Monday, December 30, 2019

Using GEOframe-NewAGE for operational modelling

Finally we did it ! Thanks to ARPA Basilicata and the work of my co-authors, Marialaura Bancheri  (GS) and Salvatore Manfreda (GS)  this long term objective of mine had a first realisation. We think GEOframe is a brilliant platform for operational hydrology, due to its flexibility and expandability.
we did not produce much new science with this paper. However, I think the introduction is brilliant, the explanation of how the models work of unsurpassed clarity, thanks to the use of EPNs, and, obviously, the system informatics really outstanding. You can find below the Figure representing the core modelling structure with this graphic system.
 Below you also find the representation of  how routing was implemented.  The latter figure shows how a dam was inserted in modelling. Because the EPN is actually reflected into the internal informatics, based of Net3, the dam can be inserted or excluded, according to what we want to simulate, without breaking the model, just on the basis of scripting.
It will be interesting from now on to monitor  how the system actually work in the operational context, and we will give proper information of it in the future. The paper is open access on Water, and you can see it here.

What do I have to do with polyacrylate ?

It happens that a researcher deviates a little from his mainstream research. This is one of the cases. Dott. Pier Giuseppe Marcon came to us suggesting that polyacrylate could have peculiar thermodynamics characteristics and decreasing its and surrounding temperature when wet and around to 20-30 Centigrades. He arrived to me because of this blog. I suggested that I was certainly able to figure out a way to simulate the dynamics of the substance but, at the state of art of our knowledge, I was not the right person to talk about because the polyacrylate needed some charcgerisation before I could envision its thermodynamics modelling. Therefore I involved a  colleague, Rosa di Maggio, for getting the work done.  The result is this paper, in which I learned a few things. First of all that phases of matter are not that well defined as I believed initially. Secondly that water can form compounds when it is not free. That cannot be considered exceptional findings but made me to reflect that neglecting water chemical bounding can bring to mistakes.
The paper can be found by clicking on the Figure above (from Britannica) you get the paper. Its abstract reads: "Super-adsorbent polymers have the capacity to immobilize huge quantities of water in the form of hydrogel, thanks to their confguration. A commercial sodium polyacrylate (PA) was analysed as such and at diferent water uptakes, indicated through the weight ratios PA:H2O. The hydrogels were prepared using diferent type of water (tap, distilled and deuterated) and characterized by Infrared and Raman spectroscopic analyses, nuclear magnetic resonance experiments, CHN elemental analysis, measurements of thermal conductivity and difusivity. All the measurements were done in order to assess applications of PA:H2O gels as Thermal Energy Storage systems for improving thermal performances of building envelope through passive solar walls. It has been observed that the behaviour of the hydrogels depends both on temperature and water content. In certain conditions such as low weight ratios, a spontaneous and quick cooling of the hydrogel could be observed. The curves of heat fow and average specifc heat (cp) were determined as a function of temperature in order to investigate the states of water in PA hydrogels. When a few water molecules are present, they are mainly and strongly bonded with carboxylate groups. Increasing the amount of water, greater shells of solvation around ionic groups form and water molecules can even interact with neighbouring non-polar hydrocarbon groups. At very high amount of water molecules, they are much more involved into H-bonds among themselves, rather than with PA, so that water pools form into the links of polymeric network. Bulk-like water can freeze and melt. Whatever the amount of water in the hydrogel, its thermal capacity is higher than dry polymer, because the heat can be absorbed by the continuous desorption of water from polymer to bulk-like water (watergel→waterliquid), which can evaporate as temperature approaches 100 °C (watergel→waterliquid→watervapour)."

Next will be to envision a theory for the behavior shown. A glimpse of it can be found on this note.

Wednesday, December 11, 2019

Green Water and Blue Water, the Alps and the Climate Change

Thanks mostly to the work of Theodoros Mastrotheodoros and Simone Fatichi (GS), we submitted a paper to Nature Climate Change that was entitled "More green and less blue water in the Alps during warmer summers" which was eventually accepted. It  investigates under the climate change pressure the partition on water between runoff and evapotranspiration on the whole Alps with simulation on a grid of 250 m.

It is not certainly the first effort on the Alps. However,  for its resolution and quantity of data used the paper marks a benchmark for present research. Here it is its abstract:

Climate change can reduce surface-water supply by enhancing evapotranspiration in forested mountains, especially during heatwaves. Here, we investigate this “drought paradox” for the European Alps combining a new database of more than 1200 stations and hyper-resolution ecohydrological simulations to quantify the blue (runoff) and green (evapotranspiration) water fluxes. We show that during the historical 2003 heatwave, evapotranspiration in large areas over the Alps was above average, despite the exceptionally low precipitation, amplifying the runoff deficit by 32% in the most runoff- productive areas (1300 to 3000 m above the sea level). An increase in air temperature by 3 °C could enhance annual evapotranspiration by up to 100 mm (45 mm on average), which would reduce annual runoff at a rate similar to a 3% precipitation decrease. This suggests that green water feedbacks, which are often poorly represented in large-scale model simulations, pose an additional threat to water resources, especially in dry summers. We conclude that integrating hyper-resolution ecohydrological modelling into climate change impact assessment studies can support more realistic predictions of water availability in mountain regions.

By clicking on the figure you can access a preprint.

Wednesday, December 4, 2019

How to read and decently plot a DEM with Python

I worked for long time to build  GISes (e.g. JGrass, uUdig and so on), an adventure that was supported and eventually taken in charge by Hydrologis. After accepting the reality the QGIS won the battle, I am not still satisfied with it and always looking to alternatives. One that I practice a little is to use as vehicle for mapping Jupyter and Jupyterlab. Therefore,  copying  around, I was able to produce decent maps. You can find one of the result of my search in the figure below.

Nothing really original from me: I copied from the bests I found and adapted to my desiderata. Clicking on the Figure above you access the Jupyter notebook where all the procedure is explained. Aa I wrote,  it is very much a work in progress. Therefore any suggestion is welcomed.

Monday, December 2, 2019

On a flooding vignette that is often posted on the web

This picture whose I do not know the authorship is going around the web to support the idea (Which I also support) that streams should be left as natural as possible to avoid flooding. But is this image really hydrologically sound? 

Let say that the top row is highly simplified and objects size incorrect. In the first top figure, it is unconceivable that vegetation stays at tens or hundreds of meters from the stream. Usually vegetation goes very close to the stream, at least the vegetation that can have its roots inside the water table. This also means that, in figure 2, top row, when the flood comes, it will inundate part of the forest. Finally figure 3 top row should have more evident traces of the flood, for instances some sediment here and there. Correctly, streams are  not channels, as the first figure on bottom row wants to convey, where humans make what it should not be done. The human in the picture, however, is not represented at a size compatible with the trees dimensions on top row. From passing for figure on top to the bottom ones, there is a zooming in or the digger should be something like 40 m high if proportion were right. The same for the houses in figure 2, bottom row: they are certainly not proportionate with respect to the trees dimensions. Let’s say that the picture is made to convey sense of disproportion and emphasize that human intervention is wrong. Art freedom, maybe, where the concept is more realistic than the real. 
Certainly the rectification of the river is a bad thing and the houses were built too close to the river. Streams are source of ecosystem services and boost the economy so, in the past,  it was taken the risk  to build close, or even over the river. This was done many times, in a trade-off that was deemed reasonable decades ago, but  that it does not seems justifiable anymore now.  We bear the weight of history here. 

As many knows, human activities alter infiltration in soils and rainfall, consequently, rainfall is more efficiently transformed in runoff. However, unless we claim an extraordinary intervention of climate, the flood in the last figure is grossly exaggerated, if the cause is the city itself. If we think the houses are no more than 15 m (not 40 m as  could be suggested by the the proportionality between the top and the bottom rows), the last picture show a ten or more meters of water over the usual level. By far, this cannot be generated (all over and upstream the city until the horizon) by the changes happened in urban soil use. The flood, in fact, is instead reasonably caused by a  massive runoff generated in the upstream basin, not by the local urban runoff. 

To sum up, the message is shareable "Please give room to river to expand" and "Do not build too close to river" (this increases exposition and vulnerability). However the cause for the flood in the last picture is not the city itself. Certainly, the inappropriate urban planning increased the risk and the losses but it cannot have enhanced the flood that much.

There are obviously cases in which the floods are caused by the city impermeability: this is when the catchment is smaller or of a size comparable to city itself. Just in this case, the soil modifications cause the runoff which in turn causes the flood. The city of Genova, in Italy, is one of these cases in which "urban rivers" exist: but there are many others in our contemporary world where we have many huge megacities (but this it is not the case of this figure).

Concluding, the message is right but the hydrology is wrongly represented.  Yes, I know: I have been too picky.

P.S. - Besides water in floods is rarely blue though. Usually, it is full of sediment and of the color of the soil it transports.