Search

To evaluate the role of a dam reservoir in the runoff of pollutant loadings from a forested watershed, the input-output budgets in the Ikuno dam reservoir had been investigated for eight years since 1996. The T-N, T-P, TOC and major ionic species in the bulk precipitation, stream water, and outflow were measured. The residence time calculated by using the data of the inflow and outflow was 0.3 year. The average precipitation was 1,772mm during the investigation period (1996-2004). The direct deposition to water surface was less than one percentage to total loadings of nutrients and major ionic species. The ratios of output to input of TOC, TN, and TP were 1.04 to 1.42, and those of major ionic species were from 0.83 to 0.99 except for NO3- ; which was 1.12. However, the ratios of output to input of major ionic species except for NO3- at the Ikuno dam reservoir will be larger, and those of NO3- ; TOC, TN, and TP will be smaller, if we also include rain events. These results suggested that the dam reservoir played a role as a sink for pollutants in forested watershed, and that the pollutant loadings to downstream may decrease. [ABSTRACT FROM AUTHOR]

Water quality and flow rates at a weir installed on the end of Aburahi-S Experimental Watershed (3.34 ha) were measured once a week from 2001 to 2003 and in appropriate intervals from 30 mm to 6 h during five storm runoff events caused by each rainfall from 8 mm to 417 mm. The average annual loads of total nitrogen (TN) and total phosphorus (TP) were calculated to be 19.0 and 0.339 kg ha-1 y-1 from the periodical data by using the integration interval-loads method (ILM), which did not properly account for Storm runoff loads. Three types of L(Q) equations (L = aQb) were derived from correlations between loading rates L and flow rates Q obtained from the periodic observation and from storm runoff observation. L(Q) equation method (LQM), which was derived from the storm runoff observation and allowed for the hysteresis of discharge of materials, gave 9.68 and 0.159 kg ha-1 y-1, respectively, by substitution of the sequential hourly data of flow rates. L(R) equation (L = c(R - r)d) was derived from the correlations between the loads and the effective rainfall depth (R - r) measured during the storm runoff events, and L(R) equation method (LRM) calculated 9.83 ± 1.68 and 0.175 ± 0.0761 kg-1 ha-1 y-1, respectively, by using the rainfall data for the past 16 years. The atmospheric input-fluxes of TN and TP were 16.5 and 0.791 kg ha-1 y-1. [ABSTRACT FROM AUTHOR]

Describes the application of an automatic sampling and measurement system to a mountainous stream investigation during rain events. Efficient gathering of water samples; Testing of the system in a stream in a forested watershed; Water quality.

Studies the runoff characteristics of nutrients in the forest streams of Hyogo Prefecture in Japan. Concentrations of suspended solids; Chemical oxygen demand; Total organic carbon; Daily fluctuation of water quality.