If you squint really hard, you can just barely make out the
first tiny trickle of water melting off the snow on the mountains towering over
the Fraser Valley. Okay, maybe not. But if the last few days of balmy weather are
to be trusted, the spring freshet can’t be far off.
I’m back in British Columbia to sample the Fraser River
during the most dynamic time of year: the spring freshet. This is the most exciting period when the
river shifts from its quiet, winter-time state to a rushing torrent of water and
mud. As the ground warms and the water
level rises, vast stores of sediment, nutrients, and organic matter are flushed
off the land and into streams across the basin, drastically changing the chemistry of the
water. This is the most important time
to sample a river, because the composition of many chemical
properties is so different from the rest of the year, and the amount of
material exported dwarfs that of the summer, fall, and winter.
Our sampling campaign during the 2011 freshet captured a
snapshot of this period all over the basin, in tributaries from the Rocky
Mountains to the floodplain. This year,
I’m sitting in one spot – our time series location in Fort Langley, near the
river mouth – and collecting samples every day to make sure I don’t miss the
chemical pulse I expect to see right as the water level begins to rise.
