Estimation of a suitable NDVI oriented for ecological water savings and phytoremediation in Baiyangdian Lake, North China

Abstract

To maintain the ecosystem services of wetlands, this study developed an estimation method for suitable normalized difference vegetation index (NDVI) values by theintegration of ecological water savings and phytoremediation requirements based on experiments and literature surveys in Baiyangdian Lake, North China. In terms of ecological water savings (namely, reducing wetland water consumption by reducing vegetation evapotranspiration), the upper limit of the reed community area was determined by the water replenishment plan of the lake to achieve water balance. In terms of phytoremediation, Grade III of the Chinese water quality grade scale, the target water quality of the lake, was considered to calculate the lower limit of the reed community area for the purpose of good water quality. Considering the two aspects of the requirements of ecological water savings and phytoremediation comprehensively, the suitable reed planning area and NDVI threshold were determined. The results indicated that the suitable reed planting area was 138.05 ∼ 146.43 km2, and the NDVI threshold was 0.155 ∼ 0.316 in the high-water-lever situation (6.8 ∼ 7.0 m). Concurrently, the appropriate reed planting area was 122.39 ∼ 128.24 km2, and the NDVI threshold was 0.137 ∼ 0.277 in the low-water-lever situation (6.5 ∼ 6.8 m). These findings expanded the use of NDVI in the relationship research between wetland vegetation patterns and water resource utilisations, providing support for making vegetation pattern adjustment decisions for wetland protection and restoration in water-scarce regions.