Dec 29, 2014

The R version of PT estimation

This is R code  for estimating the Priestley-Taylor evapotranspiration model by M.Todd Walter and his co-workers in  Cornell Soil & Water Laboratory. Actual it has solar radiation (both shortwave and longwave estimation based on the topographic information) and uses the radiation data into the ET modelling. Its seems pretty nice and I hope  will  see it soon and compare with our JGrass-NewAGE components

Dec 12, 2014

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:

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.

Dec 8, 2014

The new high resolution DEM for Africa (SRTM)

I discover that the 30m SRTM DEM data is available for the whole Africa, which was originally available only for USA. This will be very important inputs for hydrogeomorphological and environmental researches and resource planning. Here is the news by NASA (California Institute of Technology).
30m X 30m resolution  SRTM DEM for Africa. It is interesting to clearly see that Ethiopian highlands are  highly visible as Tower of Africa, along with some other spots such as Mount Kilimanjaro.