Long-term changes in pollutant load outflows and purification function in a paddy field watershed using a circular irrigation system

Takeda, Ikuo; Fukushima, Akira

doi:10.1016/j.watres.2005.08.034

Cited by 51 publications

(29 citation statements)

References 10 publications

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“…This is because some paddy fields can perform as pollutant sinks (Tabuchi and Hasegawa, 1995;Iwata et al, 1995) and paddy fields account for approximately 50% of the agricultural land in Japan. In addition, effective phosphorus purification has been observed in a paddy field watershed located in the downstream area of the Hii River (Takeda and Fukushima, 2004;Takeda and Fukushima, 2006). However, there is insufficient data to clearly indicate the relationship between poorly managed agricultural land and the increasing trend of pollutants in rivers, although some simulation results support this hypothesis (Masumoto et al, 2003;Sagehashi et al, 2008).…”

Section: Discussionmentioning

confidence: 99%

Long-term trends in water quality in an under-populated watershed and influence of precipitation

Takeda

Fukushima

Somura

2009

J. of Wat. & Envir. Tech.

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An investigation of the water quality in an under-populated watershed was conducted over a 15-year period in which data was collected at weekly intervals. The purposes of this study were to analyze the long-term trends in water quality and to evaluate the relationship between the water quality and precipitation. Concentrations of total phosphorus (T-P), chemical oxygen demand (COD), and suspended solids (SS) reached remarkably high values under heavy precipitation conditions, and these concentrations increased exponentially with the amount of precipitation. Over the course of this study, the population, number of factories, animals (cow and pig), and area of agricultural land exhibited clearly decreasing trends, while steady progress in domestic wastewater treatment was realized. However, no clear decrease in the parameters of water quality was observed, and some nitrogen, phosphorus, and COD concentrations increased even though no significant change in precipitation occurred. A possible hypothesis explaining this lack of a clear decrease in water quality is that specific pollutant outflows from forests and agricultural lands may have increased in recent years. This is because poorly managed forests and agricultural lands in the under-populated watershed have adversely affected the water quality of the rivers.

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Section: Discussionmentioning

confidence: 99%

Long-term trends in water quality in an under-populated watershed and influence of precipitation

Takeda

Fukushima

Somura

2009

J. of Wat. & Envir. Tech.

Self Cite

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“…A lot of environmentally-friendly agriculture is implemented to paddy fields to reduce effluent load. Increase of the hydraulic retention time of drainage water in a paddy field area by controlling flow rate and reuse of drainage water is considered effective for reducing nutrient load (Takeda and Fukushima, 2006). However, it is suggested that the drainage canal can act as pollutant source when there is no appropriate maintenance of the canal (Hama et al, 2010;Iwasaki et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Effect of Bioturbation by Tubificid Worms on Nutrient Release from the Sediment in an Agricultural Drainage Canal

Hama

Iwasaki

Nagai

et al. 2014

J. of Wat. ^|^ Envir. Tech.

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Nutrient effluent load from paddy fields has a large impact on water quality in the downstream areas. The sediment in drainage canals can act as nutrient source by releasing nutrients to the overlying drainage water. In this study, we evaluated the effect of bioturbation caused by tubificid worms, which live commonly in paddy fields, on nutrient release from the sediment in drainage canals. We investigated a low-lying paddy field district adjacent to Lake Biwa. We also sampled drainage water and the sediment in the study site and conducted incubation experiment of the sediment for four weeks. In the sediment incubation experiment, we added different densities of tubificid worms to the sediment. The effect of tubificid worms on nitrogen release was much larger than that on phosphorus. Nitrogen was mainly released as ammonium nitrogen by the excretion of tubificid worms.

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“…Paddy-field-scale practices include reducing the amount of chemical fertilizer used by applying slow-release fertilizer (Choi and Nelson, 1996;Fan and Li, 2010). District-scale practices include restructuring of vegetation and the reuse of drainage water through irrigation recycling, which can reduce the load of suspended solids (SS) (Hama et al, 2010) and nutrients (Takeda et al, 1997;Feng et al, 2004Feng et al, , 2005Takeda and Fukushima, 2006). However, increased implementation of these measures may cause ponding of water with high SS and P loads in drainage canals.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of Phosphorus in Sediments in Drainage Canals in Paddy-Field Districts around Lake Biwa

Iwasaki

Hama

Osuga

et al. 2013

J. of Wat. ^|^ Envir. Tech.

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Phosphorus (P) is a limiting factor of eutrophication in many lakes. Paddy-field districts are major non-point sources of P; water pollution prevention measures are to be implemented in these districts. However, sediment in drainage canals has a large P buffering capacity and can release P to the water column when input of P from paddy fields is reduced. Therefore, it is necessary to evaluate the amounts of P in the sediment in drainage canals. In this study, the sediments in drainage canals in paddy-field districts around Lake Biwa were investigated. The amounts and fractions of P in the sediments during both the irrigation period and the non-irrigation period were analyzed. Results showed that the mean value of total P in the sediment was 0.6 g/kg in both periods, but total P in non-irrigation periods tends to be greater than that during irrigation periods for each site in the study. Furthermore, over 70% of total P was inorganic on the average. Moreover, the fractions of organic and inorganic P exhibited seasonal variability. The potential contribution of water-extractable P in the sediment to total P in drainage water increased from June to November.

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Long-term changes in pollutant load outflows and purification function in a paddy field watershed using a circular irrigation system

Cited by 51 publications

References 10 publications

Long-term trends in water quality in an under-populated watershed and influence of precipitation

Long-term trends in water quality in an under-populated watershed and influence of precipitation

Effect of Bioturbation by Tubificid Worms on Nutrient Release from the Sediment in an Agricultural Drainage Canal

Characteristics of Phosphorus in Sediments in Drainage Canals in Paddy-Field Districts around Lake Biwa

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