Lakes wind drift

Figure 2-6 a shows the simplest pattern of water movement in a lake, caused by wind exerting a force on the water at the lake surface. The downwind surface current is called wind drift and typically moves at a rate of 2 to 3% of the average wind speed. Clearly, the water moving downwind cannot pile up indefinitely at the end of the lake instead, it flows back upwind, typically at... 

CMorinated pesticides enter the atmosphere primarily through spray drift during application, wind-blown dusts, and volatilization from treated surfaces. Heavy use of chlorinated pesticides generally means that spray drift is the most important means of entry to the atmosphere. In general, application by airplane results in more drift than application by ground equipment, and dusts drift more than sprays. For example, ZDDT particles measuring 2 /rni in diameter drifted about 35 km compared to 70 m for 50 jum droplets (Spencer, 1975). Wind-blown dusts are the most important source of entry to the atmosphere in areas where the use of chlorinated pesticides is either limited or curtailed. The dust source category will continue to contribute substantially to the world-wide redistribution of pesticides, particularly DDT and its derivatives, for many years to come. This partially accounts for the presence of detectable levels of pesticides in the sediments of remote Arctic lakes. 

The basic assumptions in the equation jffe that the ice is deforming by wind blowing towards the shore and drifting freely during offshore winds. Note that = (Xdim - Xf) /xdim wherc Xam IS the horizontal dimension of the lake. 

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