With our current understanding of the "drainage basin ratio" method we can continue to understand the operation of the system. Reminding ourselves of pertinent data concerning the projects.
The year-by-year flows at the USGS gage site above Lake Burton is available here . But suffice it to say the average annual flow at this site is about 184 cfs. So, why is the hydraulic capacity of Burton 1400 cfs. Well, a couple of things are involved. First that 184 cfs is at a point where the drainage basin is 58.4 square miles. The drainage basin at the dam is about 118 square miles. Using our drainage basin ratio method, the average annual flow at the dam (powerhouse) is about (118/58.4) times 184. And this math gives us a average flow at the dam of about 371 cfs. But this is still quite different than 1400 cfs which is the hydraulic capacity.
The other thing which plays into this is the "plant factor" of the Burton Hydroplant. That is to say what portion of the time does it operate at full capacity. Given the above tabular data on Burton the average annual enerty is 21.3 gigawatt-hours and the generators have a total capacity of 8.10 mega-watts. With the proper conversions of giga to mega and realizing there are 365 days per year then the plant ON AVERAGE would run about 7.2 hours per day, or a plant factor of about 7.2/24 equals 0.30. That is to say it will run about 30 percent of the time at full capacity (ON AVERAGE). So, now with an average flow of 371 cfs but running only 30 percent of the time then there is about 1250 cfs available during generation, much closer to this hydraulic capacity of 1400 cfs. By the way, merely because the hydraulic capacity is 1400 cfs it will certainly operate at a lower value and maybe even slighly more efficient. One more "by the way", plant factor is also referred to as capacity factor. "Doing the math" on the other projects would lead to the average hours of operation per day at full capacity (just the math):
- Burton 7.2 hours per day
- Nacoochee (Seed) 8.3 hours per day
- Terrora (Rabun) 8.3 hours per day
- Tallulah Falls 6.5 hours per day
- Tugalo 7.0 hours per day
- Yonah 8.2 hours per day