I received a host of answers on this one. Most people directed me to a website where I could download a script, apr, etc. that has been created for hydro analysis. An extension is available in the ESRI samples that come with the software. I've tried this and have had somewhat good luck. All the functions work (Flow Direction, Accumulation, Fill) except the "Watershed" selection. For some reason I cannot even select it. Any suggestions?? Also, a couple of people directed me to websites that had training lessons to work through. Listed below are the suggestions, websites, scripts, etc....... Richard Gleason: Try downloading the USACE's Geo-HMS tool. These terrain processing tools are in there. Bill Huber: An introduction to using the Map Calculator for tapping into such functions is at http://www.quantdec.com/SYSEN597/GTKAV/section9/map_algebra2.htm . This is part of a sequence of pages; the preceding and following pages contain more examples. Orhan Gunduz: Try to open the sample apr called 'hydro11.apr' in your arcview directory probably somewhere like: C:\ESRI\AV_GIS30\ARCVIEW\Samples\ext You will find an additional menu and all the required tools there. Good luck with it. Tim Loesch: Look at http://www.dnr.state.mn.us/mis/gis/tools/arcview/Training/training.html - you'll find the materials I created for a workshop that uses ArcView for Hydrologic Modelling... Sam Litschert: But, more importantly and possibly heresy!. There is an extension freely available from David Tarboton at Utah State called "Sinmap" that uses a superior algorithm (IMHO). ESRI's algorithm designates flow from each cell into only 1 of 8 directions (D8). Tarboton's algorithm directs flow direction proportional to the flow from each cell (Dinf). He explains it much better if you look at the documentation on his website: http://moose.cee.usu.edu/sinmap/sinmap.htm This gives a more "realistic" approximation of flow direction and accumulation, it is easy to use and results in many fewer no data values. Greg Slutz: Load the Hydrologic Modeling extension that comes with ArcView in the samples directory. Daniel Cespedes: If you want to use the hydrological functions, you need to use the request functions with the avenue language and you need to do do a script like this: Here it's an example that do some hydrological functions. theView=av.getProject.FindDoc("View1") theGTheme=theView.findTheme("Soilsgrid").getGrid 'Soolsgrid is the name of the grid themes for create the different hydrologic grid themes ' calculate flow direction flowDirGrid = theGTheme.FlowDirection(FALSE) ' create a flowDirGrid theGTheme0 = GTheme.Make(flowDirGrid) theGTheme0.setname("Flow Direction") ' add theme to the view theView.AddTheme(theGTheme0) ' calculate flow accumulation flowAccGrid = flowDirGrid.FlowAccumulation(NIL) ' extract streams from flow accumulation streamGrid = (flowAccGrid < 600.AsGrid).SetNull(1.AsGrid) ' delineate stream links streamLinkGrid = streamGrid.StreamLink(flowDirGrid) ' delineate watersheds for each stream link watershedGrid = flowDirGrid.Watershed(streamLinkGrid) ' create a flowAccGrid theGTheme1 = GTheme.Make(flowAccGrid) theGTheme1.setname("Flow Accumulation") ' add theme to the view theView.AddTheme(theGTheme1) ' create a streamLinkGrid theGTheme2 = GTheme.Make(streamLinkGrid) theGTheme2.setname("flow streamlinkgrid") ' add theme to the view theView.AddTheme(theGTheme2) ' create a watershedGrid theGTheme3 = GTheme.Make(watershedGrid) theGTheme3.setname("watershedgrid") ' add theme to the view theView.AddTheme(theGTheme3) 'end of script Also Thank you to Thorsten Behrens, Kelly Runyon, Joe Miller, & Joe Martinetti. Thanks to all. Aaron Brault Mapping Specialist Vandewalle & Associates 120 East Lakeside Street Madison, WI 53715 608-255-3988 abrault@vandewalle.com