|that's a lot of gauges|
There are 7500 stream and reservoir gauges, v. 850 snotel sites. I haven't modified the code to be more selective about how many stations get displayed at once, so users with slower, older machines may find their browser slowing down after enabling the water gauge layer. If this proves to be problematic, let me know - if enough people complain, I'll look into fixing it. On my 3 year old laptop, it was a non-issue.
Much like the snotel layer, zooming in displays the current real-time value for individual gauges. Streams show the flow in cfs (cubic feet per second), and also the water temperature in degrees F, if available. Reservoirs show the current capacity in acft (acre feet). When you mouse over a station, the tooltip shows the time at which it was last updated.
Click on a station to bring up a graph of the last week. Cubic feet per second is in blue, degrees F in red, and acre feet in black - although no station will support all 3 values at once. Mousing over the graph brings up a vertical bar and provides the time and reported values at that point. Because station update frequency varies, there is no time range selector like with the snotel sites, at least for now.
The layer is available via the "Water Gauges" checkbox underneath the Snotel layer, or click here to try it.