9:30 AM - 9:45 AM
[AHW19-03] Impact of rainfall on nutrients and iron concentration in a shallow and small lake, Lake Kibagata
Keywords:Lake water environments, Effects of rain on water quality, primary production
Lake water environments play an important role on biodiversity, water resources, and human recreation in terrestrial region. However, global warming affects water level, water quality, primary production, and watershed conditions of lakes, especially shallow and small lakes. It needs to investigate the present lake environments for better understanding their response and the countermeasure to global warming. We focuses on the effects of rainfall on water quality in shallow and small lakes in Japan which lies in the Asian Monsoon Zone.
The research was performed at a shallow and small lake, Lake Kibagara (lake area of 1.09 km2, average water depth of 2.2 m, and watershed area of 37.4 km2) in Ishikawa Prefecture, Japan by using an automatic water sampler (ISCO 6712 water sampler) at one hour interval during rain events. Nutrients concentration was determined by an autoanalyzer. Major cation and iron concentration was determined by an ICP-OES. Water isotope composition, dD and d18O values, was measured by wavelength-scanned cavity ring-down spectroscopy.
The continuous monitoring research was carried at three times from August to October 2022. Total precipitation was 44.5 mm during August 16-17, 53.0 mm during September 19-20, and 21.0 mm during October 17-18. Variation of major cation concentration is different from the August-October samples and the September samples. For example, Na+ concentration ranged from 9.1 to 9.7 ppm for the August samples, 9.3 to 13.0 ppm for the September samples, and 9.9 to 10.7 ppm for the October samples (Fig. 1). The δD values of lake water is also different variation between the August samples (-57.8‰ to -55.2‰) and the September samples (-61.0‰ to -45.5‰). The September samples show the maximum at 2 hours and the increase in NO3-N, PO4-P, and Fe concentrations from 7 hours after the maximum precipitation (Fig. 2), though the August samples have a small variation. The variation pattern shows two response to the rainfall event, that is different transport pass and/or their sources at the first 8 hours and after 10 hours. The results suggest that precipitation over 50 mm and continuous precipitation (broad maximum of 11.5 and 12.5 mm) affect lake water quality in Lake Kibagata.
Fig. 1 Temporal variation of Na+ concentration in the lake water from Lake Kibagata during August 16-17, September 19-20, and October 17-18.
Fig. 2 The monitoring results of water quality during September 19-20.
Precipitation data was cited from the AMeDAS data at Komatsu Observatory from the Japan Meteorological Agency. The water level was cited from Water Information System of the Ministry of Land, Infrastructure, Transport and Tourism.
The research was performed at a shallow and small lake, Lake Kibagara (lake area of 1.09 km2, average water depth of 2.2 m, and watershed area of 37.4 km2) in Ishikawa Prefecture, Japan by using an automatic water sampler (ISCO 6712 water sampler) at one hour interval during rain events. Nutrients concentration was determined by an autoanalyzer. Major cation and iron concentration was determined by an ICP-OES. Water isotope composition, dD and d18O values, was measured by wavelength-scanned cavity ring-down spectroscopy.
The continuous monitoring research was carried at three times from August to October 2022. Total precipitation was 44.5 mm during August 16-17, 53.0 mm during September 19-20, and 21.0 mm during October 17-18. Variation of major cation concentration is different from the August-October samples and the September samples. For example, Na+ concentration ranged from 9.1 to 9.7 ppm for the August samples, 9.3 to 13.0 ppm for the September samples, and 9.9 to 10.7 ppm for the October samples (Fig. 1). The δD values of lake water is also different variation between the August samples (-57.8‰ to -55.2‰) and the September samples (-61.0‰ to -45.5‰). The September samples show the maximum at 2 hours and the increase in NO3-N, PO4-P, and Fe concentrations from 7 hours after the maximum precipitation (Fig. 2), though the August samples have a small variation. The variation pattern shows two response to the rainfall event, that is different transport pass and/or their sources at the first 8 hours and after 10 hours. The results suggest that precipitation over 50 mm and continuous precipitation (broad maximum of 11.5 and 12.5 mm) affect lake water quality in Lake Kibagata.
Fig. 1 Temporal variation of Na+ concentration in the lake water from Lake Kibagata during August 16-17, September 19-20, and October 17-18.
Fig. 2 The monitoring results of water quality during September 19-20.
Precipitation data was cited from the AMeDAS data at Komatsu Observatory from the Japan Meteorological Agency. The water level was cited from Water Information System of the Ministry of Land, Infrastructure, Transport and Tourism.