Adjacent to the north end of Bear Lake is a large (65 km2) freshwater marsh. Prior to 1912, Dingle Marsh was separated from Bear Lake by a naturally occurring sandbar and covered approximately 100 km2. Seventy years ago, Utah Power and Light constructed a canal system which effectively diverted the Bear River into Dingle Marsh. The present water system operates by diverting spring water from the Bear River through the marsh and into Bear Lake. During late summer when irrigation demand is high, water is removed from the lake, passed through the marsh, and released into the river. The major objective of this portion of the Clean Lakes Study was to determine the nitrogen, phosphorus, and carbon budgets of Dingle Marsh and define the factors that may regulate the flux of these nutrients into Bear Lake. Sixteen sites within the marsh and all major inflows and outflows were sampled over an 18-month period. The data indicated specific seasonal trends within the marsh (sources or sinks) of the target nutrients. Furthermore, the marsh mass balances indicated that on an annual basis, the marsh acted as a sink. However, during specific periods of time, nitrogen, phosphorus, and carbon were produced within the marsh system and exported (the marsh was a source). Management alternatives were generated as a result of this portion of the project to maximize the marsh as a nutrient sink for inflowing Bear River water.