The Effects of Antecedent Rainfall Upon Stream Runoff in the Coastal Plain of Georgia
A 47-year data base (1948-1994) derived from 15 stream and 8 rain gaging stations was used to analyze the effects of antecedent rainfall upon subsequent runoff within the Coastal Plain of Georgia. One hundred and twenty 12-month periods were used to classify antecedent rainfall into "high" (+15 to +59% normal), "low" (-11 to -42% normal), and "normal" (-9 to+ 8%normal) populations. Subsequent rainfall following each of these 120 periods was classified in a similar manner. A "production ratio" (runoft7rainfall) was defined for each subsequent period and then normalized with the long-term ( 4 7-year study period) average production ratio for those months. This permitted the comparison of normalized production ratios for nine subpopulations consisting of various pairings of antecedent and subsequent rainfall conditions. Drought (below normal rainfall for at least one year) depresses streamflow in southern Georgia for a period of one to two years, given a return to normal rainfall. Production ratios associated with above normal antecedent rainfall remain greater than normal for a period of two years following a return to normal rainfall conditions.