## 4 Discussion
### Impact of Reservoir Construction on Land Use  
Reservoir construction significantly altered land use patterns, particularly impacting the distribution of water bodies, forests, cultivated land, and barrens. These changes are closely linked to the fundamental attributes of reservoirs. For instance, following the construction of the LJ reservoir, the water area increased by 200%, primarily due to the expansion of the watershed after reservoir impoundment. In most reservoir areas, cropland and barren areas decreased, while forest and water areas expanded, reflecting the direct impact of reservoir construction on land use. Seasonal water level fluctuations following impoundment led to the conversion of some agricultural land into watersheds. Specifically, cultivated land in the LJ reservoir area decreased by 34.7%, which was closely tied to land reclamation and ecological restoration measures around the reservoir. Government policies, particularly the \"returning farmland to forest\" policy implemented in 1999, have also played a significant role in land use changes, notably increasing forest areas, especially around reservoirs. For example, forest cover around the LJ and KY reservoirs increased by about 120% over 20 years. These changes, in conjunction with reservoir construction, contributed to the rapid expansion of forests in the region, reflecting the synergistic effects of policy and reservoir development [44]. Additionally, reservoir construction often involves large-scale resettlement and land rezoning, which reduces agricultural land and accelerates urbanization, further promoting the conversion of cropland and grassland. Socio-economic factors further accelerate land use transformation. The resettlement of migrants, agricultural abandonment, and resource development in reservoir construction areas, especially the rise of fisheries and tourism, have contributed to land use changes [45]. For example, the development of fisheries and tourism around the HF reservoir led to a decrease in surrounding grasslands and croplands, with an increase in watersheds and urbanized lands. After resettlement, some farmland was abandoned or repurposed, resulting in further reductions in cultivated land. A complex feedback mechanism exists between hydrological processes, land use, and climate. Water storage in reservoirs alters hydrological conditions, which in turn influences climate patterns and land use. For instance, water level fluctuations and the evapotranspiration effects of reservoirs regulate the regional climate and affect vegetation growth and land use. In the case of the ZG reservoir, seasonal water level fluctuations significantly altered hydrological characteristics during spring and fall, promoting the conversion of former agricultural land into wetlands or watersheds. These hydrological changes indirectly promoted land use transformation by influencing soil moisture and water distribution [46, 47]. Climate change and land use changes create a positive feedback loop that plays a key role in ecosystem succession after reservoir construction. In this study, we utilized the ERA5-Land dataset and the China Land Cover Dataset (CLCD), which provide valuable support for remote sensing techniques. However, we acknowledge certain uncertainties in these datasets. The ERA5-Land dataset, due to its relatively low spatial resolution and reliance on numerical weather prediction models, may introduce biases in estimating local climate changes. Additionally, the CLCD dataset may suffer from classification errors and insufficient spatial resolution in land use change analysis, which could impact the accurate prediction of land cover change trends. To enhance the credibility of our findings, future studies should integrate ground observation data with remote sensing data for cross-validation and conduct comparative analyses between ground meteorological data and ERA5-Land data to verify the effectiveness of remote sensing in capturing climate trends.