Seasonal hydrological and nutrient loading forecasts for watersheds over the Southeastern United States

19 We show useful seasonal deterministic and probabilistic prediction skill of 20 streamflow and nutrient loading over watersheds in the Southeastern United States 21 (SEUS) for the winter and spring seasons. The study accounts for forecast 22 uncertainties stemming from the meteorological forcing and hydrological model 23 uncertainty. Multi-model estimation from three hydrological models, each forced 24 with an ensemble of forcing derived by matching observed analogues of forecasted 25 quartile rainfall anomalies from a seasonal climate forecast is used. The attained 26 useful hydrological prediction skill is despite the climate model overestimating 27 rainfall by over 23% over these SEUS watersheds in December-May period. The 28 prediction skill in the month of April-and May is deteriorated as compared to the 29 period from December-March (zero lead forecast). 30 A nutrient streamflow rating curve is developed using a log-linear tool for this 31 purpose. The, skill in prediction of seasonal nutrient loading is nearly identical to the skill 32 in predicting the seasonal streamflow. 33 34