# Extreme Droughs in the Peruvian Amazon Region (2000-2024)
## 3 Results
### Spatial Distribution of Drought Regions  
The spatial distributions of the estimated MCWD in the Peruvian Amazon region are shown in Figure 7 for the years classified as extreme drought, as obtained from ERA5 precipitation and evapotranspiration data and by the CHIRPS and MSWEP precipitation data, combined with ERA5 evapotranspiration. The upper row of panels shows the spatial distribution of MCWD according to ERA5. In this case, the droughs of 2004-05 and 2009-10 emerge as the ones with the most extended area inside the two higher thresholds (3 and 4, orange and red colors), but if the second threshold is considered, the 2023-24 drought turns out to be the most extended. It is important to note that, following this dataset, only in 2022-23 and 2023-24 can a drought signal in the northern part of the Loreto region be found. In the four HYs, the main drought areas were in the Madre de Dios and Ucayali regions, while in the Andes-Amazon transition region, the lower threshold was accomplished. Figure 6: Average annual cycles of precipitation (Pr) and evapotranspiration (Et) for the extreme drought (ED) hydrological years (2004-05, 2009-10, 2022-23, and 2023-24) and the climatology (CLIM) of the study period (2000–2024). The legend shows the colors of the lines corresponding to evaporation and precipitation for the two classifications. The CHIRPS dataset was characterized by a more extended threshold 4, including all the Andes-Amazon transition region, while Madre de Dios and Ucayali were also affected by drought, which reached the southern extreme of Loreto. Only in 2022-23, most of Loreto was affected by drought, within its lower threshold. The distribution for MSWEP was very similar to CHIRPS for the first two HYs but showed relatively weak drought for 2022-23 and the strongest signal in 2023-24, covering all the Peruvian eastern border area and extending threshold 2 till most of Loreto. The most striking difference across datasets is the low drought threshold in the Andes-Amazon region for ERA5. This is related to the overestimation of ERA5 in precipitation for mountain areas [55; 56]. The area covered by the lower threshold in 2004-05 by any of the datasets can be compared with the area of moderate drought identified by more than six datasets in Figure 1 of [1], where most of the Peruvian Amazon territory is covered by drought, except north of Loreto. The area of maximum threshold in the present paper, covering Ucayali and Madre de Dios, is included in the six coincident datasets area in [1]. However, for the 2009-10 drought, at least five datasets show drought in [1], while in our case, most of Loreto is free of drought. On the other hand, at least in part of the Amazon-Andes region, all the datasets in [1] detected drought, while in our case, the whole region is covered by drought following CHIRPS or MSWEP. The climatological distribution of MCWD, estimated by the three datasets, is shown in Figure 8, considering the study period from HY 2000-01 to 2023-24. It evidences that the dry conditions in the southeast of Peru are a climatological feature that gets worse in conditions of extreme drought. These conditions can also be found in the central-south Andes-Amazon transition region, in the Apurimac department, as can be seen from the ERA5 dataset. However, the satellite-based datasets CHIRPS and MSWEP show high MCWD values all along the right slope of the Andes, which must be considered with caution because of uncertainties in satellite-based estimation of precipitation over mountains, which is characteristic of satellite-based datasets [57]. The evaluation of the area affected by each level of drought, corresponding to MCWD ranges delimited by the thresholds inside the Peruvian Amazon region obtained from each of the datasets for the HYs with extreme drought, was calculated from the number of grid points within each range.