Predicting Drought

by Jordan Steele

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What would the value be in your operation if you could predict drought? I know we can’t predict the weather, but we can keep track of monthly rainfall. Rainfall is going to be a darn good predictor of forage growth. In addition to rainfall, we can also keep track of monthly livestock head counts and their approximate weight to determine the total grazing demand. When we compare those two numbers, the Stock Days per Acre per Inch of Precipitation (SDA/1”) is a wonderful tool to help production and marketing decisions on the ranch.

Back to value, Bud Williams always talked about managing three inventories: grass, money, and livestock. He followed that by saying you can never go broke having too much grass or money, but you can go broke by having too many animals at the wrong time. What would the value be of destocking two months before the rest of your region? It could be several hundred dollars per head. What would the value be of having extra grass when the rest of your region is looking for grass? This depends on the going rate for custom grazing in your area. 

The SDA/1” along with a written drought plan that includes critical dates can help you manage those three inventories by comparing the amount of forage growing, based on rainfall, to the amount of forage being grazed by the herd. 

It starts by predicting your baseline, which is a factor of long-term carrying capacity, animal numbers and weights, and average annual precipitation. This will give you a flat baseline (shown in red below) to start comparing your actual numbers to. Next you will calculate the trendline each month by recording actual precipitation and actual stocking rates. We can then start analyzing the cumulative 12-month totals. If the 12-month total precipitation starts dropping, that isn’t good or bad news, it is just news. Depending on what the stocking rate is doing in those same twelve months, will determine if it is good or bad news. In the example below, the actual trendline (green line) is rising, meaning there is more grazing than growing forage. That means, go look at your grass! It may mean destocking should be considered; and remember destocking doesn’t mean the cows need to be sold. It just means go look at your grass, and make an informed decision for ecological and economical impacts.

Two other important factors are effective precipitation and the timing of precipitation. Effective precipitation is the moisture that falls that is actually available for plants to grow. If there is a big thunderstorm gully washer, how much rain stays put? Or huge snow events? Those are going to be big questions depending on your climate. The timing of precipitation will also depend on the ranch’s cool and warm season forage mix. Last week, we just got a wonderful rain here in Wheatland, WY, over an inch of rain in a two day period. Rain is generally always good, but let’s be honest, how much is growing in southeast Wyoming in October? And how much moisture will be available next May and June when the peak of our forage grows? Summer rains can be beneficial to cow herd conception rates because they provide a quality bump when the cows need it.

Drought should be expected; what is important to us as ranchers is our response to it. Better yet, our response before it is too late. Our Australian friends try to resist using the word “drought” because it makes us think of it as an exceptional event. Instead they say “just missed a bit of rain!” If you are a member of RFP Online (any Ranching for Profit School alumni business can join), you can head over to the platform to check out the SDA/1” spreadsheet template for your own operation. If you are interested in attending a Ranching for Profit School this winter to learn about managing drought risk, seats are filling up but we still have spots available in a few schools, click here to check out our schedule!

10 Responses to “Predicting Drought”

October 25, 2023 at 5:40 am, Taylor Moyer said:

I have been struggling with what my lines mean and this article somewhat clears it up. My baseline is set off of severely overgrazing the farm. We have had a similar amount of moisture but grazed in a much more managed fashion and left ALOT more standing cover. However my SDA/1″ rain actual for this year has been moving below my baseline. It has left me staring at my grazing chart a lot thinking I am miscalculating. I then presumed with the extreme management change that my baseline is actually off, and next year under similar management my actuals will look more like my baseline with similar precip.

But based off of your description of rising (or falling) trendline, in my case falling, it is indicated correctly. My falling trend line indicated there is more growing than grazing? (That is what is actually happening)


October 27, 2023 at 9:20 am, Jordan Steele said:

Hey Taylor, yes I think you got it! We have discussed how often to revisit your baseline numbers with others who used this too. It seems 3-5 years is a good time to do, but if something drastic changes then annually is obviously better. And you also mentioned trusting your instinct too, which I appreciate.


October 25, 2023 at 11:04 am, Mark Vetsch said:

Good thoughts, however your October rain comment made me recall a conversation with an old timer 20 years ago, where he stated “If, in October I know the condition of your plants and your ground moisture I have a fairly accurate prediction of next year’s grass production “ ( now this may be different in other places than northern Alberta), but at the time I was already coming to that realization and it has been confirmed many times since, including this year’s low production levels until we got late summer rains, where the HEALTHY stands exploded


October 26, 2023 at 11:37 am, Rafa Flores said:

Great observation. In South Texas the same thing applies, now that you mention it.


October 27, 2023 at 9:24 am, Jordan Steele said:

Thank you for bringing this up Mark! Did they grow right then in those October rains or wait until next spring? We got our first hard freeze (12 degrees when I woke up) this morning, so I am guessing that pushed everything into dormancy. You would know more about winter growing than me in your climate so I would love to hear your thoughts!


October 27, 2023 at 1:23 pm, Rob Van Deren said:

Dormancy is a funny thing. The plant will look dormant. But we can go out in Jan. & Feb. and there is a little bit of green still around the base of the plants. Ground will be frozen like ice cream. Once the sward is winter grazed, the soil will freeze solid. This is in SW MT at 5000 ft.


November 02, 2023 at 4:06 pm, Jordan Steele said:

Thank you for both comments Rob, always good to have boots on the ground examples!


October 25, 2023 at 2:02 pm, Rob Van Deren said:

After last winter, I would be nice to have a spreadsheet to track wind chills vs. the 18F critical cattle temp and increased forecast hay and forage consumption.


October 27, 2023 at 9:26 am, Jordan Steele said:

Great point, I wonder if you could add to the SAU equivalent to capture that higher requirement? Or if that is coming from fed feed, the forage being consumed might not change much?


October 27, 2023 at 1:26 pm, Rob Van Deren said:

Researched this earlier in the week. Every degree below 18F, including wind chill requires 1% more ENERGY. I had remembered it as 1% more forage. If your sward is 50% TDN, it then requires 2% more forage per 1F.


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