Aquatic Selection Index

This dataset represents the selection index used to create aquatic ecosystem-based cores. The selection index is a continuous surface in which every cell is assigned a value (0-1) based on its relative ecological integrity within each HUC6 watershed. Specifically, the selection index is equal to the index of ecological integrity except in headwater creeks where it is the average of IEI and USGS's stream temperature tolerance index. Aquatic core areas are created, in part, by choosing cells above a certain index value and spreading from these "seed areas" through adjacent aquatic cells to build larger, buffered cores of relatively high ecological value.