# Controlled Drainage Effectiveness in Reducing Nutrient Outflow in Light of Climate Changes
## 5 Conclusions  
The results of the simulations of two FD and CD methods affecting water management in a drainage facility in the near future over a period of 30 years made it possible to analyze the impact of CD on water balance and the GWT under different conditions of the predicted climate changes of the GFDL, MPI, and UKESM models. Based on the simulated scenarios, the following conclusions were made:  
1. The results indicated that the earliest start of CD practice is the most effective in increasing GWT. In the near future, starting CD practice on 1 March will increase the average GWT by 24-35, 23-28, and 19-25 cm for wet, normal, and dry years for selected climate change prediction models compared to the FD practice. Compared to present climate conditions, the application of CD with an initial GWT of 40 cm b.s.l. will raise water depths by 4% in the near future. In contrast, comparing the start of the CD practice to 15 March, there will be a 2% average GWT rise in the near future;
2. The earliest application of CD on 1 March reduced average annual outflow by 52, 44, and 35 mm for wet, normal, and dry years, respectively. Compared to current climatic conditions, when applying CD on 1 March in the near future with an initial GWT of 60 and 80 cm b.s.l. in wet years, drainage outflows will increase by 33% and 80% for the GFDL model, by 30% and 40% for the MPI model, and by 17% and 23% for the UKESM model. These are the results of the increase in the total precipitation predicted by the models for 2021-2050;
3. Comparing the surface runoff values obtained to current climate conditions, the MPI, GFDL, and UKESM models predict a significant increase in surface runoff in the near future, which is due to a predicted increase in precipitation. The GFDL model shows surface runoff above 30 mm for all scenarios in wet years. For normal years, the GFDL and UKESM models show a value of 25 mm; meanwhile, the MPI model shows20 mm. In dry years, the models indicate lower surface runoff values of less than 15 mm;
4. Annual NO\({}_{3}\)-N was reduced by 22, 19, and 15 kg per hectare for wet, normal, and dry years, respectively, in the near future. Among the climate scenarios, the UKESM model predicted higher NO\({}_{3}\)-N and PO\({}_{4}\) leaching values compared to the MPI and GFDL models. The highest reduction close to 100% of the NO\({}_{3}\)-N and PO\({}_{4}\) loads was shown for CD application compared to FD on 1 March due to a reduction in drainage outflow. For the 15 March CD date, individual climate models indicated much greater variability in nutrient reduction.  
Conceptualization, B.K., R.S. and M.K.; methodology, B.K., M.K. and R.S.; software, B.K. and M.K.; validation, B.K., M.K. and R.S.; formal analysis, B.K., M.K. and I.P.; investigation, B.K.; resources, B.K., M.K. and R.S.; data curation, B.K.; writing--original draft preparation, B.K.; writing--review and editing, M.K., R.S. and I.P.; visualization, B.K., R.S. and I.P.; supervision, R.S. and M.K.; project administration, B.K.; funding acquisition, B.K. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
This study was conducted within the project \"Technological innovations and system of monitoring, forecasting and planning of irrigation and drainage for precise water management on the scale of drainage/irrigation system (INOMEL)\" under the BIOSTRATEG3 program, funded by the Polish National Centre for Research and Development, contract No. BIOSTRATEG3/347837/11/NCBR/2017.  
The authors declare no conflict of interest.