Land use effect on nutrient loading – nutrient models new assessment tools

1. Land use effect on nutrient loading – nutrient models new assessment tools Inese Huttunen, Markus Huttunen and Bertel Vehviläinen Finnish Environment Institute

3. Basic structure of WSFS-Vemala • Hydrological WSFS-model: • Inputs daily precipitation and temperature • Simulates hydrological cycle on daily time step • Covers all Finland, 6200 sub-basins, 58 000 lakes • Simulated daily • Data-assimilation, ensemble forecasts • Water quality simulation with Vemala • Diffuse loading (agriculture and non-agriculture) • Point load, settlements, atmospheric deposition • Simulates transport in rivers and lakes • Total phosphorus, total nitrogen, suspended solids, organic carbon (TOC)

5. VIHMA tool (Puustinen, SYKE) is used to simulateannualagriculturalload and Vemalaload is adjust • 1 100 000 fieldplotsaresimulatedseparatelybyknowingslope, plant, soiltype, P soil Relationshipbetweenconcentration and runoff / use of VIHMA annualloads • Runoff r (= r1+r2+r3+r4+r5) is divided into 5 classes rx, • each class has Ptot concentration cx,x which is calibrated • r1: runoff in runoff class 1, 0-1 mm/day • r2 runoff in runoff class 2, 1-3 mm/day • r3 runoff in runoff class 3, 3-6 mm/day • r4 runoff in runoff class 4, 6-10 mm/day • r5 runoff (unlimited) in runoff class 5, > 10 mm/day • Concentrationrelationshipwithrunoff

6. Nutrientbalance in lakes Internal load Outflowing load Inflow loading Sedimentation Accumulation = Loading – outflow – sedimentation + internalloading AnnualPhosphorusbalance for Karhijärvi Inflowloading 10.2 t Outflowload 8.9 t Sedimentation 5.9 t Internalloading 3.2 t

7. Calibration • Calibration is the process of modifying the parameters to a model until the difference between output from the model and observed data sets is minimum • Optimization criteria is: • all observation points located at the same calibration area are taken into calibration: • + there is a need to use all available observations in the calibration even if the are very infrequent (few times per year), • − more frequently observed points gets more weight in the calibration procedure. • appropriate weights for each type of observations are found and tested to reach the best possible calibration result • Water quality observations are not daily

8. Phosphorusconcentration

9. Phosphorusload

10. Agricultural load 59% of the totalloading into ArchipelagoSea

11. Use of VEMALA to simulatedifferentscenarios • Vemalacanbeused to simulatedpresentsituation • Wecanchangepresentloadings and simulateconcentrations and loadings in the rivercatchments in changedconditions: • Possiblechangesare: • Crop management changesby VIHMA / ICECREAM • Wetlandeffect • Scatteredsettlementloadingchanges • Pointloadchanges • Climatechangescenarios • Combination of abovementioned • Scenariosimulationshasbeendone in TEHO project for Aurajoki, Loimijoki and Eurajoki

12. Wetlandsimulation • Allpossiblesmallditchcatchmentswitharea 20 – 200 ha • Whichhas at least 20% of agriculturalfields • Itspossible to simulate the effect of allpossiblewetlands, wecansimulatenutrientsedimentaion in wetland, plantuptake

14. Scenarios of agriculturalpractices in TEHO • Bufferzones • Increase of vegetationcoverduring the winter (30%, 50%, 70% of the totalagriculturalarea): • Equally in allcatchment • On the steeperslopedfields • Using of mannuredecreasedby 50% • Decresedusing of P fertilizer Conclusionsfrom TEHO scenarios: • There is no one single method to reduceagriculturalloading, seceralreductionmethodsneed to becombined • The bestreductioncanbeachievedbycombination of: • Increasedvegetationcover on fieldsover 3% slope • Bufferzonesareestablished • Reduced P fertilizerapplication, that P soil < 14 mg/l • Best management practices of mannureapllication

15. Summary • Agricultural load needs to be reduced to improve the state of the Baltic Sea • Mitigation measures are done on the field scale and there are needed tools to estimate what is the effect of mitigation measures on the river catchment scale • Nutrient load models (Vemala) can be used to simulate different scenarios how should the agricultural practices be changed to reduce the agricultural loading • There are no one single method to reduce agricultural loading, its a combination of methods • More detailed process description improves the models capability to simulate climate change or agricultural management scenarios

16. Thank You! www.environment.fi/waterforecast