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The seasonal nature of the stream thermal regime has been recognized as an important factor for the structure of benthic macroinvertebrate communities. In this study, we show the importance of temperature and the potential implications of global warming on the composition of benthic macroinvertebrate communities in Andean watersheds. Here we show that thermal factors (mean temperature and monthly range) partially explain the seasonal variability of macroinvertebrates in Andean streams. Different thermal requirements were observed for macroinvertebrate families. Optimal monthly mean temperatures estimated for Gripopterygidae (Plecoptera), Hydrobiidae (Gastropoda) and Helicophidae (Trichoptera) were lower than 7 °C, while temperatures for Ameletopsidae, Baetidae (Ephemeroptera), Ecnomidae, Limnephilidae, Hydropsychidae, Leptoceridae (Trichoptera), Elmidae (Coleoptera) and Notonemouridae (Plecoptera) were close to 9.5 °C. According to our estimations, future global warming could cause important changes in the macroinvertebrate composition of Andean watersheds. Gripopterygidae, Austroperlidae, Diamphipnoidae (Plecoptera), Hydrobiidae and Helicophidae (Trichoptera) would be the most vulnerable families under the 2090 temperature predictions due to their preference for low temperature. [ABSTRACT FROM AUTHOR]

• SWAT is modified to simulate NPS NH 4 + pollution in the Jiulong River Watershed. • NPS inputs contribute about 15.3 % to 17.3 % of NH 4 + load at watershed outlet. • NH 4 + enters water mainly via surface runoff and lateral flow, with minimal leaching. • Land-to-water NH 4 + delivery varies spatially, with high levels in agricultural areas. • Reducing fertilizer usage by 30 % lowers the NH 4 + load at outlet by 2.5∼4 %. Watershed water quality modeling is a valuable tool for managing ammonium (NH 4 +) pollution. However, simulating NH 4 + pollution presents unique challenges due to the inherent instability of NH 4 + in natural environment. This study modified the widely-used Soil and Water Assessment Tool (SWAT) model to simulate non-point source (NPS) NH 4 + processes, specifically incorporating the simulation of land-to-water NH 4 + delivery. The Jiulong River Watershed (JRW) is the study area, a coastal watershed in Southeast China with substantial sewage discharge, livestock farming, and fertilizer application. The results demonstrate that the modified model can effectively simulate the NPS NH 4 + processes. It is recommended to use multiple sets of observations to calibrate NH 4 + simulation to enhance model reliability. Despite constituting a minor proportion (5.6 %), point source inputs significantly contribute to NH 4 + load at watershed outlet (32.4∼51.9 %), while NPS inputs contribute 15.3∼17.3 % of NH 4 + loads. NH 4 + primarily enters water through surface runoff and lateral flow, with negligible leaching. Average NH 4 + land-to-water delivery rate is about 2.35 to 2.90 kg N/ha/a. High delivery rates mainly occur at agricultural areas. Notably, proposed NH 4 + mitigation measures, including urban sewage treatment enhancement, livestock manure management improvement, and fertilizer application reduction, demonstrate potential to collectively reduce the NH 4 + load at watershed outlet by 1/4 to 1/3 and significantly enhance water quality standard compliance frequency. Insights gained from modeling experience in the JRW offer valuable implications for NH 4 + modeling and management in regions with similar climates and significant anthropogenic nitrogen inputs. [Display omitted] [ABSTRACT FROM AUTHOR]