The influence of groundwater storage on floodflow

The purpose of this thesis is to determine the relationship between groundwater storage and floodflow through case studies of two drainage basin with contrasting size and geo-hydrological qualities. It is assumed that empty groundwater storage space is capable of reducing the magnitude of a flood. Water balance analysis is used to evaluate the degree of flood reduction due to groundwater recharge by computing the amount of storm water that went into storage. The availability of empty groundwater storage is assessed through an evaluation of the moisture conditions that preceded each flood, the antecedent moisture conditions. Simple correlation and multiple regression analysis were employed to evaluate the relationship between floodflows, volume of storm precipitation, Fantecedent moisture conditions, and the calculated storage. or one basin, that of the Grand River in Missouri and southern Iowa, the anticipated relationships showed up clearly and proved statistically valid. For the other basin, that of the Powell River in northeastern Tennessee and southern Virginia, the flood reducing effect was not evident from the data used. However, it is believed that for this basin also, a similar effect would become apparent if better data were available. It is concluded, that under some circumstances, groundwater storage can reduce the magnitude of floods, and that this effect should be taken into consideration by flood prediction models.