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    The role of low-permeability rocks in regional flow
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    Abstract:
    Summary The role of low-permeability rocks in determining fluid migration within sedimentary basins has been shown to be crucial for deriving the direction and rate of fluid movement. The magnitude of the flows depends on the geometry of the sedimentary basin and on the bulk hydrogeological properties of the various strata and their relative values. Measurements of head and pore-water compositions of argillaceous formations show separate evidence for the existence of cross-formational flow resulting in groundwaters of mixed origins. Numerical and analytical models have been developed and applied to some basinal systems in England. They have been used to assess the directions of groundwater flow likely to be encountered by repository site investigation programmes and to aid in the interpretation of groundwater head and chemistry data. Such flow models still require detailed validation. Our knowledge of the flow mechanism and the physical properties of mudrocks at depth is still elementary, but the indications are that the role of low-permeability rocks in controlling fluid migration has been much underestimated.
    The study examines the hydrogeological conditions and the hydraulic characteristics of the water bearing horizons within the hydrogeologic regime of the study area located west of Iraq to the west of longitude 40°40'. Also the study shed light on the flow behavior regime and its impacts on the groundwater movement, ground water flow velocities (permeability and hydraulic gradients) considering the regional structural phenomena. The Hydrogeological data presented as spatial distribution maps and three dimensional models. The results which were achieved from the field measurements are correlated with the main hydrogeologic control points such as storage and transmissivity coefficients, groundwater depths, aquifers thickness, lateral extensions and groundwater recharge to classify the hydrogeologic districts for development and exploitation. The hydrogeologic regime of the study area is classified and screened into various aquifers, including Ga'ra, Mullusi, Mullusi-Ubaid, Hartha, Tayarat-Digma (Jeed), Muhaywir-Ubaid and Rattga aquifers. The statistical results of the hydraulic and hydrochemical parameters were examined for explaining the spatial distribution of each parameter within the uppermost aquifers and determining the preference hydrogeologic districts for future groundwater exploitation as hereinafter order, Ubaid Mullusi aquifer within district-6, Rattga and Digma-Tayarat aquifer within district-7, Mullusi aquifer within district-2, Hartha aquifer within district-3, Digma-Tayarat aquifer within district-4, Ga'ra aquifer within district-1, Muhaywir-Ubaid aquifer within district-5 and Digma-Tayarat within district-8, respectively.
    Aquifer properties
    Aquifer test
    Specific storage
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    Declining groundwater levels resulting from groundwater withdrawals in the Santa Fe, New Mexico, area have caused concern about the future availability of water in the Tesuque aquifer system. This report describes the geohydrology of the Tesuque aquifer system in the Santa Fe area and presents a three-dimensional regional groundwater flow model which assesses the effects of existing and possible future groundwater withdrawals on the regional aquifer system. The model was calibrated using simulations of the predevelopment steady-state condition and the 1947-82 historical period. The response of the aquifer to two scenarios of future groundwater withdrawals from 1983 to 2020 was simulated. (USGS)
    Groundwater model
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