Full ecoregional plan - Conservation Gateway

Condition ResultsGIS ScreeningSize 2 Watershed: Within System Relative AnalysisA “Within System” Analysis was run to highlight the highest ranked watershed within eachsystem type. A subset of the related condition variables were used in a Principle ComponentsAnalysis (PCA) Ordination within each of 3 relatively non-correlated impact categories. PCAOrdination runs were made separately within each EDU for the Land Cover/Road Impact and forthe Dam/Drinking Water Supply Impact. The 1 st output axis, which explained most of thevariance of watersheds in terms of that impact area, was used to create a single reduced “rankvariable” to rank the watersheds from best to worst in terms of that impact area. Simple ranking,instead of ordination, was ultimately used to create a summary rank for the Point Source Impactbecause all the input point source response variables were extremely highly correlated with thevariable total point sources / stream mile.The input variable set for PCA Ordination/Ranking Analysis was as follows:Land Cover/Road Impact Ordination Variables:P_imp - % impervious surfacesP_nat - % nat land coverRdx_pstmi - # road stream crossings per stream mileRdtot_psqmi - total miles of roads per square miles of the watershedDam / Hydrologic Alteration Impact Ordination Variables:Damst_stmi - total NID dams per stream mileLdam_stmi - # large dams ([Nid_height] >= 20 or storage > 1000 if NID height was lessthan 20 feet)Tsto_pstmi = total storage in acre/feet per stream mileDwspmi - # drinking water supply per stream milePoint Source Impact (simple ranking):TPS_pstmi - total point sources per stream mile (CERCLIS, IFD, PCS, TRI, MINES)Figure 9 displays the size 2 watersheds that ranked high within their system type. This maphighlighted watersheds that had scored 1 st –4 th within the system type in terms of land cover/roadimpacts as a solid, those that had scored 1 st or 2 nd in dam/drinking water supply impacts as ahatch, and those that had scored 1 st in point source impacts as a dot.REVISED 6/2003AQUA-RESULTS-26