A Dynamic Reservoir Modeling Approach to Assess Water Security under Climatic and Anthropogenic Pressures: Application to the Aburrá Valley, Colombia

Nathalia Jastrombek Vieira, Néstor Jaime Aguirre Ramírez, Fabio de Jesús Vélez Macías

Water security in Aburrá Valley, Colombia, relies heavily on the Riogrande II and La Fe reservoirs, which face increasing
pressures from climate variability, land use change, and rising demand. Although SWAT+ is a powerful hydrological
modeling tool, its reservoir module cannot represent dynamic changes in demand, land use, or external water inflow. To
address these limitations, we developed resv_dyn, a Python algorithm that integrates: (i) annual land use changes derived
from Dinamica EGO, (ii) progressive demand growth, and (iii) operation with pumped inflows from non-tributary rivers.
The validation of resv_dyn was conducted using the Riogrande II Reservoir as a case study, comparing its performance
with the SWAT+ reservoir module. The results show that resv_dyn effectively simulates the operational conditions of the
reservoir, achieving outcomes comparable to those of SWAT+. Application to La Fe Reservoir under three climate scenarios
shows that increased extreme rainfall temporarily boosts natural inflows, but these isolated peaks cannot be effectively stored
due to reservoir capacity constraints. As a result, the system remains continuously dependent on pumping, and supply
deficits are not substantially reduced. The proposed approach improves the representation of reservoir behaviour and
provides a transferable tool for assessing reservoir resilience under combined climatic and anthropogenic pressures.