Developing Trigger Dates for Drought Contingencies Back »

Written by Roger Gates (former SDSU Extension Rangeland Management Specialist).


The topic of critical dates has received some discussion this spring, particularly in response to the Managing Drought Risk on the Ranch webinar series originating from the National Drought Mitigation Center. Webinars are presented the last Wednesday of each month this spring. The first two webinars included an introduction to drought planning and a discussion of the development of critical dates and response plans. These webinars have been archived and can be accessed for viewing on the Ranch Planning page of the NDMC website.

A useful synonym for critical date is “trigger date.” The implication of irreversible action when the “trigger is pulled,” is valuable. The diagram provides an example for developing trigger dates and the resulting contingency or action.

The first annual trigger is based on growing conditions from the previous year. In extensive portions of the Northern Great Plains, 2012 was warm and dry; plant growth was severely reduced. 

Two certainties accompany conditions from last year:

  • Carry-over forage is non-existent and soil moisture is severely low.
  • Average precipitation during 2013 will not recharge soil moisture, it will require rainfall considerably above normal rainfall. 

Many operations have reduced herds simply because of winter feed supply shortages. Current conditions demand a tactic to reduce animal demand going into the growing season. Reductions of 10% would seem to be a minimum. Specific decisions should be developed appropriate to each ranch.

Trigger Dates

Three trigger dates are suggested in the example. If actions are carefully planned and implemented, fewer triggers might be sufficient. If a new drought response plan is being developed, keep it simple and commit to following it. As experience develops over time, refining the plan should be expected.

  1. The first trigger might approximate the earliest possible turn-out date. Final adjustments to livestock number and classes should be made, based on early season rainfall and predictions from climate experts. In the Northern Plains, where rangelands are dominated by cool-season plants, spring precipitation (April, May, June) is the best single predictor of vegetation production for the entire growing season. By mid-April, climate prediction models for spring rainfall are correct more often than not. If predications suggest below normal rainfall for the following 3-months, further reductions in livestock demand should be made. The nature of those reductions (which class of livestock and which individuals) needs to be determined ahead of time.
  2. A second trigger date in mid-spring requires planning for further adjustments, again depending on rainfall accumulation and forecasts. Improvement in moisture conditions might suggest no change or actions to provide alternative feed sources, such as an annual forage. Continued moisture deficits would require further reduction in livestock numbers or implementation of alternative feed plans (additional leased pasture, moving yearlings to the feedlot, etc.) Again, precise numbers in response to a target condition established in advance reduce the uncertainty about appropriate action.
  3. A final growing season trigger date might be included in early summer. In the Northern Plains, from 75 to 90% of vegetation growth has been completed by July 1. At this time of year, there is very little uncertainty about feed supply for the balance of the grazing season. Decisions need to be made knowing that very little additional accumulation of plant growth will occur. 

Each ranch needs to develop the trigger dates, target conditions, and appropriate actions based on their own experience, historical information and livestock inventory. Brainstorming a list of all possible enhanced feed alternatives and demand reduction tactics might be a starting point in developing trigger date responses. Historical rainfall patterns are critical to informed selection of trigger dates. Multi-year averages from the closest climate station are likely to be adequate for starting the planning process. However, having rainfall records for the ranch (perhaps from several locations) is helpful. In order to respond accurately within the current growing season, nearby information is much less useful compared with accurate rainfall records for the ranch. 

Developing a drought response plan, including trigger dates and contingency actions may not be needed every year. Having a plan in hand may be particularly important this year. Further information and worksheets for developing such a plan is available in the Managing Drought Risk on the Ranch Handbook also available on the NDMC website.

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