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Figure 7
Set-up:
Each bar in this graph represents the annual average for each year during 1999-2004. The years are identified along the bottom of the graph, while phosphorus is scaled on the left side in micrograms per liter (parts per billion). The horizontal line within the graph represents the overall average phosphorus value for this site (an average based on all data). Bars that extend above this line indicate years with higher than average phosphorus values, while bars that extend downward represent years with lower than average phosphorus.
Interpretation:
Annual average phosphorus concentrations were above the overall average in 1999 and 2000, with values of ~70 and ~100 micrograms per liter. Annual averages have been below the overall average since the treatment plant upgrade, with values ranging from ~55 to ~35 micrograms per liter. The data show that there is less phosphorus at this upper James River site since the treatment plant upgrades.
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