The humic content of lake water and its relationship to watershed and lake morphometry

Abstract

The relationship of lake water color (mg liter−1 Pt) to watershed and lake morphometry, derived from topographical, hydrological, and bathymetric maps, was examined by log‐linear multiple regression on a data set obtained from 337 lakes from the northern United States and Canada. Color was positively related to the drainage ratio, and negatively related to watershed slope, mean lake depth, and lake area. Lakes that receive significant indirect drainage from other lakes were less colored than headwater lakes. The best regression model explained 60% of the variance in lake water color. Regression models were calculated separately for four geographic regions (the Laurentians of Quebec, eastern Quebec‐Maine, northeastern Wisconsin, and the Experimental Lakes Area of western Ontario). The regression coefficients for the most significant variables, drainage ratio, watershed slope, and lake area were similar over these four areas, but the regional models still had significantly smaller standard errors than the general model based on the whole data set.