Teleconnections and disconnections in central Texas: A guide for water managers

Although significant progress has been made in understanding “teleconnections” between large-scale atmospheric circulation patterns and regional climate anomalies, there is a lingering perception among water managers that seasonal hydrologic forecasts are not accurate enough to be used in operational decision making. This work investigates the validity of this perception for a particular water management problem in central Texas, where long-term hydrologic prediction is limited due to the predominance of runoff from convective and cyclonic storms. Streamflow persistence and three wide-scale teleconnection patterns-El Nino/Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), and the Pacific Decadal Oscillation (PDO)-are identified as predictors, and their skill in forecasting seasonal and annual inflows to the Highland Lakes reservoir system in central Texas is assessed. Skill scores indicate little or no improvement over climatology, validating the view of water managers that accurate annual hydrologic forecasts are currently not available. However, the forecasts may provide valuable information for minor or short-term variances from historical operating policies based on critical period hydrology. Towards this end, the paper describes a procedure for incorporating the climate predictors in ensemble streamflow forecasts used as inputs to a decision support model being implemented by a regional water management agency. Future work includes evaluating additional predictors and conducting retrospective simulations to assess forecast value.