VEMALA – a water quality and nutrient load model system for Finnish watersheds


The VEMALA model is an operational, national scale nutrient loading model for Finnish watersheds (Huttunen et al., 2016). It simulates nutrient processes, leaching and transport on land and in rivers and lakes. The model simulates nutrient gross load, retention and net load from Finnish watersheds to the Baltic Sea. It includes two main sub-models, the WSFS hydrological model (Vehviläinen, 1994) and the VEMALA water quality model (Huttunen et al., 2016). The model was developed through the years and two versions are operational today simulating different nutrients and processes (Table 1 and Figure 1). Successive versions of the model have been developed leading to a more process-based nutrient loading model.

Table 1. Description of the four VEMALA versions.



Hydro-logical model

Terrestrial model

River model

Lake model



non-agricultural loading




VEMALA-ICECREAM (TP,TN), concentration-runoff relationship (SS)

concentration-runoff relationship, VEMALA-N


nutrient transport  model

nutrient mass balance model


TN, TP, SS, TOC, PO43-, PP, Porg, NO3-, NH4+, Norg, phytoplankton, O2



(TN, TP, PO43-PP, Porg, NO3 NH4+, Norg),  concentration-runoff relationship (SS, TOC)

 concentration-runoff relationship, VEMALA-N


biogeo-chemical model

biogeo-chemical model

VEMALA modelFigure1. Structure of the VEMALA model.

VEMALA can simulate the water quality on a daily basis in rivers and lakes larger than one hectar in Finland and provide real-time results. It can also analyse the contribution of the different loading sources to the total or biologically available nutrients (Figure 2) as well as the proportion of biologically available fractions in the run off to the sea. VEMALA can also be used to simulate the impact of various farming actions and loading reduction actions on the total or biologically available nutrient loads to help implement the Water Framework Directive (Figure 3). Moreover, it can take into account the effect of climate change on the total or biologically available nutrient loads reaching the sea. Finally, VEMALA can simulate the transport of inert components in the river network to determine the toxicity downstream of an accidental leak.

Sources of P loading

Figure 2. Contribution of various sources to the phosphorus loading to the Baltic Sea without taking into account the direct deposition to the Sea.


Figure 3. Present, realistic and target scenarios of phosphorus loading to the Baltic Sea from Finnish catchments.



VEMALA-N simulates nitrate (NO3-), organic nitrogen (Norg) and total nitrogen (TN) leaching and load formation at a catchment scale. The simulation unit is crop/land use class with 5 agricultural crop classes and one forest class. The model simulates the dependency of the main processes (mineralisation, nitrification, denitrification, plant uptake) on the soil moisture and temperature. VEMALA-N can be used to run scenarios to simulate the effect of a changing climate on the nitrate leaching and its sub-processes or the effect of changing crops and fertilisation (both mineral and organic) on the nitrate leaching. The results form the VEMALA-N sub-model and the forest loading for P are then adjusted to the Metsävesi results (Metsävesi, 2020).


Figure 4. Scheme of the conceptual hydrological model and VEMALA-N




Figure 5. Simulation of phosphorus flows in the ICECREAM model.

VEMALA-ICECREAM simulates particle bound and dissolved phosphorus (PP and DP) load and erosion from agricultural areas. It is a field-scale, process based model (e.g. Jaakkola et al. 2012), applied to all fields in Finland. The field characteristics – soil type (clay, silt, coarse and peat), field slope and the size of a rectangle-shaped field plot – are used in the simulations. The output from the ICECREAM model (daily total P load) is used as an input to the VEMALA model. Agricultural measures that are taken into account in ICECREAM and can be used in management scenarios are

  • Amount, depth of application and type of fertilizer (mineral/manure)
  • Annual crops (also over winter), perennials and root crops, 13 different crops parameterized
  • Conventional tillage, direct sowing
  • Dates for agricultural practices
  • Buffer zones/strips



Process-based N simulation in ICECREAM is based on the GLEAMS model (Knisel, 1993). ICECREAM simulates the daily balance of organic matter, organic N, ammonium (NH4-N) and NO3-N pools by accounting for input of plant residues, organic and mineral fertilizer, atmospheric deposition, fixation by plants and decay of organic matter. Processes reducing N in the soil are plant uptake, denitrification, volatilization and transport with runoff and leaching. ICECREAM application on each filed provides the total agricultural loading of following N fractions – TN, organic N, ammonium (NH4-N) and NO3-N as input to the VEMALA model for catchment scale loading simulations.

Figure 6: Simulation of nitrogen flows in the ICECREAM model.

















TOC model

During the project new version of the VEMALA TOC model was developed, and it simulates TOC processes in the soils in more process-based manner. TOC leaching depends on the C storage, soil moisture, temperature and runoff conditions. C in soil is described with three storages – solid organic carbon (SOC), dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC). The main processes described in the model are mineralization of organic carbon (OC), dissociation of OC and production of DOC, association of DOC back into SOC. Model simulates TOC leaching from 5 land use classes in the model: agriculture on clay soils, agriculture on coarse soils, forests on mineral soils, forests on managed peat soils, natural peatlands. VEMALA TOC model results are available in VEMALA user interface the same way as for other substances.



The VEMALA v.3 model uses the terrestrial input from VEMALA-N for NO3- and Norg, VEMALA-ICECREAM for PO43-, PP and Porg and VEMALA 1.1 for total organic carbon (TOC) and suspended solids (SS). The phytoplankton growth is simulated using the AQUAPHY model (Lancelot et al. 1991) and the nutrient cycling using a simplified version of the biogeochemical model RIVE (Billen et al., 1994). The bioavailable nutrients are linked in the aquatic ecosystem to one another through phytoplankton dynamics, organic matter degradation and sedimentation.

VEMALA v.3 can simulate the loads of total and bioavailable nutrients (NO3- and PO43-) to the sea with the contribution of the different loading sources. The impact of the different farming actions, loading reduction actions and climate change impact on the nutrient loads.

VEMALA scheme

Figure 7. Scheme of the biogeochemical model in VEMALA v.3.




sVEMALA is an excel based nutrient loading simulation tool based on VEMALA model results. sVEMALA is developed to provide the possibility to use VEMALA model results independently and to assess the effect of nutrient loading changes on a catchment scale. sVEMALA contains annual N, P loading, retention, source apportionment of the loading to each river stretch, lake which is simulated in VEMALA model. sVEMALA can be used to assess how the changes in nutrient loading effects on changes in nutrient concentration in downstream lakes and river stretches, as well as to the loading on catchment level.


Figure 8 sVEMALA


Examples of results

V1TP_Ecological_classes_smallFigure 9: Ecological classes based on the TN concentrations and river/lake types


Human P load versus background loading Figure 10: % of P loading from human sources vs. P background loading



Billen G., Garnier J. & Hanset P. 1994. Modelling phytoplankton development in whole drainage network: the RIVERSTRAHLER Model applied to the Seine river system. Hydrobiologia, 289, 119-137.

Huttunen, I., Lehtonen, H., Huttunen, M., Piirainen, V., Korppoo, M., Veijalainen, N., Viitasalo, M., Vehviläinen, B. 2015. Effects of climate change and agricultural adaptation on nutrient loading from Finnish catchments to the Baltic Sea. Science of The Total Environment. Volume 529, pp 168-181,

Huttunen, I., Huttunen, M., Piirainen, V., Korppoo, M., Lepistö, A., Räike, A., Tattari, S., Vehviläinen, B., 2016. A national scale nutrient loading model for Finnish watersheds – VEMALA. Environmental Modelling and Assessment 21(1), 83–109. DOI: 10.1007/s10666-015-9470-6

Jaakkola, E., Tattari, S., Ekholm, P., Pietola, L., Posch, M. & Bärlund, I. 2012. Simulated effects of gypsum amendment on phosphorus losses from agricultural soils. Agricultural and Food Science 21: 292–306.

Korppoo, M., Huttunen, M., Huttunen, I., Piirainen, V., Vehviläinen, B., 2017. Simulation of bioavailable phosphorus and nitrogen loading in an agricultural river basin in Finland using VEMALA v.3. Journal of Hydrology, 549, 363–373.

Lancelot C., Veth C. & Mathot S. 1991. Modelling ice-edge phytoplankton bloom in the Scotia-Weddell sea sector of the Southern Ocean during spring 1988. Journal of Marine Systems (2):333-346.

Leena Finér, Ahti Lepistö, Kristian Karlsson, Antti Räike, Sirkka Tattari, Markus Huttunen, Laura Härkönen, Samuli Joensuu, Pirkko Kortelainen, Tuija Mattsson, Sirpa Piirainen, Sakari Sarkkola, Tapani Sallantaus, Liisa Ukonmaanaho, 2020: Metsistä ja soilta tuleva vesistökuormitus. Valtioneuvoston selvitys- ja tutkimustoiminnan julkaisusarja 2020:6 ISSN 2342-6799 ISBN PDF 978-952-287-826-7.

Vehviläinen B. 1994. The watershed simulation and forecasting system in the National Board of Waters and the Environment. Publications of the Water and Environment Research Institute. National Board of Waters and the Environment, Finland No. 17.


Working group

Markus Huttunen, Inese Huttunen, Marie Korppoo, Tiia Vento, Bertel Vehviläinen


-BlueAdapt: Adaptive governance creates blue growth in Finland

-KIPSI project: Peltojen kipsikäsittelyn aiheuttaman vesistöjen sulfaattikuormituksen arviointi (Kipsi report)

-KLIVA: Vesitase, ekosysteemipalvelut ja metallikulkeuma muuttuvassa ilmastossa (Kliva project)

-VEMALA TOC: VEMALA TOC mallin kehitys (VEMALA TOC report, VEMALA TOC report II)

-KaiHali: Kaivosvesiä vastaanottavien vesistöjen hallinta ja kunnostaminen

-SulfaII: Toimintamallit happamuuden ennakoimiseksi ja riskien hallitsemiseksi turvetuotantoalueilla.

-Lohkon ominaispiirteet huomioiva ravinnekuormitusmallinnus ja sen kehittäminen -jatkohanke (LOHKO II):

-Lohkon ominaispiirteet huomioiva ravinnekuormitusmallinnus ja sen kehittäminen (LOHKO): (LOHKO_final_report.pdf)

-N-SINK: (N-SINK_VEMALA_final_report.pdf)


-Rannikon kokonaiskuormitusmallin kehittäminen ja soveltaminen Suomenlahdelle ja Selkämerelle:

-Saaristomeren valuma-alueen kokonaiskuormitusmallin kehittämishanke:


More information

Hydrologist Markus Huttunen, Finnish Environment Institute SYKE,

Published 2014-12-01 at 15:08, updated 2021-03-26 at 15:27
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