Analyzing water balance characteristics with remote sensing evapotranspiration data in Zhangwu County, Liaoning Province, China.

Clarifying the characteristics of water balance is the key to ecological environment protection and sustainable management of water resources. Based on 2017, 2020 and 2023 land use remote sensing images, MOD16A2 remote sensing evapotranspiration images and meteorological data, using land use dynamic degree model and remote sensing data inversion, we examined the temporal and spatial dynamics, evapotranspiration dynamics, and precipitation dynamics of different land-use types in Zhangwu County of Liaoning Province, and quantified the interannual and seasonal dynamics of regional water balance. The results showed that Zhangwu County featured an agricultural-dominated with mixed farming-grazing system. During the study period, farmland and grassland accounted for 86.5% of the total area, serving as primary evapotranspiration sources, while construction land only accounted for 9.0%. The comprehensive land-use dynamic degree decreased, suggesting stabilization of ecological elements toward a sustainable pattern. The evapotranspiration (388.2 mm) was the main water loss pathway, with a threshold temperature of 15.9 ℃ triggering significant evapotranspiration increase. Evapotranspiration exhibited higher values in growing season than non-growing season, and in years with abundant precipitation versus dry years. The annual water budget showed an average surplus of 86.7 mm, with soil moisture dynamics cycling through stable (November-February), depletion (March-June), and replenishment (July-October) periods. A water balance management strategy for soil moisture in farmland should be formulated during the soil moisture depletion and replenishment periods, to meet the water balance and ensure the sustainability of water resources of Zhangwu County.