Developing a Real-Time Water Supply Forecasting System with Hydrologic State Tracking and Observed SWE Updating

Abstract Submission: Real-time water supply forecasts provide vital information for proper allocation of the resource. Given the benefit of timely and accurate forecasts, a reliable system for creating these forecasts is highly valuable. Throughout the western US, current snow water equivalent (SWE) and soil moisture are critical factors in short-term to seasonal water supply forecasts. Since these hydrologic states are critical pieces of information for water supply forecasting, maximizing the accuracy of those forecasts requires consistent, accurate state estimation.

This presentation describes an operational forecast system for the Merced Irrigation District (MIDH2O), built on the HEC-RTS system. This forecast system has adapted the HEC-RTS system for real-time tracking of hydrologic states in time, then generating real-time forecasts from those states. This system generates spatially-distributed hydrologic state estimates across the Merced River watershed, progressing those states forward in time every 6 hours. This maintains current estimates of SWE and Soil Moisture throughout the Merced River. Additionally, this system supports updating of hydrologic states based on observed information. Currently, the system is adapted to ingest SWE observations from the Airborne Snow Observatories, updating the SWE estimates as they become available. Through this process, the most accurate possible SWE estimates are developed. From these continuously created and updated hydrologic states, two forecast products are generated: 1) The 7-day hydrograph at all gage locations within the Merced River watershed, and 2) the seasonal (April-July) volumetric inflow forecasts to Lake McClure. Since the hydrologic states are kept current, the forecast products are generated every 6-hours, based on the latest 7-weather forecasts and current hydrologic states.

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