End the hating!

OK, look. Flood and furrow irrigation is not necessarily a primitive, wasteful irrigation technique. It can get distribution uniformities up in the eighties, which is about as good as a decent irrigation foreman should expect*. Of course, getting furrow irrigation that high takes an unusual amount of management.

To do a good job on furrows, in addition to annually shaping the furrows and beds, you would torpedo every furrow. (Drag a heavy, torpedo-shaped weight the length of every furrow, to smooth the run and get rid of clods. You can attach several of these to the bar behind your tractor, so you get several rows done at once.) You would also keep track of your wheel rows. Those are the furrows that your tractor wheels went down. The soil in wheel rows is compacted; the water will run down those faster. You have to match them to smaller siphons. You would use surge flows, to push the water to the tail of the furrow faster, so that water sits on the tail of the field for about as long as it sits on the head of the field. You constantly monitor your soil moisture, so that you don't start your irrigation event before the soil is dry enough to hold the water you put on. Every irrigation event changes the furrows (compacts and slicks them down), so you manage each one differently from the last. You keep a notebook, every year, noting daily soil moisture, date of irrigation events, size of siphons in each run, duration of event, and when the water reached the quarter, half, three-quarters and full length of field. You MANAGE your furrow irrigation system.

That said, flood or furrow** can be very sloppy and has the potential to let huge amounts of water run off the field. It is what you'd do if you have more water than management capacity, or if water is cheap and your drainage is good. The image of wasteful flood and furrow irrigation is well-founded.

So where do you see flood and furrow irrigation? You see it where water is so cheap that you don't need to do careful applications. You also see it where the grower is constrained by the irrigation district. Some districts deliver water on rotation. They don't keep all their lateral canals full all the time; you take your water when your canal is full, once every three weeks. If your district is on rotation, you have to use flood irrigation. You can't put down enough water to last you for three weeks through some pansy little sprinklers***. You also see flood and furrow in modern irrigation districts, where the grower chose the method. Maybe the grower prefers labor costs to capital costs. Maybe the grower is experienced with furrow and wants to stay with his expertise.

My whole point is that flood and furrow irrigation are not themselves proof of wasting water. If you're in a real old-school atmosphere, where the growers are contemptuous of water management, yeah, furrows are a strong signal of waste. But in a district where the manager and growers are alert to the modern ways of conservation, furrow and flood irrigation can be very good.









*An irrigation fanatic gets them in the very low nineties, but that is astonishing. That indicates a lot of interest and maintenance. If you saw irrigation efficiencies in the nineties in nature, you would wonder what was motivating the grower.

**Furrow irrigation is, like, furrows. Flood irrigation is in border checks.

***Everyone is always all "ooooh, switch to drip! Drip irrigation is Teh Cool!", but for drip irrigation, you have to have a constant, clean supply, preferably with some head on it. You can re-create that on your farm, by building a small reservoir, pumping and filtering. That takes space and capital and maintenance. Drip isn't a good solution for everyone. Resist the peer pressure!