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Discussions like this are why I love this site. I've seen these from airplanes, but never even thought about it enough to know it was called center-pivot irrig

Discussions like this are why I love this site. I've seen these from airplanes, but never even thought about it enough to know it was called center-pivot irrigation. Now I know how big they are, their density, why we can't arrange them in a hex, etc. Alright, so here's my question: Since we can't arrange the roads in a hex, why not make the grid a little smaller or the irrigation arm a little longer so that it can reach the corners of the grid. It would obviously run over the road at the midpoint of each side, so if the road needs to stay dry-ish, shut off the water supply automatically somehow at the ends of the arms. Then you can make the whole square green. This creates an obstacle to watch out for when using the road, but otherwise what am I thinking wrong here?

Roritharr 10y ago
Or just make the arm retractable.
- Noseshine 10y ago
  The more moving parts the more expensive, especially in maintenance. It's just like harddrives in server farms, even small changes in drive reliability have a big influence due to the number of them in operation in parallel.
deleted 10y ago
[deleted]
riskable 10y ago
The big cost in these systems is the water since they're placed in locations where land is cheap (read: otherwise worthless). So conquering the spaces between circles really isn't very important. The key is to increase yield-per-gallon of water not yield-per-acre as is typical with farms. In yield-per-acre scenarios we already have horizontal irrigation systems that roll across a given area kind of like that giant lane-spanning Chinese bus that recently made the news. The only disadvantage to these systems is they have more moving parts (two sets of wheels) and are limited in how far they can roll (they're usually hooked up to coiling hose systems) so you need more of them.
bluGill 10y ago
Even we assume you solve the engineering and cost issues, I don't think it is a good idea. Irrigation systems are used where there isn't enough rain. Those corner areas that do not get irrigation absorb rain into the aquifer which can be drawn out latter. The aquifers are shrinking in areas with irrigation systems and this is a concern for farmers who are looking for ways to mitigate this issue. They know that if they don't solve the problem now in a few years they will be forced to take extreme measures. (some farmers already plant their irrigated fields one year out of 3)
GregBuchholz 10y ago
>or the irrigation arm a little longer so that it can reach the corners of the grid. You'll want to investigate "corner pivot". See also page 3 of http://az276019.vo.msecnd.net/valmontstaging/docs/default-source/valleyirrigation-com---usa---brochures/valley-corners---june-2016.pdf http://az276019.vo.msecnd.net/valmontstaging/docs/default-so... ...or... http://www.pivotirrigation.com.au/valley-corner-73.cfm http://www.pivotirrigation.com.au/valley-corner-73.cfm
crikli 10y ago
One thing I didn't point out in my answer about why hex wouldn't work is that a single pivot does not to irrigate an entire section of land (a section is 1 square mile) [1]. Some pivots will irrigate a quarter of a section, but even this is rare. The standard pivot with a corner system [2] and will cover 152 acres out of a 160 acre field. Roughly a quarter of a one mile section. [1] At least in Nebraska, I don't know about the rest of the country/world. My source is my brother-in-law a 5th generation farmer. [2] Basically a swingarm that extends the effective length of the pivot for better corner coverage Edit: hit enter too soon.
jasonwatkinspdx 10y ago
> It would obviously run over the road at the midpoint of each side This isn't going to work for three reasons: drainage ditches, hedge rows, and power lines. You could maybe build an irrigation system that traverses the drainage ditches on each side of a rural road but I'm skeptical it'd price out as a good buy for anyone. You aren't gonna build one that can go through a hedge row.

Roritharr 10y ago

Or just make the arm retractable.

Noseshine 10y ago
The more moving parts the more expensive, especially in maintenance. It's just like harddrives in server farms, even small changes in drive reliability have a big influence due to the number of them in operation in parallel.

deleted 10y ago

[deleted]

riskable 10y ago

The big cost in these systems is the water since they're placed in locations where land is cheap (read: otherwise worthless). So conquering the spaces between circles really isn't very important. The key is to increase yield-per-gallon of water not yield-per-acre as is typical with farms. In yield-per-acre scenarios we already have horizontal irrigation systems that roll across a given area kind of like that giant lane-spanning Chinese bus that recently made the news. The only disadvantage to these systems is they have more moving parts (two sets of wheels) and are limited in how far they can roll (they're usually hooked up to coiling hose systems) so you need more of them.

bluGill 10y ago

Even we assume you solve the engineering and cost issues, I don't think it is a good idea. Irrigation systems are used where there isn't enough rain. Those corner areas that do not get irrigation absorb rain into the aquifer which can be drawn out latter. The aquifers are shrinking in areas with irrigation systems and this is a concern for farmers who are looking for ways to mitigate this issue. They know that if they don't solve the problem now in a few years they will be forced to take extreme measures. (some farmers already plant their irrigated fields one year out of 3)

GregBuchholz 10y ago

>or the irrigation arm a little longer so that it can reach the corners of the grid. You'll want to investigate "corner pivot". See also page 3 of http://az276019.vo.msecnd.net/valmontstaging/docs/default-source/valleyirrigation-com---usa---brochures/valley-corners---june-2016.pdf http://az276019.vo.msecnd.net/valmontstaging/docs/default-so... ...or... http://www.pivotirrigation.com.au/valley-corner-73.cfm http://www.pivotirrigation.com.au/valley-corner-73.cfm

crikli 10y ago

One thing I didn't point out in my answer about why hex wouldn't work is that a single pivot does not to irrigate an entire section of land (a section is 1 square mile) [1]. Some pivots will irrigate a quarter of a section, but even this is rare. The standard pivot with a corner system [2] and will cover 152 acres out of a 160 acre field. Roughly a quarter of a one mile section. [1] At least in Nebraska, I don't know about the rest of the country/world. My source is my brother-in-law a 5th generation farmer. [2] Basically a swingarm that extends the effective length of the pivot for better corner coverage Edit: hit enter too soon.

jasonwatkinspdx 10y ago

> It would obviously run over the road at the midpoint of each side This isn't going to work for three reasons: drainage ditches, hedge rows, and power lines. You could maybe build an irrigation system that traverses the drainage ditches on each side of a rural road but I'm skeptical it'd price out as a good buy for anyone. You aren't gonna build one that can go through a hedge row.