It's time to revise the GIUH

GIUH has been a valuable approximate tool for getting the hydrologic response. A review can be found in:

• Rigon, Riccardo, Marialaura Bancheri, Giuseppe Formetta, and Alban de Lavenne. 2016. “The Geomorphological Unit Hydrograph from a Historical-Critical Perspective.” Earth Surface Processes and Landforms, EGU Reprint Series, 41 (1): 27–37

The question of maximum discharges treated inside the theory can be found in

• Rigon, R., P. D’Odorico, and G. Bertoldi. 2011. “The Geomorphic Structure of the Runoff Peak.” Hydrology and Earth System Sciences 15 (6): 1853–63.

The role of hillslope and channels was treated in:

• D’Odorico, P., and R. Rigon. 2003. “Hillslope and Channel Contributions to the Hydrologic Response.” Water Resources Research. https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2002WR001708.

Jointly with my first paper that proved the role of the geometric/topological structure of the river network in forming the hydrologic response,

• Rinaldo, Andrea, Alessandro Marani, and Riccardo Rigon. 1991. “Geomorphological Dispersion.” Water Resources Research 27 (4): 513–25.

these papers constitute, on my side, quite a body of contribution on the topic.  There are other greater contributor and their work is cited in the review paper I cited for first.

However, the theory has some limitations. Its applicability is based on the:

• assumption that the rainfall is uniformly distributed (but C. Cudennec and coworkers were able to generalize it, see review paper)

having some recipes to get the effective runoff (i.e. separation of the total rainfall in quick surface water and baseflow and, besides, in evapotranspiration). Another limitation derives from the fact that

• the river network is dynamic (e.g. https://www.erc-dynet.it/publications/ or previous studies by M. Marani, Biswal and coworkers)

That’s why I went back to consider simpler reservoirs systems to get a clue of the interplay of the acting processes. This research work brought to the studies on representation of these reservoir models, to get the good old models streamlined for their structure, e.g.

• Bancheri, Marialaura, Francesco Serafin, and Riccardo Rigon. 2019. “The Representation of Hydrological Dynamical Systems Using Extended Petri Nets (EPN).” Water Resources Research 55 (11): 8895–8921.

and see especially the interactions among processes. The preprint-paper

• Rigon, R., and M. Bancheri. n.d. “On the Relations between the Hydrological Dynamical Systems of Water Budget, Travel Time, Response Time and Tracer Concentrations.”

is (among other things) a trial to get all the types of lumped models related with understanding where the diverse theories can be plugged together. Maybe a little convoluted as way of thinking but hopefully effective.
Another remark regards that once upon a time I was looking and satisfied with discharge, now I try to check the water and the energy budget and, therefore, the overall budget. Let’s see what comes next and if I am able to close the circle.  For who is still interested to implement a GIUH solver, please look at here.

P.S. - In the whole GEOframe/NewAge stuff, river geomorphology is present through the connectivity of the Hydrologic Response Units. Hence geomorphology is not absent: it is just not present in the simple way allowed by the GIUH that permitted to obtain those remarkable semi-analytic results present in the cited papers.