Tuesday, July 8, 2014

Quickness and exactitude

I put here an internal review of one of our manuscript, because, I hope, it can be useful in general. The topic is evaluating the rainfall runoff of a small catchment (but I hoped it was en estimation of the global hydrological cycle, even if without evapotranspiration measurements).

"The paper is written in a good English (finally). However good English does not mean is a good paper. It lacks of focus and is not concise (lack of exactitude and quickness, see at the end of the post). Objectives are not clear, and the novelties of the paper not evident. However, I am not desperate to obtain at the end something reasonable: but this just because I know the amount of work behind it, and, in part, the row-material.

Making a rainfall-runoff model cannot be usually considered an exercise at the frontier of our science (citing conversations with Ignacio Rodriguez-Iturbe. However, it could be, as testified by Gunther Bloschl's ERC). It, making rainfall-runoff, I mean, certainly can bring information about a certain basin. However, in our case, the works of N* and M* already filled this space. So what it is the goal of this paper ?
The initial idea was to assess the uncertainty in prediction of discharges by using appropriate statistical techniques. In particular, the idea was to assess the uncertainty inherent to rainfall extrapolation from point measurements to spatial measurements. 
This task has been only partially fulfilled. For the following reasons: errors due to instruments precision were not included (just the hypothesis of perfect functioning measures was applied);  the way rainfall has been included in the model (is not yet clear if average rainfall, one point for each hillslope was used, average rainfall volume for any information or other approximations were utlised: and no sensitivity analysis with respect to the way distribute rainfall was squeezed into the model was performed); the interplay between rainfall and discharge forecasting is not well developed, at least as it could be, i.e. explaining how it works inside the whole procedure is not explained well.  
Therefore the overall rainfall prediction analysis is incomplete, and I expect it would be completed for the thesis. 
The technical novelty we apply in this work is that we use a calibration tool (LUCA) to assess variograms, and we do it at hourly time step, while others do usually at daily time step. A few questions here: how much this approach improves rainfall estimates ? i.e., taking uncalibrated variograms and/or constant variograms (not varying in time) how much difference do we get ? How much this affects the forecasting of the volumes of water? Which comprehensive effect has this on the forecasting of the discharges ?

It could be that all of these approximation have negligible effects on the forecasting of discharges. But this would be indeed good to know and an achievement, which was not obtained so far. 

A second topic of interest was the simulation of the whole hydrological cycle, and a tentative to close the hydrological budget with the Priestley-Taylor simulation of evapotranspiration. This simulations were done but not shown at all in the manuscript. Why not ? Do the simulated discharges and the  simulated ET sum to the total volume of rainfall ? If not, which interpretation do we have about the missing mass ?  Are we able to assess the uncertainty in predictions of each single component of the hydrological cycle obtained with this method? Are we able to observe interannual variability (both in discharges and evapotranspiration, and, if the case, in storage) ? Is this variability estimate reliable, at least as a gross budget ?

Having missed to answer to each one of the questions above the paper results a wandering around that breaks our karma (citation from Vijay K. Gupta).  Please save us with more rigor. 

Regarding quickness and exactitude, I suggest the reading of Italo Calvino's Six Memos for the next Millennium.^1^2

^1 - Here a video seminar on the Six Memos by Paolo Granata
^2 - Hainging around, in a digression maybe, and unfortunately in Italian, the Discorso sulla Matematica (Talk on Mathematics) inspired and guided by Calvino's lectures, written by Gabriele Lolli

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