Methods

For each contribution and threat layer, the distribution of watershed index values was determined, and a percentile ranking was assigned to each watershed. Threats to particular contributions were evaluated in two steps. First, the averages of the contribution and threat percentile rankings were calculated on a watershed-by-watershed basis. Second, the distribution of the averages was determined and used to assign a new percentile ranking to each watershed. The results are depicted using percentile-based categories similar to those used for individual contributions and threats.