Fine weather snowmelt

Stage = 44cm and crystal clear water

The peak of the snowmelt season seems to have passed now. Today we can see that the water is crystal clear for the first time in several weeks (compare to March 28 photo in earlier post which also had stage of 44cm). The river is no longer carrying the greyish coloured sediment that we saw during early spring. Looking at the hydrograph below we can see how the flow decreases rapidly after the previous rain-on-snow peak, followed by two weeks of fine weather snowmelt. The only influence on the discharge is the daily pulse of snowmelt (often called diurnal melt pattern) caused by warmer day-time temperatures, plus the background groundwater flow. Studying the diurnal melt pattern it seems very consistent from day to day, with the minimum flow around 12 noon and the daily peak around 1800 hours. We can also clearly see that snowmelt is "on the wane" or decreasing over this period, as the mountain snowpack is retreating and disappearing.


Decreasing snowmelt with diurnal melt pattern



Rain-on-snow

Stage = 88cm, too deep to wade!

First visit to Takiya this month. The water was even higher than last time on 27th April, due to continued snowmelt and some heavy rain over the past few days. Rain-on-snow events bring high water levels when rain falls on a melting snowpack. Especially if the rainy weather comes after a period of warm snowmelt conditions, and if the rain occurs with a strong warm wind. Warm winds can be more effective in melting snow than sunny weather! Early morning on 10th May a weather system passed over Niigata which brought very warm and strong winds, and heavy rain. Miomote AMeDAS station recorded 46mm precipitation with hourly rates up to 23mm. This caused a large rain-on-snow peak stage of 1.31m, as you can see in the stage hydrograph below. On other days with fine weather snowmelt, you can see the daily fluctuation in stage caused by the daily pulse of snowmelt entering the river (click on the chart to enlarge).

Takiya stage hydrograph (27 April - 13 May 2011)

Looking upstream to the bridge and gauging point

May 13th and still a patch of snow in the shade of the cedars at near sea-level (40m)

Snowmelt Season

April 27 (flow stage = 74cm, snow depth = 30cm)

Usually March, April and May is snowmelt season for the Takiya River catchment. However, this year snowmelt season is about a month later than usual due to record snowfalls during the winter and cold spring temperatures. The photo above shows the main gauging station, and most of the flow in the river is coming from snowmelt, plus some overnight rain. About 30cm depth of snowpack remains under the cedar trees. Compare this photo with those taken on my earlier field trips this spring. Note how the snowpack is receeding on the river banks, and how the colour of the water changes as more sediment is carried by the rising waters.

April 15 (flow stage = 69cm)

April 6 (flow stage = 51cm, snow depth = 95cm)

March 28 (flow stage = 44cm, snow depth = 99cm)