began) on computed stream depletion rates and a noticeable effect on aquifer drawdown distributions. groundwater withdrawals near a stream, the water table can be lowered below the streambed elevation, thereby severing the saturated exchange between the stream and the aquifer, creating disconnection, and forming an unsaturated zone Copyright 1991 by the American Geophysical Union. Paper number 91WR00001. 0043-1397/91/91WR-00001 $05.00 below the streambed (Figure 1 c). Under these conditions, as long as the water level in the stream does not change, a further drawdown of the water table due to pumping does not significantly affect the seepage rate from the stream. Several analytical solutions are available for computing drawdowns and stream depletions caused by pumping near a stream [e.g., Theis, 1941; Glover and Balmer, 1954; Jacob, 1950; Hantush, 1965]. These solutions typically incorporate image well theory to predict the rate at which a pumping well depletes flow in a nearby stream. The solutions are based on simplifying assumptions, e.g., (1) the stream fully penetrates the aquifer, (2) the stream and the aquifer are hydraulically connected, (3) the streambed is unclogged, (4) the stream is infinitely long and straight, and (5) the aquifer underlying the stream is isotropic, semi-infinite in extent, of constant transmissivity, and that only horizontal flow (i.e., Dupuit flow) occurs in the aquifer. To account for the effects of vertical seepage from streams that only partially penetrate the full aquifer thickness and whose beds and banks are much less permeable than the aquifer, the method of additional seepage resistances [e.g., Streltsova, 1974] has often been applied [Hantush, 1965]. This technique extends the actual distance between the stream and the pumping well by an additional length, horizontal flow through which results in head losses equivalent to the additional losses created by partial penetration and clogging layer effects. Extended flow lengths based on the Hahtush [1965] solution are, however, smaller than those based on the Jacob [1950] solution. The new "effective distance" replaces the actual distance between the stream and the well as used in the Theis [1941] solution.

Computational Water, Energy, and Environmental Engineering, 2014

This study evaluates the feasibility of groundwater banking in the Central Basin. The Central Basin is located in Sacramento County in northern California, USA. The study basin is bounded by three rivers (the Sacramento, the American, the Consumes and Mokelumne rivers), and by the Sierra-Nevada mountain range. This study focuses on the potential for groundwater recharge in the Central Basin for three water years (critical, wet, above normal). For that purpose, a 3-D Groundwater Modeling System (GMS) with MODFLOW was created. Three recharge wells were added to the calibrated groundwater model to recharge the water table with 10,000 Acre-Feet (AF) of water to the Central Basin. The banking of 10,000 AF during the critical and wet years was effective in raising the water table elevation in the cone of depression area without causing any negative impact elsewhere in the basin. According to the findings of the Central Basin model, banking up to 10,000 AF of groundwater during any year type is feasible. More than 10,000 AF of groundwater banking might cause more negative impacts than positive benefits.

Water, Air, & Soil Pollution, 2014

To date, studies on the geological conditions in inland aquifers leading to pathways for upwelling deep saline groundwater due to pumping have not been published yet. Therefore, this paper conducted a theoretical modeling study to raise two hypotheses about deep saline-groundwater pathways leading to saltwater upconing below a pumping well in an inland aquifer based on the field situation at the Beelitzhof waterworks in southwestern Berlin (Germany), defined as follows:

Ground Water, 2005

Siting wells near streams requires an accurate estimate of the quantity of water derived from the river due to pumping. A number of hydrogeological and hydraulic parameters influence this value. This study estimates stream depletion under steady-state conditions for a variety of hydrogeological systems. A finite differences model was used to analyze several hydrogeological situations, and for each of these the stream depletion was estimated using an advective transport method. An empirical equation for stream depletion was obtained for the case of a stream that partially penetrates the aquifer and a pumping well that is screened over a portion of the aquifer. The derived equation, which is valid for both isotropic and anisotropic conditions, expresses stream depletion as a function of the unit inflow to the river, the discharge of the pumping well, the well screen length, the distance between the river and pumping well, the wetted perimeter, and a new parameter called ''overlap,'' which is defined to be the distance between the riverbed and the top of well screen. The overlap parameter makes it possible to consider indirectly the vertical component of flow, which is accentuated when the well is screened below the streambed. The formula proposed here should be useful in deciding where to locate a pumping well and to decide the appropriate length of its screen.

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.

Scientific Investigations Report, 2021

Aquifer storage and recovery (ASR) expands the portfolio of public water supply and improves resiliency to drought and future water demand. This study investigated the feasibility of ASR in the Bedell Flat Hydrographic Area using land-based methods including in-channel managed aquifer recharge (MAR) and rapid infiltration basins (RIB). Bedell Flat, one of two flow-through groundwater basins near Reno, Nevada, was a likely candidate for ASR because of its deep basin fill, proximity to supplemental water sources and infrastructure, and lack of development. In-channel MAR feasibility was determined from seepage losses along the Bird Springs ephemeral channel measured using Parshall flumes and heat-as-a-tracer inverse modeling. The feasibility of RIB was evaluated by characterizing vadose zone boreholes installed with roto-sonic drilling to water table. Field characterization of sediment and lithologic descriptions was accomplished at 1-foot (ft) increments. Bulk sediment samples were collected every 5 ft and cores from a split spoon were sampled at 10, 20, 30, 40, 60 and 100 ft below land surface (bls). Collected samples were analyzed for texture, moisture content, and geochemistry. Infiltration rates in Bird Springs channel increased downgradient with the hydraulic conductivity of the upper reaches ranging from 0.002 to 0.14 meter per hour (m/h) 1 USGS Nevada Water Science Center 2 Truckee Meadows Water Authority A thorough understanding of site hydrologic, hydrogeologic, and geochemical characteristics was needed to determine the potential success of a long-term ASR program before making the substantial capital investments necessary to import advanced purified water from more populated North Valleys of the Reno metropolitan area.