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The hydrology of alpine and subalpine areas in the Colorado Front Range (USA) is evolving, driven by warming and by the alteration of precipitation patterns, the timing of snowmelt, and other components of the hydrologic budget. Field measurements of soil hydraulic conductivity and moisture along 30-m transects (n = 13) of representative soils developed in surficial deposits and falling head slug tests of shallow groundwater in till demonstrate that hydraulic conductivity in the soil is comparable to hydraulic conductivity values in the shallow aquifer. Soil hydraulic conductivity values were variable (medians ranged from 5.6 × 10−7 to 4.96 × 10−5 m s−1) and increased in alpine areas underlain by periglacial deposits. Hydraulic conductivities measured by a modified Hvorslev technique in test wells ranged from 4.86 × 10−7 to 1.77 × 10−4 m s−1 in subalpine till. The results suggest a gradient from higher hydraulic conductivity in alpine zones, where short travel paths through periglacial deposits support ephemeral streams and wetlands, to lower hydraulic conductivity in the till-mantled subalpine zone. In drier downstream areas, streambed infiltration contributes substantially to near-channel groundwater. As summer temperatures and evapotranspiration (ET) increase and snowmelt occur earlier, alpine soils are likely to become more vulnerable to drought, and groundwater levels in the critical zone may lower, affecting the connectivity between late-melting snow, meltwater streams, and the areas they affect downstream.
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This content will become publicly available on August 6, 2026
Fractal signatures of hydraulic head variations reveal aquifer heterogeneity
Understanding subsurface heterogeneity is critical for predicting groundwater flow, pollutant transport, and managing water resources. While traditional methods often rely on sparse borehole or geophysical data, this study explores a spectral analysis approach to infer aquifer structure from groundwater level fluctuations. We use a coupled surface–subsurface flow model to simulate hydraulic head time series in synthetic aquifers with bimodal hydraulic conductivity distributions. The frequency characteristics of these head fluctuations are analyzed to compute the scaling exponent (defined as the slope of the log-power spectral density of head fluctuations versus log-frequency) and its spatial gradient magnitude. Results show that areas with significant heterogeneity, such as transitions between high- and low-permeability zones, exhibit strong spatial gradients in the scaling exponent. These features can be used to delineate unsaturated zones, groundwater flow systems, and aquifer heterogeneity. By testing four scenarios with different hydraulic conductivity contrasts, we demonstrate that this method is sensitive to aquifer configuration. Our findings suggest that the gradient magnitude of the scaling exponent may serve as a diagnostic tool for characterizing heterogeneity in groundwater models and has the potential for future applications in estimating permeability distributions from monitored groundwater level data.
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- Award ID(s):
- 2500969
- PAR ID:
- 10648034
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Journal of hydrology
- ISSN:
- 0022-1694
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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