You made a pretty common mistake that people make when first learning to work with ArcMap. .mxd files can be thought of as a set of instructions for Arcmap, like, what color the legend is, the map layout, what _layer_s are included, etc.

However, NONE of the actual data is included in an .mxd file; ArcMap references the _layer_ files that are on your hard drive to recreate the saved project. Please start using ArcCatalog to move the files you want into a folder, and then zip that folder up and send it off. If you have any questions, just post them.

Sorry about that, here are the actual files. Let me know if you can't see them or they don't line up correctly with the rest of the data or anything. I had the keylines drawn too but for some reason that _layer_ isn't working so I'll post that later.

· The feature labeled “potential atajado” in the southwest corner of the site- is that exactly where you want to put the atajado or is that just a general idea? I drew out the theoretical watershed of that potential atajado and it wasn’t very large because the topography just above the atajado seems like it would direct water away from the dam site instead of into it. Other than that, it looks like a good site to me. I drew in a couple of potential diversion channels for increasing the catchment area of the atajado.

· Yeomans suggests using a lockpipe system with keyline irrigation dams- a pipe is inserted in the bottom of the dam during construction, and it can then be opened to let water into an irrigation channel- the irrigation channel can be blocked (with a weighted piece of waterproof cloth) at any point so that it overflows and flood irrigates the land below it. For this application I think, as you suggest, that drip irrigation (with a hydraulic ram pump) might be a more efficient use of water depending on how it will be used, but let me know what you think of the lockpipe idea.

· I must be looking at it wrong, because from looking at the map I can’t figure out how Moises’ irrigation canal would flow into the atajado because it looks like it would have to flow uphill to do so. Can you set me straight?

· What do you think of possibly building a smaller atajado near the ephemeral stream (FID 1 in the paths_streams_roads _layer_) and pumping it either to the main atajado or directly to the area to be irrigated so that we could make use of that water?

· I just heard back from Ken Yeomans and he is willing to assist with the project- I’ll ask if he would like to be part of this forum.

Great work! The canals look great. If you could give a little detail about how exactly you determined the irrigated area, that would be great. I'm starting to think we should use the wiki to develop a technical manual.

In a few hours Moises, Greby and I will have a participative design session and we will post the results in the GIS download section. Might be time to move on to Phase 2: Design.

The potential atajado site is an area Moises felt was a good spot. Partly because of the land curvature, but also because the soils in that area seem to retain water a little better.

I think taking water from the ephemeral stream is a fine idea. In our design session I'll pick Greby's brain about where to best put some ferrocement tanks and ram pumps. The idea is to use drip irrigation closer to the house, but also could be used for things like cherimoya and other fruit/nut trees further from the house.

I like the idea of the lockpipe system. The further away from the house, the more appropriate it seems to water things like forage paddocks and reforestation areas. Do you have any photos of this?

Also, I've posted a new photo gallery with 10 photos from the target site. Visit the Image Gallery section and have a look. Hope that helps you to visualize a few things.

One thing you should keep in mind when looking at some of the curves and elevations, is that this is NOT a survey grade map. To actually build the design we would have to go through with survey grade equipment and redo everything. But the idea is to develop a model/toolkit for shaping policy initiatives.

Are we having fun yet?

Post edited by: frank, at: 2006/05/02 13:22

The irrigated area was just a rough estimation of the area with elevation below the atajado that might be reached by drip irrigation. If we were using flood irrigation we might be more limited by canal location. I haven't done any actual calculations yet, but I can work on that and get a more definite idea of where we can irrigate. As I do that, I'll document what I'm doing to include in the manual. I'll assume:
1. That the hydraulic ram pump will definitely be included in the design.
2. That we'll use only drip irrigation and not flood irrigation.

If either of those assumptions are incorrect, just let me know.

I was also assuming when I drew out the irrigation area that only the area below the atajado in elevation would be cultivated. Do you think any type of rain-fed agriculture would be possible on the higher slopes above the atajado? Yeomans recommends planting trees on the uphill side of the diversion canals. But with rainfall so minimal for part of the year that might be difficult.

I also have a copy of the NRCS manual on pond design that I can post- I've been working on summarizing some of the more relevant parts. I think it's pretty close to Yeoman's ideas for pond siting and design. I think I'll leave most of the actual pond design to you, Greby, and Moises since it requires a detailed survey, but since I have a little bit of experience in pond building from working with the NRCS last summer I can write up a mini-manual on how to do the survey, etc.

I'm also working on some estimates of runoff into the pond so we'll know how big a pond to build- I'll post that once it's done.

After our design session (it was a great one) I've started to zero in on exactly what we need you to do.

You focused on the potential atajado site that we drew on the map, which was fine but it might have distracted you a little from the broader picture.

We are thinking of putting maybe a couple of large atajados further downslope, and a series of small ones on the upper reaches of the slope.

What we need from you is to take your keyline analysis and draw potential canal areas all along the micro watershed. Don't worry about anything else, just focus on the canaling system.

That will show us exactly where we can put certain types of infrastructure. On top of that we will be able to draw a much more elaborate design.

The canals can be used in a number of ways, for agroforestry, filling atajados or tanks, lockpipe systems, etc. So you need to come up with an idealized canaling schematic so that we can maximize the water that flows through the microwatershed when it rains.

Sounds good, I’ll focus on the canals. I think putting a larger atajado lower in the valley is a great idea because then we could divert water from the stream- I’ll include a canal to do that.

A little more about the lockpipe system: I’ve attached a diagram from Ken Yeomans’ Keyline website (http://www.keyline.com.au/form02LP.html). The website itself has some more details about the system. Basically it is a steel pipe that runs under the dam (perpendicular to the dam wall) with its intake in the atajado. You can put a floater on it so that the intake is about 1 meter below the water level of the atajado. What makes a lockpipe system different from just a regular old pipe is that steel baffles are attached at about eight places along the length of the pipe under the dam, which prevents seepage along the outside of the pipe.

The pipe empties into an irrigation trench, with a valve on the end so that it can be turned on and off. The idea is that the irrigation trench can then be blocked off with a waterproof piece of cloth with weights on the end (called a “flag”) so that it overflows its downhill bank and floods the land below it. I attached some pictures of this too, from an article written by Prof J. MacDonald-Holmes that describes some of the basics of Keyline: http://www.yeomansplow.com.au/basis-of-keyline.htm.

In order to spread out the water that floods over the canal, Yeomans recommends cultivating in a pattern that follows the Keyline of the valley, which from my understanding is the inflection point where the slope changes from steep to more gradual. It is difficult to tell without a survey map exactly where the Keylines would be in the microcatchment, but I can get a general idea from the survey data and we can include that in a technical manual (a wiki would be ideal because then Ken Yeomans could consult on it).