Agricultural pollution is a major cause of water eutrophication, of which large part is non-point pollution. The amounts of non-point losses of nitrogen and phosphorus from farmlands and the assessment of its impact on the surface water quality are one of the major research topics in agricultural pollution. Current research generally focuses on isolated systems, such as individual lakes or specific streams stretches. Although this approach leads to valuable output for individual systems, it misses the connection between streams and lakes that are commonly part of a connected ecological system.
This study aims to quantify nitrogen (N) and phosphorus (P) flow from farmland through a connected Land-River-Lake system, taking into account loads, retentions, and the effects on water quality and ecology. This will help to better understand the role of rivers and lakes in the fate of nutrients in the Erhai ecosystems. With the results, water quality management strategies can be designed.
A Land-River-Lake model system will be established to evaluate the source and fate of nitrogen and phosphorus and the management strategies thereof. The newly developed model framework will integrate three submodels: MARINA (nutrient flow to rivers), PCDitch (rivers/streams) and PCLake (lakes/reservoirs).
This Land-River-Lake model will be applied to the Fengyu River Basin in Erhai watershed (China). Fengyu River Basin is a typical Land-River-Lake system. In the region there has been long-term comprehensive monitoring of environmental quality, resulting in useful data for the study purpose. This makes Fengyu River Basin an interesting case-study for establishing a connected Farm-River-Lake system.

The overall research question of this proposal is:
How can nitrogen and phosphorus transport and retention be controlled within the Land-River-Lake ecosystem of the Fengyu River Basin in order to reduce eutrophication of ecological systems?
The specific research questions are:
1) What are the current and future sources and fate of N and P from farmland in the Fengyu River Basin?
2) How much nutrients are currently and in the future transported by and retained within the Fengyu River on a seasonal basis?
3) What are the current and future nutrient dynamics and ecological quality in the downstream lake Cibi?
4) What are promising pollution control options for lake Cibi within the Land-River-Lake system?

To answer the four research question, the following research steps will be taken:
(1) quantify nutrient the current and future (2050) nutrient losses from the farmland systems to surface waters
(2) quantify the current and future (2050) nutrient transport and retention in ditches by season
(3) quantify the current and future (2050) nutrient dynamics and ecological quality in the downstream lake
(4) identify options for effective pollution management control in the Land-River-Lake system

The directions for four papers:
o Quantification of the current and future agricultural nutrient sources from farmland to the Fengyu river basin.
o Quantification of the current and future nutrient retention and nutrient transport within the Fengy river.
o Quantification of the current and future nutrients dynamics and ecological quality in the downstream lake Cibi.
o Options for pollution control within the Land-River-Lake system of the Fengyu river basin.