Spring Snowmelt Forecasting

Weekly snowmelt forecasts are provided each spring to assist water management entities in dealing with the timing and magnitude of the spring snowmelt peak. Coordination is required with many cooperators. The CADWR Snow Survey section participates in the process for watersheds in California. Weekly forecasts are provided for all major reservoirs and several important control points.

To generate the weekly forecasts, the CNRFC uses the flood forecast model described above in an ensemble mode. This approach, called Ensemble Streamflow Prediction or ESP, provides a distribution of future streamflow outcomes that can be sampled in any way desired. The process starts with the current model conditions (or states), and then develops a set of forecast scenarios based on the historical observations of temperature and precipitation (Figure 1). The approach is extremely flexible in that any time window and any attribute of streamflow can be analyzed. The most typical use is for weekly, monthly, and seasonal volumes and peaks. In addition, the system can be used to describe a whole host of information such as the distribution of low flow stages during the upcoming summer.

Figure 1 - Ensemble Streamflow Prediction technique

Figure 2 shows the distribution of future outcomes for one of the CNRFC forecast points. Spring snowmelt forecasts are available on the CNRFC Home Page.

Figure 2- Trace outcomes of ESP procedure