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"Groundwater flow."
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Assessing Structural Geological Controls on Groundwater Processes in Mountain Settings: Insights From Three‐Dimensional Numerical Modeling
Mountains play a critical role in the hydrological cycle by transferring heavy precipitation to lowland aquifers. However, their complexity and remoteness limit our understanding of groundwater flow, particularly the influence of faults. To fill the gap, semi‐idealized 3D numerical models calibrated using the mountain river network and the lowland piezometric gradient were developed. The impact of faults on groundwater flow was explored by varying their hydraulic conductivity, position, orientation, and length. The metrics evaluated were flow partitioning, seepage area, flow path lengths, and residence times. It was found that the hydraulic conductivity contrast between a fault and the pervasive rock controls recharge partitioning as much as the overall transmissivity of the pervasive rock. Regional conductive faults parallel to the orogen promote mountain‐block recharge over surface flow, as significantly as thick systems do, and vice versa. Local‐scale faults can exert as much influence as regional faults when crossing the catchment outlet, highlighting the importance of local heterogeneity in regional flow dynamics. Intercatchment flow is primarily governed by lithology and topography and is modulated by the fault position relative to major topographic features. Faults influence seepage areas within a multi‐kilometer distance in characteristic patterns useful for segregating their effective role. By lowering the water table, conductive faults systematically reduce the seepage areas. Meanwhile, barriers decrease seepage areas downstream of their trace and increase them upstream, without affecting the extent of seepage. Finally, the distributions of flow path lengths and residence times are uncorrelated, highlighting the importance of numerical modeling for groundwater dating.
Journal Article
Implications of Lateral Groundwater Flow Across Varying Spatial Resolutions in Global Land Surface Modeling
Accurate groundwater representation in land surface models (LSMs) is vital for water and energy cycle studies, water resource assessments, and climate projections. Yet, many LSMs do not consider key processes including lateral groundwater flow and aquifer pumping, especially at the global scale. This study simulates these processes using an enhanced version of the Community Land Model (CLM5) and evaluates their roles at three spatial resolutions (0.5°, 0.25°, 0.1°). Results show that lateral flow strongly modulates water table depth and capillary rise at all resolutions. The magnitude of mean lateral flow increases from 25 mm/year at 0.5° to 36 mm/year at 0.25°, and 52 mm/year at 0.1° resolution, with pumping inducing lateral flow even at 0.5° (∼50 km), a typical grid size in global LSMs. Further, lateral flow alters runoff in regions with high recharge and shallow water table (e.g., eastern North America and Amazon basin), and soil moisture and ET in regions with comparatively low recharge and deeper water table (e.g., western North America, central Asia, and Australia) through enhanced capillary rise. Runoff alteration by lateral flow increases substantially with resolution, from a maximum of 15 mm/month at 0.5° to 20 mm/month and 25 mm/month at 0.25° and 0.1°, respectively; the impact of resolution on soil moisture and ET is less pronounced. While the model does not fully capture deeper water tables—warranting further enhancements—it provides valuable insights on how lateral groundwater flow impacts land surface processes, highlighting the importance of lateral groundwater flow and pumping in global LSMs.
Journal Article
Effects of structure and volcanic stratigraphy on groundwater and surface water flow: Hat Creek basin, California, USA
Hydrogeologic systems in the southern Cascade Range in California (USA) develop in volcanic rocks where morphology, stratigraphy, extensional structures, and attendant basin geometry play a central role in groundwater flow paths, groundwater/surface-water interactions, and spring discharge locations. High-volume springs (greater than 3 m3/s) flow from basin-filling (<800 ka) volcanic rocks in the Hat Creek and Fall River tributaries and contribute approximately half of the average annual flow of the Pit River, the largest tributary to Shasta Lake. A hydrogeologic conceptual framework is constructed for the Hat Creek basin combining new geologic mapping, water-well lithologic logs, a database of active faults, LiDAR mapping of faults and volcanic landforms, streamflow measurements and airborne thermal infrared remote sensing of stream temperature. These data are used to integrate the geologic structure and the volcanic and volcaniclastic stratigraphy to create a three-dimensional interpretation of the hydrogeology in the basin. Two large streamflow gains from focused groundwater discharge near Big Spring and north of Sugarloaf Peak result from geologic barriers that restrict lateral groundwater flow and force water into Hat Creek. The inferred groundwater-flow barriers divide the aquifer system into at least three leaky compartments. The two downstream compartments lose streamflow in the upstream reaches (immediately downstream of the groundwater-flow barriers) and gain in downstream reaches with the greatest inflows immediately upstream of the barriers.
Journal Article
Surface and subsurface runoff generation processes in a poorly gauged tropical coastal catchment : a study from Nicaragua : dissertation
Hydrological research in humid tropics is particularly challenging because of highly variable hydrological conditions and high socio-economic stresses caused by rapid population increase, as is the case of Nicaragua. The objective of this research is to understand the surface and subsurface runoff generation processes in a poorly gauged coastal catchment in Nicaragua under variable humid tropical conditions. Specifically, it focuses on identifying geomorphological and hydro-climatic controls on catchment response at different spatio-temporal scales and studies the link between hydrological processes and ecosystem conditions.
Book
Effect of exponential decay in hydraulic conductivity with depth on regional groundwater flow
Regional groundwater flow is critical for understanding a variety of geologic processes. Unfortunately, few studies have considered the impact of gradual decrease in hydraulic conductivity (K) with depth on groundwater flow. In this study, regional groundwater flow through a basin is analyzed under conditions of exponentially decaying K with depth. We found that the development of local versus regional flow systems is sensitive to the decay exponent of K. With higher rates of decrease in K with depth, the penetration depth of local flow systems increases, the regional flow weakens, the amount of recharge decreases, and less water reaches the regional discharge zone. Therefore, the depth decay of K should not be neglected when analyzing hydrologic problems related to regional groundwater flow.
Journal Article
Groundwater well fields in ice-margin valley aquifers – is it easy to protect them, or not? An overview of hydrogeological and legal aspects of determining wellhead protection zones
This paper discusses principles for delineating wellhead protection zones (WHPZ) of groundwater well fields in ice-margin valleys. A distinctive feature of such well fields is that, apart from the often geogenically contaminated water of ice-margin valleys, they are largely supplied with high-quality water from intertill aquifers of neighbouring uplands. However, much of this inflow can be intercepted by wells for agriculture that are increasingly being constructed in the capture zones of existing municipal well fields, thus posing a threat to the quality of water for the public. This problem has been investigated using the example of a municipal well in Wroniawy (Poland) by analysing changes in the recharge components of this well field with a groundwater flow model. The results indicate that the commissioning of agricultural abstractions in the capture zone of this well field reduces inflow from intertill aquifers (8.5 per cent) and precipitation recharge (3.3 per cent), following a change in the extent of the capture zone. The loss of these qualitative recharge components is substituted by an increase in poor-quality water, i.e., surface water (7.3 per cent) and geogenically contaminated water from the ice-margin valley centre (3.8 per cent). Protecting well fields in such locations from adverse water quality changes requires the implementation of quantitative shielding of best-quality water, calling for WHPZ to cover the entire capture zone regardless of water flow timing, which is not provided for in Polish legislation. Costs and constraints of implementing such a WHPZ can be reduced by dividing it into sectors that differ in the scope of limitations, with the only quantitative protection applied to the outermost, medium- and low-vulnerable parts of the capture zone.
Journal Article