Modelling climate change impacts on the hydrology of an agricultural watershed in southern Québec

Impacts of climate change on nutrient losses from the Pike River watershed of southern Québec

“…Deslandes et al (2007) demonstrated that 70% of P in the Pike River Watershed was exported as particulate P. As TP is typically bound to sediments (Gollamudi et al 2007) and sediment loads were projected to decrease in this watershed, a decrease in TP would also have been expected. However, some of the soils are highly saturated in P (Gangbazo et al 2005) and received a large amount of fertilizer and manure (up to about 400 kg ha (1 ) ( Table 2).…”

“…SWAT (Arnold et al 1998) has the ability to simulate the hydrologic response of large, heterogeneous, and agriculturally intensive watersheds, based on sound conceptual and physical foundations (Borah et al 2002;Borah and Bera 2003;Deslandes et al 2007) and was used several times within the studied watershed. Gollamudi et al (2007) and Eastmann et al (2010) tested the performance of SWAT2000 at simulating the hydrology, sediments, and nutrient losses from four fields within the Pike River watershed and observed that the model had some difficulties partitioning surface runoff and subsurface flow during high flows, which impeded its ability to achieve high performances in simulating sediments, particulate P, dissolved P, and TN exports. Nevertheless, they noticed that the model performance remained acceptable especially at annual and seasonal scales.…”

“…The upstream section was first calibrated and validated before the downstream section of the Pike River watershed. The detailed results of the hydrological calibration are presented in Gombault et al (2015). Sediment load was first calibrated followed by TP and then TN loads to ensure adequate reproduction of physical processes and consequently better modelling of related processes (Arnold et al 2012).…”

“…However, some of the soils are highly saturated in P (Gangbazo et al 2005) and received a large amount of fertilizer and manure (up to about 400 kg ha (1 ) ( Table 2). It is also known that a relatively significant amount of phosphorus can be transported through subsurface flow in the watershed with clayey soils, as a result of preferential flow (Gollamudi et al 2007;Eastmann et al 2010). SWAT does not model subsurface phosphorus processes, but a P concentration of 0.07 mg P L (1 was entered for the calibration parameter GWSOL_P (Table S2 Á section GW.dbf) to account for the presence of P in subsurface flow.…”

“…Particulate P bonded to sediments is typically the dominant form of P (70%) exported out of fields. Gollamudi et al (2007) and Eastmann et al (2010) measured sediment and nutrient exports from agricultural fields with different soil, drainage and fertilization characteristics. They observed substantial loss of sediment and particulate P (1.8 kg ha (1 for TP) from clayey soil sites through subsurface runoff, which they attributed to preferential flow.…”