5. CONCLUSIONS
In this work, we developed a description of the atmospheric moisture sources that define rain over the Caribbean and Andean subregions in Colombia. This contribution integrates relevant information from the isotopic composition of precipitation with results from the mathematical modeling FLEXPART to better describe the structure of the regional moisture sources and the relative contribution in terms of amount and ecological relevance. This approach refines the strategy of moisture accounting by considering the optimal transport day instead of the canonical 10-day mean lifetime of water vapor in the atmosphere, avoiding, as much as possible (under)overestimations in the moisture contributions. In this sense, our calculations are more realistic and robust.
The differentiation between regions in the country allowed us to identify a variation in the amount and seasonality of moisture contribution from different sources.  Our results indicate a predominance of terrestrial moisture sources (56% and 59% annual mean contributions for the Caribbean and Andes regions, respectively), followed by oceanic moisture sources, dominated by the contribution from the Pacific in the Andean Region (26% contribution) and the Atlantic in the Caribbean region (28%).
The quantification of moisture sources in each region reveals that precipitation regimes depend on the seasonality of the regional composition of moisture sources and the diverse underlying mechanisms, and the physical variables related to each zone, including variables such as topography, geographic location, and environmental features. The isotopic analysis results reveal that the processes which give origin to precipitation in the Andean region are linked to the advance of moisture flow into the continent, and are related to orographic ascent, as can be seen in the LMWLs. For the Caribbean region, the closeness factor to the main sources such as the Caribbean Sea and the Atlantic Ocean has a high influence on the precipitation regime. However, an important influence from the Pacific Ocean is also evident for this region.
The teleconnections between the sources and targets clarify that water resources management should consider not only surface hydrology, but also the links that directly influence the precipitation regime. The dynamics of the climate system at the local level is conditioned by phenomena that depend synergistically on other places, involving the transfer of vital ecosystem services. In this work, in particular, we found that the precipitation regime of the Colombian Andes is highly conditioned by meteorological and ecological processes within the region, as well as in neighboring Amazon and the Orinoco, such that ecological alterations associated with deforestation or land use could have impacts on the amount of moisture that is transported from these regions, threatening water, energy and economic security in the region.