Now each parameter has a scale that makes sense. A series of pie charts would not have done the job quite as well, because it's harder for viewers to directly compare areas of pie slices than heights of stacked bars. This graph requires some sophistication to interpret. The viewer needs to know, or be told in a caption, that most mayflies, stoneflies, and caddisflies are pollution sensitive, most beetles are moderately sensitive, and most worms and midges are pollution tolerant. With this information, the story becomes clear.
Loading is calculated by multiplying instream total nitrogen by stream flow.
A table showing the loading calculations helps readers interpret the graphs. Each of these graphs tells a different piece of the story. The bar chart tells you about conditions in the rivers themselves, while the pie chart tells you which rivers have the greatest impact on the estuary. So if you're interested in lowering nitrogen concentration in the estuary, you'd probably want to target your efforts at Big River. But if you're more concerned about levels in the rivers themselves, you would target Bear Creek.