Abstract
The covered-ice breakup in subarctic to arctic rivers in the early snowmelt season often gives any damage to instruments monitoring physical and chemical factors of water. The serious condition has brought few time series data during the snowmelt runoff except the river stage or discharge. In this study, the contribution of snowmelt runoff to the discharge and sediment load is quantified by monitoring water turbidity and temperature at the lowest gauging station of U. S. Geological Survey in the Yukon River, Alaska, for more than 3 years (June 2006 to September 2009). The turbidity was recorded by a self-recording turbidimeter with a sensor of infrared-ray back-scattering type, of which the window is cleaned by a wiper just before a measurement. The turbidity time series, coupled with frequent river water sampling at mid-channel, produce time series of suspended sediment (SS) concentration, particulate organic carbon (POC) concentration and particulate organic nitrogen (PON) concentration (mg?L–1) by using the high correlation (R2 = 0.747 to 0.790; P 11 to 2.01 × 1011 m3), 8.7% - 22.5% of the annual sediment load (3.94 × 107 to 5.08 × 107 ton), 11.6% - 23.7% of the annual POC flux (4.05 × 105 to 4.77 × 105 ton), and 10.3% - 24.5% of the annual PON flux (2.80 × 104 to 3.44 × 104 ton). In the snowmelt season, the peak suspended sediment concentration preceded the peak discharge by a few days. This probably results from the fluvial sediment erosion in the river channels.
Highlights
Many subarctic to arctic rivers are frozen in winter, and the snowmelt runoff starts in March or April, often accompanied by covered-ice breakup (URL http://aprfc. arh.noaa.gov/)
In this study, associated with river discharge to the ocean [7,8], the water turbidity and temperature of the Yukon River are monitored at the lowest gauging station of US Geological Survey (USGS) for more than three years, and the contribution of snowmelt runoffs to the annual river fluxes of water, sediment, particulate organic carbon (POC) and particulate organic nitrogen (PON) is evaluated
For 18 March-1 April 2007 and 22 March-2 April 2008, the temperature recorded below 0 ̊C, indicating that the temperature data logger was frozen into ice (Figure 5(a))
Summary
Many subarctic to arctic rivers are frozen in winter, and the snowmelt runoff starts in March or April, often accompanied by covered-ice breakup (URL http://aprfc. arh.noaa.gov/). The breakup ice could often give any damage to the equipment for monitoring physical and chemical factors of water by jamming rivers (URL http://www.denniskalma.com/ice.html). For such rivers, up to date, there are few time series data during the snowmelt runoff except for water level (or discharge). In this study, associated with river discharge to the ocean [7,8], the water turbidity and temperature of the Yukon River are monitored at the lowest gauging station (site PLS) of US Geological Survey (USGS) for more than three years, and the contribution of snowmelt runoffs to the annual river fluxes of water, sediment, POC and PON is evaluated
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