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I want to find two locations H difference in elevation between two locations on a DEM.

Ex: point A and B are my output after search on DEM. conditions are:

  1. buffer R distance around point A and
  2. difference of H elevation to point A

I am very poor in programing and looking for a tool or program/script to achieve this.

No...Q is storage capacity of reservoir to generate min power as power capacity is propotional to Qh (Q storage capacity, h head availability).

Yes..I did my analysis as you mentioned above procedure by using archydro. But it can used if you know the location and general power project which has one reservoir.

My case require two reservoirs with difference of elevation of two outlets H. I want to find two locations at a time by search(condition of H) on DEM.

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I am assuming that Q capacity represents something like "basin/area above a (pour) point".

If so, SpatialAnalyst (an ArcGIS extension) has hydrology routines you can use to derive the watershed above any so-called pour point.

To go from a raw DEM to a watershed; however, you have to do some preprocessing first. And I suspect you'll need to do some of these anyway regardless of what your ultimately needing to accomplish.

If memory serves, the workflow to derive a small watershed is this:

  1. create a DEM without pits/sinks using the fill routine
  2. derive a flow accumulation raster from your filled-DEM
  3. define a pour point(s) in a vector layer, then convert it to a raster dataset
  4. "snap" your pour point(s) to a nearby cell with greatest flow accumulation
  5. derive a flow direction raster
  6. derive a watershed for each pour point

Now if you're wanting the software to identify best locations based on some criteria, I believe you'll need write a routine using ArcObjects that "daisy-chains" some of the previous methods together.

Next, if you're interested in comparing alternative GIS platforms for your project, I understand SAGA has a nice set of hydrology tools. Moreover, since SAGA is open-source, you can look under the hood if you need too defend any algorithms used in your analysis, such as would be necessary for a peer-reviewed paper, et cetera.

Finally, if I have missed the point here (i.e. Q is not basin area), let me know and I'll delete my answer. Otherwise, I think you'd do something like I suggested above.

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