Water yield model

[Eshetu]

Dear, The user guild says that the water yield model considers not only annual average runoff, but also the proportion of surface water that is available for hydropower production.
However, the model result shows that lakes have the lowest water yield value. Could you clarify why this happens?

[swolny]

Hi @Eshetu -

To understand the results, first look at the model inputs. Do lakes have their own land use land cover class? If so, is it assigned an “lulc_veg” value of 0? If it is assigned 0 (which it should be), then the model uses equation 3 in the User Guide to calculate AET, which is different than the equation used in the vegetated classes.

One thing that both of the AET equations are dependent on is the value of Kc, so you can also consider how the value of Kc compares with the other LULC classes. If Kc is relatively low, that is likely to contribute significantly to the low water yield values you’re seeing.

~ Stacie

[Eshetu]

Thank you for your fast reply and fantastic advice. Water body is classified as one LULU category. For water body, I assigned 0 to LULC_veg and 1 to KC value. KC value of water body is the highest, next to forest cover (KC=1.01). Water body are a source of spring and surface water supply permanently, unlike rainfall runoff. This is why I confused about low value of water yield at water bodies.

Thank you !

[swolny]

Ok. It sounds like the model should predict high actual evapotranspiration (AET), since the Kc value is high. And high AET causes low water yield (you can look at the AET model result to verify this). So the low values make sense from the modeling point of view.

The model does not take any inputs related to springs, and doesn’t consider groundwater at all. It’s a simple rainfall-runoff model that is mostly concerned with precipitation, evapotranspiration, and vegetation type. If you need to consider groundwater/spring effects, you’ll need to use a more complex model.

~ Stacie

[Eshetu]

Thank you so much dear !!!