Triggers” are used in drought planning as a specific sign that activates a management response. A trigger might be percent of average precipitation, or a stock pond that fills (or doesn’t) by a certain date, couple with an action like “de-stock by a certain amount” or other action. 

For example, a Nebraska ranch has formulated their trigger this way:

• They usually receive 75% of the precipitation between Nov. and June 15.
• If they receive less than 80% of average precipitation between Nov. 1 and June 15, they estimate that the forage crop will be reduced by 30%, and de-stock accordingly (de-stock 30% by weight).

• A “trigger date” should be something that is meaningful to you, and greatly depends on the operation type, and where the operation is. There is not one indicator that is appropriate for all operations. The key is  a point at which monitoring information prompts a specific decision within a drought plan.
•  It can help reduce stress and in a livestock framework, it can help encourage early decision-making (i.e., deciding you make not have enough forage so culling calves early, etc), before feeding hay or other decisions that may have expensive ramifications
• Considerations by Region 
  • Generally, long-term winter forecasts have higher predictive power in Colorado, while long-term summer forecasts are only marginally better than flipping a coin. 
    • Eastern Plains: A 70-year experiment revealed that a majority of cattle weight gain could be explained by long-term forecasts (like El Nino/ La Nina). For eastern Colorado, GrassCast is one tool to understand forecasts for forage production. This tool gives estimates based on precipitation scenarios and years of rangeland production data.  
      • Long Range Stocking Rate Decision Tool; (17 minutes) Retta Bruegger CSU Extension Range Specialist visits about a 78 year stocking rate study, sharing a stocking rate decision tree for producers based on PDO, El Nino/La Nina, and local moisture.  https://youtu.be/rlqZ9sbif-o
    • Colorado Plateau/Valleys: In western Colorado, the bulk of forage production comes from cool season grasses, which stop producing when temperatures reach 75 degrees. Spring precipitation is essential as the period most favorable to grass growth. Some of our years of highest production in recent memory were years with very wet, cool springs. 
    • Mountains: Monsoons are hard to predict, and essential for high mountain forage, since cooler temperatures allow grass to grow for a longer period.