Spatio-temporal characterization of nutrient and organic pollution along with nutrient-chlorophyll-a dynamics in the Geum River

Abstract

River water pollution is one of the biggest environmental challenges in the world. Therefore, it is imperative to assess the spatial and temporal variability of surface water quality to manage water resources from pollution. This study aimed to identify spatio-temporal variations of Geum River surface water quality and the factors that influence it. Summer monsoon, land-use land-cover (LULC), and weirs are dominant factors determining the dynamics of river water quality. Empirical analysis showed that total phosphorus (TP), total nitrogen (TN), biological oxygen demand (BOD), and chemical oxygen demand (COD) had positive linear functional relations with the agricultural and built-up cover but negative linear relations with forest cover. The results showed that the total suspended solids (TSS), chlorophyll-a (CHL-a), TP, and COD levels were higher in the summer than in any other season. On the other hand, total nitrogen (TN) and electrical conductivity (EC) levels were lower during summer in the river due to the dilution effect. Pollutant-transport theory shows that TSS acts as a TP carrier (R2 = 0.83, p < 0.001). The empirical model suggested that TP (R2 = 0.76, p < 0.001) was the better predictor for CHL-a compared to TN (R2 = 0.13, p < 0.001) as well as showed strong P-limitation based on TN:TP ratios. The high average WQI values of the Geum River (except for S01 and S02) show a higher pollution level, indicating its unsuitability for drinking, irrigation, and industrial usage. Our results suggest that industrial and domestic sewage treatment and agricultural diffuse pollution control could improve the Geum river water quality.