Drought and post-drought rain effect on stream phosphorus and other nutrient losses in the Northeastern USA

Abstract

Study region: Our study was conducted in the Owasco Lake watershed, which is part of the Finger Lakes, located in Central NY. Study focus: In the Northeastern United States (NE US), nutrient pollution is receiving increasing attention, and particularly phosphorus (P), in response to the recent increasing frequency of toxic blue-green algal blooms. This study assesses how land use, seasonal weather patterns, and climate extremes interact to control runoff and nutrient loading from tributaries into Owasco Lake. In 2016, NE US experienced a prolonged drought, which resulted in unusual and extreme low flows between August and October. The drought was ended by an intense rain event at the end of October. New hydrological insights for the region: The results show that during the drought period the expected influence of agricultural and mixed land use on P loads was masked. However, high P loads were observed during the first rain event after the drought, exacerbating the agricultural impact on water quality. This study aids in understanding how climate extremes might affect nutrient runoff dynamics in the NE US. These findings are an important contribution from a management perspective, as projections for the NE US suggest that total precipitation will slightly increase, but large changes are expected in the extremes, with summer rains becoming concentrated in fewer events of higher intensities, interspaced with prolonged dry periods. Keywords: Nutrient runoff, Climate extremes, Land use, Algal blooms