This PhD is focused on the eastern region of Colombia and the practical development of this work was composed of three stages that lead to three different articles which are the main body of this study. The first stage was focused on a systematic review of the climate characteristics over the last decades at eastern Colombia including a data survey and evaluation of the historical available data records. In the second stage, the Statistical Downscaling Model (SDSM) was used as a tool for downscaling meteorological data statistically over four representative water districts at the eastern side of Colombia. Here, data from the two Global Climate Models CanESM2 and IPSL-CM5A-MR, which are part of the CMIP5-project have been used to project future maximum and minimum temperature, precipitation and relative humidity for the periods 2021–2050 and 2071–2100. For both models, the Representative Concentration Pathways RCP2.6 and RCP8.5 were considered, representing two different possible future emission trajectories and radiative forcings. In the third stage, the results of the second stage together with the hydrological model BROOK90 and complementary data were utilized to determine the future changes in the water balance components in the previously selected four water districts in Eastern Colombia.