Regional relationships between geomorphic/hydrologic parameters and surface water chemistry relative to acidic deposition

Abstract We determined geomorphic and hydrologic parameters for 144 forested, lake watersheds in the Northeast (NE) of the United States based primarily on measurements from topographic maps. These parameters were used to test for relationships with selected surface water chemistry relevant to acidic deposition. Analyses were conducted on regional and subregional scales delineated based on soils, land use, physiography, total sulfur deposition and statistical clustering of selected geomorphic/hydrologic parameters. Significant relationships were found among the geomorphic/hydrologic parameters and the surface water chemistry for the NE. Elevation had the most significant relationship with surface water chemistry, particularly in the mountainous areas of the NE. Other factors occurring consistently as significant predictors of surface water chemistry were maximum relief, relief ratio, runoff, and estimates of basin elongation. Results suggest that elevational parameters might be surrogates for other watershed characteristics, such as soils or spatial deposition patterns. Stream order was a significant class variable with lower order systems tending to be associated with low pH and acid neutralizing capacity high sulfate and total aluminum. Analysis at the sub-regional level improved the correlations among the descriptive parameters and surface water chemistry over the findings for the total NE. This improvement in correlation is probably due to reduced heterogeneity within the data at the sub-regional level. Also, stratifying the data based on factors such as soils and sulfur deposition removes some of the influence these factors have on surface water chemistry.