The first iteration of the GIS data was created using a number of different data sources for the target area.

The soils, coverage, and capacity maps were created in 1990 by the PDAR group and then digitized by Agricultural Innovations in 2002. Though the information is in Spanish, the Spanish is fairly simple and can be easily understood with an online dictionary.

English translations of the soils de_script_ions can be found in the Appendix of my thesis, but I will also post them here on the web page, perhaps in the wiki, in the very near future.

As with most maps developed by IGM (Instituto Geografico Militar), these use the Provisional South American Datum of 1956 (PSAD 56), and the UTM zone is Zone 20S.

All of the tin (3D imagery), contour, and infrastructure maps were developed using a mix of GPS, CAD, and GIS technology. All of it should be viewable via ArcMap. Again, this data was generated using the PSAD 56 datum.

The satellite image was given to me by PROMIC, and is a slice of a larger image. The image should be used for reference and backdrop, but be careful of using it to digitize other land features, as the projection and coordinate system are in WGS 84, and it won't line up properly with the PSAD 56 stuff. If you have ERDAS and want to reproject the image, feel free.

In the next step of the process, Meryl, you should design the water harvesting infrastructure, with a strong emphasis on developing a solid tool kit for a "keyline" system a la P.A. Yeomans. Keep us posted on your progress via this forum, and if you have any questions, post those here too.

Some questions about the data:

1. I notice that you have a potential atajado site- can you give me sort of a general verbal de_script_ion of the site and why you chose that site? Actually, if it’s possible, a verbal de_script_ion and/or some photos of the entire site would be really helpful to get a better mental picture of what I’m actually looking at in the GIS data.

2. Do you and Greby have an idea of pond size requirements for the kind of aquaculture that the pond will be used for (just sort of a general minimum is all I need to know)?

3. Are the old atajados no longer in use? I think that's what I remember from reading Peace Corps reports from Tipa Tipa.

4. The only problem that I foresee at this point is that the area you have selected for the potential atajado site is in an area with a Typic Ustorthent soil, which according to the soil de_script_ion doesn’t sound like it would hold water at all, but the old atajados are on the border of that soil type as well, so either there must be some clay there or they lined the pond or something- I know those atajados were constructed awhile ago, but do you know if they lined them?

5. I see three streams on the property, one which is labeled as the canal, one as an ephemeral stream, and the third one is unlabeled (the one that flows out of one of the old atajados)- is that an irrigation ditch? Also, the ephemeral stream that’s right on the border of the property- is the source of that stream way off the property or is there any possibility of diverting it to the atajado?

6. For the “capacity” map, what is meant by “capacity”?

7. Do you have a data table that goes with the water balance figure from your thesis? I can estimate monthly rainfall figures from the graph, but a data table would be more accurate. Do you consider that rainfall and evapotranspiration data pretty accurate for this property (i.e., can I use it to reliably predict how much water we have to work with)?

I think that's all for now. In a couple days I hope to have a general idea of where things should go, and when I do I'll post that here.

One other thing: P.A. Yeomans emphasizes that in farm planning, water use should not be designed around reliability of water supply but instead around complete usage of all water available (even if this means there isn't always enough water for every use it has been planned for). What do you think about this?

One more thing: what is the drainage that goes through the middle of the property? Is that a perennial stream?

1. We chose the site because we've been working on land rehabiliation at this site for over 5 years now. From a degraded, rocky, waterless parcel that hardly produced corn, we've already come a long way in building up soil, infrastructure, and ideas to make this parcel produce. That said, there is still much work to be done.

As far as pictures, I do have some pictures of the site and I will try my best to get them up in the Project Permaculture picture gallery ASAP.

2. After talking with Greby we quickly came to agreement that the primary goal should be to take full advantage of the water resources that move through the site instead of designing the system around the concept of aquaculture. Greby says that an ideal pond size is 1/4 hectare, or: HUGE! So, we'll include aquaculture as a system component to take better advantage of the water we capture, but it really shouldn't be an important consideration in terms of pond design (there are so many other factors that are more important).

3. The atajados are working fine. The picture in the article I wrote is a recent picture of the larger atajado on the site.

4. Actually I was present when the first atajado was built, and put quite a bit of manual and intellectual labor into designing the production system. Yes, the large atajado is lined with clay, which isn't too big of an expense, but still fairly labor intensive. Labor is always cheaper than materials in most Third World contexts. We could also line with impermeable materials, which has been done, and improves efficiency but is much more expensive.

5. You might want to play around with the labels on the "points of interest" _layer_, as that might help to give you a better idea of some of the features on the site. One canal is the irrigation canal, which is labeled

The other is a canal Moises dug to capture water from the ephemeral stream and bring it to the atajado, exactly as you are suggesting. That canal doesn't flow out of the atajado, it flows into it.

Greby and I would like to include hydraulic ram pumps as an important system component, along with storage tanks made out of ferrocement. Both of these are affordable, durable options. Greby is well versed in the construction of both of these system components. From the tanks we can run some polytube for drip irrigation.

6. Capacity means what the land is capable of producing, as per the PDAR, which is the NGO that made those maps. Essentially, the notion that only forests and grasses can be produced on these lands is incorrect, as water harvesting, terracing, and clever soil management opens up hundreds of possiblities aside from what they are suggesting.

7. I do have that data, I'll try to look for it and email it or post it to the downloads sections ASAP.

In terms of water reliability, remember the standard deviation for annual rainfall is about 125mm, so we can expect drought and abundance from year to year. Nobody knows how global warming will affect the variables in the water equation, my guess is it will make the area drier. But overall, you should consider the data to be reliable.

I think that Yeoman's is 100% right when he says planning should be made to take advantage of all water available. We know that we can't rely on x amount of water being delivered to the system every year, and our climatological systems are shifting drastically globally.

I'm not sure what drainage you're referring to. Please label the points of interest in ArcMap, and try asking some questions _base_d on those labels as a point of reference.

I've attached a general sketch of my ideas for the site so far- I've drawn out two diversion ditches to increase the catchment area of the atajado (I drew out it's theoretical watershed and it looked fairly small because the topography just about the atajado seems like it would divert water away from the atajado.)

(Here's the sketch)