Determining the width of lake riparian buffer zones for improving water quality base on adjustment of land use structure

Abstract

Lake buffer riparian zones play an essential role in maintaining the sustainability of water quality, reducing sediment accumulation, regulating surface runoff, and protecting biodiversity. However, they are massively degraded over most of the lake basins in the world due to human activities and land-use change in adjacent areas. In this study, the width of the riparian buffer zone was determined around three lakes to achieve a balance between ecological benefits and costs. A modified export coefficient model was used to assess land use and land cover effects on the trophic status of the lake and the environmental benefits of land use structure adjustment. The maximum ratio of benefits obtained to funds invested was utilized for determining the optimal width. The simulation results show that the best results can be obtained after the implementation of the two measures of returning cultivated land to forest and grassland in the buffer zone of 450 m, 100 m and 150 m around Dianchi Lake, Erhai Lake and Fuxian Lake (China), respectively. The ratio of benefits obtained to funds invested of returning cultivated land to grassland was higher than returning cultivated land to forest, about 1.5 times. The results indicated that 24.89 km2, 2.94 km2, 4.30km2 of cultivated land need to be returned to grassland in the riparian buffer zones of Dianchi Lake, Erhai Lake, and Fuxianhu Lake, respectively. It was found that the hydrogeography approach can be successfully implemented to determining the width of lake riparian buffer zones for improving water quality.