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K in an Urban World: New Contexts for Hydraulic Conductivity
Citation:
Shuster, W., L. Schiffman, C. Kelleher, H. Golden, A. Bhaskar, A. Parolari, R. Stewart, AND D. Herrmann. K in an Urban World: New Contexts for Hydraulic Conductivity. JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION. American Water Resources Association, Middleburg, VA, 57(3):493-504, (2021). https://doi.org/10.1111/1752-1688.12918
Impact/Purpose:
We aim to improve practitioner understanding of K in urban contexts by providing a brief historical perspective of this property, discussing how urbanization can affect soils and their ability to conduct water, analyzing a comprehensive field dataset to illustrate issues in the selection and measurement of different K types, and finally, demonstrating how K can be constrained via simulation in urban systems. We ultimately recommend that K should be measured in ways that are most representative and physically authentic to the hydrologic setting and processes of interest.
Description:
Hydraulic conductivity (K) is a key hydrologic parameter widely recognized to be difficult to estimate and constrain, with little consistent assessment in disturbed, urbanized soils. To estimate K, it is either measured, or simulated by pedotransfer functions, which relate K to easily measured soil properties. We measured K in urbanized soils by double-ring infiltrometer (Kdring), near-saturated tension infiltrometry (Kminidisk), and constant head borehole permeametry (Kborehole), along with other soil properties across the major soil orders in 12 United States cities. We compared measured K with that predicted from the pedotransfer function, ROSETTA. We found that regardless of soil texture, Kdring was consistently larger than Kminidisk; with the latter having slightly less sample variance. Kborehole was dependent upon specific subsurface conditions, and contrary to common expectations, did not always decrease with depth. Based on either soil textural class, or percent textural separates (sand, silt clay), ROSETTA did not accurately predict measured K for surface nor subsurface soils. We go on to discuss how K varies in urban landscapes, the role of measurement methods and artifacts in the perception of this metric, and implications for hydrologic modeling. Overall, we aim to inspire consistency and coherence when addressing K-related challenges in sustainable urban water management.
