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3 Hydrogeological Considerations
Pages 47-108

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From page 47...
... ? • What are the short- and long-term impacts of the MUS system on the aquifer matrix, groundwater flow, or surface waters?
From page 48...
... The chapter includes discussion of the hydrological properties of the geological formation to be used for storage, the aquifer boundary conditions, recharge and recovery methods to be used, and potential impacts of the MUS system on the groundwater flow and aquifer integrity. In addition, knowledge gaps and research needs related to the hydrogeology of MUS systems are identified.
From page 49...
... Withdrawals from the unconsolidated and semiconsolidated sand and gravel aquifers, including the High Plains aquifer, Central Valley aquifer system, Mississippi River Valley alluvial aquifer, and Basin and Range basin-fill aquifers, accounted for 80 percent (or 62,400 Mgal/d) of total fresh groundwater withdrawal for the above listed uses.
From page 50...
... Unconfined aquifers are also referred to as water table aquifers because the upper surface of the saturated zone is at equilibrium with the atmospheric pressure. This surface is called the water table, which often follows the land surface topography with variations due to recharge and boundary conditions.
From page 51...
... Open basins that reflect a broad shallow paleocoastal margin depositional environment for sediment deposition may contain sheet-like strata comprising the storage zones; hence, the lateral boundary conditions can often be considered infinite. On the other hand, vertical boundary conditions exert an important control on the behavior of the system in this hydrogeological setting, especially with regard to ASR.
From page 52...
... With artificial recharge, water levels will typically rise, which can lead to increased discharge. As a result, the recoverable water may diminish as the length of storage time increases.
From page 53...
... The second type of storage space is created by displacement of native water with recharge water creating a zone of freshwater around the recharge well (Figure 3-1)
From page 54...
... The hydraulic conductivity of an aquifer can vary with location in the aquifer -- termed heterogeneity -- and/or with the direction of groundwater flow -- termed anisotropy. The Heterogeneity and anisotropy of aquifer hydraulic properties must be known in order to plan an MUS system and develop accurate groundwater flow or solute transport models for such a system.
From page 55...
... In the context of aquifer storage, a dual porosity aquifer system can be considered a dual reservoir. While most of the water may exist within connected primary pore spaces through which water moves relatively slowly, water residing in the secondary porosity may travel at greater velocities (e.g., conduit flow in a carbonate aquifer)
From page 56...
... Variations in lithology, depositional environment, and position of bedding planes also contribute to evolution of conduits that may yield complex flow systems. Water Movement Between Aquifers or Between Aquifers and Surface Water Aquifer Interaction In an aquifer system, it is possible for water to move from a semiconfined aquifer of higher hydraulic pressure into an unconfined one or vice versa when the semiconfined aquifer hydraulic head is reduced by pumping.
From page 57...
... For example, water reuse projects could be implemented in coastal aquifers, where water delivered to canal systems that recharge the aquifer prevents saltwater intrusion from wellfield drawdown. HYDRAULICS OF RECHARGE As noted in the previous chapter, managed underground storage of recoverable water can be achieved using three different methods, namely surface spreading (e.g., recharge basins, modified stream beds, pits and shafts)
From page 58...
... The factors that affect infiltration capacity of artificial recharge projects include the composition of surface soils, the geology, subsurface hydrologic conditions, source water quality, and procedures used in the construction, operation, and maintenance of the recharge structure. The operational factors can ordinarily be managed to maintain favorable infiltration capacity.
From page 59...
... Water flows down the Santa Ana River from Riverside and San Bernardino Counties, together with Anaheim Lake, one of OCWD's recharge basins. Photo supplies imported from the courtesy of Orange County Water District.
From page 60...
... Recharge Wells Recharge of water into abandoned wells and wells specifically designed for artificial recharge has been practiced for many years with varying degrees of success. The use of recharge wells is confined largely to those areas where surface spreading is not feasible owing to the presence of low-permeability layers overlying the principal water-bearing deposits.
From page 61...
... Difficulties encountered in maintaining adequate recharge rates have been attributed to silting, bacterial and algae growths, air entrainment, release of dissolved gases, rearrangement of soil particles, deflocculation caused by reaction of high-sodium water with soil particles, and chemical reactions between recharged waters and native groundwaters resulting in precipitates in the aquifer or well-casing perforations (Bouwer, 2002)
From page 62...
... between the source water and native groundwater, tend to produce relatively amorphous shapes that describe the three-dimensional limits of the recharge water (e.g., bottle brush [Vacher et al., 2006] , upside-down Christmas tree [Missimer et al., 2002]
From page 63...
... . The thickness of the storage zone's open interval at the Boynton Beach site is 105 feet, and transmissivity is reported to be about 9,400 square feet per day (CH2M Hill, 1993)
From page 64...
... The proposed storage zone in the upper Floridan Aquifer System is highly transmissive and porous fossiliferous limestone, and based upon test data and water quality sampling data, the ASR well was completed with an open-hole interval from 1,268 to 1,700 feet below land surface. The storage zone represented a confined leaky aquifer with a transmissivity of about 570,000 feet per day (CH2M Hill, 1989)
From page 65...
... Recharged water is depicted as a "mound" on native groundwater. The base of the lens is a mixture of recharge water and native groundwater, termed transitional water.
From page 66...
... Recharge/ASR well in an unconfined aquifer FIGURE 3-1 Mixing of waters with different recharge methods: source water (SW) , either surface water, groundwater, or reclaimed wastewater; recharge water (RW)
From page 67...
... Recharge and recovery of fresh water into a freshwater aquifer requires careful selection of the water quality parameter used to distinguish between the recharge water and the native groundwater, given that CRE and ORE should not exceed 100 percent. Operational recovery efficiency (Equation 3-2)
From page 68...
... has done an extensive analysis of these factors. The dispersivity, thickness of the storage zone, preexisting groundwater gradient, recharge volume, rock type, presence of high-permeability zones, length of storage time, density of ambient groundwater relative to recharge water, ambient groundwater quality, and number of recharge and recovery cycles can all be important.
From page 69...
... During storage, solutes in the primary and secondary pore spaces will move toward equilibrium through diffusion. The figure shows that when native groundwater quality is poor, MUS that employs wells for recharge in dual porosity aquifers faces greater challenges in recovery efficiency because of degraded water quality than systems in more homogeneous aquifers, such as sands and gravels.
From page 70...
... even at an early time. This suggests that the application of ASR in aquifers with poor water quality faces more challenges in high-dispersivity environments than in lower-dispersivity environments, such as homogeneous sands and gravels.
From page 71...
... Second, for an unconfined aquifer, pumping tests cannot characterize the behavior of the vadose zone located immediately above the current groundwater surface, through which the injected water will pass. Therefore, pumping tests cannot be used to replace the injection-pumping cycle test for performance evaluation of injection wells.
From page 72...
... water and poorer-quality native groundwater and the effects of water-rock interactions. If a cycle test monitoring plan is to fully assess potential water quality changes and system performance that may occur at the scale of full operation, long-term monitoring is required (NRC, 2001)
From page 73...
... If there are significant water quality differences between stored and native water, a larger number of cycles is required. After the first cycle, the next three cycles have the same recharge volume and storage period in order to determine the improvement in recovery efficiency with successive identical cycles.
From page 74...
... The effect of buoyancy on system efficiency is evaluated using longer recharge duration. Upward migration of recharge water will also be evaluated by monitoring units above the confining units.
From page 75...
... Storage of geologic or hydrogeologic data in three dimensions allows interpolation of 3D hydrogeologic units, designation of measured or interpreted properties to the units, volume calculations, morphology analysis, representation of complex fault systems, parameter flux (i.e., groundwater flow, chemical diffusion) between units, and interpolation of hydrologic properties within the unit volumes.
From page 76...
... determine aquifer properties such as porosity and hydraulic conductivity; (3) determine movement of the recharge water, including the degree of mixing between recharge and native waters, as well as dispersion and diffusion; and (4)
From page 77...
... Among the wide array of data types are sedimentological, groundpenetrating radar, gravimetric, isotopic, and physical water quality parameters; results of pump and infiltration tests; and hydraulic heads. Through implementation of this database, all hydrologic and hydrogeologic data are accessible "on demand" for development of semiautomated, internally consistent 3D model units, from which hydrogeologic framework models, and subsequently, groundwater flow models are generated.
From page 78...
... , which may be present within recharge basins, can also serve as indicators of the recharge water. Additional water quality parameters commonly used as tracers include, but are not limited to, NO3−, SO42−, and boron.
From page 79...
... ; available time, funds, and computational resources; experience of the investigator; and availability of geologic or hydrologic data for calibration or verification of the geophysical data. The most common land surface or airborne (fly-over)
From page 80...
... Each method has its own limitations; therefore, multiple methods are employed to have a better understanding of the aquifer system. Dual or secondary porosity in an MUS storage zone can be identified using caliper logs, which provide borehole diameter.
From page 81...
... However, they are less versatile than numerical solutions since the problem has often been simplified. Numerical models simulate groundwater flow using algebraic equations.
From page 82...
... 82 PROSPECTS FOR MANAGED UNDERGROUND STORAGE OF RECOVERABLE WATER TABLE 3-3 Common Geophysical Characterization Methods that are Used to Assist in Hydrogeological Investigations Acquisition Characterization Attributes Typically Examples of Approaches Methods Obtained Hydrogeological Objectives Airborne Remote Sensing Electrical resistivity, Mapping of bedrock, freshwater gamma radiation, mag- saltwater interfaces and faults, netic and gravitational assessment of regional water field, thermal radiation, quality electromagnetic reflec tivity Surface Seismic refraction P-wave velocity Mapping of top of bedrock, groundwater surface, and faults Seismic reflection P-wave reflectivity and Mapping of stratigraphy, top of velocity bedrock, and delineation of faults or fracture zones Electrical resistivity Electrical resistivity Mapping aquifer zonation, groundwater surface, top of bedrock, freshwater-saltwater interfaces and plume boundaries estimation of hydraulic anisot ropy, and estimation or monitor ing of water content and quality Electromagnetic Electrical resistivity Mapping aquifer zonation, groundwater surface, freshwater saltwater interfaces, and estima tion or monitoring of water con tent and quality Ground- Dielectric constant val- Mapping of stratigraphy and penetrating radar ues and dielectric con- groundwater surface, estimation trasts and monitoring of water content Crosshole Seismic P-wave velocity Estimation of lithology and frac ture zone detection Electrical resistivity Electrical resistivity Mapping aquifer zonation and estimation or monitoring of water content and quality Radar Dielectric constant Estimation or monitoring of wate content and quality, mapping aquifer zonation Wellbore Geophysical well Electrical resistivity, Lithology, water content, water log seismic velocity, and quality, and fracture imaging gamma activity Laboratory/ Electrical, seismic, Electrical resistivity, Development of petrophysical Point dielectric, and x- seismic velocity and relationships, model validation, ray methods attenuation, dielectric investigation of processes and constant, and x-ray instrumentation sensitivity attenuation SOURCE: Modified from Rubin and Hubbard (2005)
From page 83...
... Analyses using groundwater and solute transport numerical modeling may help to • Evaluate the performance of a regional set of ASR wells to aid in estab lishing the design, spacing, orientation, and capacity of those wells; • Evaluate regional changes in hydraulic head and flow patterns; • Evaluate the impact on the environment, including neighboring surface water flow, and existing users; • Evaluate the critical pressure for rock fracturing or widening of existing fractures; • Analyze the relationship between storage interval recovery rates and recharge volume so that the recovery of water is optimized; • Visualize the movement of stored water throughout the wellfield, which is of special interest where the storage zone contains water of lesser quality or where dual porosity is present; and • Evaluate the extent of potential water quality changes in the aquifer during storage and movement. Modeling Protocol A protocol should be followed when developing a model, as documented in relevant ASTM (American Society for Testing and Materials)
From page 84...
... The MUS model builds on calibration against seasonal water levels and water quality, as well as performing transient calibration at existing ASR and well sites where aquifer test or ASR cycle testing data are available. Once the model is calibrated, a sensitivity analysis is recommended to quantify and show the effects of uncertainty in the calibrated model.
From page 85...
... HST3D (Kipp, 1997) is a heat and solute transport program that simulates groundwater flow and related heat and solute transport in three dimensions.
From page 86...
... WASH123D is a physically based, spatially distributed, finite-element, integrated surface water and groundwater model. WASH123D is applicable to a variety of problems, including flood control, water supply, water quality, structures, weirs, gates, junctions, evapotranspiration, and sediment transport for both event and continuous simulations.
From page 87...
... Geological maps and cross sections should be shown and should identify the hydrostratigraphic units. Standard groundwater flow model properties, such as hydraulic conductivity or transmissivity and storativity, must be defined spatially and in the context of the physical framework.
From page 88...
... . Vertical resolution is increased in the confining units directly above and below the recharge zone (i.e., UFA)
From page 89...
... During this extraction cycle the hydraulic head at and im mediately surrounding the ASR well decreases substantially. Part C of the figure shows a cross-sectional view of the concentration profile in the vicinity of the ASR well at the end of the storage period.
From page 90...
... determining regional changes in aquifer water quality TDS, sulfate, and chloride; (3) estimating groundwater recharge, discharge, and storage at larger spatial scales; (4)
From page 91...
... Depending on the project, modeling tools can be implemented to help define the storage zone, buffer zone, and native groundwater area in conjunction with technical experience, especially since deep monitoring is expensive. As in any modeling effort, it is advisable to start collecting data early, start model development early (including running sensitivity analyses to determine data gaps)
From page 92...
... . Groundwater flow through unconsolidated sandy aquifers is usually the result of local flow systems (http://capp.water.usgs.gov)
From page 93...
... If surface water is well connected hydraulically to the shallow aquifer, a rise in the water table will likely increase groundwater flow into local streams, lakes, and wetlands via seeps and springs. In the case of wetlands, this could potentially have a major effect on water budgets (and, therefore, water depth)
From page 94...
... . If a significant temperature difference exists between native groundwater and recharge water, the MUS system will affect the hydraulic gradient between the native and recharge water.
From page 95...
... developed conceptual models to assess impacts of different scenarios of cycle loading of the ASR system on aquifer materials and concluded that confining units, especially clay layers or interlenses, will deform and result in additional subsidence during recovery of the stored water, and partial recovery of subsidence or seasonal uplift is also expected under a favorable condition even with an ASR system to retain groundwater levels. The magnitude of subsidence associated with water-level decline appears to be related in large part to geologic factors such as (1)
From page 96...
... Army Corps of Engineers and the South Florida Water Management District were tasked with evaluating the feasibility of the proposed CERP ASR projects individually and through the development of a regional feasibility study. A component of the ASR Regional Study, outlined in Brown et al.
From page 97...
... The legal aspects of land surface subsidence caused by groundwater withdrawal are additional concerns facing water resource managers (Kopper and Finlayson, 1981)
From page 98...
... At a project scale, they can aid in establishing the design, spacing, orientation, and capacity of wells and recharge basins, evaluating their impact on the environment and existing users, estimating the critical pressure for rock fracturing, visualizing the movement of stored water throughout the system (especially useful for systems with waters of varying density or quality) , and evaluating the extent of potential water quality changes in the aquifer during storage and movement.
From page 99...
... surface and borehole geophysical methods to determine hydrological properties and the ex tent of recharge water volumes during cycle testing; (2) optimization of cycle test design (frequency, duration, and intensity)
From page 100...
... 1976. A slug test method for determining hydraulic conductivity of unconfined aquifers with completely or partially penetrating wells.
From page 101...
... 1993. Boynton Beach aquifer storage and recovery system: Engi neering report prepared for the City of Boynton Beach, Florida.
From page 102...
... 2002. ASR-UK: Elucidat ing the hydrogeological issues associated with aquifer storage and recovery in the UK.
From page 103...
... 2005. Positive gadolinium anomaly in surface water and ground water of the urban area Berlin, Ger many.
From page 104...
... 2006. Aquifer storage and recov ery: Recent hydrogeological advances and system performance.
From page 105...
... 2002. Lumped parameter estima tion of initial recovery efficiency during aquifer storage and recovery.
From page 106...
... 2005. An aquifer storage and recovery systems with reclaimed wastewater to preserve native groundwater resources in El Paso, Texas.
From page 107...
... 1993. Natural Groundwater Flow.


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