Search

Copyright of Bulletin of Soil & Water Conservation is the property of Bulletin of Soil & Water Conservation Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Miyun Reservoir plays a vital role as a source of drinking water for Beijing, however it grapples with nitrogen contamination issues that have been poorly understood in terms of their distribution, source, and associated health risks. This study addresses this knowledge gap by employing data on nitrate nitrogen (NO3−–N), chloride (Cl−), dual isotopic compositions of NO3− (δ15N–NO3− and δ18O–NO3−) data in water ecosystems, systematically exploring the distribution, source and health risk of nitrogen contaminants in Miyun reservoir watersheds. The results showed that over the past 30 years, surface water runoff has exhibited a notable decrease and periodic fluctuations due to the combined influence of climate and anthropogenic activities, while the total nitrogen (TN) concentration in aquatic ecosystems presented an annual fluctuating upward trend. The TN concentration in the wet season was predominantly elevated because a large amount of nitrogen contaminants migrated into water ecosystems through heavy rainfall or river erosion. The concentration of NO3−–N, the main contaminant of the water ecosystems, showed distinct variations across different watersheds, followed as rivers over the Miyun reservoir. Moreover, NO3−–N levels gradually increased from upstream to downstream in different basins. NO3−–N in surface water was mainly derived from the mixture of agricultural ammonia fertilizer and sewage and manure, with a minority of samples potentially undergoing denitrification. Comparatively, the main sources of NO3−–N in groundwater were soil N and sewage and manure, while the denitrification process was inactive. The carcinogenic risks caused by NO3−–N in groundwater were deemed either nonexistent or minimal, while the focus should predominantly be on potential non-carcinogenic risks, particularly for infants and children. Therefore, it is crucial to perform proactive measures aimed at safeguarding water ecosystems, guided by an understanding of the distribution, sources, and associated risks of nitrogen contamination. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Dalian Ocean University is the property of Journal of Dalian Ocean University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The impact of large reservoirs on regional climate extremes, such as heatwaves, is not yet well understood, primarily due to the complex interactions of heat, moisture, and momentum over mountainous terrains and the dynamic nature of water surfaces. In this study, we investigate the role of the Miyun Reservoir (MYR), one of the largest reservoirs in northern China, covering an extensive water surface area of 180 km2, in influencing a severe heatwave event that occurred southwest of MYR from 2nd to 6th July 2010. Using high-resolution simulations from the Weather Research and Forecasting Model, our findings reveal contrasting thermodynamic effects of MYR on near-surface air temperatures, with up to three degrees of warming during night-time and up to five degrees of cooling during daytime, with a spatial extent of impact reaching up to 20 km away from the reservoir. These impacts are attributed to a combination of synergized land-lake breeze and mountain-valley winds during the night, leading to the transport of warm air plumes downwind towards the plain and intensifying the heatwave. Furthermore, we observe an increase in surface water vapor brought to higher atmospheric levels due to strong vertical mixing, resulting in lowered surface-specific humidity. Our study emphasizes the dual role of large reservoirs in exacerbating remote heatwaves while providing cooling effects in their proximity. Gaining a comprehensive understanding of the intricate interactions between reservoirs, topography, and regional climate extremes is of paramount importance for accurate climate risk assessments and the formulation of effective mitigation strategies..

Copyright of Arid Zone Research / Ganhanqu Yanjiu is the property of Arid Zone Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Remote Sensing is the property of Editorial Office of Journal of Remote Sensing & Science Publishing Co. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Miyun Reservoir, located in the Miyun District, Beijing, China, is the largest comprehensive water conservancy project and is an important ecological protection area in the North China region. Changes within the basin are the driving factors affecting the ecosystem in the watershed; therefore, it is important to analyze the changes in the ecological environment of Miyun Reservoir. For the analysis of a long time series of image data remotely sensed by satellite, the outliers caused by atmospheric, lighting, and sensor measurement errors are significant, and it is difficult for traditional algorithms to effectively recover the true image value. To address this, this paper proposes a theoretical model for predicting spatio-temporal variation based on deep learning to identify and correct invalid and anomalous values in extended time series data. This study corrected and analyzed the results of Remote Sensing based Ecological Index inversion of Landsat data of the Miyun Reservoir watershed from 1985 to 2021. The findings and conclusions of this study are important for the analysis of long time series image data from satellite remote sensing and for improving regional ecological evaluation and sustainable development planning.

Inland lakes or reservoirs are the main surface water resources, related to people's survival and social development. On-site water level data are critical for water resource management, while satellite laser and remote sensing data are a significant tool for long-term change monitoring. In this study, we took the Miyun Reservoir, the most important source of drinking water in Beijing, as the research area. We used Landsat images and the Ice, Cloud, and Land Elevation Satellite (ICESat-2) for small-scale water level change monitoring and inversion across unrecorded periods. First, we proposed a new two-step denoising method based on local statistics to denoise the ATL03 single photon data from 2018 to 2020, and extracted the effective elevation information of Miyun Reservoir. Second, based on Landsat images from 1984 to 2020, the MNDWI index was used to extract the water area and generated a percentage map of water occurrence. Finally, the water and land boundary elevation were selected from the effective photon elevation information according to the boundary position under each percentage of the water generation percentage graph, the area, and the water level elevation model (A–E model) was established, and the water level values of unrecorded periods were inverted. The denoising results showed that the denoising accuracy of all data is higher than 95%. The area of Miyun Reservoir has changed greatly in the past 37 years, especially in the northeast corner and northern region. The inverted water level elevation had a strong correlation with the measured value, the correlation coefficient reached 0.97, the root mean square error (RMSE) was 0.553 m, and the estimated water level value was highly consistent with the recorded value and fluctuated dramatically from 1984 to 2020. This method complements the traditional water level mapping method, provides a new idea for the monitoring of water level changes in lakes or reservoirs without field records, and also contributes to the timely and effective monitoring and management of global lake and reservoir water level and time changes. [ABSTRACT FROM AUTHOR]

Ammonia oxidation driven by ammonia-oxidizing archaea (AOA) and bacteria (AOB) plays a significant role in the nitrogen cycle, but the mechanism of this important action in reservoir sediments is unclear. In this study, based on quantitative PCR and Illumina high-throughput sequencing of the ammonia monooxygenase (AMO) gene, the abundance, diversity and community structure of AOA and AOB in Miyun Reservoir sediments were investigated. The key environmental factors for regulating community structure, as well as the response of AOA and AOB abundance and transcriptional activity to external ammonia and organic carbon, were also explored. The results showed that the diversity and abundance of AOB in the reservoir sediments were higher than those of AOA, and the community structure of AOA showed a different spatial distribution characteristics compared with those of AOB. AOA community structure was closely related to ammonia nitrogen concentration and water depth, while that of AOB were not significantly affected by environmental factors. AOB were more sensitive to concentration variations of ammonia nitrogen and organic carbon from exogenous sources. Therefore, in Miyun Reservoir sediments, AOA were more sensitive to the influence of environmental factors in the reservoir area, while AOB were more sensitive to the influence of exogenous sources. [ABSTRACT FROM AUTHOR]

The Miyun Reservoir, located in the Miyun District of Beijing, China, is the largest comprehensive water conservancy project in northern China and an important ecological protection area. The combined effects of many factors produce ecosystem changes in the basin; thus, it is important to analyze the spatial and temporal changes that occur here. Based on multi-source satellite remote sensing data, we analyzed changes in water body area, water level height, and water storage in the Miyun Reservoir from 2013 to 2022 and determined whether these changes were natural or caused by human activity. As traditional water body area extraction methods can misidentify buildings and mountainous areas as water bodies, we fused multiple deep learning models (U-Net and SegNet) using the adboost method, which combined the advantages of the basic models and achieved an overall recognition accuracy of > 90 %. Using annual variations in water storage at the reservoir, we determined that the water body area increased to 157.58 km2 between 2013 and 2022, nearly doubling in size, which corresponded to decreases in cultivated land and vegetated areas. Cultivated land is the main land use type affected by water body erosion. The overall water level height exhibited an upward trend (cumulative increase of 14.8 %), eventually reaching 146.11 m. The water storage volume also increased over time, with a cumulative increase of approximately 436 million m3. On this basis, the influences of temperature, precipitation, and human activity on the spatial and temporal variability of the Miyun Reservoir basin were analyzed. The findings have important implications for global change research within and outside the ecosystem.

Abstract Purpose Nitrate/nitrite-dependent anaerobic methane oxidation (N-DAMO) connects the global cycle of carbon and nitrogen in aquatic ecosystems. The aims of this study were to investigate the spatiotemporal variation of N-DAMO bacteria and its driving factors in a drinking reservoir which are strongly affected by human consumption. Methods Cloning analyses were used to study the pmoA and 16S rRNA genes of N-DAMO bacteria. Sequencing and phylogenetic analyses were used to investigate the bacterial composition and structure. Redundancy analyses (RDA) and spearman’s correlations analyses were applied to analyze the relationships between bacterial distribution and environmental factors. Result There were remarkable spatial variations of N-DAMO bacteria in winter. Shannon biodiversity of 16S rRNA genes was higher in winter than that in summer. Compared with other freshwater ecosystems, there was higher diversity of N-DAMO bacteria in Miyun Reservoir. The N-DAMO bacterial communities (16S rRNA and pmoA genes) in sampling sites near to dam were different from the bacterial communities in other sampling sites. The N-DAMO bacterial community structure in dam areas may be associated with the water column depth in front of the dam. Moreover, Spearman’s correlations revealed that DO, NO3 − -N, NO2 −-N, and NH4 +-N in interstitial water and sediment were potential determinant factors influencing the diversity of N-DAMO bacteria (16S rRNA and pmoA genes). Conclusion There were distinct seasonal variations in 16S rRNA and spatial variations in pmoA genes. N-DAMO bacterial communities contained novel Methylomirabilis oxyfera-like pmoA genes in Miyun Reservoir. Nitrogen (NO2 −-N, NO3 −-N, and NH4 +-N) were the dominant factor influencing the N-DAMO bacterial community structure in the drinking reservoir. N-DAMO bacterial community structure in dam areas indicates that water depth and DO might be the dominant factor influencing the N-DAMO bacterial communities in the reservoir.

Inland lakes or reservoirs are the main surface water resources, related to people’s survival and social development. On-site water level data are critical for water resource management, while satellite laser and remote sensing data are a significant tool for long-term change monitoring. In this study, we took the Miyun Reservoir, the most important source of drinking water in Beijing, as the research area. We used Landsat images and the Ice, Cloud, and Land Elevation Satellite (ICESat-2) for small-scale water level change monitoring and inversion across unrecorded periods. First, we proposed a new two-step denoising method based on local statistics to denoise the ATL03 single photon data from 2018 to 2020, and extracted the effective elevation information of Miyun Reservoir. Second, based on Landsat images from 1984 to 2020, the MNDWI index was used to extract the water area and generated a percentage map of water occurrence. Finally, the water and land boundary elevation were selected from the effective photon elevation information according to the boundary position under each percentage of the water generation percentage graph, the area, and the water level elevation model (A–E model) was established, and the water level values of unrecorded periods were inverted. The denoising results showed that the denoising accuracy of all data is higher than 95%. The area of Miyun Reservoir has changed greatly in the past 37 years, especially in the northeast corner and northern region. The inverted water level elevation had a strong correlation with the measured value, the correlation coefficient reached 0.97, the root mean square error (RMSE) was 0.553 m, and the estimated water level value was highly consistent with the recorded value and fluctuated dramatically from 1984 to 2020. This method complements the traditional water level mapping method, provides a new idea for the monitoring of water level changes in lakes or reservoirs without field records, and also contributes to the timely and effective monitoring and management of global lake and reservoir water level and time changes.

Water scarcity is a major problem faced by many parts of the world and seriously affects local development. Most of the previous water resources assessment only considered the water quantity and quality separately, and few studies had converted it into an indicator for assessment. We proposed a linear additivity indicator to calculate the amount of water resources by combining water quantity and water quality. The indicator named Water Quantity and Quality for Water Yield Equivalent (QQWYE). We calculated the water yield in the upstream watershed area of Miyun reservoir near Beijing, China in the year of 2000, 2008 and 2013. At the same time, we also used the QQWYE indicator to calculate the water yield equivalent on the basis of water yield, and made a sensitivity analysis of the results. Then the results of water yield and water yield equivalent were used to assess the amount of water resources. The results showed that the water yield in the study area in 2000, 2008 and 2013 were 372 × 106 m3, 723 × 106 m3 and 700 × 106 m3, respectively, and the water yield equivalent calculated using QQWYE were-206 × 106 m3, 553 × 106 m3 and 509 × 106 m3. This indicates that using the QQWYE indicator to assess water resources is more accurate than calculating water yield alone. In the sensitivity analysis, precipitation and evapotranspiration are highly sensitive to water yield and water yield equivalent, because climate change will significantly affect local precipitation and evapotranspiration. In the future watershed management, water consumption should be saved and water use efficiency should be improved to prevent climate change from having a significant impact on water resources. Beyond that, using a linear additivity indicator QQWYE to assess water resources can meet the principle of conservation of water resources. The calculation results of this study are relatively reliable and can provide a scientific basis for the sustainable management and rational utilization of water resources in the Miyun Reservoir watershed.

Soil erosion by water is a major cause of land degradation. Agricultural practices and many other ecological environmental problems contribute to land degradation worldwide, especially in arid and semi-arid areas. Miyun County, which is located in a mountainous region of North China, is an important natural ecological zone and surface source of drinking water for Beijing and is very vulnerable to soil erosion due to its thin soil layer and human activities. Landsat images from 2003 and 2013 were used to analyze the land-use and land-cover change (LULCC) over this period. The revised universal soil loss equation (RUSLE) model integrated with Geographic Information System (GIS) was used to quantify soil loss and to map erosion risk. In addition, the response of soil erosion to LULCC was evaluated. The results showed that the areas under cropland, forest, and water bodies increased over the study period by 66.03, 243.44, and 9.01 km2, respectively. The increase in forested land indicated that the improved ground vegetation cover was due to the implementation of active ecological measures. Between 2003 and 2013, light soil erosion increased by 587.46 km2, and extremely severe soil erosion increased by 9.57 km2. The extents of slight, moderate, severe, and very severe soil erosion, however, decreased by 8.02, 445.21, 142.69, and 1.11 km2, respectively. A total of 57.5% of land with moderate soil erosion has been converted to light soil erosion, which could be highly beneficial for the improvement of vegetation control of soil and water losses. In terms of area, forestland exhibited the greatest increase, while moderate soil erosion exhibited the greatest decrease over the study period. Land-use change led to an alteration in the intensity of soil erosion due to changes or loss of vegetation. The conversion from high intensity soil erosion to low intensity was attributed to the implementation of ecological environmental protection. The results generated from this study may be useful for planners and land-use managers to make appropriate decisions for soil conservation.

As natural wetlands are degrading worldwide, artificial wetlands can operate as a substitute to provide waterbirds with refuge, but they cannot replace natural wetlands. Reservoirs, one of the most common artificial wetlands in China, can be of great importance to waterbirds. Miyun reservoir in Beijing, China, has undergone a process similar to a natural lake being constructed in a reservoir. In this study, we surveyed waterbird community composition and evaluated the corresponding land cover and land use change with satellite and digital elevation model images of both before and after the water level change. The results showed that in all modelled scenarios, when the water level rises, agricultural lands suffer the greatest loss, with wetlands and forests following. The water level rise also caused a decrease in shallow water areas and a decline in the number and diversity of waterbird communities, as the components shifted from a shallow-water preferring group (waders, geese and dabbling ducks) to a deep-water preferring group (most diving ducks, gulls and terns). Miyun reservoir ceased to be an important waterbird habitat in China and is no longer an important stopover site for white-naped cranes. A similar process is likely to occur when a natural lake is constructed in a reservoir. Therefore, we suggest that policymakers consider the needs of waterbirds when constructing or managing reservoirs.

The Miyun Reservoir is the most important source of drinking water in Beijing, China. Based on the Landsat satellite series image, this paper compared four index methods (NDWI, RNDWI, MNDWI, AWEIsh-superimposed MNDWI) to extract the water body area of Miyun Reservoir from 1979 to 2018 to study its changes in the past 40 years. Furthermore, the internal and external driving forces of reservoir water body area change are studied by correlation analysis and catastrophe analysis. Compared to the characteristic curve of reservoir area calculation, it indicated that the AWEIsh-superimposed MNDWI method has the highest accuracy. The statistical, temporal and spatial analysis showed that the water body area changes of Miyun Reservoir are mainly divided into four distinct stages: (1) It increased in 1979–1997, which was mainly due to the increase in precipitation and the low level of economic development. In 1997, the maximum value (161.14 km2) was reached, which was 108.64 km2 higher than the minimum value. (2) It shrank rapidly in 1997–2004. The areas had dropped by 101.61 km2. By 2004, it was 59.61 km2. The main reason is that the reservoir has suffered from persistent drought for many years after discharging water. (3) It maintained at a lower water level in 2004–2015, with an average annual area of 78 km2. The reason is the low precipitation and rapid economic development. (4) It grew rapidly after 2015, mainly due to water from the South-to-North Water Transfer Project, coupled with the increased precipitation. By 2018, the water body area reached 125.42 km2. [ABSTRACT FROM AUTHOR]

It is widely acknowledged that dams affect sediment transport and water quality. To support water management of reservoirs, it is useful to explore how the fractions of phosphorus (P) in sediments were changed after the dam was built. The aim of this study was to assess the spatial and temporal trends of the P fractions in sediments from the Miyun Reservoir, a pivotal drinking water supply for Beijing City, the capital of China. Nine surface sediment samples, together with a sediment core, were collected. The concentrations of total P (TP) and their fractions were then determined by using a sequential extraction method. The results showed that the reservoir was classified into three areas spatially based on the TP concentrations, i.e., high (Baihe area), medium (transitional area), and low (Chaohe area) concentrations. The concentrations of iron-bound P (BD-P) and metal oxide–bound P (NaOH-P) were higher in the Baihe and Chaohe regions than those in the transitional area and tended to increase with water depth. Dam construction can lead to the concentrations of P increased in sediments and further increase the potential of internal P loadings. This study revealed the effect of dam construction on sedimentary P accumulation. The results will be helpful in better understanding the mobility and bioavailability of P in the aquatic ecosystem, which aim to achieve a more highly targeted environmental management for this important region. [ABSTRACT FROM AUTHOR]

Purpose: Nitrate/nitrite-dependent anaerobic methane oxidation (N-DAMO) connects the global cycle of carbon and nitrogen in aquatic ecosystems. The aims of this study were to investigate the spatiotemporal variation of N-DAMO bacteria and its driving factors in a drinking reservoir which are strongly affected by human consumption. Methods: Cloning analyses were used to study the pmoA and 16S rRNA genes of N-DAMO bacteria. Sequencing and phylogenetic analyses were used to investigate the bacterial composition and structure. Redundancy analyses (RDA) and spearman’s correlations analyses were applied to analyze the relationships between bacterial distribution and environmental factors. Result: There were remarkable spatial variations of N-DAMO bacteria in winter. Shannon biodiversity of 16S rRNA genes was higher in winter than that in summer. Compared with other freshwater ecosystems, there was higher diversity of N-DAMO bacteria in Miyun Reservoir. The N-DAMO bacterial communities (16S rRNA and pmoA genes) in sampling sites near to dam were different from the bacterial communities in other sampling sites. The N-DAMO bacterial community structure in dam areas may be associated with the water column depth in front of the dam. Moreover, Spearman’s correlations revealed that DO, NO3− -N, NO2−-N, and NH4+-N in interstitial water and sediment were potential determinant factors influencing the diversity of N-DAMO bacteria (16S rRNA and pmoA genes). Conclusion: There were distinct seasonal variations in 16S rRNA and spatial variations in pmoA genes. N-DAMO bacterial communities contained novel Methylomirabilis oxyfera-like pmoA genes in Miyun Reservoir. Nitrogen (NO2−-N, NO3−-N, and NH4+-N) were the dominant factor influencing the N-DAMO bacterial community structure in the drinking reservoir. N-DAMO bacterial community structure in dam areas indicates that water depth and DO might be the dominant factor influencing the N-DAMO bacterial communities in the reservoir. [ABSTRACT FROM AUTHOR]

Some essential water conservation areas in China have continuously suffered from various serious problems such as water pollution and water quality deterioration in recent decades and thus called for real-time water pollution monitoring system underwater resources management. On the basis of the remote sensing data and ground monitoring data, this study firstly constructed a more accurate retrieval model for total phosphorus (TP) concentration by comparing 12 machine learning algorithms, including support vector machine (SVM), artificial neural network (ANN), Bayesian ridge regression (BRR), lasso regression (Lasso), elastic net (EN), linear regression (LR), decision tree regressor (DTR), K neighbor regressor (KNR), random forest regressor (RFR), extra trees regressor (ETR), AdaBoost regressor (ABR) and gradient boosting regressor (GBR). Then, this study applied the constructed retrieval model to explore the spatial-temporal evolution of the Miyun Reservoir and finally assessed the water quality. The results showed that the model of TP concentration built by the ETR algorithm had the best accuracy, with the coefficient R2 reaching over 85% and the mean absolute error lower than 0.000433. The TP concentration in Miyun Reservoir was between 0.0380 and 0.1298 mg/L, and there was relatively significant spatial and temporal heterogeneity. It changed remarkably during the periods of the flood season, winter tillage, planting, and regreening, and it was lower in summer than in other seasons. Moreover, the TP in the southwest part of the reservoir was generally lower than in the northeast, as there was less human activities interference. According to the Environmental Quality Standard for the surface water environment, the water quality of Miyun Reservoir was overall safe, except only for an over-standard case occurrence in the spring and September. These conclusions can provide a significant scientific reference for water quality monitoring and management in Miyun Reservoir.

While scholars have studied extensively the individual determinants of willingness to pay (WTP) for improvement in environmental quality, few have delved into the nonparametric nature of such determinants. This study identifies the different major determinants for high and low WTP groups for improvement of water quality in Miyun Reservoir, Beijing. Using QR, interval regression, and Tobit model, this study finds that household income is highly and positively correlated with maximum WTP. In addition, attitude towards the environment, environmental knowledge, demand for improvement in environmental quality, education, and being male are all positively correlated with maximum WTP. In contrast, age is negatively correlated with maximum WTP, consistent with many existing studies. Compared with interval regression and Tobit, QR reveals more interesting results. We find that household income is more significantly correlated with WTP above the median maximum WTP value than below. For the top 1% of maximum WTP group, all nine determinants are highly significant, suggesting that the well-educated ones who command high salaries should be the target group of such policy initiative. By using QR, this paper sheds light on the varying public preferences rooted in income distribution and ability to pay in a fine-grained manner, and thus provides insight into effective policy targeting to implement water policies. [ABSTRACT FROM AUTHOR]

Soil in riparian zone can alleviate the risk of nitrogen pollution for water by releasing gaseous nitrogen (N) fluxes. As a critically terminal riparian zone in China, the Miyun Reservoir riparian zone is dramatically submerged by water delivered by the South-to-North Water Transfer Project (SNWTP), which is the largest inter-basin water transfer scheme worldwide. However, few studies have proposed a framework to estimate the effect of SNWTP on N removal by soil at the scale of the riparian catchment. Therefore, a framework that integrates the eco-hydrological model, remote sensing technology, and scenario setting was developed in this study to simulate the spatiotemporal variation of N emissions and to estimate the influences of SNWTP on N removal by soil in the Miyun riparian catchment between April and September of 2015. The simulated results indicate that N removal in the whole catchment ranged from 48.83 t to 290.58 t between April and September and the total N removal was 871.97 t in 2015. With water level exceeding 150 m and 160 m, the riparian soil had about 35%-60% of its original N pollution mitigation ability. Changing farmland and grassland into forestland can effectively offset the impacts of SNWTP. [ABSTRACT FROM AUTHOR]

Although algal growth in drinking water reservoirs has attracted worldwide attention, its spatial–temporal distribution and limiting factor variation are still not well described. In this study, three-dimensional environmental fluid dynamic code of Miyun reservoir had been established and numerical simulation was conducted to reveal the detailed temporal–spatial variation and interrelationship of temperature, total nitrogen, total phosphorous, chlorophyll a at specific time points and locations in a drinking water reservoir in China. The limiting effect of light, temperature, nitrogen and phosphorus on algae growth was also quantified throughout the year. The results suggested that thermal stratification and internal sources of nutrients played an important role in the algal bloom development; the surface layer of shallow regions was identified as the originating algal habitat. The dominant controlling factors for algal growth varied throughout the year. Temperature was the main limiting factor before May 4 and after November 25, while total phosphorous became the dominant limiting factor from May 4 to November 25. Variation of chlorophyll a and phosphorous concentration was closely related during the phosphorous limiting period. This study suggests that comprehensive measures, including external nutrient reduction, internal nutrient reduction and mixing condition improvement, should be implemented to reduce algal bloom events. [ABSTRACT FROM AUTHOR]

Based on a simulated annealing algorithm, this study empirically determined the optimal stand-level forest management strategies for the Miyun Reservoir Catchment (MRC), the important protective screen and ecosystem service provider for Beijing City. The optimization results of wood provisioning indicate that the objective yield can be more effectively and sustainably attained over longer planning horizons. In terms of carbon sequestration service, the slowed growth rate or capacity in the longer planning horizons was associated with a growing proportion of old-growth forest results in an adverse change from carbon sink to source. Given the integrated forest management scenarios combined with the above two objectives, the total carbon sequestration service consisting of growing and harvesting stocks is positively correlated with the wood provisioning service over the longer planning horizons when based on an assumption of no carbon leakage (i.e., synergy). Similar variation trends are also reflected in the aspect of related economic value. Therefore, a set of longer-term integrated forest management strategies combined with wood and carbon services, as well as their values, should be applied to balance the supply of different services over the long term, to guide short-term adaptive management tactics integrated with close-to-nature forest management technology, and to fundamentally alter decisions regarding optimal ecosystem services for megacities. • Optimize long-term, stand-level wood and carbon services in different scenarios. • Underline the importance of integrating service values into management decisions. • Present a set of integrated strategies to improve optimal ecosystem management. [ABSTRACT FROM AUTHOR]

Abstract The uptake of nitrogen (N) and phosphorus (P) by plants in riparian zones can significantly decrease the water pollution risk. Moreover, the vegetation area in riparian zone can be impacted by raising of water level and afforestation. As the largest reservoir in North China, the Miyun Reservoir is affected by the South-to-North Water Transfer (SNWT) and large-scale afforestation. However, few efficient technology frameworks that can be used to assess the effects of similar anthropogenic projections on N and P uptake by plants at riparian zone catchment scale have been reported. Therefore, this study proposed a framework including an ecological simulation tool coupled with multi-source data and scenario setting methods to identify the effects of these two projects on the uptake of N and P by plants in Miyun Reservoir riparian zone from April to September in 2015. The results show that the total N and P uptake by plants in Miyun Reservoir riparian zone are 1214.18 t and 148.66 t in growing seasons. After afforestation, the N (P) removal will increase by 2.56 (2.17) times in the impacted area (below 160 m in elevation). When the water level rises to 150 m in elevation, the joint effects of afforestation and SNWT will increase the total N and P removals by 851.18 t and 83.33 t. This implies that the afforestation can offset the negative effect on N (P) removal caused by SNWT. Overall, this study can provide useful scientific reference for the design and effective management of the riparian zone. Graphical abstract Unlabelled Image Highlights • Miyun Reservoir is affected by SNWT and large-scale afforestation. • A framework including an ecological simulation tool and scenario setting methods is proposed. • It can identify the effects of these two projects on N and P uptake by plants in Miyun Reservoir riparian zone. • The afforestation can offset the negative effect on N (P) removal caused by SNWT. • This study can provide useful scientific reference for the effective management of Miyun Reservoir. [ABSTRACT FROM AUTHOR]

Abstract As the sole drinking water source for Beijing City, Cd has been previously assessed as the major contaminant in Miyun Reservoir (MYR) riparian soils. However, the potential release risk of Cd in such soils, and the labile-Cd release–resupply process from the soil solid phase to solution after water impoundment remain poorly understood. We established a geochemical baseline concentration (GBC) of Cd in MYR riparian soils, combined with the diffusive gradient in thin films (DGT) technique and DGT-induced fluxes in soil (DIFS) model, to reveal a dynamic release–resupply process and influencing factors of labile Cd in riparian soils. The results showed that Cd GBC in riparian soils was 0.12 mg/kg, which was higher than the Cd background value (BV) for Beijing. Using Cd GBC as BV to assess the Cd contaminant level, the geo-accumulation index showed that Cd in riparian soils was at the uncontaminated level. In addition, Cd in the soils belonged to the non-residual fraction using the Community Bureau of Reference method. Cd mobility coefficients (F1/C Total -Cd) of soils at low elevation had relatively high values, implying that Cd may be released during the initial impoundment of the MYR. Moreover, correlation analysis was used to found the major influencing factors between DGT-labile Cd and several parameters. The results showed that the DGT-labile Cd was positively correlated to the reducible and oxidizable fraction, C DGT -Fe, and total organic carbon, illustrating that the release of Cd from soils was controlled by Fe oxides and organic matter. The resupply ability (R values) and DIFS model parameters revealed that Cd in MYR soils belonged to the partially sustained case, and the slow desorption rate suggested that the release risk of Cd was low in the MYR riparian soils. Graphical abstract Unlabelled Image Highlights • DGT/DIFS and GBC were applied to assess Cd release risk in reservoir riparian soils. • I geo revealed uncontaminated level in soils using GBC of Cd as background value. • Cd release risk in soils was low due to slow desorption rate fitting by DIFS model. • Organic matters and iron oxides in soils controlled the Cd release from soil solid. [ABSTRACT FROM AUTHOR]

• The spatial extension of the climatic impact caused by the reservoir is approximately 5 ∼ 20 km. • Land-lake breezes and mountain-valley winds act synergistically to enhance local wind anomalies reaching up to 2 ∼ 3 m/s. • The hotter and drier air phenomenon in the plain area lasts several hours around noon, exacerbating the heatwave conditions. The impact of large reservoirs on regional climate extremes, such as heatwaves, is not yet well understood, primarily due to the complex interactions of heat, moisture, and momentum over mountainous terrains and the dynamic nature of water surfaces. In this study, we investigate the role of the Miyun Reservoir (MYR), one of the largest reservoirs in northern China, covering an extensive water surface area of 180 km2, in influencing a severe heatwave event that occurred southwest of MYR from 2nd to 6th July 2010. Using high-resolution simulations from the Weather Research and Forecasting Model, our findings reveal contrasting thermodynamic effects of MYR on near-surface air temperatures, with up to three degrees of warming during night-time and up to five degrees of cooling during daytime, with a spatial extent of impact reaching up to 20 km away from the reservoir. These impacts are attributed to a combination of synergized land-lake breeze and mountain-valley winds during the night, leading to the transport of warm air plumes downwind towards the plain and intensifying the heatwave. Furthermore, we observe an increase in surface water vapor brought to higher atmospheric levels due to strong vertical mixing, resulting in lowered surface-specific humidity. Our study emphasizes the dual role of large reservoirs in exacerbating remote heatwaves while providing cooling effects in their proximity. Gaining a comprehensive understanding of the intricate interactions between reservoirs, topography, and regional climate extremes is of paramount importance for accurate climate risk assessments and the formulation of effective mitigation strategies.. [ABSTRACT FROM AUTHOR]

With decreasing water availability as a result of climate change and human activities, analysis of the influential factors and variation trends of chlorophyll a has become important to prevent reservoir eutrophication and ensure water supply safety. In this paper, a structurally simplified hybrid model of the genetic algorithm (GA) and the support vector machine (SVM) was developed for the prediction of monthly concentration of chlorophyll a in the Miyun Reservoir of northern China over the period from 2000 to 2010. Based on the influence factor analysis, the four most relevant influence factors of chlorophyll a (i.e., total phosphorus, total nitrogen, permanganate index, and reservoir storage) were extracted using the method of feature selection with the GA, which simplified the model structure, making it more practical and efficient for environmental management. The results showed that the developed simplified GA-SVM model could solve nonlinear problems of complex system, and was suitable for the simulation and prediction of chlorophyll a with better performance in accuracy and efficiency in the Miyun Reservoir.

As the local strategic surface water source for Beijing City, the Miyun Reservoir catchment is suffering from the challenges of forest landscape degradation (FLD) under various natural and anthropogenic disturbances. This study developed a cause–effect Bayesian network model, consisting of three tiers of nodes, site indicators, external disturbance, and the outcome of FLD, to perform a regional ecological risk assessment to better understand the FLD risks (1998–2013) in the catchment. The effects of the Beijing–Tianjin sandstorm source control (BTSSC) Phase I program, a typical forest landscape restoration program, on the FLD were further examined. Overall, the higher level of either current occurrence or risk probability for FLD suggests the urgency of the following restoration efforts. The dominance of soil erosion for FLD indicates that soil erosion control should be a priority in the following Phase II program. Meanwhile, the uneven spatial distribution of high‐risk areas suggests that the following efforts should be focused within the upstream Hebei Province. In addition, based on the comparison of site indicators between different risk areas, the study concluded that community livelihood activities and land degradation due to climate change have been the other two dominant driving forces contributing to FLD. Furthermore, the study found that the forest landscape has not been restored into the best state by the BTSSC program due to the multiple and complex challenges. Thus, the technical concept of nature‐based solutions, including close‐to‐nature forest management technology and a comprehensive community‐involvement governance model, was proposed for the following Phase II program. [ABSTRACT FROM AUTHOR]

As the world's largest water diversion project, the South-to-North Water Diversion Project in China will have potential environmental effects on the Miyun Reservoir (MYR). However, Cu is a toxic pollutant, and the potential risk of Cu remobilization in MYR soils after water impoundment remains unknown. Riparian soils (five land use types and three vertical elevations) were collected from the MYR before water impoundment. Soil properties, total concentrations of Cu in soils (C total -Cu) and pore water (C sol -Cu), and chemical fractions were measured. Diffusive gradients in thin films (DGT) and the DGT-induced fluxes in soils (DIFS) model were applied to investigate Cu availability. The average C total -Cu was higher than the Chinese background values, indicating potential anthropogenic input of Cu. No significant influences of land use types/vertical elevations on DGT-labile Cu (C DGT -Cu) and C total -Cu were observed. A significant positive relationship between C DGT -Cu and C sol -Cu showed that C DGT -Cu can effectively predict bioavailable Cu fraction in MYR soils, whereas C DGT -Cu had no correlation with different chemical fractions measured by European Community Bureau of Reference (BCR) geochemical fractionation, suggesting that BCR chemical fractions cannot reflect Cu mobility in MYR soils. Risk assessment code showed a low risk of Cu remobilization in MYR soils, but a reducing environment would cause higher mobilization of Cu associated with Fe/Mn oxides after water impoundment. Moreover, the DIFS model reported a deficient soil resupply capacity; this agreed with low R values, which were mostly attributed to the limited available pool of Cu in the soil solid phase. [ABSTRACT FROM AUTHOR]

The middle route of the South-to-North Water Diversion project alleviates drought in northern China, especially reducing water shortage pressure in Beijing. However, after submersion, the potential release risk of metals in newly submerged soils into the water in the receiving reservoir remains unclear. Here, we assess the labile Zn in the riparian soils of Miyun Reservoir (MYR) using the diffusive gradients in thin films (DGT), DGT-induced fluxes in soils (DIFS) model, and Community Bureau of Reference (BCR) sequential extraction. The results showed that the average Zn concentrations at three sampling sites (S2, S3, and S5) exceeded soil background value (74.8 mg/kg), indicative of Zn accumulation in the MYR. The concentrations of DGT-labile Zn varied within 39.7–62.4 μg/L (average: 56.7 μg/L), with the greatest value observed at 145 m at sampling site S3, attributed to anthropogenic activities in recreational areas. The DGT-labile Zn showed no correlation with classes of land, elevations, or soil properties. Sequential extraction results demonstrated that Zn predominantly existed in the residual fraction, but still showed a strong capability for resupply from the solid phase (R >1). The DIFS model simulation results showed that Zn underwent irreversible diffusion of intra-particle metals from the solid phase to the soil solution. Therefore, the potential release risk of labile Zn in riparian soils in MYR cannot be ignored, especially for areas experiencing human disturbance. [ABSTRACT FROM AUTHOR]

Quantifying the relationship between the land use and water nutrient concentrations would help guide land use management and water eutrophication control. Previous studies mainly focus on the quantitative structure of land use and lack a comprehensive characterization of the intensity and spatial distribution of land use. Taking the upper catchment of Miyun Reservoir as the study area, we analyzed the impacts of land use on surface runoff nutrient concentrations. We set 52 water quality monitoring sites within sub-basins of the entire upper catchment of Miyun Reservoir and collected water samples in each month. Using the remote sensing interpretation and spatial analysis techniques, land use information was extracted, which included the intensity, slope, distance to the rivers and sampling sites, and spatial arrangement. The land use information was used as independent variables for the multiple regression models to predict the changes of total nitrogen, total phosphorus and chemical oxygen demand concentrations. The consideration of the above four aspects of land use information significantly promoted the explanatory capability of models, with the coefficients of determination of multiple linear regression models changing from 0.294, 0.471 and 0.223 to 0.532, 0.685 and 0.489, respectively. We also compared the mean cumulative contribution rates of land use to nutrients and the corresponding cumulative area percentages with different flow path distances to river. Results showed that the flowing migration path distance to the river in the range of one kilometer was the key area to control water eutrophication in the upper catchment of Miyun Reservoir. Finally, we proposed three measures to control and regulate the water eutrophication, including optimizing the farmland fertilizer management, strengthening the livestock manure handling, building forested filter strips and riparian buffer zones. [ABSTRACT FROM AUTHOR]

The eco-environment in Miyun Reservoir in Beijing city has received more attention as the main surface source of the drinking water natural ecological zone for the capital of China. Meanwhile, the changes in land use and land cover (LULC) are a major cause of eco-environmental changes and represent an important part of the global change affecting the environmental quality. Therefore, in this paper, taking the Miyun county as the evaluation unit, supported by RS (remote sensing) and GIS (geographical information system), the spatio-temporal changes of land use from 2003 to 2013 were analyzed with the Landsat TM (OLI) images, and then several synthetic evaluation indices were set up including, natural condition, environmental pollution, geologic hazard and local social economy factors. Combining AHP methods with GIS, the regional environmental evaluation model was established and ecoenvironmental quality was evaluated. The results showed that the areas of cropland, forestland and water body increased, with the annual change rate of 3.2%, 2.27% and 0.89% respectively. While the annual change rate of grassland, unused land, and built-up land decreased by (-) 5.35%, (-) 3.96% and (-) 1.04%, respectively. In 2003, the medium level area occupied the most, followed by the light level area, which was 899.90 and 823.73km2, respectively. However, in 2013, light level dominated the position of the study region, the potential level occupied the subordinate position, with the area ratio of 48.57% and 28.59%, respectively. The sum area of potential and the light level area increased from 46.64% in 2003 to 76.52% in 2013, which indicated that the study region maintained a better grade of the eco-environmental quality. During the past decade, the regional eco-environmental quality has been transferred from worse status to better status, especially in hilly region, due to the implementation of eco-environmental protection measures, such as the Grain for Green and Natural Forest Protection since 1998. [ABSTRACT FROM AUTHOR]

Compensation programs ensure the efficacy of water conservation programs and sustainability of interregional water cooperation. Here, a water conservation compensation standard model based on the cost and contribution to benefits regarding water quality and quantity was constructed and then applied to the Paddy Land-to-Dry Land Program (PLDLP) in the Beijing-Hebei region of China. We found that the PLDLP reduced the pollution load of total nitrogen and total phosphorous to downstream areas by 27.63% and 88.53% respectively; runoff to downstream areas increased by 4.22%. Without considering the labor costs of family members, the net income of farmers decreased 41.65%, and the compensation standard was calculated at 5165.41 CNY per ha. From the perspective of social comprehensive value, income generated from becoming migrant worker was treated as an opportunity cost for farmers and under this model the net income of farmers decreased 10.99% and compensation standard was calculated at 1362.95 CNY per ha. [ABSTRACT FROM AUTHOR]

The South-to-North Water Diversion Project has been initiated to address the problem of water shortages in north China. However, the environmental impact of this project is currently unclear, especially for the geochemical process of toxic trace metals in reservoir riparian soil following water submergence. The mobility of Ni in Miyun Reservoir riparian soil samples was investigated using diffusive gradients in thin films (DGT), considering five different land use types and three vertical elevations. The DGT-induced fluxes in soil (DIFS) model was applied to simulate the kinetics of Ni mobilization in the soil. The results showed that the average concentration of Ni was 36.58 mg/kg, which was slightly higher than the corresponding background values reported for both Beijing and China. Coincidentally, the highest concentrations of both total Ni and DGT-labile Ni (C DGT -Ni) were observed at the same site (recreational area), indicating that anthropogenic activities may have contributed to the release of Ni. Land use type and vertical elevation had no significant influence on C DGT -Ni. In addition, C DGT -Ni was positively correlated with reducible fraction, C DGT -Fe, C DGT -Mn, and TOC, indicating that Ni in the soils was adsorbed mainly on the Fe/Mn oxides and organic matter. Moreover, the low values of R (C DGT -Ni/C sol -Ni, R < 0.25) indicated that the replenishment of Ni from the solid phase was poor, and the rate of Ni desorption was considerably lower than its depletion rate, thus leaving only a small proportion of Ni was available. [ABSTRACT FROM AUTHOR]

Investigation on decreased runoff and driving forces in the water source and water destination catchments is vital to the water resources protection and water supply security assurance. Danjiangkou Reservoir Basin (DRB) and Miyun Reservoir Basin (MRB) are the water source and water destination regions for the middle route of South-to-North Water Diversion Project (MSNWDP) in China. Variations in runoff and driving forces behind these variations during 1960–2005 in the DRB and the MRB were comparatively analyzed and investigated by the climate elasticity method based on the Budyko hypothesis. The results showed that the runoff change process was diagnosed as the same three sub-periods (1960–1979, 1980–1989, and 1990–2005) by the cumulative anomaly analysis. The variations in the runoff exhibited large fluctuations with an overall decreasing trend of −2.5 mm/year in the DRB and −1.1 mm/year in the MRB. The variations in average annual runoff among the three sub-periods had significant differences in magnitude and direction. The runoff in the DRB increased by 81.6 mm during 1980–1989, and decreased by 67.1 mm during 1990–2005. However, the decreased runoff in the MRB during 1980–1989 and 1990–2005 were 37.3 and 31.7 mm, respectively. The specific spatio-temporal differences of climate factors (precipitation and potential evapotranspiration) and catchment characteristics jointly resulted in the differences of the runoff change. The climate elasticity method revealed that the leading factors to runoff changes in the three sub-periods had significant differences. The climate factors were the leading factors before 1990, however, the human activities became more intensive to be the leading factors after 1999. The relative contributions of climate factors and catchment characteristics to runoff change varied from (88.5%, 8.2%) during 1980–1989 to (30.9%, 73.9%) during 1990–2005 in the DRB. However, in the MRB, the relative contributions were from (51.0%, 48.2%) during 1980–1989 to (−8.0%, 110.0%) during 1990–2005. An effective way to reduce risk is to take the dynamic or elastic water resources management and the differentiated protection measures. In addition, green water management, the water demand management and saving water both in the water source regions and in the water destination regions of the MSNWDP are recommended and persistently advocated to reduce water consumption. [ABSTRACT FROM AUTHOR]

Inter-basin water transfer projects are designed to relieve water scarcity around the world. However, ecological problems relating to reductions in protection zone functions can occur during inter-basin transfers. This paper uses the largest inter-basin water transfer project in the world, namely, the South-to-North Water Transfer Project (SNWTP) in China, as an example to analyze the variation of Miyun Reservoir's inner protection zone functions when water is transferred. Specifically, a riparian model (RIPAM) coupled with remote sensing data were used to calculate the nitrogen (N) and phosphorus (P) losses due to plant uptake, and these results were validated by in situ survey data. Then, correlations between water levels and N and P removal were analyzed. The results show that water table disturbances resulting from elevated water levels strongly influence the growth of plants and have obvious negative impacts on N and P removal in the inner protection zone. With the implementation of the middle route of the SNWTP, the water level of Miyun will rise to 150 m in 2020, and subsequently, the total net primary productivity (NPP) could decline by more than 40.90% from the level in 2015, while the N and P uptake could decline by more than 53.03% and 43.49%, respectively, from the levels in 2015, according to the modeling results. This will lead to declines in the inner protection zone's defense effectiveness for N and P interception and increases in risks to the security of water resources. The results of this study provide useful knowledge for managing the defense function of the terminal reservoir's inner protection zone and for ensuring that water quality is maintained during the diversion process. [ABSTRACT FROM AUTHOR]

As the only surface water source for Beijing, the Miyun Reservoir and its catchment (MRC) are a focus for concern about the degradation of ecosystem services (ES) unless appropriate payments for ecosystem services (PES) are in place. This study used the contingent valuation method (CVM) to estimate the costs of two new PES programs, for agriculture and forestry, and to further calculate the economic value of ES in the MRC from the perspective of local rural households' willingness to accept (WTA). The results of Logit model including WTA and the variables of household and village indicate that the local socio-economic context has complex effects on the WTA of rural households. In particular, the bid amount, location and proportion of off-farm employment would have significant positive effects on the local WTA. In contrast, the insignificance of the PES participation variable suggests that previous PES program experiences may negatively impact subsequent program participation. The mean WTA payments for agriculture and forestry PES programs were estimated as 8531 and 8187 yuan/ha/year, respectively. These results consistently explain the differentiated opportunity costs on both farmland and forestry land. Meanwhile, the differentiated WTA values in Beijing vs. the surrounding Hebei Province follow the interest differences and development gaps between jurisdictions. Finally, the total economic value of ES in the MRC area was estimated at 11.1 billion yuan/year). The rational economic value of ES for the restoration priority areas reaches 515.2 million yuan/year. For the existing budget gap (299 million yuan/year), the study proposed that decision makers increase the water tariff by 0.08 yuan to raise the funds needed. The study also concluded that these results are not only financially and politically feasible but also cost-effective. This study has policy implications for improving the implementation efficiency and providing quantified supports for PES programs in megacity source water area. [ABSTRACT FROM AUTHOR]

The South-to-North Water Diversion Project, one of China's largest water diversion projects, has aroused widespread concerns about its potential ecological impacts, especially the potential release of trace metals from shoreline soils into Miyun Reservoir (MYR). Here, riparian soil samples from three elevations and four types of land use were collected. Soil particle size distributions, contents and chemical fractionations of trace metals and lead (Pb) isotopic compositions were analyzed. Results showed that soil texture was basically similar in four types of land use, being mainly composed of sand, with minor portions of clay and silt, while recreational land contained more abundant chromium (Cr), copper (Cu), zinc (Zn) and cadmium (Cd), suggesting a possible anthropogenic source for this soil pollution. The potential ecological risk assessment revealed considerable contamination of recreational land, with Cd being the predominant contaminant. Chemical fractionations showed that Cu, arsenic (As), Pb and Cd had potential release risks. Additionally, the 206 Pb/ 207 Pb and 208 Pb/ 207 Pb values of soils were similar to those of coal combustion. By combining principal component analysis (PCA) with Pb isotopic results, coal combustion was identified as the major anthropogenic source of Zn, Cr, Cu, Cd and Pb. Moreover, isotope ratios of Pb fell in the scope of aerosols, indicating that atmospheric deposition may be the primary input pathway of anthropogenic Zn, Cr, Cu, Cd and Pb. Therefore, controlling coal combustion should be a priority to reduce effectively the introduction of additional Zn, Cu, Cd, and Pb to the area in the future. [ABSTRACT FROM AUTHOR]

The Middle Route of the South-to-North Water Diversion Project is a significant water diversion project intended to alleviate water shortages in the north China plains, especially for the capital (Beijing). After water retention, the potential ecological risk of metal contamination in the riparian soils of the Miyun Reservoir (MYR) to water quality has raised public concern. The remobilization characteristics of cobalt (Co) in MYR riparian soils are still unknown. Riparian soil samples (considering five different land use types and three vertical elevations) were collected from the MYR prior to water impoundment. Total Co concentrations, soil properties, total Co in soil solution, Co chemical fractions and labile Co measured by diffusive gradients in thin films (DGT) are applied to investigate the Co remobilization characteristics. The results showed that the total concentrations of Co (C total -Co) were approximately equal to background values of Co in Beijing and China at most of the sites. The highest values of C total -Co were observed at 140 m and 145 m in recreational land (S3), which may be influenced by the anthropogenic activities. No obvious differences in C total -Co and DGT-labile Co (C DGT -Co) were found with the variation of land use types and vertical elevations in the soils of the MYR. C DGT -Co made up 9%-52% of the total dissolved Co, with an average value of 25%, indicating that Co in the soil solution was partially sustained by the solid phase. The highest C DGT -Co were observed in grassland and mountain land, indicating that the previous intensive mining in the upstream areas of the MYR is responsible for the release of Co. The results of the sequential extraction showed that Co is mainly bound to the residual fraction. DGT-labile Co had no correlation with non-residual fractions measured by sequential extraction, but had a significantly positive relationship with C DGT -Mn, indicating that Co trapped by DGT mainly came from the dissolution of MnO x . When the MYR riparian soils are submerged, a reducing environment will be formed. In this case, Co associated with MnO x may be also released into the water. [ABSTRACT FROM AUTHOR]

Assessing the impact of human intervention on flow regimes is important in policy making and resource management. Previous impact assessments of dam regulation on flow regimes have focused on long-term average patterns, but interannual variations, which are important characteristics to be considered, have been ignored. In this study, the entire signatures of hydrograph variations of Miyun Reservoir in northern China were described by forty flow regime metrics that incorporate magnitude, variability and frequency, duration, timing, and rate of change for flow events based on a long-term synchronous observation series of inflow and outflow. Principal component analysis and cluster analysis were used to reduce the multidimensionality of the metrics and time and to determine impact patterns and their interannual shifts. Statistically significant driving factors of impact pattern variations were identified. We found that dam regulation resulted in four main impact classes on the flow regimes and that the regulated capacity was interannually attenuated from 1973 to 2010. The impact patterns alternated between the highly regulated class with extremely decreasing flow magnitude, slight variability, and extreme intermittency and the slightly regulated class with extremely increasing flow magnitude, slight variability, and extreme intermittency from 1973 to 1987 and then stabilized in the latter class from 1988 to 2001. After 2001, the pattern gradually changed from the moderately regulated class with moderately decreasing flow magnitude, extreme variability, and extreme intermittency to the slightly regulated class with slightly decreasing flow magnitude, slight variability, and no intermittency. Decreasing precipitation and increasing drought were the primary drivers for the interannual variations of the impact patterns, and inflow variability was the most significant factor affecting the patterns, followed by flow event frequency and duration, magnitude, and timing. This study shows that the use of interannual characteristics can help to gain more insight into the impact of dam regulation on flow regimes and will provide important information to scientifically guide the multi-purpose regulation of dams. [ABSTRACT FROM AUTHOR]

An essential task in evaluating global water resource and pollution problems is to obtain the optimum set of parameters in hydrological models through calibration and validation. For a large-scale watershed, single-site calibration and validation may ignore spatial heterogeneity and may not meet the needs of the entire watershed. The goal of this study is to apply a multi-site calibration and validation of the Soil andWater Assessment Tool (SWAT), using the observed flow data at three monitoring sites within the Baihe watershed of the Miyun Reservoir watershed, China. Our results indicate that the multi-site calibration parameter values are more reasonable than those obtained from single-site calibrations. These results are mainly due to significant differences in the topographic factors over the large-scale area, human activities and climate variability. The multi-site method involves the division of the large watershed into smaller watersheds, and applying the calibrated parameters of the multi-site calibration to the entire watershed. It was anticipated that this case study could provide experience of multi-site calibration in a large-scale basin, and provide a good foundation for the simulation of other pollutants in followup work in the Miyun Reservoir watershed and other similar large areas. [ABSTRACT FROM AUTHOR]

Purpose: In recent years, climate change, particularly rising carbon dioxide (CO) concentration and global warming, has attracted much attention around the world. Forest ecosystems still play a crucial role in global carbon (C) fixation. Quantifying forest aboveground biomass (AGB) and its temporal variations is essential for understanding external impacts (e.g., urbanization, environmental change) as well as assessing the potential of forest ecosystems assimilating the atmospheric CO. Materials and methods: In this study, we established regression models for AGB estimation in the Miyun Reservoir region, based on relationships between Landsat-derived variables and ground truth AGB values, which were obtained from both plot measurements and estimations using Light Detection and Ranging (LiDAR) dataset. The models were applied to calibrated Landsat images acquired in 1990, 2000, and 2010 to track the forest AGB temporal variations and the corresponding spatial distributions for each period. The AGB estimations using LiDAR showed high consistency with values based on the plot measurements, while the established models presented an acceptable accuracy. Results and discussion: The AGB density in the Miyun Reservoir experienced an overall increase since 1990 and was averaged at 52.20 and 32.12 t ha, for stand forest and shrub in 2010, respectively. Total AGB in 2010 was estimated to be 4.5 × 10 t, which increased by 8% when compared with the level in 1990. Our results are in the similar range of AGB density reported by other studies carried out in Northern China. Ecological programs including Three-North Shelter Forest Project and Returning Farming to Forest promoted the forest expansion and development during this period, while local farming activities exerted certain negative effects on the surrounding forest systems. Conclusions: Absolute AGB density values indicated that regions with less external interventions present more consistent biomass accumulation. However, the coarse spatial resolution and 10-year interval of the datasets limited detailed analysis of impacts from urbanization of Beijing City. Future studies incorporating sophisticated ecosystem research methods are expected to uncover the mechanisms and key drivers for the observed variations in the AGB in the Miyun Reservoir region of Beijing, China. [ABSTRACT FROM AUTHOR]

Miyun Reservoir is one of the most important drinking water sources for Beijing. Thirteen atmospheric PM sampling sites were established around this reservoir to analyze the mineral composition, morphological characteristics, element concentration, and sources of atmospheric PM pollution, using transmission electron microscope, X-ray diffraction, and inductively coupled plasma mass spectrometry analyses. The average monthly dry deposition flux of aerosols was 15.18 g/m, with a range of 5.78-47.56 g/m. The maximum flux season was winter, followed by summer, autumn, and spring. Zn and Pb pollution in this area was serious, and some of the sample sites had Cr, Co, Ni, and Cu pollution. Deposition fluxes of Zn/Pb in winter and summer reached 99.77/143.63 and 17.04/33.23 g/(hm month), respectively. Principal component analysis showed two main components in the dry deposition; the first was Cr, Co, Ni, Cu, and Zn, and the other was Pb and Cd. Principal sources of the trace elements were iron mining and other anthropogenic activities in the surrounding areas and mountainous area north of the reservoir. Mineralogy analysis and microscopic conformation results showed many iron minerals and some unweathered minerals in dry deposition and atmospheric particulate matter, which came from an iron ore yard in the northern mountainous area of Miyun County. There was possible iron-rich dry deposition into Miyun Reservoir, affecting its water quality and harming the health of people living in areas around the reservoir and Beijing. [ABSTRACT FROM AUTHOR]

As the largest reservoir in North China, the Miyun Reservoir is the most important surface drinking water source in Beijing. Bacteria are key regulators of reservoir ecosystem structure and function, and exploring the community distribution characteristics of bacteria is important for maintaining water quality safety in reservoirs. The spatiotemporal distribution and environmental factors of bacterial communities in the water and sediment of the Miyun Reservoir were explored using the high-throughput sequencing method. The results showed a higher α -diversity and non-significant seasonal variation of the bacterial community in the sediment, and the abundant sedimental species were affiliated with Proteobacteria. For planktonic bacteria, Actinobacteriota was the dominant phylum, and the seasonal variance was represented by CL500-29&#95;marine&#95;group and hgcI&#95;clade in the wet season and Cyanobium&#95;PCC-6307 in the dry season. Additionally, obvious differences in key species were also found in water and sediment, and more indicator species were obtained in sedimental bacteria. Further, a more complex co-existence network was identified in water compared to that in sediment, indicating the strong ability of planktonic bacteria to resist environmental changes. Environmental factors had a significantly higher effect on the bacterial community of the water column than that of the sediment. Furthermore, SO 2- and TN were the main factors affecting planktonic bacteria and sedimental bacteria, respectively. These findings revealed the distribution patterns and driving forces of the bacterial community in the Miyun Reservoir, which will provide important guidance for reservoir management and water-quality assurance.4 and TN were the main factors affecting planktonic bacteria and sedimental bacteria, respectively. These findings revealed the distribution patterns and driving forces of the bacterial community in the Miyun Reservoir, which will provide important guidance for reservoir management and water-quality assurance.

Inter-basin water transfer projects are designed to relieve water scarcity around the world. However, ecological problems relating to reductions in protection zone functions can occur during inter-basin transfers. This paper uses the largest inter-basin water transfer project in the world, namely, the South-to-North Water Transfer Project (SNWTP) in China, as an example to analyze the variation of Miyun Reservoir’s inner protection zone functions when water is transferred. Specifically, a riparian model (RIPAM) coupled with remote sensing data were used to calculate the nitrogen (N) and phosphorus (P) losses due to plant uptake, and these results were validated by in situ survey data. Then, correlations between water levels and N and P removal were analyzed. The results show that water table disturbances resulting from elevated water levels strongly influence the growth of plants and have obvious negative impacts on N and P removal in the inner protection zone. With the implementation of the middle route of the SNWTP, the water level of Miyun will rise to 150 m in 2020, and subsequently, the total net primary productivity (NPP) could decline by more than 40.90% from the level in 2015, while the N and P uptake could decline by more than 53.03% and 43.49%, respectively, from the levels in 2015, according to the modeling results. This will lead to declines in the inner protection zone’s defense effectiveness for N and P interception and increases in risks to the security of water resources. The results of this study provide useful knowledge for managing the defense function of the terminal reservoir’s inner protection zone and for ensuring that water quality is maintained during the diversion process.