I dont have any other soil maps for my study area.. How can i use this data to convert it into Hydrological soil groups A,B,C or D ?
Hi Kushal,
If you are comfortable with a ~250m resolution, there is this global dataset of hydrologic soils from which you can cookie-cut your region of interest. This way, you'll not need the above data (There may be better datasets out there, though!). https://daac.ornl.gov/SOILS/guides/Global_Hydrologic_Soil_Group.html
However, if you really need to use the given data, AND if you have %sand, %silt, and %clay as attributes for each of the above soil types, you can do a reclassification based on the thresholds which are used to determine the different hydrologic soil group types. If you know how to script, a simple arcpy script will do the trick!
I am not familiar with SOTER. But have they given the soil properties (eg: hydraulic conductivity)?
The hydrologic group classification of USDA is according to the infiltration capacities.
Dr. Kushal, I think SOTER in a unique model that classifies soils using more complex data like PDD, RI,Slope, hypsometry. However the HMS simultinulate PR processes, Data from the SOTER database may not match the inputs require on the HMS package. In my opinion you will need to adjust ur data to suit HMS
thank u dear seniors for ur suggestion..I have the % of sand silt and clay of the topsoil layer of this SOTER soils data.. Can i assign the soil group manually based on the texture of the soil?
most of the soil is "loamy" and i have assigned B as the HSG .. is this estimation correct?
Prosper Kpiebaya
Miyuru Bandara Gunathilake
Dinuke Munasinghe
hope u all are staying healthy and safe..
If you know the proportions of sand and silt in each sample, I think u can use the textural triangle which can also be used for the classification base on the data you have.
Dear Kushal, you already received the straight forward answer to your question, but maybe it is useful for you to get some background on them.
The approach that Prosper Kpiebaya suggested is what is now known as a pedotransfer function. The soil data that Dinuke Munasinghe mentions is also based on a pedotransfer function. To put it simply and in the context of your question, a pedotransfer function is a relationship between soil physical characteristics such as texture and its "hydrologic" properties. These "hydrologic" properties can be anything, from a physical quantity e.g. saturated hydraulic conductivitiy / infiltration rates to a categorical empirical one like the hydrologic soil types of the NRCS. These functions can also show many different forms, from a multivariate regression equation or a nomogram to a look-up table.
The reason why these functions emerged (long time ago), are still in use and continue to be developed is that physical soil data for larger areas is more readily available than for example infiltration rates or runoff coefficients. By now, you might have rightfully guessed, that there is no universally valid pedotransfer function. I believe it is safe to say that there are literally dozens of such functions. Thus, the problem you are faced with is choosing the proper one for your purposes and for the area you are working in. In fact, you could define classification criteria for a number of variables in your database that would allow you to assign them to a given hydrological soil group. This would be your own home-backed pedotransfer function.
But no matter what pedotransfer function you use, you need to be critical about it. Again you have to consider the context in which they were developed, how representative they are, their uncertainty and so on. In many cases, it is even preferable for you to device your own pedotransfer function or in other words, your classification scheme. Even if you decide to use the HYSOGs250m soil groups from
https://daac.ornl.gov/SOILS/guides/Global_Hydrologic_Soil_Group.html
you may want to evaluate them and if required modify the hydrologic group.
By the way, the FAO soil maps are the basis for both the SOTER database and the hydrological soil classification from the site above. However, I am sure that the authors of the HYSOGs250m did not consider much of the information that is available to you. So again, you should be critical about it and if necessary modify it.
I hope it helps you some
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