[1] The relationship between soil moisture and outflow is fundamental to land surface water and energy balance monitoring and modeling. However, characterizing it at levels above a point scale is complicated by factors including climate and surface heterogeneity, presence of lateral transports, and mismatches between spatial resolutions of measurements and models. We investigate the distinct roles of heterogeneity and nonlocal interactions in scaling this relationship from points to areas. Locations are modeled as independent columns, using measured soil moisture and precipitation data in a conditional averaging approach to estimate the local moisture outflow relationship. These estimates are aggregated using a distributional approach to account for the effect of heterogeneity. The locations are then treated as one large column; that is, the moisture outflow relationship is estimated directly from spatially aggregated data. We demonstrate that statistically significant differences between the two estimates indicate that the system is not well represented by the independence assumption; that is, local outflow is dependent on local moisture and is also independently influenced by large-scale moisture. We applied these methods to data from a hillslope, a watershed, and the state of Illinois and found that heterogeneity and nonlocal processes significantly affected scaling in all three. The identified nonlocal effect is to decrease (increase) local outflow during large-scale dry (wet) anomalies. A possible pathway is through decreased wind speed during dry anomalies. The combined effect increases the sensitivity of outflow to soil moisture as scale increases. These results could have implications for specifying parameters in large-scale models, especially those calibrated with smaller-scale field data.Citation: Arrigo, J. A. S., and G. D. Salvucci (2005), Investigation hydrologic scaling: Observed effects of heterogeneity and nonlocal processes across hillslope, watershed, and regional scales, Water Resour. Res., 41, W11417,
Fluid circulation in the Earth's crust plays an essential role in surface, near surface, and deep crustal processes. Flow pathways are driven by hydraulic gradients but controlled by material permeability, which varies over many orders of magnitude and changes over time. Although millions of measurements of crustal properties have been made, including geophysical imaging and borehole tests, this vast amount of data and information has not been integrated into a comprehensive knowledge system. A community data infrastructure is needed to improve data access, enable large-scale synthetic analyses, and support representations of the subsurface in Earth system models. Here, we describe the motivation, vision, challenges, and an action plan for a communitygoverned, four-dimensional data system of the Earth's crustal structure, composition, and material properties from the surface down to the brittle-ductile transition. Such a system must not only be sufficiently flexible to support inquiries in many different domains of Earth science, but it must also be focused on characterizing the physical crustal properties of permeability and porosity, which have not yet been synthesized at a large scale. The DigitalCrust is envisioned as an interactive virtual exploration laboratory where models can be calibrated with empirical data and alternative hypotheses can be tested at a range of spatial scales. It must also support a community process for compiling and harmonizing models into regional syntheses of crustal properties. Sustained peer review from multiple disciplines will allow constant refinement in the ability of the system to inform science questions and societal challenges and to function as a dynamic library of our knowledge of Earth's crust.
Hydrologic science has largely built its understanding of the hydrologic cycle using contemporary data sources (i.e., last 100 years). However, as we try to meet water demand over the next 100 years at scales from local to global, we need to expand our scope and embrace other data that address human activities and the alteration of hydrologic systems. For example, the accumulation of human impacts on water systems requires exploration of incompletely documented eras. When examining these historical periods, basic questions relevant to modern systems arise: (1) How is better information incorporated into water management strategies? (2) Does any point in the past (e.g., colonial/pre-European conditions in North America) provide a suitable restoration target? and (3) How can understanding legacies improve our ability to plan for future conditions? Beginning to answer these questions indicates the vital need to incorporate disparate data and less accepted methods to meet looming water management challenges.
OPEN ACCESSWater 2011, 3 567
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