Spatial variability on hydrological modelling

In my view, the advancement of hydrological modelling towards distributed and semi-distributed approach is aims to identify which spatial variability of model inputs are important and which one is not.  That is why the forward and backward effort in favour of  the two approach. In summer 2014(about five month), I have been working "a little" on the effects of one of model (structural) inputs, routing (flow) distance, on model results.   Since I started working on the effects of spatial variability of hydrological model inputs,  I have seen new (very interesting) papers came out. Some of these are attached in the reference (I try to upgrade the references as they came by me). My work  can be seen as a look into  one aspect of the whole issues, the spatial variability of model inputs (and structures) in hydrological response modelling.

References

• McMillan, H. , M. Gueguen, E. Grimon, R. Woods, M. Clark, D. Rupp. (2014). Spatial variability of hydrological processes and model structure diagnostics in a 50 km2 catchment. Hydrological Processes 28(18): 4896-4913. Pre-print Article
• J. M. Schuurmans, M. F. P. Bierkens. Eect of spatial distribution of daily rainfall on interior catchment response of a distributed hydrological model. Hydrology and Earth System Sciences Discussions Discussions, 2006, 3 (4), pp.2175-2208. <hal-00298750>
• Minet, J., Laloy, E., Lambot, S., and Vanclooster, M.: Effect of high-resolution spatial soil moisture variability on simulated runoff response using a distributed hydrologic model, Hydrol. Earth Syst. Sci., 15, 1323-1338, doi:10.5194/hess-15-1323-2011, 2011.
• Yang, D., Herath, S. and Musiake, K. (2000), Comparison of different distributed hydrological models for characterization of catchment spatial variability. Hydrol. Process., 14: 403–416. doi: 10.1002/(SICI)1099-1085(20000228)14:3<403::AID-HYP945>3.0.CO;2-3
•  Marthews, T. R., Dadson, S. J., Lehner, B., Abele, S., and Gedney, N.: High-resolution global topographic index values for use in large-scale hydrological modelling, Hydrol. Earth Syst. Sci., 19, 91-104, doi:10.5194/hess-19-91-2015, 2015.

Renaissance Dam by Egyptian hydrologists

I have seen this paper on the newly dam being constructed in Ethiopia, actually we call it Renaissance dam. The authors tried to simulate the geographical and geometrical simulation of the Dam. Using the functionalities of the  GIS, and DEM data, they simulate different scenarios of the total area of the artificial lake. However, in the paper, I didn't see anything hydrological estimation and prediction as claimed in the result and introduction section. You can find the paper here. 

Basin Digital Watershed Modelling

Digital watershed modelling (DWM) is an important component of the hydro-geomorphological analyse, hence is required in modern hydrological simulation. The separate fields that quantitatively deals with the DWM and other terrain parameters is called Geomorphometry. For most hydrological modelling, DWM is a first steps. Since topography is the first controlling factor in the water flow, hydrologists have to understand and incorporate the topographic information in model development.  In this section, I briefly describe the topographic characteristics, more specifically the hydrogeomorphology, of the large river basin, Upper Blue Nile.   I used uDig Spatial Toolbox (uST) for this purpose.  It starts from the acquiring the DEM to the sophisticated channel and HRU coding and numbering. There are many online DEM  sources, some of these are: 

- http://earthexplorer.usgs.gov
- http://gdex.cr.usgs.gov/gdex/

- http://srtm.csi.cgiar.org

This DEM can be imported to the GIS system. The imparting process varies according to the GIS software we use. In uDig GIS, once you have set processing region, as required by the spatial toolbox,  its really easy. It is possible to import (1) as right click  -> import ascii or tiff file, then add the DEM data downloaded, or (2) it is possible to  drag and drop the DEM to the map layer or map view section.

Then thanks to the uDig GIS tools specialised to hydro-geomorphological analyse,  spatial toolbox, one of those tools can be selected, assign the input and the output, run the tools. Here, the geomorphological setting of Upper Blue Nile  basin is analysed.

The DEM is processed for the usual  routine steps for hydrological conditioning i.e   flowdir, accumulation area (Tca), subbasin extraction and channel ordering. Here I have the maps of the sub basin  extracted from UBN basin and the channel coding in the automatic procedures of uST. 


a. DEM

b. Hack ordering

c. Strahler ordering 

d. Pfafstteter ordering

e. Similarly the subbasin extraction can be done using the netNumbering tool to extract raster DEM, and extract into shapefile using the BasinShape tool of uST, and in this case, the screenshow cast is :

For  brief description of the uDig  uST and their capabilities, you can refereed at this paper and this paper.