Revisiting Hydrologic Sampling Strategies for an Accurate Assessment of Hydrologic Connectivity in Humid Temperate Systems

Hydrologic connectivity is crucial to our understanding of catchment dynamics, yet there is no consensus among hydrologists about what it is exactly, nor is there any unambiguous way of assessing it from field observations. This review is articulated around the questions: (i) what are the main variables to investigate? and (ii) what is the optimal sampling strategy for hydrologic connectivity prediction in humid temperate systems? Because there are multiple definitions for the concept of connectivity, we first identify the major variables to monitor. Then, the ability of several sampling schemes to meet specific criteria is assessed. None of the schemes fully complies with the criteria even if they are combined in a strategic way, and their individual performance is highly dependent on data resolution. While a two-stage sampling is recommended, it reflects the difficulty in depicting the complex spatial patterns in hydrologic connectivity.