FIG. 3. Conceptual diagram showing the estimated extent (m) of measurements and the spacing in time. The extent of the watersheds is determined from the major axis of a 2:1 ellipse and surface areas according to Zielinski (2002). B, basin (2500–25,000 km²); SB, subbasin (250–2,500 km²); W watershed (80–250 km²); SW, subwatershed (1–80 km²); C, catchment (0.1–1 km²). Current technology is constrained to measuring processes with space and time scales consistent with boxes having solid lines. The new technologies and methods (dashed lines) form a bridge between current sensor and remote sensing capabilities. They improve our ability to monitor rapid soil moisture change at small watershed scales.