From Rainfall Forecasts to Drought Management Strategies: Lessons Learned in Tailoring Climate Information Needed to Implement Drought Contingency Triggers for Water Supply Reservoirs in Texas

In response to the exceptional drought of 2011, the Texas Water Development Board (TWDB) adopted new rules for its water planning process in 2012. The new rules require all regional water planning groups to include a chapter on drought management in their respective 5-year water plans with the aim of implementing short-term water demand reductions in the face of impending or existing drought conditions. Each water user group in a water planning region is required to develop drought contingency plans and drought action triggers for their respective water supply sources. Water user groups need to consult existing information on impending or current drought conditions before making a decision on whether to implement drought contingency triggers, which set in place voluntary or mandatory water use restrictions.

Reliable forecasts of summer (May, June and July; MJJ) reservoir storage issued at the end of April is vitally important for reservoir operators in Texas because such forecasts could help reservoir operators decide on whether the implementation of drought contingency triggers is warranted for the upcoming summer season.

We report on lessons learned in the application of improved forecasts of MJJ rainfall, issued at the end of April in a given year, for seasonal storage forecasts at three reservoirs managed by the Brazos River Authority (BRA) on the Brazos river basin in Texas. We also report on the process followed for the development of a framework by which the BRA, and other reservoir operators in the state, could use seasonal rainfall forecasts to inform the implementation of drought contingency triggers for water supply reservoirs.