Effects of interannual variation of precipitation on stream discharge fromRhode River subwatersheds

The purpose of this study was to determine the relationships between precip itation at the seasonal and annual scale and water discharge per surface ar ea for seven contiguous first- and second-order tributaries of the Rhode Ri ver, a small tidal tributary to Chesapeake Bay, Maryland, USA. The goal was to quantify the effects of a wide range of precipitation, representative o f interannual variations in weather in this region. The discharges measured included both overland storm flows and groundwater, since the aquifers wer e perched on a clay aquiclude. Precipitation varied from 824 to 1684 mm/yr and area-weighted Rhode River watershed discharge varied from 130 to 669 mm /yr with an average of 332 mm/yr or 29.1 percent of average precipitation. Average annual discharges from three first-order watersheds were significan tly lower per surface area and varied from 16.0 to 21.9 percent of precipit ation. Winter season precipitation varied from 125 to 541 mm. Area-weighted Rhode River winter discharge varied from 26.3 to 230 mm with an average of 115 mm or 43.9 percent of average precipitation. Spring season precipitati on varied from 124 to 510 mm and watershed discharge varied from 40.0 to 32 1 mm with an average of 138 mm or 46.9 percent of average precipitation. In the summer and fall seasons, watershed discharge averaged 40.6 and 40.9 mm or 13.5 and 14.3 percent of average precipitation, respectively Except in winter, the proportion of precipitation discharged in the streams increased rapidly with increasing volume of precipitation. Stream order showed a hig her correlation with volume of discharge than vegetative cover on the water shed.