Lake eutrophication is the natural process of aging in the lake body with establishment and multiplication of organism over time. The sediment and decaying matter accumulate, gradually filling in the lake basin, transforming the lake from a deep lake to dry land. This process affects the physical make-up of the lake as well as the ecological and biological composition. Eutrophication usually takes thousands of years. However, human interference has greatly accelerated the process by increasing rates of sedimentation and phosphorus loading. China lake has undergone accelerated eutrophication in recent years causing a growing concern for water quality. Algal populations, stimulated by nutrient loading, primarily phosphorus, is a prime indicator of lake eutrophication. The blooms have decreased the aesthetic value of the lake and the quality of drinking water. The small-scale but widespread pollution of China Lake resulting from the everyday activities of residential development and agriculture has accelerated the lake's eutrophication process, causing the most dramatic decline in water clarity ever documented in Maine (Tiejen, 1987).
The intent of the study, conducted by SCOALE, a group of 14 Colby College students, is to examine sources of phosphorus loading through water and land use assessment, and to identify mitigation procedures which would decrease the rate of lake eutrophication and improve water quality. The project is divided in three parts according to the natural division of the watershed: lake body, tributaries, and land within the watershed. These division exhibit all aspects of phosphorus loading. A major source of phosphorus loading is from soil erosion, and can be accelerated by unregulated land use procedures such as agriculture and silviculture. Present water quality within the lake will be determined and compared with historical patterns by the lake proper division. This component includes testing abiotic and biotic parameters, with the primary focus being on phosphorus loading. The tributary component determined water characteristics of selected tributaries leading into the lake in order to assess potential trouble spots. They sampled during normal conditions and during a storm event. The tributary component then compared the data from the two conditions to determine changes in phosphorus levels due to increased water flow. The land use division assessed historical and present day land use within the watershed area. This component includes evaluation of the trends of historical land use patterns in relation to phosphorus levels in the lake proper.
The primary purpose of this report is to provide qualitative information, a data base, and recommendations for improvement programs in the China Lake watershed through an integrated approach describing the etiology and particular problem sources within the watershed. The study will be useful for community education to encourage understanding of the fragile ecosystem of China Lake and to encourage proper land use management.
Student Collective Organized Against Lake Eutrophication, Colby College and Problems in Environmental Science course (Biology 493), Colby College, "An Analysis of the Factors Influencing Eutrophication within the China Lake Watershed" (1989). Colby College Watershed Study: China Lake (2005, 1989). 14.