Index Value Plot

Index value plots show the differences between two extremes with the normal being placed in the middle. In this case it is being related to stream flow and where normal lies. This type of graph is helpful when it comes to showing anomalies in water flow over time. And also shows that for the most part the water flow has been closer to the dry side.

http://waterwatch.usgs.gov/?m=real&w=plot&r=nm