# Evaluating CHIRPS and ERA5 for Long-Term Runoff Modelling with SWAT in Alpine Headwaters
## 3 Results
### Performance Evaluation Using Gauge Observations
\begin{table}
\begin{tabular}{c c|c c c|c c c c|c c c c} \hline \hline
**Matrix** & **Product** & _menta a_ & **Annual** & & \multicolumn{3}{c|}{_mean_} & \multicolumn{3}{c|}{_Warm_} & \multicolumn{3}{c|}{_mean c_} & \multicolumn{3}{c|}{_Cold_} \\ \hline (**H**) & & & Elev.3 & Elev.2 & Elev.1 & & Elev.3 & Elev.2 & Elev.1 & & Elev.3 & Elev.2 & Elev.1 \\ \hline _TP_ & OBS & 51 & 57 & 52 & 42 & 18 & 34 & 6 & 18 & 33 & 23 & 46 & 24 \\ (mm) & CHIRPS & 64 & 52 & 64 & 83 & 49 & 42 & 50 & 57 & 15 & 10 & 14 & 26 \\  & ERA5 & 68 & 67 & 64 & 80 & 36 & 46 & 30 & 34 & 32 & 21 & 34 & 46 \\ \hline \(B\) & CHIRPS & **13** & \(-\)5 & 12 & 41 & 31 & 8 & 44 & 39 & \(-\)18 & \(-\)13 & \(-\)31 & 2 \\ (mm) & ERA5 & 17 & 10 & 12 & 38 & **18** & 12 & 24 & 17 & \(-\)1 & \(-\)2 & \(-\)12 & 21 \\ \hline _PB_ & CHIRPS & 25\({}^{*}_{-}\) & \(-\)10\% & 24\% & 98\% & 170\% & 22\% & 20\% & 221\% & \(-\)34\% & \(-\)57\% & \(-\)69\% & 7\% \\  & ERA5 & 33\% & 17\% & 23\% & 91\% & 107\% & 35\% & 388\% & 93\% & -4\% & -99\% & -26\% & 89\% \\ \hline _MAE_ & CHIRPS & **25** & 9 & 25 & 48 & 38 & 21 & 48 & 45 & 24 & 25 & 33 & 3 \\ (mm) & ERA5 & 25 & 27 & 17 & 38 & **25** & 23 & 29 & 19 & **16** & 4 & 23 & 21 \\ \hline (**V**) & & & & b1 Sill & \multicolumn{3}{c|}{b2} & \multicolumn{3}{c|}{b3 Isel} & \multicolumn{3}{c|}{b1 Sill} & \multicolumn{3}{c|}{b2} & \multicolumn{3}{c|}{b3 Isel} \\ \hline _TP_ & OBS & (+\(S1\) & 39 & (+\(S6\)) & 55 & (?18 & (?38) & (?1)\({}^{-}\)15 & (?31) & (+\(S33\) & 1 & (?5) & 24 \\ (mm) & CHIRPS & 64 & (+\(S37\) & 83 & (?73) & (?4)9 & 29 & (?53) & 64 & (+\(S15\)) & 8 & (+\(S30\)) & (+\(S8\) \\  & ERA5 & 68 & (+\(S4\)) & 87 & (?69) & 36 & 39 & 28 & 42 & 32 & 10 & 59 & 28 \\ \hline \(B\) & CHIRPS & **13** & \(-\)**2** & **23** & 17 & 31 & \(-\)9 & 68 & 33 & \(-\)18 & 7 & \(-\)45 & \(-\)16 \\ (mm) & ERA5 & 17 & 10 & 27 & **14** & **18** & **1** & **43** & **11** & \(-\)1 & 9 & \(-\)**16** & **3** \\ \hline _PB_ & CHIRPS & **25** & \(-\)**6**\% & **39** & 31\% & 170\% & \(-\)24\% & \(-\)45\% & 10\% & \(-\)54\% & 618\% & \(-\)60\% & \(-\)65\% \\  & ERA5 & 33\% & 25\% & 45\% & **26**\% & 101\% & 33 & \(-\)298\% & 35\% & \(-\)4\% & 807\% & \(-\)21\% & 14\% \\ \hline _MAE_ & CHIRPS & **25** & **6** & **27** & 42 & 38 & 9 & 68 & 38 & 24 & 7 & 45 & 19 \\ (mm) & ERA5 & 25 & 10 & 33 & **32** & **25** & **9** & **43** & **22** & **16** & 9 & **21** & **19** \\ \hline \hline \multicolumn{2}{c|}{**Monthly**} & \multicolumn{3}{c|}{_mean m_} & \multicolumn{3}{c|}{**Jan**} & \multicolumn{3}{c|}{**Feb**} & \multicolumn{3}{c|}{**Mar**} & \multicolumn{3}{c|}{**Apr**} & \multicolumn{3}{c|}{**May**} & \multicolumn{3}{c|}{**Jun**} & \multicolumn{3}{c|}{**Jal**} & \multicolumn{3}{c|}{**Aug**} & \multicolumn{3}{c|}{**Sep**} & \multicolumn{3}{c|}{**Oct**} & \multicolumn{3}{c|}{**Nov**} & \multicolumn{1}{c}{**Dec**} \\ \hline _TP_ & OBS & 4.2 (?17.9) & (?12.4) & \(-\)2.3 & (+)9.7 & (+)10.1 & \(-\)5.8 & \(-\)3.3 & (?26.6) & 0.5 & \(-\)13.0 & 15.7 & 1.9 \\ (mm) & CHIRPS & 5.4 (?17.2) & (?107.0) & \(-\)6.2 & (? )\(-\)17.1 & 1.9 & (?7.7) & 2.3 & (*20.1) & (? The results of the precipitation trend estimates show a lower bias for CHIRPS but a higher correlation with fewer misses of statistically significant monthly trends for ERA5. Both products overestimate annual precipitation trends, primarily due to overestimation during the warm season and in valley regions. Spatial performance for _TP_ aligns with performance for _P_: CHIRPS performs better in catchments b1 and b2, while ERA5 performs better in b3. Both products poorly estimate seasonal precipitation trends in catchment b2.