# How to find Q in m3/sec from a raster having Q in mm for hydro power calculation

I am having a raster file with runoff depth Q in mm which was obtained from SCS method.

I want to calculate hydro power potential at any location on my DEM. In the formula Q is in m3/s but we are getting Q in mm from SCS method. Is there any tool/script/software dealing this? How to find Q in m3/sec from a raster having Q in mm for hydro power calculations?

I am using arcgis (9.3 and 10).

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1. Get your units converted to cubic meters. Your raster file has an area associated with each grid - use this area to multiply your mm of water to get volume. For example, if your grid cells are 100m x 100m (10,000 square meters), you first would convert your Q from mm to meters: `Q in mm = 0.001 Q in m`. Now you can multiply Q in m by the area to get your volume: `0.001m * 10,000m2 = 10m3`
2. Convert your time units. Your data should have some specified time period associated with them (Q in mm per sec/day/month/year/etc.). If your time units are `per second` and you need `per day`, your conversion factor is `60*60*24 = 86,400 seconds per day`.
3. Convert to Q in volume/time. If your grid cell size is 100m x 100m and your time units are seconds, you can convert to cubic meters per day: `(10m3/sec)*86,400 sec/day = 864,000 m3/day`