4/30/2013

Homework:  (Due 4/7/2013)  Great Pond has an average depth of 6.4 meters, a surface area of 3452 ha and a shoreline length of 74.2 km.   The residence time of water in the lake is 2.3 years.  Assume the outflow of water over the Great Pond Storage Dam has a phosphorus concentration of 8 ppb (as P), and the inflow water (streams and rain) has phosphorus concentration of 4 ppb.   The average annual sediment flux of phosphorus is 5 milligrams (as P) per meter squared.   If the lake is 30% developed with an average shorefront lot length of 100 meters, what is the annual flux of P per lot?

If the average P in the lake has increased 0.3 ppb per decade for the last 50 years, what was the anthropogenic flux from each lot 50 years ago?

If the number of developed lots increases by 40% over the next two decades, what will be the new steady state P concentration in the lake in twenty years?  Assume the same anthropogenic P flux per lot as today.

Which of the assumptions in this problem is the worst?

Resources:   An Excellent Overview of Redox Chemistry,  CH217-Redox.1.2012,  Nutrient Data

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