Title:: Hydraulic Property Correspondence and Upscaling for Arid and Semi-Arid Hydrologic Processes
Project Type: Research
Start Date: 03/01/2006
End Date: 02/28/2007
Congressional District: Nevada 01
Focus Categories: Hydrology, Water Supply, Methods
Keywords: soil hydraulic properties, hydraulic correspondence, upscaling, averaging schemes, heterogeneous soils
Principal Investigator: Zhu, Jianting Julian (Desert Research Institute)
Federal Funds: $8,955
Non-Federal Matching Funds: $17,909
Abstract: Simulations of unsaturated flow and solute transport in soil typically use closed-form hydraulic properties to represent water-retention characteristics and unsaturated hydraulic conductivities. Gardner and Russo exponential model and van Genuchten S-shaped model represent some of the most widely used hydraulic functions. Two issues related to hydraulic functions need to be addressed. The first issue is the forms of hydraulic functions that are used to characterize hydraulic properties. Conditions for which alternative forms of the hydraulic functions give the same or similar hydrologic responses are important in many applications. The second issue is the upscaling of hydraulic properties. Based on point-scale measurements, those parameter models are only valid at the point or local scales. When those models are used in larger (plot, field, watershed or regional) scale processes, major questions remain about how to average the spatially variable hydraulic properties over a heterogeneous soil volume. Using some locally measured hydraulic parameter data sets for these two models, this study investigates the above mentioned two major issues related to soil hydraulic properties: (1) hydraulic parameter correspondence between two of the more commonly used soil hydraulic property functions (i.e., the Gardner and the van Genuchten equations), and (2) its applications to upscaling of hydraulic properties for heterogeneous soils. We will establish hydraulic parameter correspondence based on hydrologically significant criteria of producing same surface soil moisture and predicting same vertical moisture flux across land-atmosphere boundary and then cast the established correspondence into hydraulic upscaling framework for large scale hydrologic processes.
The novelty of the proposed research is to use two conceptually new equivalence criteria based on important hydrologic process equivalence to establish correspondence among different hydraulic property models and to adopt p-norm averaging schemes that are better defined and less variable in relation to heterogeneity of soil hydraulic properties and other environmental conditions.
The developed conceptual approach can be extended to other large scale hydrologic processes that are critical in Nevada's water resources and budget studies. The expected outcomes from this project will be relationships of effective averaging schemes for the two most widely used hydraulic property models and optimal averaging schemes for the hydraulic parameters for a variety of hydrologic processes and conditions with an emphasis on dry scenarios, typical for arid and semi-arid regions in western United States.
Progress/Completion Report, PDF