Assessing the impact of climate variability on phosphorus transport in the Cannonsville Watershed using the SWAT model

This study investigates the impact of climate variability on phosphorus transport in the mostly forested and agricultural Cannonsville watershed in Upstate New York. Different climate scenarios are studied in order to better understand the possible changes in seasonal phosphorus loading to the reservoir, which is an important source of drinking water for New York City residents. The study is carried out using a calibrated SWAT 2005 model along with a weather generator created specifically for the watershed. The study includes two parts. The first part investigates the historical trends in phosphorus loading. This is done by using climate data from the mid 1960s to the present day with the SWAT model. The results show that over time the phosphorus loading to the reservoir is increasing, with most of this increase occurring in the spring, summer and fall. This is worrisome since climate change is likely to make these seasons longer. The second part of the study investigates the impact of different climate scenarios under the same watershed conditions as the first part of the study. This is done in order to understand the changes in timing as well as the amount of phosphorus loading to the reservoir. The study also investigates the changes in crop growth, in terms of timing and magnitude. Since the watershed is mostly forest and agricultural land, the impact of warmer or colder climates is quite apparent. All model outputs are investigated on a yearly, as well as a seasonal basis since climate change is likely to impact seasons differently. The results show significant changes in phosphorus loading due to different climate scenarios. This shows that any type of phosphorus management planning for the future needs to include the possible uncertainty associated with changing climates.