Dear all,

I have three layers in ArcMap 9.2: a shapefile representing major river basins (approx. 250 polygons), a simple shapefile showing the outline of the continents and a raster layer showing data points of a 'runoff' variable.

The first two layers mentioned are single files. However, I have runoff data for 106 years, each year in separate files.

What I hope to do is automate the process of selecting a particular river basin polygon (is it possible to do this by its ID number as shown in the attribute table?) and summing the values of the associated raster points which fall within the area of the polygon.

As I have 106 raster input files and would probably want to analyse the point data within the bounds of approx. 20 polygons (of which the ID number would change each time, depending on the polygon selected), I would imagine that this would need to be programmed (as manually extracting and summing data point values for approximately 2120 polygons wouldn't be too much fun!).

I have no programming experience in the Arc domain, so I have no idea how tricky this process would be. If anyone would be kind enough to design some code which I would be able to tailor (e.g. entering the raster file name and the polygon ID - i.e. the variables) to do this, then I'd be very grateful indeed.

Many thanks for any help offered. If you have any questions which would help clarify my problem, then please do not hesitate to ask.

Best wishes,

Steve