Abstract: Seasonal water-level fluctuations in large reservoirs profoundly alter terrestrial-aquatic interfaces, yet their impacts on climate-soil-microbe interactions in dry-hot valleys remain poorly understood. Here, we combined field monitoring across four cascade reservoirs in the lower Jinsha River (Wudongde, Baihetan, Xiluodu, and Xiangjiaba) with multivariate analyses to evaluate ecosystem responses to hydrological regulation. Diversity indices showed clear seasonal dynamics, i.e., both Shannon and Pielou indices exhibited significant spatial heterogeneity in April (H=13.997 3, p<0.01; H=15.095 5, p<0.01), but not in September, whereas microbial biomass (PLFA) remained spatially homogeneous across both months. This suggested niche stability or substrate convergence. Principal component analysis (PCA) indicated stronger clustering and clearer reservoir separation in April, with PC1 explaining 60.4% of variance in climate-soil interactions and 69.2% in climate-microbe associations. By contrast, explained variance declined in September (38.6% and 42.3%, respectively), reflecting dispersed associations and weakened spatial differentiation. Structural equation modeling (SEM) further revealed that during stable water levels, climate was positively driven by soil (0.561***) and vapor pressure deficit (0.701*), while soil exerted a positive effect on microbes (0.323*). During water-level rise, direct climatic control on microbes intensified (0.531*), and soil effects were dominated by TN (0.592*), SAP (0.774*), and pH (0.65**), with SOC contributing marginally (0.002 3). These findings demonstrated that cascade reservoir impoundment reshaped climate-soil-microbe linkages. The microbial diversity responded sensitively to hydrological disturbances while biomass remained stable. Our study provided quantitative evidence for assessing ecological impacts of reservoir operation in dry-hot valleys and highlighted the role of hydrological regulation in mediating land-microbe coupling.