Are runoff models fit for purpose?

I’ve seen a couple of really interesting papers recently illuminating problems with common conceptual hydrological models. These models are embedded in most of the major regional and global hydrological models as well as more local models used for planning and management of water resources. According to some new research, they’re not very good. Especially during drought.

First, from Keirnan Fowler and colleagues at University of Melbourne:

Recently, during a 13‐year drought in Australia, river catchments gradually started to dry up. With each passing year, the depth to groundwater increased gradually as the water used by trees was not replenished by rainfall. We compare this long, slow behaviour to that of five commonly‐used ‘bucket’ models. The models don’t show the long, slow drying up ‐ they only show the seasonal ups and downs, and their predictions of streamflow over the drought are poor. This is surprising, and it means we should choose our models carefully and seek out models that can simulate this behaviour and its impact on streamflow.

Paper in Water Resources Research here.

And from the nicely-titled “Where is the bottom of a watershed”, by Laura Condon and colleagues:

As a first step, we advocate simply a critical assessment of whether “deep” flow paths (in this case referring to paths that extend deeper than one’s current conceptual model) are potentially relevant in a particular place or to a given research question.

Both papers highly recommended. I hope to see new models emerging that address these groundwater connection problems.