Calculating irrigation networks and irrigated land for archaeology

Discussion created by thorondor on May 20, 2014
I am trying to determine the possible locations of irrigation networks and amount of irrigated land for an archaeological project.

The best elevation data I can get for my area is a DEM derived from a 15m SRTM, which is not ideal because a large part of my research area falls across three elevation points. My research area is a valley in a coastal desert plain. I have a polygon of the mid-20th century limits of the valley and I can clip my DEM to this area. There is only one source of water in the valley, a river that flows northeast-southwest. The valley slopes gradually east-west (to the coast) and is mostly flat, but there is considerable local topography in places and some large canyons, especially in the east part of the research area.

Essentially I need to determine the amount of land that theoretically could have been irrigated at different points in time. Is there some way that I can calculate the amount of land that could theoretically be irrigated, based on elevation data, that also cuts through a 200m buffer zone around several sites. The buffer around sites is needed to account for differences between the two periods I am looking at, with the idea being that unoccupied parts of the valley were not irrigated and were desert.

Are there other analyses that I could do to show how irrigation networks might have developed through time? Quantitative data comparing the two periods is always good, but this can be primarily qualitative and descriptive too. I want to be able to show change between the two periods on a map, too.