# Evaluating CHIRPS and ERA5 for Long-Term Runoff Modelling with SWAT in Alpine Headwaters
###### Abstract
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Dataset** & **Variable** & **Author(s)** & **Study Area** & **Assessment** \\ \hline \multirow{8}{*}{PERSIAANN-CDR} & \(p\) & [PERSON] et al. [51] & Upper Adige basin, Italy & o \\  & \(p\) & [PERSON] et al. [69] & Fella basin, north-east Italy & o+m (RIBS) \\  & \(p\) & [PERSON] et al. [59] & Swiss and Italian Alps, French & o \\  & \(p\) & [PERSON] et al. [51] & Ceverne, es, & o \\  & \(p\) & [PERSON] et al. [65] & Trentino-Alto, Adige region, Italy & o \\  & \(p\) & [PERSON] et al. [70] & Upper side basin, Italy & m (ICHYMOD) \\  & \(p\) & [PERSON] et al. [70] & Oklahoma/Ar Kansas (USA) & o+m (HL-RDRHM) \\  & \(p\) & [PERSON] et al. [84] & Irrawaddy (Myanmar) & o+m (SWAT) \\  & \(p\) & [PERSON] et al. [73] & Kear and Meis basins (Ethiopia) & o+m (GR4J) \\  & \(p\) & [PERSON] [54] & Lake Tlicaca (Pern/Bolivia) & o+m (GR4J) \\  & \(p\) & [PERSON] et al. [76] & USA & o+m (SWAT) \\  & \(p\),\(T\) & [PERSON] et al. [8] & Viterham & m (GR4J, HMETS) \\ \hline \multirow{2}{*}{PGF} & \(p\) & [PERSON] et al. [51] & Upper Adige basin, Italy & o \\  & \(p\) & [PERSON] et al. [68] & Shiyang River (China) & m (SWAT) \\ \hline \multirow{2}{*}{SAFRAN} & \(p\) & [PERSON] et al. [66] & Garonne basin, France & m (SWAT) \\  & \(p\) & [PERSON] et al. [67] & France & m (GR4J) \\ \hline \multirow{8}{*}{SM2 RAIN} & \(p\) & [PERSON] et al. [48] & Global & o \\  & \(p\) & [PERSON] et al. [80] & Global & o+m (HBV) \\ \cline{1-1}  & \(p\) & [PERSON] et al. [58] & Austria & o \\ \cline{1-1}  & \(p\) & [PERSON] et al. [54] & USA & o \\ \hline \multirow{8}{*}{TRMM} & \(p\) & [PERSON] et al. [69] & Fella basin, north-east Italy & o+m (RIBS) \\  & \(p\) & [PERSON] et al. [51] & Upper Adige basin (Italy) & o \\  & \(p\) & [PERSON] et al. [60] & Ceverne and Europe) & o \\ \cline{1-1}  & \(p\) & [PERSON] et al. [64] & Upper Adige basin (Italy) & m (SWAT) \\ \cline{1-1}  & \(p\) & [PERSON] et al. [70] & Oklahoma/Ar Kansas (USA) & o+m (HL-LDHM) \\ \cline{1-1}  & \(p\) & [PERSON] et al. [82] & Missouri (USA) & o+m (SWAT) \\ \cline{1-1}  & \(p\) & [PERSON] et al. [71] & Ethiopia & o+m (SWAT) \\ \cline{1-1}  & \(p\) & [PERSON] et al. [68] & Shiyang River (China) & m (SWAT) \\ \cline{1-1}  & \(p\) & [PERSON] et al. [72] & Lancane-Mekoo River (China) & o+m (SWAT) \\ \cline{1-1}  & \(p\) & [PERSON] et al. [73] & Kear and Meis basins (Ethiopia) & m (SWAT) \\ \cline{1-1}  & \(p\) & [PERSON] et al. [74] & Lake Tlicaca (Pern/Bolivia) & o+m (GR4J) \\ \cline{1-1}  & \(p\) & [PERSON] et al. [54] & USA & o \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._reanalysis-based product with a spatial and temporal resolution between that of CHIRPS and ERA5, we aimed to include GPPs representing different methodological approaches. An overview of hydrological studies reveals an information gap in the application of grided precipitation products (GPPs) for long-term hydrological modelling in the inner Austrian Alps. While some research has explored the application of GPPs in the Alpine region, no studies to date have directly compared CHRIPS and ERA5 precipitation products within this specific pilot area. Furthermore, to our knowledge, the SWAT model has not been applied with GPP forcing in the headwater of the Drava and Inn rivers. This study addresses this gap by evaluating the performance of two GPPs, CHIRPS-V2.0 (a gauge and satellite-based product) and ERA5 (a reanalysis product), as inputs to the hydrological model for assessing long-term environmental changes in mountainous regions. The specific objectives of this study were to evaluate the following: (a) the agreement between GPPs and observed precipitation indicators (amount \(P\), trend \(TP\)) at annual, seasonal and monthly time steps; (b) the agreement between SWAT runoff with GPP forcing and observed runoff indicators (amount \(Q\), trend \(TQ\)) at different temporal scales (annual, seasonal, monthly); (c) the overall suitability of CHIRPS and ERA5 as alternative precipitation inputs for long-term SWAT simulations in the pilot basins.