input parameters were chosen to represent habitats at the lower flow volume end of this range. The estimated velocity of this system is approximately 0.14 m/s, or about 0.3 mph. m3/sec). Bin 4. High-flow habitats (>100 Water bodies characterized as rivers typically have flow m3 rates of >100 (~3,500 cfs), and very large rivers may exceed a mile in width and have flow m3. volumes that exceed 10,000 Model input parameters were chosen to represent habitats at the lower flow volume end of this range. This represents a faster moving system with an estimated velocity of about 1.4 m/s (3+ mph). Static aquatic habitats. aquatic habitats. Pools, ponds, lakes and several other aquatic habitats are relatively static. Flow is less likely to substantially influence exposure in these habitats because it is generally lacking. Static habitats are broken up into three size categories below based on dilution volume. m3). Bin 5. Low-volume static (0 – 100 Some examples of low volume habitats used by endangered species include vernal pools, small ponds, floodplain habitats that are cut off from main channel flows, underground pools, and seasonal wetlands. Model parameters were selected to represent the lower end of the range used by listed species. m3). Bin 6. Moderate-volume static (100 – 20,000 Some examples of habitats in this category include ponds, some wetlands, and even small shallow lakes. m3). Bin 7. High-volume static (>20,000 This volume was chosen as a point of reference because it is equivalent to the size of habitat typically modeled by EPA in PRZM5/VVWM, a one hectare (~2.5 acre) water body that is 2 meters deep. Additional categories could be added to address endangered species that occur in larger volume habitats; however, it may not be necessary to model larger habitats for step 2. The smaller volume habitats specified here could be used to estimate concentrations around the outer margins of larger lakes. Estuarine and marine habitats. and marine habitats. Three marine habitats are identified and characterized by their position relative to the shoreline and each other. Current pesticide models do not account for transport via tidal and wind generated currents in marine systems. As such, surrogate bins have been identified among the flowing and static bins to represent pesticide concentrations that may be expected in these environments (see Section 3.1.3.3.3 below for more information on which surrogate bins are selected). Bin 8. Intertidal nearshore. The intertidal zone represents the nearshore area between the ordinary high water mark and the extreme low water mark. Depth of intertidal habitats are variable and generally range from 0 to <10 m. Depth within the intertidal habitat depends on the tidal cycle and tidal range. At some locations along the shoreline, there is no discernable difference between high and low tides (tidal range). The greatest tidal range is about 16.3 meters at the Bay of Fundy in eastern Canada. The width of the intertidal area is also location specific and depends on the tidal range and the gradient/slope of the substrate. A depth of 0.5 m and width of 50 m were selected to represent this habitat, considering that exposure to the more vulnerable microhabitats could occur within the intertidal zone.