A novel framework for tracking hydrological processes and identifying key factors in mountain-lowland mixed catchments: Implications of forty years of modeling for water management.

Quantitative analysis of runoff, total suspended solids, and total nitrogen dynamics, along with the identification of key factors within catchments, is essential for accurately addressing issues related to turbid and polluted water. Nevertheless, their implementation encounters significant challenges when applied to a mixed catchment containing mountain areas and lowland polder regions, due to the highly heterogeneous hydrological behaviors and consequently the lack of an appropriate approach. Faced with this problem, this study developed a framework by coupling the Soil and Water Assessment Tool (SWAT) and improved Polder Hydrology and Nitrogen modelling System (PHNS), and Random Forest analysis method to track the spatio-temporal changes in runoff, total suspended solids, and total nitrogen loading and identify their environmental determinants in a representative mountain-lowland mixed catchment, southeastern China.

Framework for quantifying rural NPS pollution of a humid lowland catchment in Taihu Basin, Eastern China.

Controlling of rural non-point sources (NPS) pollution has been a major priority of Chinese government in an initiative to improve the rural living environment. However, quantifying NPS pollution remains a considerable challenge in the humid lowland rural areas of Eastern China, which are characterized by complicated hydrological and nutrient processes and exhibits intensified artificial interference. In this study, a new and feasible framework was developed to estimate different NPSs specifically for this area by combing hydrological modelling, export coefficient, and sediment release experiment.

Modelling the regulation effects of lowland polder with pumping station on hydrological processes and phosphorus loads.

Exploring the hydrological regulation of a lowland polder is essential for increasing knowledge regarding the role of polders associated with pumping stations in lowlands. In this study, the Lowland Polder Hydrology and Phosphorus modelling System (PHPS) was applied to the Jianwei polder as a case study for quantifying the regulation effects of a lowland polder with pumping on discharge and phosphorus loads. The results indicate that the polder significantly affected the temporal distribution and annual amount of catchment discharge.

Hydrology and phosphorus transport simulation in a lowland polder by a coupled modeling system.

Modeling the rain-runoff processes and phosphorus transport processes in lowland polders is critical in finding reasonable measures to alleviate the eutrophication problem of downstream rivers and lakes. This study develops a lowland Polder Hydrology and Phosphorus modeling System (PHPS) by coupling the WALRUS-paddy model and an improved phosphorus module of a Phosphorus Dynamic model for lowland Polder systems (PDP). It considers some important hydrological characteristics, such as groundwater-unsaturated zone coupling, groundwater-surface water feedback, human-controlled irrigation and discharge, and detailed physical and biochemical cycles of phosphorus in surface water.

How can we reduce phosphorus export from lowland polders? Implications from a sensitivity analysis of a coupled model.

Phosphorus (P) export from lowland polders has caused severe water pollution. Numerical models are an important resource that help water managers control P export. This study coupled three models, i.