Seasonal River Export of Nitrogen to Guanting and Baiyangdian Lakes in the Hai He Basin

We developed a seasonal version of the MARINA-Lakes (Model to Assess River Inputs of Nutrients to lAkes) model for Guanting and Baiyangdian while assessing N flows from the land to the lakes. The model accounts for the seasonality in human activities (e.g. cropping systems, fertilizer practices), climate and hydrology. The effective seasons are winter (December–February), spring (March–May), summer (June–August), and fall (September–November).

The model results for the year 2012 indicate that river export of DIN was highest in winter and lowest in summer. Point sources accounted for over 50% of DIN exports to Guanting and Baiyangdian across seasons. Avoiding direct discharges of animal manure (point source) in winter is needed to reduce future lake pollution.

We argue that effective lake pollution control requires accounting for seasonal N cycles. Our study can support effective nutrient management and environmental policies.