331 long-term closure measures, especially in sensitive areas such as the Peruvian Andes where the retreating cryosphere (e.g., glacier loss) and El Niño/La Niña events can drastically alter water recharge. Currently, closure plans often underestimate how extreme precipitation scenarios could reactivate acid generation in seemingly stable deposits, or how prolonged droughts could deepen sulfide oxidation by exposing a larger reactive area to air, thus amplifying the risk of DAM through changes in precipitation patterns, temperature, and water recharge (IPCC, 2021). This points to the need for innovation with predictive tools that dynamically combine hydrology and geochemistry. A model capable of simulating variable infiltration pulses, partially saturated conditions, and oscillating availability of oxidants (O2) would provide a more realistic view of post-closure chemical evolution under different climate futures. Such an advance would allow for the design of adaptive closure strategies, optimizing covers, barriers, and passive treatment systems based on projected risks and not just current conditions. This work contributes to the theme of the conference “Science and Mining Innovation in the Face of Climate Change Impacts” by presenting an integrated geochemical-climatic modeling framework. Specifically, it proposes a conceptual predictive model aimed at assessing sensitivity to hydroclimatic variations, which couples geochemical reactive transport simulations (with PHREEQC) with transient hydrological forcings derived from climate scenarios (e.g., RCP 4.5). Through a sequential approach of monthly infiltration pulses, the model represents the unsaturated behavior of the deposit and the reactions of reactive sulfides (pyrite oxidation, neutralization, precipitation of secondary compounds, etc.) under a variable climate regime. The result is a metric that summarizes the system's propensity to reactivate acidity generation under certain future climate conditions. This proposal is novel in that it directly links climate change projections to acid drainage chemistry, something that has been little explored in conventional planning. This approach makes it possible to identify in advance the most vulnerable areas of the deposit and the critical periods (e.g., the first heavy rain after a prolonged drought) for water quality. In this way, it provides a scientific basis for strengthening closure measures: cover designs that consider future water balance, drainage systems sized for extreme events, and monitoring schemes focused on early indicators of acidification. In short, the interdisciplinary integration achieved by this model (hydrogeology, climate science, and geochemistry) provides a proactive strategy for managing DAM in a changing climate, contributing to safer and more sustainable mine closures in the long term. 2. METHODOLOGY The geochemical model developed to simulate the behavior of reactive fill material is based on the integration of advective-dispersive transport processes, thermodynamic equilibrium reactions, and heterogeneous mineral kinetics under unsaturated flow conditions. Given the inherent complexity of modeling partially saturated porous media with multiple reactive lithologies, a sequential approximation approach was adopted that combines three complementary strategies to represent unsaturation without resorting to the complete resolution of the Richards equation: (i) a simplified Lagrangian mixture between “new water + resident water” in each infiltration pulse, implemented with MIX based on a meteoric solution and representative interstitial water solutions; (ii) a scheme equivalent to series reactors using
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