Monday, March 25, 2013

Contributions to the Hydrology Days 2013

Hydrology days are a tradition that repeated since 33 years at Colorado State University in Fort Collins (CO). Last year I just participate to observe. This year, thanks to the fact that Giuseppe Formetta was at FC for finishing his Ph.D., we present two contributions:



The first paper is a further contribution to the JGrass-NewAGE saga. The second is a glimpse to what GEOtop 2.0 could be, once integrated in the OMS3 system.
Have a nice reading.

Friday, March 22, 2013

The Horton Machine: JGrasstools resources for DEM treatment and delineation (in Italian)

Ecco dunque la documentazione e vari esempi dell'utilizzo della Horton Machine, ovvero come si analizzano i dati digitali del terreno con i Jgrasstools/STAGE

  • Il tutorial (ancora in bozza - 38Mb)
  • Il vecchio manuale di riferimento della Horton Machine (in Inglese) per capire qualcosa di quello che si sta facendo ed avere un po' di bibliografia.
E le varie presentazioni:
  • p-JGrassTools (jgt) (ovvero: scaricare e installare STAGE, iniziare ad usare QGIS, creare una location in QGIS, usare il plugin per legende con scale colori continue
  •  p-SpatialToolbox (con: un'introduzione ai jgrasstools, una spiegazione di come utilizzare i comandi dei jgt attraverso lo spatial toolbox di STAGE e di come utilizzare Mosaic12 per unire le tavole del DTM)
  • p-HortonMachine (ovvero come utilizzare i comandi HortonMachine dei jgt per fare un analisi idro-geomorfologica)
    •  Qui trovate alcuni DEM per esercitarvi e per confrontare, nel caso, i vostri risultati:  il rio Valpiana (100 Mb). Contiene anche una relazione tipo fatta sullo stesso bacino.

    Quanto sopra è il bagaglio che serve per il mio corso di idrologia. A questo proposito

    Per la vostra curiosità: qui potete avere qual è il costo delle nozioni apprese (costi del software a parte) in una iniziativa commerciale.

    uDig Jgrasstools resources for urban hydrology, culverts and water supply systems design (in Italian)

    Ho sempre pensato che affrontare i problemi del dimensionamento di un acquedotto e di una fognatura pluviale, potesse essere semplificato dall'uso di un GIS. L'idea, naturalmente, non l'ho avuta da solo, ma  ragionando assieme ad altri, in particolari, i miei ex-allievi di Hydrologis e di Hydromates e i colleghi Paolo Bertola e Maurizio Righetti. Hydrologis and Hydromates, già per conto loro, avevano provveduto ad implementare in uDig i nettools, una serie di strumenti che consentono l'accesso al software Epanet per la verifica delle reti in pressione. In parallelo, ho chiesto la loro collaborazione per portare il mio software di calcolo delle fognature pluviali Trento_p, nello stesso sistema.
    Con l'ulteriore aiuto di Federico De Col, Leonardo Perathoner e di Bilal Adem Esmail (sempre supportati da Hydromates)   ho poi lavorato per documentare il tutto.

    Ora uso il tutto nel mio corso per la laurea magistrale di Ingegneria Civile: quest'anno, per la prima volta.  Ecco dunque la documentazione che serve:
    Per quanto riguarda l'utilizzo dei Nettools (Epanet) si può fare riferimento:
    Per quanto riguarda Trento_p abbiamo implementato il tutorial che si può trovare qui. Le slides delle lezioni, mirate a Trento_p, si possono trovare qui di seguito:

    Naturalmente può essere utile dare un'occhiata alla documentazione del vecchio Trento_p
    Caricheremo, con l'avanzare del corso nuovo materiale. Tenete d'occhio la pagina!

    Bibliografia

    Rigon, R., Bertola, P. - La progettazione con un metodo geomorfologico delle reti di drenaggio urbane, II Conferenza Nazionale sul Drenaggio Urbano, Palermo, 10-12 maggio 2000

    D. Tamanini, A.B. Esmail, F. Zanotti, S. Simoni, P. Bertola, R. Rigon (2009). Trento_p : un modello
    geomorfologico per lo studio del drenaggio urbano. L'ACQUA, vol. 2009, p. 73-74, ISSN: 1125-1255

    _______________________________________________________________________________

    ^1 - La teoria soggiacente a Trento_p, oltre che negli articoli riportati appena sopra,  è spiegata nel materiale linkatonel post sulle costruzioni idrauliche ai punti 10 ed 11



    Thursday, March 14, 2013

    Alpine Spring Festival

    From march 4 to march 8 at EURAC in Bozen was held the Alpine Spring Festival. This was the occasion for some of the Alpine Convention Water Platform participants to meet.
    The topic covered during the meeting were the impacts of the climate change on alpine water catchments and ecosystem.

    Besides the presentation of the water platform three presentations were given about:





    Friday, March 8, 2013

    Can I simulate the effects of changing patterns of land use on hydrographs using simple unit hydrograph models ?


    Dependently from what you are really interested you should consider different type of models. If you are looking to investigate influence of land-use changes on hydrological responses for producing a sound scientific paper you will never publish a paper on a major journal using UH and CN curves.

    If you want a quick and dirty solution for an engineering/management problem,  you can certainly gain some rough idea with a modeling like this (UH+CN is something better than the complete ignorance) but is mandatory to move to a semi-distributed model, i.e. using a (Geomorphologic Unit Hydrograph) GIUH  instead a UH. In theory a GIUH model contains the possibility to include land use for sub-basins, and therefore to perform the investigations you require. Land use, in all of these models will impact infiltration (according to some rule), but not evapotranspiration (unless you add a module for it), and the CN part will take care of it.

    These lumped models usually work fine (for rainfall-runoff prediction) after a calibration of the parameters. So, what they guarantee is that you can eventually reproduce  with some degree of reliability the same variable which you calibrated (discharge).  In other words, the parameters of these models are always "ex-post" and never "ex-ante".
    The only rational way to obtain information about land use from this procedure and type of models is therefore to perform calibrations before and after a land use change happened. If you are bold and brave, you can try to extends the results to other basins.  Therefore GIUH+CN can work where you have records of discharges, and, at the same time, a record of land-use changes   for so long time in a basin that some land use change happened, and you registered it. 

    I guess this is not your case.



    However, I have some concern about CNs. Many distinguished hydrologists suggest to use CN for describing the role of land use. But this is largely "a conspiracy": since engineers (agro-meteorologists, and hydrologists) "must do it", they have mandatorily to come out with some number, many agreed that using CNs could have been e way to get it. Actually, as I already told, when CNs works is because the curve numbers were calibrated before (and not because the tables in literature magically work), and possibly they can reproduce good results, just for those basins and situations where they were calibrated.  Finally, CNs cover just infiltration aspects and do not even recognise the existence of evapotraspiration which is clearly a main issue when talking about land-use. Certainly you could try, at your risk, a type of GIUH+CN+ET modelling.

    People that have really to concern with land use/land cover, i.e. those working in agro-meteorology, in fact directed themselves to use more complex models, which recognise a very detailed partition of the landscape, and a variety of processes. Among these models, those that came to may attention are MHYDAS by Morel-Seytou/Roger Moussa and AGEs, by ARS/Jim Ascough.  Also our JGrass-NewAGE can possibly be used  to try to give some answer.
    The latter are possibly the most simple models that can be used successfully to try to assess the role of land-use, by parameterising - a priori - its influence. I remark however, that this would require a painstaking verification of the modelling of sub-processes, that was seldom pursued in literature (hydrologists like shortcuts). 

    The best choice, would be, however, to use process-based models like our GEOtop, or Paniconi-Putti CATHY, or Garrote-Ivanov-Vivoni-Bras tRibs, or Wigmosta-Lettenmaier's DHSVM, or Zehe's CATFLOW where the right processes are explicitly modeled. 


    You can also find useful this old post, always in this same blog.