Early winter

Stage = 47.5cm

First snow survey of the winter season today. About 30-50cm of snowpack around the gauging station in the lower elevations. The students carried out the snow survey while I checked on all the lysimeter drains and data loggers. Before the snow accumulates it is usual for the drains to become blocked by needles from the trees. Therefore, it is important to dig out the snow over each drain, clean it out, and then return the snow over the top. At the mature cedar site, all 3 drains were blocked and the lysimeter trays were filled with freezing water (runoff data lost up to December 28). Nothing like dipping your hand into that freezing water to clean out the drains!

Lysimeter at the young cedar site

Winter preparation

Snow lysimeter at the larch site

Today we did the last of the winter preparation by completing the cleaning and checking of the snow lysimeters at Takiya River. There are three snow lysimeters (larch site shown above, mature cedar site, and young cedar site) that monitor the runoff below the snowpack throughout the winter and spring seasons. At each site three large plastic trays collect the runoff and feed it through pipes to a large tipping bucket device (capacity 200mL and 500mL). In short, we are measuring the snowmelt and rain-on-snow runoff, and comparing between the three sites. This experiment has been running for 10 years now! So we can also look at the long-term trends and patterns.



Cleaning finished

Rainy November

The hydrograph above shows the river water level (at 10 minute intervals) from 19 October to 22 November. Compared to the last hydrograph I uploaded on 19 October, we can see that rain storms are becoming more and more frequent as we move into November. On 23 October there is a medium size flood peak of about 1.1m, but the peak is short-lived and by 28 October the water level has fallen rapidly to only 43cm, close to the summer low flow level of 40cm. In November the rain storms are much more frequent so that water levels are almost always above 60cm. The soils in the basin are becoming wetter and wetter and the ground water levels are on the rise as we head towards winter.



Takiya River stage = 57cm

Autumn storms

Takiya River, stage = 60cm, Ta = 11C, Tw = 12C

The season has really changed now that we are into November. The autumn rains are really picking up, and today we got hit by several thunderstorms. The rain was torrential at times, but when we arrived at Takiya River the water level was still only moderate. This was good. It allowed us to get into the river to make a couple of discharge measurements. We always need more data for discharge measurements when the water level is up - these are vital for making the stage-discharge curve (H-Q curve). But when the river is really high, it's too dangerous or even impossible to make a measurement.

Today we had five members in our team, including one first time member. To everyone, thanks for getting out and working in the rain!

New water year

Flows are up! Stage = 48.2 cm

October marks the start of the new water year in many temperate climates of the northern hemisphere. September brings the late summer minimum flows and generally the river basin is in a very dry condition. The new water year begins in this season when water storage within the basin is at a minimum. The groundwater levels are at their lowest, and soil water content is also at a minimum.

During the autumn season, rainfall becomes more frequent, evapotranspiration levels decrease with falling temperatures and shortening day length, and so the soil moisture and groundwater levels begin to rise. Look at the hydrograph above and see how the low flows between the rainfall events are starting to increase above the summer minimum of around 40 cm stage.

Come early winter and snowpack will begin to accumulate, adding further to the storage of water resources in the basin. In winter, we will switch from measuring the streamflow to measuring the snowpack to keep track of the water resources of Takiya River.

New team members

Stage = 43.5 cm, summer low flow continues

Today we were joined by two new team members. The typical induction to Team Hydrology is to take a discharge measurement, our all-important work at Takiya River. Fourth year student team members pass on their skills to the new third year members.

The hydrograph below shows that there have been three rainfall events during the second half of September, including one small size flood on September 24th. However, streamflows quickly return to a summer low flow condition. The minimum stage of 40 cm around September 18-19th is likely to be the minimum flow for the year.

Summer low flows

This summer continues to be relatively dry, as shown in the hydrograph above for the first half of September. The months of June and August have been especially dry as we can see for the precipitation data at Miomote (Amedas):

2012 Monthly Precipitation (with 1981-2010 mean)
June  59 mm (180)
July  201 mm (263)
August  81 mm (209)

No rain fell at all during the 18 days from July 26 to August 12, and the 13 days from 17-29 August. In fact the month of August recorded only 5 days with rainfall.

Stage = 41.5 cm, close to the minimum flow for the summer