Lake Assessment Program - Fifth and Sixth Crow Wing Lakes, Hubbard County

Fifth and Sixth Crow Wing Lakes are located in South-central Hubbard County approximately seven miles east of the City of Park Rapids. Fifth and Sixth Crow Wing Lakes are medium sized lakes with surface areas of 392 and 321 acres respectively. Fifth and Sixth Crow Wing Lakes were sampled for water quality data during the summer of 1992 by MPCA staff along with representatives of the Fifth and Sixth Crow Wing Lake Association. The work described in this study was undertaken upon a request from the Fifth and Sixth Crow Wing Lake Association. The analysis of water quality data collected during the study period indicates that Fifth and Sixth Crow Wing fall within the transition from mesotrophic to eutrophic classification of lakes. Eutrophic lakes can be described as those lakes that are nutrient rich (phosphorus and\\or nitrogen), have limited oxygen available in the hypolimnion (bottom layer of water) during summer stratification, and are frequently subject to nuisance algal blooms. Oligotrophic lakes are relatively nutrient-poor, clear and have a hypolimnion high in dissolved oxygen. Mesotrophic lakes are intermediate between the two. Based on data from 1992, the mean total phosphorus concentrations of Fifth and Sixth Crow Wing were approximately 24-25 ug/1 (parts per billion), and chlorophyll a approximately 8 ug/L and 11 ug/L (parts per billion) for Fifth and Sixth respectively. The summer mean Secchi disk readings were 9.5 and 7.9 feet for Fifth and Sixth respectively. Based on this data it was estimated that during the summer of 1992 nuisance algal blooms (chlorophyll a > 20 ug/L) occurred less than 2 percent of the time.