Figure 3. Fish passability in low (a), intermediate (b), and high (c) water level conditions. Rock weirs that provide 100% fish passability are represented by green keystones, rock weirs that provide fish passage for 4 or fewer fish species are represented by yellow keystones, and rock weirs that do not provide gap or over-weir flow pathways are represented by red keystones. Note that red keystones allow orifice flow and leaping opportunities for fish passage. Further, recirculation zones indicate potential locations for fish refuge during unsuitable swimming conditions.