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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., submitted). 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., submitted). The model was developed through the years and four 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.

Version Substance Hydrological model Terrestrial model River model Lake model
agricultural loading non-agricultural loading
Table 1. Description of the four VEMALA versions.
VEMALA 1.1 TP, TN, SS WSFS concentration-runoff relationship concentration-runoff relationship nutrient transport model nutrient mass balance model
VEMALA-ICECREAM TP WSFS, ICECREAM in fields field scale process based model concentration-runoff relationship
VEMALA-N TN, NO3- WSFS semi-process based, 5 crop classes semi-process based, 1 forest class
VEMALA v.3 TN, TP, SS, TOC, PO43-, PP, Porg, NO3-, NH4+, Norg, phytoplankton, O2 WSFS VEMALA-ICECREAM (TP), VEMALA-N (NO3-, Norg), VEMALA 1.1 (SS, TOC) biogeochemical model biogeochemical model

VEMALA model

Figure1. 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.


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





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.


Larger picture
Figure 6. Scheme of the biogeochemical model in VEMALA v.3.





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., 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.

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, Bertel Vehviläinen


-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 2017-05-19 at 4:45
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