*2.2. Observed Baseline and Projected Future Climate Data*

The daily climate data: Tmax and Tmin (in ◦C), precipitations (P in mm), wind speed (V in m/s), relative humidity (Hr in %) and sunshine duration (S in hours), observed during the baseline (or reference) period (BP) 1981–2010 are collected from the professional Meteorological stations The last belong to the National Meteorological Office (ONM) of Setif and BBA. The Setif station is located in the Soummam watershed, and the BBA station is located in the Hodna watershed; the geographic coordinates and elevation of these two stations are shown in Table 1.

**Table 1.** Geographical coordinates and altitudes of the of the Setif and BBA meteorological stations.


The global simulated future climate data of P, Tmax, Tmin, net sunshine radiation (Nr), Hr, and V used in this study, comes from the Coordinated Regional Climate Downscaling (CORDEX) experiment, Europe domain. It must be mentioned that these data were downloadable from the website https://euro-cordex.net/060378/index.php.en (accessed on 5 January 2022). They are simulated under the RCPs scenarios: RCP 4.5 and RCP 8.5 during the future period 2035–2064. The RCPs are four greenhouse gas concentration trajectories adopted by the IPCC on its Fifth Assessment Report (AR5). The numerical values of the RCPs (2.6, 4.5, 6.0, and 8.5 W m<sup>−</sup>2, respectively) refer to radiative forcing in 2100 [24,25]. These projected radiative forcings are estimated based on the forcing of greenhouse gases, mainly CO2 and other forcing agents. The above four selected RCPs were considered to be representative of the literature and included one mitigation scenario leading to a very low forcing level (RCP2.6), two medium stabilization scenarios (RCP4.5 and RCP6), and one very high greenhouse emission scenario(RCP8.5), induced by a massive use of fossil energy and a high change in land use [26]. Generally, in CC impact studies, the RCP 4.5 and RCP 8.5 are used.

Then, to obtain the local future climate data projected for Setif and BBA meteorological stations, the above projected global climate data were downscaled by applying a dynamic downscaling method on a grid with a very fine resolution of 0.11◦ (~11 km). This downscaling is performed by the use of a Regional Circulation Model (RCM) called KNMI forced by a Global Circulation Model (GCM) called ICHEC. The choice of this combination GCM/RCM: ICHEC\_KNMI is justified by its best simulation of climate data observed during the BP in Algeria [27]. Then, the climate data simulation errors (or bias) present in the raw downscaled future climate data of Setif and BBA stations are corrected using the delta method [28]. According to these last authors, the basic principle of this method is the addition and/or the multiplication of the anomalies of the simulated future climate data to the daily observed climate data during the BP at Setif and BBA, as indicated with Equations (1) and (2).

$$T\_{Fcor}^\*(d) = T\_{obs}\left(d\right) + \mu\_m(T\_{Fran}(d)) - \mu\_m(T\_{eval}(d))\tag{1}$$

$$P\_{\rm Fcor}^\*(d) = P\_{obs}\left(d) \, \frac{\mu\_m(P\_{\rm Fraw}(d))}{\mu\_m(P\_{\rm Fzd}(d))}\right) \tag{2}$$

where *T*∗ *Fcor*(*d*) and *P*<sup>∗</sup> *Fcor*(*d*) are the daily bias-corrected future temperature and precipitation, *Tobs* (*d*) and *Pobs* (*d*) are the daily observed temperature and precipitation during the BP, *μm*(*TFraw*(*d*)) and *μm*(*PFraw*(*d*)) are the monthly averages of daily raw future temperature and precipitation, and *μm*(*Teval*(*d*)) and *μm*(*PEval*(*d*)) are the monthly averages of daily temperature and precipitation simulated for the BP, respectively.

The bias-correction methods such as the quantile mapping method widely used in hydrological impact studies can be difficult to validate in semi-arid climates. This is due to the limited number of rainy days, especially during summer. Moreover, the high variability of precipitations year to year, which is an atypical characteristic of the Mediterranean climate, made the quantile mapping method not easy to use in the HEPs of Algeria [29]. In contrast, the delta method did not rely on the stationary assumption of model bias and did not modify the results of the climate model [30]. Therefore, it can be considered more robust and should be preferred in cases where other approaches cannot be satisfactorily validated. Thus, these precedents results justify the choice of the deltas method for the correction of the uncertainties of the future climatic data simulated by the ICHEC\_KNMI climate model in this study. Thus, the two future CC scenarios, Sc1 and Sc2, which refer to the scenarios: RCP 4.5 in 2035–2064 and RCP 8.5 in 2035–2064, respectively, are evaluated in this study.
