In recent years, even with near-normal snowpack, springtime runoff was much lower than expected. This shows that other factors—like dry soils, low spring precipitation, or warm temperatures—can strongly influence how much snow actually reaches rivers and reservoirs.

This study tested whether adding more information to the NRCS M4 forecasting system could improve predictions, especially in dry years. We used seasonal weather forecasts from national and international agencies, as well as soil moisture and groundwater data, to predict runoff in five key watersheds that supply most of the water in the Colorado River Basin. Overall, forecast accuracy improved, especially during dry years. The biggest gains came from using precipitation forecasts. These findings show that adding additional information can help improve seasonal forecasts.