Using ratios of runoff to snow water content and to projected rainfall to-come, as a method of narrowing the water supply forecast range

The need to provide accurate, weekly water supply forecasts when snow surveys are conducted only monthly, and the need to be continuously prepared if dry conditions persisted during this last drought, led to development of a forecasting technique that uses a combination of snow survey information, and the historical relationship between runoff and snow water content and rainfall. The observed decrease in the historical ratio of runoff to precipitation as seasonal rainfall declined, was included in the forecasting technique.Initially, runoff amounts (water years) for all available years of record were compared with seasonal rainfall (rainfall years) to develop runoff to rainfall ratios, which provided the general change in the ratio from wet to dry years.