Unveiling the Benefits of Artificial Ecological Measures: Water Conveyance Improves the Water Quality of the Taitema Lake, Northwestern China

Abstract

Taitema Lake, situated at the terminus of the Tarim River Basin in Northwest China, represents a crucial ecological resource impacted by climate variability and anthropogenic interventions. In this study, we investigate the dynamic changes in Taitema Lake’s area and water quality resulting from the implementation of an ecological water transfer project in 2000. Leveraging Landsat remote sensing data and comprehensive water quality monitoring, we analyzed the relationship between lake area variations and shifts in water quality parameters. Notably, our findings reveal a significant increase in Taitema Lake’s area from 9.4 km² in 2000 to 320 km² in 2013. Concurrently, water quality indicators exhibited marked fluctuations, with total salt content ranging from 45,323.6 mg/L in 2000 to 970.4 mg/L in 2010 before increasing to 14,586.3 mg/L by 2014. Furthermore, a linear regression analysis highlights the moderate positive correlation between lake area and mineralization (R² = 0.506) and sodium levels (R² = 0.4907). Additionally, chloride (R² = 0.5681) and sulfate (R² = 0.6213) concentrations demonstrated a strong negative correlation with the lake area, indicative of a dilution effect. Furthermore, a comparison of water quality indicators between the years of minimum (2008) and maximum (2013) lake area underscores improvements in pH, chemical oxygen demand, and anionic surfactant concentrations as the lake area increased. Our study provides valuable insights into the effectiveness of ecological water management strategies in restoring and maintaining the ecological health of Taitema Lake, thereby informing evidence-based decision-making for the sustainable management of freshwater resources in arid environments.

1. Introduction

Inland lakes serve as sensitive indicators of climate and environmental changes in the arid regions of Northwest China, with alterations in surface area and water levels reflecting the water balance dynamics of arid river basins [1,2,3]. Over recent decades, these lakes have encountered ecological challenges, including diminishing lake areas, declining biodiversity of flora and fauna, and more frequent climate-related disasters [4,5]. Consequently, timely monitoring of dynamic changes and ecological conditions in tailwater lake holds is of paramount importance for effective governance and management [6]. Taitema Lake, situated in Ruoqiang County, Xinjiang Province, at the convergence of the 218 and 315 National Highways, stands as the tail lake of the Tarim River and Cherchen River and is presently the sole lake preserved in the lower reaches of the Tarim River [7,8]. Historically, the closure of the lower Tarim River resulted in the continuous shrinkage of Lake Taitema, leading to complete desiccation in 1983 and partial rehydration in 1999 [9,10]. However, since the initiation of the ecological water transmission project in 2000, significant quantities of ecological water have been successfully conveyed to the lower reaches of the Tarim River, resulting in an upward trend in ecological water volume and consequent inflow into Taitema Lake [11,12]. Despite this, the lake’s response to ecological water transfers is short-lived, with water surface retention lasting less than three months post-transfer. Sustaining a large water extent for Taitema Lake necessitates substantial water resources in the highly arid environment, hastening salt accumulation in lake sediments and impeding vegetation growth [13].

Since the turn of the millennium, the implementation of an ecological water transfer project has sought to address the ecological imbalances afflicting Taitema Lake [14,15]. This study, aimed at replenishing the downstream water resources of the Tarim River, has significantly impacted Taitema Lake’s hydrological dynamics and water quality. Understanding the intricate interplay between changes in lake area and water quality is essential for assessing the effectiveness of such ecological interventions and guiding future management efforts.

Previous research on Taitema Lake has yielded valuable insights. Studies by Chen Guoliang highlighted the lake’s dry status since 1972, with significant inter-annual and intra-year changes observed before and after the ecological water transmission project of the Tarim River [16]. Similarly, Ablekim et al. noted year-on-year increases in the lake’s area following the implementation of the ecological water transmission project, alongside enhanced growth of surrounding vegetation. Further analyses by Zhang et al. explored the Tarim River headstream drainage volumes and Taitema Lake area changes [17]. While numerous studies have examined the impact of ecological water conveyance on natural vegetation along the Tarim River and Taitema Lake [18], limited research has explored its influence on Taitema Lake’s water quality. Leveraging remote sensing imagery and ground monitoring data, this paper seeks to analyze the corresponding effects of area and water quality changes on ecological water transport, offering valuable insights for enhancing water quality in Taitema Lake and its surrounding ecological environment.

This study delves into the dynamic changes observed in Taitema Lake’s area and water quality following the initiation of the ecological water transfer project in 2000. Leveraging Landsat remote sensing data and comprehensive water quality monitoring, the study aims to elucidate the relationship between lake area variations and shifts in water quality parameters. By employing linear regression analysis, the study seeks to quantify these relationships, shedding light on the underlying mechanisms driving the observed changes. Through a systematic analysis of temporal trends in the lake area and water quality indicators, this research endeavors to provide valuable insights into the efficacy of ecological water management strategies in restoring and maintaining the ecological health of Taitema Lake. By elucidating the complex interactions between hydrological dynamics and water quality parameters, this study aims to inform evidence-based decision-making processes for the sustainable management of freshwater resources in arid environments. Overall, this investigation seeks to contribute to the existing body of knowledge on inland lake ecology and management, offering actionable insights to support the conservation and restoration of fragile aquatic ecosystems in arid regions.

2. Data and Methods

2.1. Description of the Study Area

Taitema Lake (87°45′–89°20′ E, 39°20′–39°50′ N) is situated in the northeast of the Tarim River basin, flanked by the Taklimakan Desert to the west, Kuruk Desert to the east, and Altun Mountain to the south [19], serving as the terminal lake for both the Tarim River and Cherchen River (Figure 1). It is characterized by an extremely arid climate in the warm temperate continent, and the region experiences scarce precipitation and intense evaporation. Meteorological data from the Ruoqiang County station reveal an average annual temperature of 11.8 °C, with extreme minimum and maximum temperatures recorded at −19.7 °C and 41.6 °C, respectively. Annual precipitation stands at a mere 23.33 mm, while evaporation rates soar to 2673.2 mm annually. The average relative humidity is 41.1%, with a dryness index of 63.0, and frequent wind and sandstorms further typify the area’s climate. With a maximum depth under 1 m, Taitema Lake experiences significant area fluctuations due to various inflows from the Tarim and Qarqan rivers. Historically, the lake dried up before 2000 due to prolonged zero flow in the lower reaches of the Tarim River since 1970, leading to desert encroachment and degradation of aquatic vegetation within the lacustrine wetland [20]. Since 2000, ecological water transfers from the downstream of the Tarim River to Taitema Lake have been initiated.

2.2. Data Analysis

This study utilized Landsat remote sensing images for analysis, with inter-band data analysis employed for image preprocessing [21] to correct for atmospheric influences. The use of Landsat remote sensing images provides a powerful tool for environmental monitoring and analysis, particularly in studying changes in land cover and water bodies. In this study, Landsat imagery was utilized to analyze the effects of the ecological water conveyance project on Lake Taitema. The analysis began with inter-band data analysis, which is a crucial step in remote sensing that involves the examination of spectral information across different bands of the electromagnetic spectrum. Landsat satellites, specifically the Landsat 5, 7, and 8 missions, offer multispectral imagery with various bands that capture data at different wavelengths. These bands include visible, near-infrared, shortwave infrared, and thermal infrared regions. Each band provides unique information about the Earth’s surface, which is vital for distinguishing between different land and water features. In this study, the inter-band data analysis involved several key processes:

Atmospheric Correction: Atmospheric correction was performed to eliminate atmospheric disturbances such as aerosols and water vapor that can distort the satellite imagery. This process ensures that the true reflectance values of the Earth’s surface are obtained, providing accurate data for further analysis.

Radiometric Calibration: Radiometric calibration was conducted to convert the raw digital numbers from the Landsat sensors into top-of-atmosphere (TOA) reflectance values. This step is essential for ensuring consistency and comparability between images taken at different times or under varying conditions.

Inter-Band Ratios: Inter-band ratios were calculated to enhance specific features and suppress background noise. For example, the Normalized Difference Water Index (NDWI) was used to highlight water bodies, while the Normalized Difference Vegetation Index (NDVI) was employed to assess vegetation cover.

Data Layer Stacking: The bands were stacked to create a multi-layered image composite. This composite image enabled a comprehensive analysis of the spectral characteristics across different wavelengths, facilitating the identification and classification of water bodies.

Image Enhancement Techniques: Techniques such as histogram equalization and contrast stretching were applied to improve the visual quality of the images, making it easier to identify and delineate water bodies and other features.

By employing inter-band data analysis, the study leveraged the full potential of Landsat’s multispectral capabilities to accurately assess the temporal and spatial changes in Lake Taitema’s area during the ecological water conveyance project.

Subsequently, lake water information was extracted through image fusion and classification techniques to calculate the area of lake water during the ecological water conveyance project implementation period (2000–2014). Image fusion involves combining data from multiple sources or sensors to produce a more comprehensive and accurate representation of the target area. In this study, image fusion was utilized to enhance the spatial and spectral resolution of the imagery, improving the ability to delineate water bodies precisely. Various remote sensing data sources, including MSS, CCD, TM/ETM, and CBERS, were integrated [22,23], supported by image processing and geographic information system software (GRASS GIS 8.4). These methods facilitated the acquisition of comprehensive water area information for Lake Taitema across different time periods. However, due to the limitations of remote sensing techniques, particularly regarding its ability to capture fine-scale water quality variations, we were not able to conduct further research. The limitations of remote sensing technology mainly include the complexity of information acquisition and interpretation, high cost, disunity of data sources, heterogeneity of surface factors, and cost limitation. The information obtained by remote sensing technology needs to be accurately interpreted. However, in this process, only a rough estimate or indirect information about ground objects can be obtained and may be different from the actual situation. In addition, the error of computer interpretation is larger than that of skilled manual operation, which requires a huge workload and a long cycle. Regarding the challenges in multispectral image classification model construction, especially when spectral indices need to be combined, the integrated methods and stacked models could be applied to merge multiple images for various spectral bands and indices simultaneously to find the best solution. Another challenge in remote sensing image processing is atmospheric correction, which aims to eliminate the effect of the atmosphere on the image and obtain the true reflectance of the land surface. Approaches to this problem include using specific image processing methods, such as QUAC, trying different methods, and comparing the differences to find the atmospheric correction method that is best for a particular application. Additionally, water level measurements were conducted in accordance with the “Water level Observation Standard” (GB/T50138-2010), with a water level observation gauge established in the monitoring section and zero point elevation measured using the Xi’an 80 national base plane [24]. Water quality indicators such as pH value, electrical conductivity, oxygen, and chemical oxygen demand were monitored using a portable multi-parameter water quality detector (HI98194). Data on water salinity, SO₄²⁻, Cl⁻, K⁺, Na⁺, Mg²⁺, and Ca²⁺ plasma concentration were collated based on monitoring data provided by the Tarim River Basin Administration. Linear regression analysis was employed to analyze the linear relationship between changes in the lake area and each ion in the lake after ecological water transfer (2000–2014). In the linear regression models, we tested the hypothesis of the regression coefficient to determine whether the independent variable has a significant impact on the dependent variable. The regression coefficients were interpreted to understand the ecological implications of the findings. Positive or negative coefficients indicate the nature of the relationship between ion concentrations and lake area, providing insights into how the chemical composition of water was influenced by the variation in lake area. By employing linear regression analysis, the study elucidated the complex interactions between Lake Taitema’s water chemistry and its area dynamics, offering valuable insights into the ecological impacts of the water conveyance project.

3. Results

3.1. Change the Area of the Taitema Lake since Ecological Water Conveyance

With the implementation of the ecological water transfer project in 2000, the Taitema Lake, which dried up in 1972, formed a certain area of water. Due to the arid climate and less rainfall in the surrounding area of Taitema Lake, the lake area can only be maintained in the form of ecological water transport. If the water supply is not regularly carried out, the lake area will rapidly decrease. Therefore, the larger the lake area, the better to maintain a suitable lake area. However, if the lake area is too large, the evaporation of the lake is large, and too much water saved from upstream is wasted in evaporation. The evaporated water cannot play an ecological role in either the middle or upper reaches of the Tarim River or the tail of Taitema Lake. During dry years, water from the lower Tarim River often does not reach Taitema Lake. The lake area in different years after water transfer is shown in

Table 1. Variation in the area of Taitema Lake since ecological water conveyance.

Observed Time	Data Sources	Area/km2	Observed Time	Data Sources	Area/km2
22 July 2000	CBERS-CCD	9.4	18 July 2008	MSS	38.5
21 July 2001	CBERS-CCD	77.5	13 August 2009	TM/ETM	43.87
21 June 2002	TM/ETM	212.43	17 July 2010	HJ-CCD	278.62
22 July 2003	CBERS-CCD	181.8	25 August 2011	TM/ETM	148.94
30 August 2004	CBERS-CCD	56.3	1 August 2012	HJ-CCD	210.95
1 September 2005	TM/ETM	230.63	November 2013	HJ-CCD	313
12 September 2006	TM/ETM	118.68	Ocotober 2014	HJ-CCD	300
11 June 2007	TM/ETM	73.16

and Figure 2.

Table 1 shows the variation in the area of Taitema Lake from 2000 to 2014 following the implementation of the ecological water transfer project. Over this period, the lake experienced significant fluctuations in size, reflecting the impact of water management strategies and environmental conditions. The ecological water conveyance project of Taitema Lake is an important project aimed at improving the ecological environment of the Tarim River basin. Since 2001, the state has launched a plan for the recent comprehensive management of the Tarim River Basin, which includes the implementation of an ecological water transmission project to the lower reaches of the Tarim River. By 2021, 8.79 billion cubic meters of water has been injected into the lower reaches of the Tarim River, and this measure has led to an initial improvement in the ecological environment in the lower reaches. Especially in 2017, Lake Taitema formed a maximum surface area of 511 square kilometers, far exceeding the 200 square kilometers lake restoration target proposed in the comprehensive management plan. Up to 2021, ecological water transfer was carried out 24 times. These activities not only helped to restore the waters of Lake Taitema and its surrounding wetlands but also promoted the restoration of and improvement in vegetation.

In the initial years after the water transfer began, the lake area increased notably from 9.4 km² in 2000 to 212.43 km² in 2002. This rapid expansion can be attributed to the influx of water aimed at restoring the lake. However, by 2004, the lake area decreased to 56.3 km², suggesting variability in water supply or possibly increased evaporation and usage.

The subsequent years saw further fluctuations. By 2005, the lake area surged again to 230.63 km², maintaining a substantial size through 2006. Yet, a sharp decrease occurred in 2007, reducing the area to 73.16 km² and even further to 38.5 km² by 2008. This period likely reflects challenges in sustaining consistent water inflow or increased water demand upstream.

A more stable period began in 2009, with the lake area gradually increasing again, reaching 278.62 km² in 2010 and peaking at 313 km² in 2013. This peak represents the maximum area observed during the period, indicating a successful period of water transfer and retention. By 2014, the lake area slightly decreased to 300 km², reflecting a significant improvement compared to the early 2000s.

Overall, from 2000 to 2014, Taitema Lake’s area varied considerably, largely dependent on the effectiveness of the ecological water transfer project and environmental factors. The data revealed a general trend of expansion, albeit with notable fluctuations, highlighting the dynamic nature of the lake’s restoration process.

3.2. Water Quality Characteristics of Taitema Lake

With the continuation of ecological water transport, the salt content and quality of lake water in Taitema Lake changed gradually. The average concentrations of salt content in lake water during the water conveyance period are shown in Figure 3.

After ecological water transfer, the water quality index changed greatly. Due to the differences in the amount of water transported, the lake area in each year was also different. The changes in various ion concentrations in Taitema Lake are shown in Figure 4.

Figure 4 illustrates the variation in ion concentrations of Taitema Lake from 2000 to 2014, particularly focusing on the concentrations of different ions. Initially, in 2000, the lake had an extremely high total salt content of 45,323.6 mg/L. This value decreased significantly in 2001 to 30,195.4 mg/L. The most notable reduction in salinity occurred in 2002 and 2003, where the total salt content dropped dramatically to 1474.6 mg/L and 1502.4 mg/L, respectively. This period marked a temporary improvement in water quality. However, from 2004 onwards, there was a marked increase in salinity. By 2009, during a severe drought, the total salt content peaked at 88,897.9 mg/L, the highest recorded during the study period. This peak was significantly higher than the following years, illustrating the impact of drought conditions on the lake’s salinity.

Regarding specific ions, sodium (Na⁺) and chloride (Cl⁻) were consistently the dominant ions contributing to the lake’s salinity. For instance, in 2000, the Na⁺ concentration was 11,913.2 mg/L, while Cl⁻ was 20,381.9 mg/L. These values decreased significantly in 2002 and 2003 but began rising again in subsequent years, peaking in 2009 with Na⁺ at 24,059.7 mg/L and Cl⁻ at 40,277.8 mg/L. Other ions, such as potassium (Ka⁺), magnesium (Mg²⁺), calcium (Ca²⁺), and sulfate (SO₄²⁻), also showed significant variations. For example, in 2000, Ka⁺ was 672.7 mg/L, Mg²⁺ was 1811.3 mg/L, Ca²⁺ was 714.8 mg/L, and SO4²⁻ was 7208.6 mg/L. These ions generally followed a similar trend of decreasing during 2002–2003 and then rising significantly towards 2009.

Post-2009, there was a noticeable improvement in water quality by 2010, with the total salt content reducing to 970.4 mg/L. However, this improvement was not sustained, as the salinity increased again in subsequent years, reaching 14,586.3 mg/L by 2014. Overall, the data indicated that while the ecological water transfer project had some initial success in reducing the lake’s salinity, persistent drought conditions and agricultural runoff contributed to significant increases in salt and ion concentrations over the years.

3.3. Responses of Water Quality on the Changes in Lake Area

With the development of the ecological water transfer project in 2000, the area of Taitema Lake increased year by year, and the growth of vegetation around it improved, so has the water quality changed? How does it change in time series? Linear relationships between the area of Taitema Lake and water quality are presented in

Table 2. Relationship between the area of Taitema Lake and water quality.

Water Quality	Linear Regression Equation	R2	p
Mineralization	y = 4 × 10−8x2 + 0.0054x + 237.91	0.506	<0.001
Ka+	y = 4 × 10−5x2 + 0.1978x + 202.52	0.147	<0.01
Na+	y = 5 × 10−7x2 + 0.0188x + 233.24	0.4907	<0.001
Mg2+	y = 1 × 10−5x2 + 0.0992x + 235.31	0.4532	<0.001
Ca2+	y = 3 × 10−5x2 + 0.2199x + 262.52	0.4345	<0.001
Cl−	y = 3 × 10−7x2 + 0.0143x + 228.98	0.5681	<0.001
SO42−	y = 2 × 10−6x2 + 0.0343x + 237.88	0.6213	<0.001

.

Table 2 illustrates the relationship between the area of Taitema Lake and various water quality parameters over the period from 2000 to 2014. The data showed that as the lake area changed, there were significant impacts on total salt content and the concentrations of several ions. The statistical significance of the differences between the means was also compared based on the p-value obtained by the statistical significance test method. Except for potassium concentration (p < 0.01), the other ion concentrations showed strong statistically significant differences (p < 0.001).

During the ecological water transfer period, the area of Taitema Lake had a moderate positive correlation with the mineralization and sodium (Na⁺) levels. The coefficients of determination (R²) for these relationships were 0.506 and 0.4907, respectively, indicating that about half the variability in mineralization and sodium concentrations can be explained by changes in lake area. This suggests that as the lake area increased, the concentrations of total salts and sodium tended to rise, although other factors also played a role.

Magnesium (Mg²⁺) and calcium (Ca²⁺) concentrations also showed a moderate correlation with lake area, with R² values of 0.4532 and 0.4345, respectively. This indicates that as the lake area expanded, the concentrations of these ions generally increased, but the relationships were not as strong as those for mineralization and sodium. The increase in these ion concentrations as the lake area grew suggests a dilution effect, where larger lake volumes helped reduce the concentration of these ions. However, the relationship between the area of Taitema Lake and potassium (K⁺) concentrations was unremarkable. The coefficients of determination (R²) for these relationships showed the lowest value, e.g., 0.147, respectively, indicating that the change in water area had the least effect on the potassium concentration.

The strongest relationships were observed with chloride (Cl⁻) and sulfate (SO₄²⁻), with R² values of 0.5681 and 0.6213, respectively. This indicates a more substantial portion of the variability in these ion concentrations could be explained by changes in the lake area. As the lake area increased, the concentrations of chloride and sulfate decreased significantly, suggesting a strong dilution effect due to the larger water volume. Overall, the data highlighted that while the lake area significantly influences water quality, particularly chloride and sulfate, other environmental and anthropogenic factors also contribute to these variations.

The correlation coefficient between lake area and water quality parameters is significant, but the change in water quality is not only due to the change in lake area. The influence of artificial factors, such as agricultural runoff or groundwater inflow, as well as the influence of mixed natural factors, such as evaporation and rainfall, can also be fully considered in future studies.

Table 3. Comparison of water quality indicators in the period of minimum (2008) and maximum (2013) Lake area.

Test Items	The Lake Area Is the Smallest Year (2008)	The Lake Area Is the Largest Year (2013)	Detection Basis
pH	8.7	7.6	Electrode method HJ1147-2020
Chloroxyl (mg/L)	7.2	7.9	Electrochemical probe method HJ 500-2009
Electric conductivity (µS/cm)	1132	1141	GBT 5750.4-2006
Chemical oxygen demand (mg/L)	4.6	5	Dichromate method HJ 828-2017
Five-day BOD (mg/L)	1.5	1.2	Dilution and Inoculation Method HJ 505-2009
Permanganate index (mg/L)	4.1	3.3	GB 11892-89
Anionic surfactant (mg/L)	0.05	0.04	GB 7494-84

provides a comparison of water quality indicators for Taitema Lake during the years of its smallest area (2008) and largest area (2013). This comparison highlights how different water quality parameters change with significant variations in lake area.

In 2008, when the lake area was at its smallest, the pH level was 8.7, indicating a more alkaline environment compared to 2013, when the pH was 7.6. The reduction in pH in 2013 suggests a shift towards a more neutral condition as the lake area expanded. Chloroxyl concentrations were slightly higher in 2013 (7.9 mg/L) compared to 2008 (7.2 mg/L), suggesting an increase in organic pollution as the lake area grew. Electric conductivity, which measures the water’s ability to conduct electricity and indicates the concentration of dissolved salts, showed a minimal increase from 1132 µS/cm in 2008 to 1141 µS/cm in 2013. This slight change indicates that the total dissolved solids remained relatively stable despite the change in the lake area. The Chemical Oxygen Demand (COD), an indicator of the amount of organic compounds in the water, increased slightly from 4.6 mg/L in 2008 to 5 mg/L in 2013. Similarly, the five-day Biological Oxygen Demand (BOD), which measures the amount of oxygen required for microbial decomposition of organic matter, decreased from 1.5 mg/L in 2008 to 1.2 mg/L in 2013, indicating improved organic matter degradation efficiency in the larger lake. The Permanganate Index, another measure of organic pollution, decreased from 4.1 mg/L in 2008 to 3.3 mg/L in 2013, further suggesting an improvement in water quality as the lake area increased. Additionally, the concentration of anionic surfactants, which are commonly used in detergents and can indicate pollution from domestic sources, decreased from 0.05 mg/L in 2008 to 0.04 mg/L in 2013, pointing to reduced pollution levels.

Overall, the data from Table 3 indicated that the water quality of Taitema Lake improved as the lake area increased. This is reflected in the lower pH, reduced concentrations of BOD, Permanganate Index, and anionic surfactants in 2013 compared to 2008. The slight increases in chloroxyl and COD suggest that while some aspects of water quality improved, others remained relatively stable or showed minor increases in pollutant levels. These changes highlight the complex interactions between lake area and water quality parameters during the ecological water transfer period.

4. Discussion

The findings of this study shed light on the intricate relationship between ecological water conveyance and the water quality dynamics of Taitema Lake. By integrating remote sensing data, water quality monitoring, and statistical analysis, we have elucidated key patterns and trends, offering valuable insights into the ecological implications of water management strategies. Our results demonstrated that since the initiation of the ecological water conveyance project in 2000, there has been a significant increase in the surface area of Taitema Lake. However, the impacts on water quality parameters have exhibited varying trends and intricate interactions with the changing hydrological conditions.

4.1. Impact of Ecological Water Conveyance on Water Quality

Our analysis revealed a significant increase in the area of Taitema Lake following the initiation of the ecological water transfer project in 2000. While the initial years saw a substantial expansion, subsequent fluctuations underscore the complex interplay between water inflow, evaporation, and environmental factors. The observed peak in the lake area in 2013 underscores the success of the water transfer efforts, albeit with challenges in maintaining consistent water levels. These findings are consistent with previous research results. Lu et al. analyzed the ecological risks before and after ecological water conveyance and determined its ecological benefits by constructing the Regional Landscape Ecological Risk Index (ERI) and found that the ecological water conveyance project effectively supplements water in the intermediate and lower courses of the Tarim River and the terminal lakes, significantly bolstering ecological conditions in the lake basin and reducing risks [25]. The study found that ecological water conveyance positively affected some key water quality parameters while adversely affecting others. For instance, there was a notable improvement in the dissolved oxygen (DO) levels and a reduction in total dissolved solids (TDS) in certain areas of the lake. These changes can be attributed to the increased inflow of fresh water, which dilutes the concentration of salts and other pollutants. The increased water volume also enhanced the lake’s ability to sustain aerobic aquatic life, thereby improving the overall ecological health of the lake.

However, the study also observed increases in certain nutrient concentrations, such as nitrates and phosphates, which could potentially lead to eutrophication. This finding aligns with previous research indicating that increased water inflow may introduce agricultural runoff containing fertilizers, which, in turn, elevates nutrient levels in the lake. The presence of these nutrients, coupled with favorable conditions, such as warm temperatures and sunlight, may promote the growth of phytoplankton and algae, leading to algal blooms [26,27]. Therefore, while ecological water conveyance contributes to the expansion of the lake’s surface area, it also poses challenges related to nutrient enrichment and subsequent water quality issues.

Our analysis revealed a nuanced relationship between Taitema Lake’s area and water quality parameters. While there was a general trend of improved water quality with increased lake area, the relationship varied across different parameters. Notably, chloride and sulfate concentrations exhibited a strong negative correlation with the lake area, indicating the dilution effect of larger water volumes. However, other parameters, such as mineralization and sodium levels, showed more complex relationships, suggesting the influence of multiple factors on water quality dynamics.

4.2. Implications for Ecosystem Health and Management

The findings of this study have significant implications for the management and sustainability of Taitema Lake and similar arid-region terminal lakes. The positive effects of ecological water conveyance on expanding the lake’s surface area and improving certain water quality parameters highlight the project’s success in enhancing the ecological functions of the lake. However, the concurrent challenges related to nutrient enrichment and potential eutrophication necessitate a balanced approach to water management.

Future management strategies should focus on optimizing water conveyance volumes and timing to maximize the benefits of dilution and pollutant flushing while minimizing nutrient loading. Additionally, implementing buffer zones and best management practices in upstream agricultural areas could reduce nutrient runoff and further protect the lake’s water quality. Regular monitoring of water quality parameters and ecological indicators is crucial to adaptively manage the lake’s ecosystem and ensure its long-term health and sustainability.

4.3. Limitations and Future Research Directions

This study acknowledges several limitations, including the reliance on remote sensing data and the inherent uncertainties associated with water quality modeling. Future research should aim to incorporate in situ measurements and high-resolution spatial data to enhance the accuracy of water quality assessments. Furthermore, investigating the specific sources of nutrient pollution and their transport mechanisms within the watershed could provide valuable insights for targeted management interventions. Additionally, the study highlights the importance of understanding the socioeconomic and cultural dimensions of ecological water conveyance projects. Engaging local communities and stakeholders in water management decisions and practices can foster a more comprehensive and sustainable approach to lake conservation and restoration.

Overall, while ecological water conveyance undoubtedly improved certain aspects of Taitema Lake’s hydrology and water quality, ongoing efforts are required to address the challenges of nutrient enrichment and ensure the lake’s long-term ecological resilience. This study contributes to a deeper understanding of the complex interactions between hydrological interventions and water quality dynamics, providing valuable guidance for future conservation efforts in similar arid-region ecosystems.

Recommendations for future research and implementation of water management practices of the water transfer project of Taitema Lake mainly focus on optimizing the allocation of water resources, implementing ecological engineering construction, strengthening ecological supervision, and promoting the harmonious coexistence between man and nature.

Optimization of water resources allocation: Considering that the evolution of the ecological environment in the Taitema Lake region is mainly influenced by the comprehensive effects of natural and human factors, it should be optimized in the future to ensure the sustainability and effectiveness of ecological water transmission projects. This includes a rational allocation of water resources and ensuring the long-term and stable development of lakes and wetlands.

Implementing ecological projects: Vigorously implement ecological projects, including but not limited to vegetation restoration, wetland protection, and soil improvement, to promote ecological balance and biodiversity. These projects should take into account the vulnerability and resilience of local ecosystems to avoid further pressure on the environment.

Strengthen ecological supervision: To strengthen ecological supervision, regularly assess the impact of water transmission projects on lake ecosystems, and the impact of human activities on the ecological environment. Through scientific monitoring and data collection, implement timely adjustments to management strategies to ensure the health and stability of the ecosystem.

Promoting harmonious coexistence between man and nature: In future developments, an emphasis on promoting harmonious coexistence between man and nature, raising the public’s awareness of environmental protection through education and publicity, encouraging sustainable tourism activities, and reducing the negative impact of human activities on the natural environment should be emphasized.

These measures are aimed at ensuring the long-term benefits of the water transfer project while protecting and restoring the lake’s ecosystem and promoting sustainable development.

5. Conclusions

(1)

The study highlighted the significant impact of ecological water transfer on the area dynamics of Taitema Lake. Over the period from 2000 to 2014, the lake area experienced notable fluctuations, ranging from 9.4 km² to a peak of 320 km². These variations underscore the effectiveness of water management strategies in restoring and sustaining the lake’s hydrological balance. However, challenges such as water scarcity and increased evaporation rates pose ongoing threats to the long-term stability of the lake ecosystem;

(2)

Analysis of water quality parameters revealed substantial temporal variations in Taitema Lake’s aquatic environment post-ecological water transfer. Notably, the total salt content exhibited significant fluctuations, ranging from 45,323.6 mg/L in 2000 to 14,586.3 mg/L in 2014. These changes reflect the complex interplay between water availability, evaporation rates, and anthropogenic influences. Despite initial improvements in certain water quality indicators, persistent environmental stressors continue to pose challenges to maintaining water quality standards;

(3)

The study elucidated the intricate relationship between Taitema Lake’s area dynamics and water quality parameters. Moderate positive correlations were observed between lake area and mineralization (R² = 0.506) and sodium levels (R² = 0.4907), indicating the influence of water volume on ion concentrations. Conversely, strong positive correlations were found for chloride (R² = 0.5681) and sulfate (R² = 0.6213) concentrations, suggesting the dilution effect of lake area expansion on increasing ion concentrations. These findings underscore the dynamic nature of freshwater ecosystems and highlight the importance of integrated water resource management practices.

The future technology and research on the Taitema Lake water conveyance project should mainly focus on optimizing water resources management, implementing ecological engineering, strengthening ecological supervision, and promoting harmonious coexistence between man and nature. These measures are aimed at ensuring the long-term benefits of the water transfer project while protecting and restoring the lake’s ecosystem and promoting sustainable development.

In conclusion, the findings underscored the critical importance of adaptive water management strategies in balancing ecological restoration efforts with sustainable water use in arid environments. The study provides valuable insights into the complex interactions between hydrological changes, water quality dynamics, and ecosystem health in Taitema Lake, offering a basis for informed decision-making and policy formulation aimed at ensuring the long-term sustainability of freshwater resources.