Although precipitation in much of the Peace River area has been well above average for the first four months of 2011, B.C. Hydro does not expect any problems with overflow at the Williston Reservoir.
The snow packs around the Williston Reservoir are basically normal right now, says B.C. Hydro Community Relations Co-ordinator Bob Gammer.
Gammer says the water level at the Williston Reservoir is even slightly lower than normal for this time of year and is still dropping. Thus, there is still a considerable amount of storage space for the expected spring and summer runoffs.
He says approximately 50 per cent of the runoff going into the reservoir each year comes from rain and the other 50 per cent from snow. He also says the Williston Reservoir has more than enough storage space to handle summer precipitation, along with runoff from the snow melt in late May and early June.
Gammer says the reservoir is at capacity when it reaches approximately 672 metres above sea level. At 4:30 a.m. Monday the reservoir level was at 656.949 metres above sea level.
Precipitation levels measured at the Fort St. John airport for the first four months of 2011 have been just slightly less than 178 millimetres – more than double the average. The snow pack around the reservoir is currently at 945 mm water equivalent.
If the temperature increases at minor intervals over the next few weeks to months, then the snow melt would probably not pose significant runoff problems. However, problems would occur if temperatures increase dramatically over a few days, causing the snow to melt very quickly.
Gammer says although water is continuously discharged through the generating station at the reservoir, if the reservoir level becomes too high to be able to discharge through the generating station, there is also a spillway in place. However, he says B.C. Hydro has only had to use that spillway about seven times in the past 40 years, most recently in 2002.
If the spillway is used, the water level along the Peace River could increase, depending on how much water is spilled over and for how long, but the amount of runoff from snow melt may not be known for at least another few weeks.