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. Compared with a no-pumping scenario, an agricultural polder with pumping stations generated a sharper discharge hydrograph with higher peak-values and lower minimum-values, as well as an 8.6% reduction in average annual discharge. It also decreased the phosphorus export to downstream water bodies by 5.33 kg/hm/yr because of widespread ditches and ponds, a lower hydraulic gradient, and increased retention times of surface water in ponds.