Low winter streamflow as an index to short-term and long-term carry-over effects in water supply forecasting

A study is presented of minor indices effecting annual streamflow volume forecasting in the Intermountain West. Time trend of precipitation measurements with streamflow also time trends becoming evident by gradual increases of water-use and evaporation losses. The carry over effect of groundwater storage was found to be related to size of figures representing the low-flow period or winter stream flow, i.e., February. This low-flow value is shown to be an integrator of minor indices, expressing ground water and soil moisture conditions.Mr. C.C. McDonald in discussion intimates that the date of base flow must be selected so that the actual measured flow data is available to the forecaster when needed, and that an estimated value plus or minus average will greatly effect the degree of correlation, also that the trend of streamflow is related to base flow.