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

The Tarim River is the largest inland river in China, which plays a crucial role in maintaining regional ecological security and carbon cycle/dynamic. However, the “green corridor” in the Taitema Lake region at the lower reaches of the Tarim River has unclear environmental changes and future dynamics due to the influence of the ecological water conveyance. Hence, protecting the “green corridor” at the lower reaches of the Tarim River in China is strategically important not only ecologically but also socially and economically. In this paper, the temporal and spatial features of the fractional vegetation coverage (FVC) dynamics in the Taitema Lake region at the lower reaches of the Tarim River in 2000–2018 are analyzed and calculated using Landsat TM/OLI remote sensing images and MODIS data products. Additionally, the future trend of FVC dynamics in the study region are predicted using trend analysis and the pixel-based Hurst index. The results show that FVC in the Taitema Lake region exhibit a positive development after the implementation of ecological water conveyance. Specifically, from 2000 to 2018, the areas of low, medium, and high FVC expanded from 1.28 km2 to 179.87 km2, resulting in an increase of 140.52%. Spatially, the regions around the lake entrance channel of the Tarim River saw a significant increase in FVC of 9.71%. The middle part of the study region, accounting for only 1.96% of the area, displayed relatively high and high fluctuations in FVC. In the future, the regions at the middle part of the lake and around the lake entrance channel of the Tarim River, accounting for 11.33% of the area, will likely show an increasing trend in FVC. The regions with either extremely low or low FVC are predicted to decrease to 14.16% of the overall area. Because the positive effects of ecological water conveyance were more significant on FVC in the study region than the influences of either temperature or precipitation, ecological water conveyance should remain the primary means of ecological restoration for Taitema Lake.

Section: Pixel-based Hurst Index and Future Trend Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Research on Vegetation Coverage Dynamics and Prediction in the Taitema Lake Region

Zuo

Chen

Ding

2022

“…Otherwise, in the process of artificial water transfer to natural wetlands to restore the ecology, the groundwater in the surrounding oasis is too shallow, which makes the surface soil seriously salinized, thus inhibiting the development and growth of natural vegetation or crops. Therefore, in the inland of northwest China, if the groundwater depth is too deep or too shallow, the GEF decreases or disappears [10], which may lead to the degeneration crisis of the ecological environment and seriously threaten the local ecological security [11].…”

Section: Introductionmentioning

confidence: 99%

Study on Index of Groundwater Ecological Function Crisis Classification and Early Warning in Northwest China

Cui

Zhang

Wang

et al. 2022

The natural oases in the plain area of the northwest inland basin strongly depend on the groundwater depth. With the overexploitation and utilization of groundwater, natural oases are faced with the problems of serious degradation and rehabilitation. How to evaluate the degree of the degeneration crisis of groundwater ecological function has become one of the key scientific and technological problems to be solved. In this paper, the Shiyang River basin of Gansu Province was selected as a typical research area. The remote sensing interpretation, groundwater–soil ecology comprehensive investigation, and groundwater in situ monitoring were adopted to carry out the research. Based on the correlation analysis method of natural ecology and groundwater, the interactive relationship between the natural ecological environment and groundwater depth in different ecological types of the region were studied: (1) under the arid climate condition in northwest China, the relationships between the ecological situation and the groundwater depth in different ecological types of the region were obviously different, and as a result, the optimal or limit ecological water level of groundwater in different ecological types was also different; (2) in the natural wetland area, the suitable ecological water level of groundwater was between 0.5 m to 1.5 m, and the limit ecological water level was 8.0 m; in the natural vegetation area, the suitable ecological water level was between 3.0 m to 5.0 m, and the limit ecological water level was 10.0 m; and in the farmland area, the suitable ecological water level was between 2.0 m to 5.0 m, and the limit ecological water level was 2.0 m; (3) in order to effectively protect the natural ecology in different ecological types, a five-level early warning and control index system should be established for the ecological function degeneration crisis of groundwater. It may be beneficial to promote restoration and protection of the groundwater ecological function and natural ecology in the inland area of northwest China.

“…The ecological groundwater level has attracted worldwide attention because of the close relationship between groundwater and groundwater-dependent ecosystems (GDEs) [5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…The ecological groundwater level has attracted worldwide attention because of the close relationship between groundwater and groundwater-dependent ecosystems (GDEs) [5][6][7][8][9][10]. Many concepts have been proposed to define the reasonable ranges of groundwater depth for sustaining the GDEs [11], such as critical groundwater depth [12], ecological groundwater table [13], depth-to-groundwater threshold [14], and critical groundwater level [15].…”

Section: Introductionmentioning

confidence: 99%

Influence of Multi-Layered Structure of Vadose Zone on Ecological Effect of Groundwater in Arid Area: A Case Study of Shiyang River Basin, Northwest China

Cui

Zhang

Wang

et al. 2021

The natural vegetation in arid areas of northwest China is strongly dependent on the availability of groundwater. Significantly, capillary water plays an essential role in regulating the ecological groundwater level in the multilayered structure of the vadose zone. The soil-column test and field survey in the lower reaches of the Shiyang River Basin were conducted to investigate the influence of the multi-layered structure of the vadose zone on maintaining the ecological effect of groundwater. Based on the field survey, the results show that the depth of groundwater is 3.0 m, and the rising height of capillary water is 140 cm. In the soil-column test, the height of the wetting front of the column was 125 cm. During the water releasing test, the water held by the vadose zone was 182.54 mm, which would have maintained Haloxylon’s survival in a growing season. Therefore, the multi-layered structure of the vadose zone extends the ecological groundwater depth and consequently enhances the ecological function of groundwater. Importantly, with a lower groundwater level, the clay soil layer within the rising height range of the original capillary water would hold more water and maintain a higher water content for a certain period to supply surface vegetation.