ABSTRACT:

Currently, the water demands present a continuous growth in quantity and quality, on the blue and green water resources available globally, and likewise the projected reduction of the flows of blue and green water, consequence of climate change, deduces a new level of future uncertainty. This work aims to quantitatively estimate the hydrological response in the blue and green water flows in the Cachi river basin, under climate change scenarios, for the historical period (1981 - 2016) and the 2060s (2046 - 2070). and from 2090 (2075 – 2099), using the SWAT semi-distributed hydrological model; previously calibrated and validated with the SUFI-2 algorithm, obtaining Nash – Sutcliffe values ​​(0.57, 0.62); R2 (0.57, 0.63) and KGE (0.64, 0.75), where these values ​​indicate optimal model performance. The projection of precipitation and temperature of the IPSL-CM5A-MR (France) model was used, within the 10 models evaluated, under the RCP8.5 radiative forcing scenario of the Coordinated Regional Climate Downscaling Experiment (CORDEX), using statistical downscaling with error correction by power transformation and distribution mapping for precipitation and temperature respectively, using the CMhyd tool. The results suggest that the average annual blue water flow (BWF) for the 2060s (2046-2070) decreases by -6.1% (198 mm-245.5 mm) for the southern sub-basins, on the contrary, it increases by + 19% (198 mm-245.5 mm) for the sub-basins of Huanta and San Pedro de Cachi; Meanwhile, for the 2090s (2075-2099) it presents a considerable decrease of -35.1% (269.5 mm-175 mm) for the southern sub-basins; while the green water flow (GWF) presents a small variation of 4% (767 mm-798.5 mm) for the 2060s (2046-2070), on the other hand, for the 2099s the GWF increases by +11.5% ( 767 mm-866.5 mm) at the basin level, concluding that the BWF presents a space-time variation in the future and the GWF shows an increasing trend.