This elevation graph is the only online way of estimating when the powerhouse is on or off. It can also provide a rough estimate of flow when compared to outflow figures at Millerton DailyReport - pdf. On this page, both inflow and outflow figures are 24 hour averages. The actual inflow will vary considerably during the day as the powerhouse is turned on or off, and ramped up or down. Actual inflow can range from 0 up to 5,000 cfs. The total average outflow tends to be fairly stable from hour to hour, so just assume that the outflow today is about the same as yesterday. Look at the daily fluctuations in the elevation graph. If the graph is level, the powerhouse is releasing the same flow as the reservoir outflow. If the gragh is going up, the powerhouse is releasing more than the reservoir outflow. If the graph is going down the powerhouse may be off or only releasing a small amount.
The Millerton Daily data page shows how much average flows have fluctuated for several past days. It is always two days behind in reporting.