It was clear that the expected annual power output of 280 GWh from Pak Mun Dam could not all be peak load production. Allowing for a four-hour daily peak demand15/ period which was the convention at the time, the maximum possible annual peak load generation that could have been expected from the 136 MW installed capacity at Pak Mun was only 199 GWh (4*365*136/1000), or about 70% of the claimed possible total output. That apart, the hydrological data that underlied EGAT’s assumptions were not actual historical records at all, but reconstituted flow estimates made by the consultants SOGREAH in 1985. The water discharge estimates were based on less than complete projections of other ongoing and future irrigation developments and their expected water off-takes within the Mun-Chi river basin, of which Pak Mun was a part. With actual developments to date, it is entirely possible— indeed likely—that SOGREAH’s estimate of residual water discharge at Pak Mun will prove to be erroneous on the optimistic side, by at least 10% according to one later investigation.16/ By the same token it is also likely that the peak demand power output expected by EGAT from Pak Mun, based on the optimistic reconstituted-flow calculations would likewise be an overestimate. If not all of the available water at Pak Mun can be used to support peak power on demand, and if what is actually available—the water discharge profile—is likely to be less than was first estimated, then the likely benefits over the project lifetime will be less.