Determination of the optimal ecological water conveyance volume for vegetation restoration in an arid inland river basin, northwestern China

Shun Hu; Rui Ma; Ziyong Sun; Mengyan Ge; Linglin Zeng; Feng Huang; Jianwei Bu; Zheng Wang

doi:10.1016/j.scitotenv.2021.147775

Determination of the optimal ecological water conveyance volume for vegetation restoration in an arid inland river basin, northwestern China

Sci Total Environ. 2021 Sep 20:788:147775. doi: 10.1016/j.scitotenv.2021.147775. Epub 2021 May 15.

Authors

Shun Hu¹, Rui Ma², Ziyong Sun¹, Mengyan Ge¹, Linglin Zeng³, Feng Huang⁴, Jianwei Bu¹, Zheng Wang¹

Affiliations

¹ Hubei Key Laboratory of Yangtze River Basin Environmental Aquatic Science, School of Environmental Studies & State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China.
² Hubei Key Laboratory of Yangtze River Basin Environmental Aquatic Science, School of Environmental Studies & State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China. Electronic address: rma@cug.edu.cn.
³ College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
⁴ College of Hydrology and Water Resources, Hohai University, Nanjing 210098, China.

PMID: 34029814
DOI: 10.1016/j.scitotenv.2021.147775

Abstract

Overexploitation of water resources has led to severe ecological degradation and even desertification in some arid inland river basins, northwestern China. To alleviate or restore the degraded vegetation ecosystem, ecological water conveyance (EWC) has become an important and effective measure. Scientific assessment of the impact of EWC on vegetation restoration and determination of the corresponding optimal EWC volume (EWCV) are important to formulate rational ecological water management. In this study, long time series normalized difference vegetation index (NDVI) was used to extract the restored vegetation area in Qingtu Lake area, a terminal lake in inland Shiyang River basin, northwestern China. The relationship between restored vegetation coverage and EWC was explored to determine the optimal EWCV. The restored vegetation area (RVA) increased dramatically in the first five years and became stable from 2016. The time lag of the response of RVA increase to EWC was about 2 years. A bell-shaped function between RVA and groundwater depth was obtained based on the results from Unmanned Aerial Vehicle (UAV) and micro terrain of the lake area. Based on the fitted function, five groundwater depth thresholds were obtained. The optimal groundwater depth in the hydrometric station was 2.91 ± 0.09 m for the maximal RVA (17.08 ± 3.25 km²). A polynomial function between the yearly EWCV and groundwater depth was developed and the EWCV thresholds corresponding to the groundwater depth thresholds were estimated. The optimal EWCV into Qingtu Lake was 2224.4 × 10⁴ m³ for the maximal RVA. The correspondingly optimal EWCV from Hongyashan Reservoir was 3271.4 × 10⁴ m³. The spatial distribution patterns of remotely sensed water surface and NDVI suggested that expanding the water-receiving area of conveyed water was useful to improve the vegetation growth. This study provides a reference for assessing the impact of EWC on vegetation restoration and determining the correspondingly optimal EWCV in arid inland river basins.

Keywords: Ecological water conveyance; Groundwater depth; Northwestern China; Remote sensing; Vegetation restoration.