Temporal and spatial change in phosphate–phosphorus concentration and modeling with land-use variation in Sengari reservoir basin, Japan

• Published in: Paddy and water environment 2019-04, Vol.17 (2), p.131-139
• Main Authors: Kimengich, Baobab Kibet, Takeuchi, Junichiro, Goto, Keitaro, Fujihara, Masayuki
• Format: Article
• Language: English
• Subjects: Agricultural management; Agriculture; Aquatic ecosystems; Basins; Biomedical and Life Sciences; Coefficients; Ecosystems; Ecotoxicology; Environmental degradation; Eutrophication; Forests; Geoecology/Natural Processes; Golf courses; Hydrogeology; Hydrology/Water Resources; Irrigation; Irrigation tanks; Land use; Life Sciences; Mineral nutrients; Modelling; Nutrient loading; Nutrients; Phosphates; Phosphorus; Pollutants; Prediction models; Regression analysis; Regression models; Reservoirs; Residential areas; Rice fields; Rivers; Rural land use; Septic tanks; Sewage; Sewage tanks; Sewage treatment; Sewage treatment plants; Soil Science & Conservation; Tanks; Wastewater treatment; Wastewater treatment plants; Water pollution; Water quality; Water quality management; Water treatment
• ISSN: 1611-2490; 1611-2504
• DOI: 10.1007/s10333-019-00705-6

Severe degradation of water quality from nutrient pollutants has increased eutrophication that affects aquatic ecosystems and increases the cost of water treatment. This study was conducted in the Sengari Reservoir basin, which experiences high eutrophication due to phosphorus in the nutrient load it receives. Dissolved phosphate–phosphorus (PO 4 –P) accounts for the highest ratio of total phosphorus flowing into the reservoir. The aim of this study was to quantitatively investigate the PO 4 –P load emitted from different land uses in the basin. Water was sampled at regular intervals and analyzed to understand the temporal and spatial changes in PO 4 –P concentration in the basin’s rivers. Linear regression water-quality predictive models were thereafter constructed. A comparison was made between the irrigation and non-irrigation periods, and sub-basins with septic tanks and those with rural sewage treatment plants. Results from linear regression models indicated that paddy fields and residential areas had the highest coefficients compared to forests and golf courses. The irrigation period had a high PO 4 –P concentration compared to the non-irrigation period. Sub-basins with septic tanks had a high PO 4 –P compared to those with rural sewage treatment plants. Effectively managing water quality in the Sengari Reservoir to reduce eutrophication depends on significantly reducing the nutrients in agricultural areas, particularly during the irrigation period, and adequately treating water before discharging it into the rivers. The models provided a helpful tool for conducting a non-point source phosphorous investigation in the Sengari Reservoir to prevent excessive pollution from nutrient load.