Irrigation Methods - Modern Techniques

In order to feed very large numbers of people, modern farming has become very efficiency-conscious. Every possible way of improving crop yields is pursued. Very large, complex, expensive equipment is now virtually required, in order for a farm to be profitable. This also means that extremely large farms must be used, to amortize the very high cost of such equipment.

It also means that massive use of pesticides and herbicides is necessary to process such huge areas regarding insects and weeds. More to the point here, phenomenal amounts of water is needed to permit all those plants to grow at optimal rates.

Natural soil moisture and natural rain used to be the sources that were relied on. Modern farming cannot rely on the natural variations of such things. Irrigation is central to all modern farming.

Considering how cost-conscious and efficiency-conscious modern farming has become, it amazes me at how poorly irrigation is used! Farmers tend to operate their irrigation pumps while they are awake, during the daytime. That seems to make sense, for the possibility of any mechanical malfunction. But for several reasons, it is very poor use of that resource.

  • First, during hot, sunny summer days, a significant amount of the sprayed water evaporates in the warm air between the time it leaves the spray heads and gets to the plants.
  • Second, once water lands on the leaves of the plants, the bright sun and hot temperatures causes even much more evaporation of that water, before it can be of any use to the plants.
  • Third, due to the surfaces of the leaves, many of the drops of irrigation water rest on the leaves as relatively spherical drops and not as a uniform wetting of the surfaces. This is especially true when a plant first begins to be sprayed. Unfortunately, one effect of this droplet shape is to optically focus the sunlight, very much as a glass lens would do. In the same way that a glass magnifying lens concentrates sunlight so much that it can quickly burn a piece of paper, these droplets can cause very small areas of the leaf surfaces to receive too much sunlight! Cell damage can result, even though later droplets of water are likely to cool it down to ameliorate this sunburn effect.

    Regarding this third issue, many homeowners already know that it is a bad idea to water their lawns in the middle of a very hot, sunny, summer day, because the lawn can become "burned". Why don't the technological modern farmers know that?

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An obvious solution to this exists! If irrigation was begun in the early evening, and potentially continued to a little after sunrise, fully twelve hours of watering is practical each day. FAR less water would be required, due to the much lower evaporation that occurs during the cooler, sunless nights. The plant leaves would similarly not have to endure localized focused areas of sunlight and the possible damage that can result from that.

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The benefits from this simple change can be significant. First, from a practical view, irrigation pumps would need to run fewer hours to provide equivalent usable moisture for the plants, which would lessen equipment maintenance costs and the cost of the electricity to run those very large irrigation pumps. Second, if less water is needed to fulfill the needs of the plants, less water would be removed from the underground aquifers.

On this last matter, there seems to have long been an incorrect assumption that the amount of available underground water is unlimited. It is not. In the American Midwest, there are many thousands of cities and towns that drilled wells into a large aquifer, whose water seems to have fallen in the Colorado region. This water flows horizontally rather slowly, and it apparently takes hundreds or thousands of years to seep those many miles across the country. Since there are now thousands of agricultural irrigation wells that also draw water from this same aquifer, a problem is developing.

In recent years, it has been becoming obvious that that aquifer is NOT of infinite capacity. Due to all these municipal and irrigation wells drawing so much water out, the level of the water in the aquifer has been dropping, and rather rapidly! Many wells that have operated properly for many decades have become "dry". The solution is now to have those wells drilled deeper, and many cities and towns and homes have had to do just that in recent years. But the pattern is alarming. If wasteful and extravagant use of fresh water continues, there will some day be a time when, no matter HOW deep those wells will be drilled, there will be no available water in that aquifer. Considering that water to replenish it may take hundreds or thousands of years to seep through the many miles of rocks to get there, a VERY serious problems seems likely to exist!

Now, no one knows how much that aquifer initially had, or to what percent it has already been depleted. There is not even very good data on the collective total of water that is being removed from it! Each farm considers the water under it to be "personal property" which can be used in any ways and in any amounts desired! Various States attempt to keep track of Municipal water use, but the data on irrigation consumption is very sketchy.

In any case, we can hope that we have only depleted 10% of that aquifer so far, which would imply that the millions of people who live in the Midwest can expect to have supplies of fresh water for at least a couple hundred more years, before the aquifer will be so depleted that Municipal water will no longer be available. But what if the massive consumption of water in the past 30 years has 50% depleted it? That would mean that that crisis could occur in only another 30 years! Many people living now would be faced with a total lack of available fresh water. Catching rainwater might enable survival, but rainwater contains many contaminants that are picked up from the air as the droplets fall from the clouds, so it is not really a "safe" source of drinking water.

If, when, this crisis happens, there will really be NO solution! All of those farms that REQUIRE massive amounts of irrigation will no longer be able to operate. The farmers will likely just haul their equipment to Brazil or some other country where available farming land will still have available irrigation water. But the homeowners and the business owners and the towns, what will they be able to do? How could they ever live and work, if fresh water would not be available for hundreds of years?

I realize that, as long as politicians do not see a looming crisis on this issue, that nothing will be done. And even if new laws would be passed, how could anyone monitor the operation of wells on the PRIVATE LAND of the many farms? Considering that farmers know that they MUST use irrigation water in order to be profitable, is there even the remotest chance that they would just stop?

It's a problem!

This presentation was first placed on the Internet in November 2002.

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C Johnson, Theoretical Physicist, Physics Degree from Univ of Chicago