Purpose <p>Materials and energy are continuously transferred between sediments and overlying water at sediment–water interfaces (SWIs). However, the response patterns of material exchange at the SWI to hydrostatic pressure have rarely been reported. Herein, we aim to investigate the hydrostatic pressure-driven modulation of nitrogen exchange fluxes (environmental interactions) across the SWI in deep-water reservoirs.</p> Materials and methods <p>Seven sampling points were selected along the Longyang Gorge Reservoir (LGR) from upstream to downstream. We studied nitrogen exchange fluxes and related mechanisms in experimental reactors operating at different hydrostatic pressures (0.5–1.5&#xa0;MPa) and supplemented the experimental studies with response surface methodology analysis.</p> Results and discussion <p>The exchange fluxes of total nitrogen (TN) and nitrate nitrogen (NO₃⁻-N) first increased but then decreased, whereas the exchange flux of ammonium nitrogen (NH₃-N) increased significantly with increasing hydrostatic pressure. Moreover, the model predicted that the exchange fluxes of TN, NH₃-N and NO₃⁻-N at the SWI in the LGR were 1.255–4.083, 0.244–1.513 and 0.413–1.985 mg m^− 2 h^− 1, respectively, indicating that sediments are important sources of nitrogen in the overlying water of the reservoir.</p> Conclusions <p>Environmental factors and their interactions influence nitrogen flux. Among these influences, the TN and NO₃⁻-N fluxes respond nonlinearly to hydrostatic pressure. The nitrogen release flux was greater in downstream regions than in upstream regions. These findings provide new insights into nitrogen flux at the SWI, highlighting the importance of hydrostatic pressure and interactions for analyzing the mechanism of nitrogen exchange flux and establishing SWI models.</p>