Model 'degradation' of water resources

[FraGard]

Apply the code for land degradation to the water resources, to model e.g. a) decrease/increase of water availability in water bodies and b) degradation of groundwater resources.
Or should the storage equations be used for these?

[tniet]

Hi @FraGard - can you be more specific as to the structure you're thinking about? I think the storage equations (especially the simplified ones that I created and are available in the OSeMOSYS/OSeMOSYS_GNU_MathProg/tree/AlternateStorageCode branch) would likely cover this quite nicely. You can have inflows and outflows to a reservoir, and if the reservoir is used up then there's no more water. This seems more like accounting for the in/out flows than land use degradation where the productivity changes with use.

[FraGard]

Thanks @tniet, you are right the storage equations will cover very well the cases where we want to represent the increase/decrease of water availability in water bodies or maybe even aquifers? But I wonder about how to model the degradation of groundwater resources (e.g. increasing pollution or salinity, that causes worse performance in agricultural uses) and also the land cover decrease by water bodies that are drying (first off, should we be able to model it at all?)

[tniet]

Hi @FraGard - interesting question. Could this be done with different storage technologies? So the first piece of stored water, with a given inflow, gives good quality, but if that is drained, the next storage tech produces water that requires more energy/processing to make it usable or it reduces crop yields? So if there is more withdrawal than inflows into the 'good' storage we get worse quality water? The issue there is that new inflows would be classed as 'good quality' even though the aquifer/lake is not in good shape.
The land area piece is probably relatively easy - one could have a linear relationship between land demanded and volume of storage to get a first cut, or a piecewise linear if the area varies non-linearly.
@abhishek0208 might have some insights into the land degradation piece he put together for Mongolia that might be useful for the water degradation.