Aris Severn

Lake Classification in Agriculturally Dominated Eco-Systems

Reliable indicators of eco-system function can be developed by examining patterns between organisms and their associated abiotic environment. While many of these relationships have been examined in other parts of the Midwest, functional models have yet to be established for lakes and reservoirs in areas where land use is devoted to agriculture. Nebraska provides an ideal model in which to develop a comprehensive lake classification scheme for agriculturally dominated aquatic eco-systems. It occupies the north-south temperature cline and east-west precipitation/evaporation cline for the mid-continent, with both short and tall grass prairies, the largest underground aquifer in North America, 85% of the land used for agricultural purposes, and the largest area of grass stabilized sand dunes in the world. A protocol is being deve! loped for grouping lakes and reservoirs into appropriate classification strata based on limnological water quality parameters. Seventy-seven lakes throughout the state were sampled in 2001 to fill in gaps in the current water quality database of 159 Nebraska lakes and reservoirs. From this database, lakes and reservoirs will be classified hierarchically using a combination of rule-based and data based statistical approaches. Biological indicators will be developed based on plankton assemblages, and special emphasis will be placed on developing methods to remotely sense biological indicators of water quality based on the optical phytoplankton pigment structures of lakes. In addition, the role of Geographic Imaging Systems (GIS) in the classification strategy will be established along with the formation of a technology transfer link between the p! roposed classification scheme and the end users.

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