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Observations and Modeling of Deep Perched Water Beneath the Pajarito Plateau

Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM 87545

View larger version (64K): [in a new window]   Fig. 1. Conceptual model of groundwater occurrences beneath the Pajarito Plateau. Groundwater occurs as shallow perched systems in canyon-floor alluvium, as bedrock perched systems within the thick vadose zone (primarily beneath wet canyons), and as regional saturation associated with the basin-wide groundwater flow system.

View larger version (71K): [in a new window]   Fig. 2. Locations of wells and boreholes that have penetrated perched groundwater systems in bedrock. See Table 1 for descriptions of these zones. Also included for reference are wells in which perched water was not detected. Shallow perched groundwater in canyon-floor alluvium and shallow zones of perched water issuing from bedrock springs are not shown here or included in Table 1.

View larger version (10K): [in a new window]   Fig. 3. Schematic diagram of the conceptual model geometry for the low-permeability interface between two hydrogeologic units. (Left) model without low-permeability barrier; (right) model with low-permeability barrier.

View larger version (38K): [in a new window]   Fig. 4. Predicted and measured moisture content in Wells LADP-3 and LAOI(A)-1.1. Models without the low-permeability barrier (labeled "Base Case") are compared with those with permeability reduction at the interface. Increasing the reduction factor leads to saturated conditions above the interface.

View larger version (107K): [in a new window]   Fig. 5. Predicted fluid saturation in the models in the vicinity of the high-infiltration zone near associated with the Guaje Mountain Fault. (a) Base case representing no permeability reduction at the interface, (b) interface permeability reduction factor of 0.01, (c) interface permeability reduction factor of 0.003, (d) interface permeability reduction factor of 0.001. Color scale ranges from unsaturated (0.0) to fully saturated (1.0).

View larger version (108K): [in a new window]   Fig. 6. Particle tracking simulation for traced water in the vicinity of a possible high-infiltration zone associated with the Guaje Mountain Fault. (a) Base case representing no permeability reduction at the interface, (b) interface permeability reduction factor of 0.01, (c) interface permeability reduction factor of 0.003, (d) interface permeability reduction factor of 0.001. Color scale shows relative contaminant concentration ranging from 0.0 to 0.1 times initial concentration.