Dataset - Low buffering capacity and slow recovery from anthropogenic phosphorus pollution in watersheds
Excess anthropogenic phosphorus (P) in watersheds, transported with runoff, can result in aquatic eutrophication, a serious global water quality concern. Watersheds can retain P, especially in their soils, which can serve as a buffer against the effect of excessive use of P. However, whether there is a quantifiable threshold at which a watershed exceeds its optimal P buffering capacity (beyond which riverine loads would dramatically increase) remains unknown. Here we quantified a watershed P buffering capacity threshold based on P accumulation data over 110 years in 23 watersheds of a large North American river basin with globally representative agricultural soils. We found a surprisingly low threshold of just 2.1 t P km-2 (0.03 - 8.7 t P km-2). Beyond this, further P inputs to watersheds cause a significant acceleration of P loss in runoff. Using a simple exponential decay model, the time estimated to eliminate legacy P via run-off in our watersheds ranges from ~100 to over 2000 years. The rapidity with which the watershed buffering threshold can be surpassed during accumulation, particularly given current anthropogenic P input rates, versus the long return to baseline suggests that new strategies to reconcile watershed activities and water quality are urgently needed.
Units of variables in the dataset:
year: Years for which NAPI and riverine TP export have been calculated.
Rivername: Name of the rivers draining each of the 23 watersheds of this study
DrainageArea: Drainage area of the different watersheds
spNAPI: Net Anthropogenic P inputs to watersheds (kg P km-2 yr-1)
spTP: Riverine TP loads at the outlet of each watershed in years where water quality data was available (1985-2011; kg P km-2 yr-1). Cells with zeros indicate years were no water quality data was available. Phosphorus loads in these years were estimated following the methods described in the article.