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In addition to baseline simulations, OPTAIN assessed NSWRM performance under projected climate scenarios derived from regionalised climate projections. These scenarios introduced variations in precipitation intensity, seasonal distribution and temperature patterns in order to evaluate how predicted NSWRM effects respond to altered hydrological regimes.
The simulations indicate that climate change modifies both the magnitude and variability of hydrological and nutrient transport processes. In particular:
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Increased rainfall intensity tends to amplify peak discharge and erosion-driven phosphorus transport, thereby influencing the predicted effectiveness of structural and vegetative measures.
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Extended dry periods affect soil moisture dynamics and crop water availability, modifying the relative performance of management-based measures such as reduced tillage and cover crops.
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Spatial allocation becomes increasingly important under intensified climate variability, as hydrological connectivity patterns shift within catchments.
Across case studies, the robustness of NSWRM portfolios varies considerably. Certain management-oriented measures demonstrate relatively stable performance across scenarios, particularly with respect to soil water retention and mitigation of nutrient losses under moderate climate stress. In contrast, the effectiveness of storage and structural measures often shows stronger sensitivity to altered rainfall distribution and event intensity.
Importantly, optimisation analyses reveal that portfolio combinations generally exhibit greater robustness than isolated measures, especially when spatial targeting is incorporated into scenario design.
These findings represent simulation-based projections within calibrated modelling environments and illustrate how climate variability influences predicted system responses. They provide analytical insight into the resilience of alternative NSWRM portfolios under changing environmental conditions, rather than empirical observations from implemented interventions.