Lei et al. (2025) Ecohydrological responses of vegetation changes to artificial water allocation schemes in the Heihe River Basin over the past 40 years

Identification

• Journal: Environmental Monitoring and Assessment
• Year: 2025
• Date: 2025-11-14
• Authors: Yuxin Lei, Xiaohui Jiang, Shuai Fan, Tong Nie
• DOI: 10.1007/s10661-025-14780-2

Research Groups

• Shaanxi Key Laboratory of Earth Surface System and Environmental Carrying Capacity, College of Urban and Environmental Sciences, Northwest University, Xi’an, 710127, China
• Department of Environmental Engineering, College of Urban and Environmental Science, Northwest University, Xi’an, 710127, China

Short Summary

This study investigates the ecohydrological responses of vegetation to artificial water allocation schemes and natural factors in the Heihe River Basin (China) over 40 years (1982-2022). It found a significant increasing trend in vegetation cover, primarily driven by soil moisture, with the lower reaches benefiting most from water allocations, often with a 1-year lag.

Objective

• To quantitatively characterize regional vegetation cover and growth and analyze spatiotemporal patterns of vegetation evolution using high-resolution, long-term ESTARFM-NDVI data.
• To examine the effects of natural and anthropogenic factors on vegetation cover's spatiotemporal patterns using the Geographically and Temporally Weighted Regression (GTWR) model.
• To analyze the quantitative relationship between vegetation dynamics and water quantity variations, particularly in response to artificial water allocation schemes (WAS) in both middle and lower reaches, before and after WAS implementation.

Study Configuration

• Spatial Scale: Heihe River Basin (HRB), northwestern China, extending from 98°E to 102°E and 38°N to 43°N, divided into upper, middle, and lower reaches.
• Temporal Scale: 40 years (1982–2022).

Methodology and Data

• Models used:
  • Enhanced Spatial and Temporal Adaptive Reflectance Fusion Model (ESTARFM) for NDVI data fusion.
  • Sen + Mann–Kendall trend analysis for trend detection.
  • Geographically and Temporally Weighted Regression (GTWR) model for attribution analysis.
  • Pettitt's test for mutation detection in time series.
• Data sources:
  • NDVI: Fused ESTARFM-NDVI (250 m resolution, 1982–2022) derived from MODIS (250 m, 2000–2022) and GIMMS (8 km, 1982–2015) data from the National Tibetan Plateau Data Center.
  • Temperature: Monthly average temperature (1 km resolution, 1982–2022) from the National Tibetan Plateau Data Center.
  • Precipitation: Monthly precipitation (1 km resolution, 1982–2022) from the National Tibetan Plateau Data Center.
  • Runoff: Data from Yingluoxia and Zhengyixia stations, obtained from local hydrological bureau and hydrological statistical yearbook.
  • Land-Use and Land-Cover Change (LUCC): 30 m resolution (1990–2020) from Zenodo.
  • Groundwater depth: 1 km resolution (simulated by CLMLTF model, 1981–2013) from the National Tibetan Plateau Data Center.
  • Soil moisture: 2 cm and 100 cm depths, 1 km resolution (simulated by CLMLTF model, 1981–2013) from the National Tibetan Plateau Data Center.
  • Artificial nighttime-light (HNL): 1 km resolution (1984–2020) from the National Tibetan Plateau Data Center.

Main Results

• Over the past 40 years (1982–2022), the Normalized Difference Vegetation Index (NDVI) in the Heihe River Basin (HRB) showed a significant and slow increasing trend of 0.0092 per decade (R² = 0.8853).
• Vegetation in the middle reaches exhibited the most pronounced growth rate (0.0220 per decade, R² = 0.8664), which was 1.2 times the growth rate in the upper reaches and 4.8 times in the lower reaches during the same period.
• Soil moisture at 2 cm (SM2cm) and 100 cm (SM100cm) depths were identified as the primary drivers of NDVI changes across the HRB.
• The implementation of the "97 water diversion scheme" in 2001 led to a noticeable upward trend in NDVI across the basin, with a significant mutation point in 2001 for the upper and middle reaches, and 2003 for the lower reaches (p < 0.01 for all).
• After the WAS implementation (2001–2017), vegetation change in the lower reaches was significantly correlated with current water allocations, but showed a higher correlation with allocations lagged by 1 year (correlation coefficient = 0.743, p < 0.01).
• In the middle reaches, after WAS, NDVI increased by 20% despite average water volume remaining stable, suggesting other factors (e.g., groundwater extraction, water-saving irrigation) contributed to vegetation growth. The correlation with allocated water showed a 3-year lag (correlation coefficient = 0.596, p < 0.05).

Contributions

• Provides a comprehensive understanding of ecohydrological responses to artificial water allocation schemes (WAS) in both middle and lower reaches, before and after WAS implementation, addressing a gap in previous studies that focused mainly on downstream impacts after WAS.
• Utilizes a new high-resolution (250 m) and long-time scale (1982–2022) NDVI dataset generated by fusing MODIS and GIMMS data using the ESTARFM algorithm, enabling detailed spatiotemporal analysis.
• Employs the Geographically and Temporally Weighted Regression (GTWR) model to simultaneously consider spatial and temporal effects of natural and anthropogenic factors on vegetation dynamics, offering a more comprehensive attribution analysis.
• Offers a theoretical basis and feasible approaches for investigating the long-term ecohydrological impacts of WAS in arid and semi-arid water-competing regions.

Funding

• National Natural Science Fund of China (52379025)

Citation

@article{Lei2025Ecohydrological,
  author = {Lei, Yuxin and Jiang, Xiaohui and Fan, Shuai and Nie, Tong},
  title = {Ecohydrological responses of vegetation changes to artificial water allocation schemes in the Heihe River Basin over the past 40 years},
  journal = {Environmental Monitoring and Assessment},
  year = {2025},
  doi = {10.1007/s10661-025-14780-2},
  url = {https://doi.org/10.1007/s10661-025-14780-2}
}