Latest news of the HYPE code

Soil model additions

One major change last year is about the modelling of nutrients in the soil: the existing soil models (e.g., default, “traveltime”) were complemented with a new soil model that accepts the concentration of root zone leakage as input and continues the calculations from there. This model has simpler nutrient process formulations than the default soil model. Now different soil models can be used for different classes in the same model set-up. In addition, it is possible to use the default soil model for some substances, while other substances use the “traveltime” or “rootzone” soil model specified for the class.

New input data

Point sources input now allow for five types of sources. There is no difference in how they are treated in HYPE. However, the loads of each source are accumulated separately in the output for source apportionment. Diffuse sources (e.g., from rural households) can be introduced as loads to the third soil layer in addition to previous introductions to the lowest soil layer or the local river. Lastly, a new input, the fraction of a class that is drained, allows for classes to be only partly tile drained.

Process changes

The soil model changes mentioned above include a new formulation of the nutrient processes of the soil. The root zone soil model simulates substance processes only for the third soil layer which is assumed to be below the root zone. In this layer, an exponential decay of the dissolved substances is applied. Organic carbon (OC) leaving the soil may be temporary delayed before joining the local stream. The delayed OC is released during high runoff. The flow in rivers depends on the net inflow to the river and the volume of the river before the inflow. The previous method depended on the volume of the river after adding the inflow, and remains as an option.