Seeing What You Want to See.

Water content controls plant water availability, slope stability, surface energy balance, and many other conditions that are critical to human safety and ecological function. The value and pattern of water content varies strongly in space and time, controlled by precipitation patterns, soil texture, geologic structure, and subsurface hydrologic conditions. The effects of water content are felt at a local scale (e.g. particle cohesion, root uptake). But, we are increasingly interested in how these local impacts scale up to much larger scales. The measurement challenge is to observe the water content (or other properties) in a manner that is most informative for understanding and predicting the process of interest. This leads to two different measurement strategies for end member process types that can be referred to as critical paths and bulk behaviors. Critical path processes are controlled by a relatively small network of interacting regions within a largely inactive background (e.g. solute transport through fractures, landslide generation). The measurement challenge for these behaviors is to identify the discriminatory measurement times, locations, and types, that characterize these key processes. Bulk behaviors occur throughout the majority of a domain at varying rates (e.g. recharge, surface energy exchange). The measurement challenge for these behaviors is to find a measurement method that upscales in a manner that can be used to understand the upscaled process. This talk will focus on measurement methods for bulk behaviors. In particular, it will address the characteristics of measurement methods that control the nature of water content averaging and the effects of that averaging on process interpretation across a range of scales.