Miyun Reservoir Basin Research Articles

Identification of pollutant delivery processes during different storm events and hydrological years in a semi-arid mountainous reservoir basin

A comprehensive understanding of pollutant delivery processes during storm events is essential for developing strategies to minimize adverse impacts on receiving water bodies. In this paper, hysteresis analysis and principal component analysis were coupled with identified nutrient dynamics to determine different pollutant export forms and transport pathways and analyze the impact of precipitation characteristics and hydrological conditions on pollutant transport processes through continuous sampling between different storm events (4 events) and hydrological years (2018-wet, 2019-dry) in a semi-arid mountainous reservoir watershed. Results showed pollutant dominant forms and primary transport pathways were inconsistent between different storm events and hydrological years. Nitrogen (N) was mainly exported in the form of nitrate-N(NO3-N). Particle phosphorous (PP) was the dominant P form in wet years, but total dissolved P (TDP) in dry year. Ammonia-N (NH4-N), total P (TP), total dissolved P(TDP) and PP had prominent flushing responses to storm events and were delivered mainly from overland sources by surface runoff; while the concentrations of total N(TN) and nitrate-N(NO3-N) were mainly diluted during storm events. Rainfall intensity and amount had significant control over P dynamics and extreme events played a key role in TP exports, accounting for >90 % of the total TP load exports. However, the cumulative rainfall and runoff regime during rainy season exerted significant control over N exports than individual rainfall features. In the dry year, NO3-N and TN were delivered primarily through soil water flow paths during storm events; nevertheless, wet year registered complex control on TN exports via soil water release, followed by surface runoff transport. Relative to dry year, wet year registered higher N concentration and more N load exports. These findings could provide scientific basis for determining effective pollution mitigation strategies in Miyun Reservoir basin and provide important references for other semi-arid mountain watersheds.

Analysis of coniferous tree growth gradients in relation to regional pollution and climate change in the Miyun Reservoir Basin, China

Forests play a crucial role in regulating regional climate and mitigating local air pollution, but little is known about their responding to such changes. This study aimed to examine the potential responses of Pinus tabuliformis, the major coniferous tree species in the Miyun Reservoir Basin (MRB), along an air pollution gradient in Beijing. Tree rings were collected along a transect, and ring width (basal area increment, BAI) and chemical characteristics were determined and related to long-term climatic and environmental records. The results showed that Pinus tabuliformis showed an overall increase in intrinsic water-use efficiency (iWUE) at all sites, but the relationships between iWUE and BAI differed among the sites. The contribution of atmospheric CO2 concentration (ca) to tree growth was significant at the remote sites (> 90%). The study found that air pollution at these sites might have caused further stomatal closure, as evidenced by the higher δ13C levels (0.5 to 1‰ higher) during heavy pollution periods. The analysis of tree ring δ15N also revealed the potential of using δ15N to fingerprint major nitrogen (N) deposition, as shown in the increasing tree ring δ15N, and major nitrogen losses due to denitrification and leaching, as shown in the higher δ15N in tree rings during heavy rainfall events. Overall, the gradient analysis indicated the contributions of increasing ca, increasing water deficit and elevated air pollution to tree growth and forest development. The different BAI trajectories suggested that Pinus tabuliformis has the ability to adapt to the harsh environment in the MRB.

Dynamic monitoring of the largest reservoir in North China based on multi-source satellite remote sensing from 2013 to 2022: Water area, water level, water storage and water quality

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.

Gains or losses? A quantitative estimation of environmental and economic effects of an ecological compensation policy.

Ecological compensation is an innovative and effective tool to explore the coordinated development of socioeconomic prosperity and ecological protection, especially for a watershed crossing different regions. It converts the externalities of ecosystem services into practical financial incentives for local stakeholders. This empirical study applies a quantitative policy evaluation approach to evaluate the environmental and economic effects of an ecological compensation policy, using the paddy land-to-dry land (PLDL) program implemented in China's Miyun Reservoir watershed as an example. The study is based on responses to a 2017 questionnaire regarding agricultural production inputs and outputs administered to 269 households in Hebei Province, where the PLDL program has been operational for over 10 yr. The results show that the program has reduced nitrogen usage by 24% on average in 2017 and decreased the total nitrogen emission load by 16.98 tons for the entire case area, which accounts for approximately 18.6% of the total nitrogen load reduction of the Miyun Reservoir basin. However, the upstream households involved in this program have experienced agricultural income losses higher than that allowed for by the current compensation criterion. Therefore, this paper discusses the factors that should be considered in the process of determining ecological compensation criteria. In particular, the paper proposes a differential compensation scheme based on the environmental effect at the individual level to avoid a standard payment for all households irrespective of their different contributions. This differential compensation payment scheme facilitates the fair treatment of environmental contributors and maximizes environmental benefits through an equitable allocation of limited ecological compensation funds. This study serves as a theoretical and practical reference for further improvement of the current ecological compensation policy in China. The study also sheds light on practices for estimating ecological compensation criteria and formulating ecological compensation policies for other regions or countries in the future.

Future climate change impacts on streamflow and nitrogen exports based on CMIP5 projection in the Miyun Reservoir Basin, China

The projection of streamflow and nutrient exports are essential for future water resource and environmental management plans under climate change. This study investigated the responses of streamflow and total nitrogen (TN) loading to future climate scenarios in the Miyun Reservoir Basin (MRB) by coupling a physical process-based hydrologic and water quality model, Soil and Water Assessment Model (SWAT) and 42 statistical downscaled climate projections on the basis of CMIP5 models. Future climatic projections during the two future periods (2021–2035 and 2051–2065) under RCP4.5 and RCP8.5 emission scenarios, primarily precipitation and temperature, were used to drive the calibrated SWAT model. Results show that the MRB would be warmer and more humid. The ensemble mean changes in average annual precipitation (mean temperature) are expected to be more than 5.4% (0.6°C) during the period of 2021–2035 and 12.5% (1.6°C) during 2051–2065. Future streamflow and TN loading projection are expected to increase in two future periods. Meanwhile, the changes in streamflow and TN loading would be higher in summer than in other seasons. The uncertainty ranges in TN loading projection is larger than that in streamflow projection. The probability that streamflow and TN loading increase would be higher in the period of 2021–2035 than in 2051–2065. This study could be of use for providing an insight into the availability of future streamflow and pollution control for the MRB.

SWAT-Simulated Streamflow Responses to Climate Variability and Human Activities in the Miyun Reservoir Basin by Considering Streamflow Components

The streamflow into Miyun Reservoir, the only surface drinking water source for Beijing City, has declined dramatically over the past five decades. Thus, the impacts of climate variability and human activities (direct and indirect human activities) on streamflow and its components (baseflow and quickflow) needs to be quantitatively estimated for the sustainability of regional water resources management. Based on a heuristic segmentation algorithm, the chosen study period (1969–2012) was segmented into three subseries: a baseline period (1969–1979) and two impact periods I (1980–1998) and II (1999–2012). The Soil and Water Assessment Tool (SWAT) was adopted to investigate the attributions for streamflow change. Our results indicated that the baseflow accounted for almost 63.5% of the annual streamflow based on baseflow separation. The contributions of climate variability and human activities to streamflow decrease varied with different stages. During impact period I, human activities was accountable for 54.3% of the streamflow decrease. In impact period II, climate variability was responsible for 64.9%, and about 8.3 mm of baseflow was extracted from the stream on average based on the comparison of the observed streamflow and simulated baseflow. The results in this study could provide necessary information for water resources management in the watershed.

Comparative investigation on the decreased runoff between the water source and destination regions in the middle route of China’s South-to-North Water Diversion Project

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.

Spatial and Temporal Changes in Temperature, Precipitation, and Streamflow in the Miyun Reservoir Basin of China

With the influence of global climate warming, the responses of regional hydroclimatic variables to climate change are of great importance for water resource planning and management. The evolution of precipitation, mean temperature, and runoff at different timescales, was investigated using the Mann–Kendall test from 1969 to 2011 in the Miyun Reservoir Basin, China. In addition, three precipitation indices and different precipitation grades were also considered. Annual precipitation had a non-significant decreasing trend, flood precipitation trend was significantly decreasing with a magnitude of 18.50 mm/10 years, and non-flood precipitation trend was significantly increasing with a magnitude of 6.91 mm/10 years. Precipitation frequency in flood season featured a significantly decreasing trend. Meanwhile, flood precipitation intensity for large rain (25 ≤ p < 50 mm/day) and non-flood precipitation amount for medium rain (10 ≤ p < 25mm/day) also showed significant increasing trends. The mean temperature exhibited significant upward trends during the year, in flood season, and in non-flood season with rates of 0.36 °C/10 years, 0.32 °C/10 years and 0.38 °C/10 years, respectively. The magnitude of the mean temperature increase in the non-flood season was greater than in the flood season. Runoff experienced continuous and significant downward trends of 1.6 × 108 m3/10 years, 1.1 × 108 m3/10 years and 0.40 × 108 m3/10 years, respectively, during the year, in flood season, and in non-flood season. The decreased annual streamflow was more obvious after 2000 than before. The results obtained in this study could be used as references for decision-making regarding water resource management in the watershed.

Variation analysis of streamflow and ecological flow for the twin rivers of the Miyun Reservoir Basin in northern China from 1963 to 2011

In this paper, the Mann–Kendall test and F-test were combined to analyze the annual and seasonal streamflow variations and aberrance points for the twin rivers from 1963 to 2011. The Tennant method was subsequently used to evaluate the ecological flow assurance and deficit. Finally, the Double Mass Curve method was applied to identifying the human activities affecting the streamflow variations. The results were as follows: (1) Three similar stages of the streamflow variations were found for the twin rivers: fluctuations before 1980, the tiny downward trends from the 1980s to the 1990s, and the notably downward trends in the 2000s. (2) The seasonal streamflow also decreased continuously and dramatically, especially in summer, by 80.9% for the Chaohe River and 86.0% for the Baihe River. (3) During the spawning season, 83.3% and 73.1% of streamflow was not at the appropriate level for the Chaohe and Baihe Rivers, respectively, which indicated that the ecological environment was not optimal for the reproduction and breeding of aquatic organisms. While in other periods, the ecological flow assurance was better than that in spawning seasons for the Chaohe and Baihe Rivers, respectively. This indicated that the streamflow regimes of the twin rivers were not always optimal and conducive to the development of the aquatic ecosystem. (4) The streamflow variations of the twin rivers were influenced by increasingly intensive human activities such as changes of land use and land cover, and excessive exploitation and utilization of water resources. These influences were cumulative and showed a gradually increasing tendency. This research is helpful for understanding the streamflow regime and for forecasting of the regional extreme climate, such as drought and floods, and can provide a basis for decision making and formulating adaptive ecological security countermeasures in response to climate changes and human activities.

Impact of fractional vegetation cover change on soil erosion in Miyun reservoir basin, China

It is well known that soil erosion at the watershed scale is the result of interactions between various factors. Among these environmental factors, vegetation is the most important and plays a major role in the soil erosion process. The impact of fractional vegetation cover change (FVCC) on soil erosion in non-contributing areas is a heavily discussed topic. In this paper, the fractional vegetation cover (FVC) in 2002 and 2005 was calculated by using a backpropagation neural network based on remote sensing (RS) data. Then the impacts of FVCC on sediment loads at the outlets of two Miyun reservoir sub-basins were evaluated by integrating RS and geographic information system with statistical analysis. The Miyun reservoir basin (MRB) is characterized by hilly and mountainous topographies and seasonal rainy weather. The primary goal of this paper is to gain a better understanding of FVCC, its driving forces, and its impact on regional soil erosion. We discuss spatiotemporal variations in precipitation and soil erosion, identify which factors contribute to those variations, analyze the influences of FVCC on climate change and human activities and, finally, conclude that changes in FVC and climate regimes are primary factors for soil erosion in MRB. We also discuss how sediment loads may be used to quantitatively separate biophysical and anthropogenic influences and to identify critical thresholds that might have dramatic consequences for the watershed ecosystem. These findings should be quite helpful for sensible watershed development and management planning.

Hydrological projection for the Miyun Reservoir basin with the impact of climate change and human activity

Abstract Considering the impact of climate change and human activity, hydrological projection in the Miyun Reservoir basin (MYRB) was estimated by the Variable Infiltration Capacity (VIC) model with the output from NCAR-CCSM3 under A1B, A2, and B1 scenarios in 2010–2099. Climate change was the change of temperature and precipitation; and human activity included water withdrawal from river, hydraulic projects, land use/covers change, etc. The VIC model parameters were calibrated in “natural period” without the impact of human activity, i.e., before the breakpoint of the precipitation-runoff double cumulative curve. In order to consider the impact of human activity, the Hydrological Projection Revision Formula was constructed to revise the hydrological projection in two catchments (Xiakuai and Zhangjiafen catchment) covering most parts of the MYRB. Based on the output from NCAR-CCSM3, the MYRB would become warmer and wetter in future climate change scenarios. The results indicated that there might be a slight decreasing trend for runoff in 2020s (2010–2039), but the runoff would increase in 2050s (2040–2069) and 2080s (2070–2099) in MYRB under three climate change scenarios. For example, in 2050s the runoff might increase by 35.2–90.4% and 14.3–51.6% in Xiakuai and Zhangjiafen catchment, respectively, compared to the baseline period (1961–1999). Meantime, a high uncertainty for hydrological projection in MYRB should be focused, because only one GCM was used in this study.

Comparison of the streamflow sensitivity to aridity index between the Danjiangkou Reservoir basin and Miyun Reservoir basin, China

The central route of China’s South-to-North Water Diversion Project would divert water from the Danjiangkou Reservoir basin (DRB) to Beijing beginning in the year 2014. The current main surface water source for Beijing is the Miyun Reservoir basin (MRB). The observed streamflows into the DRB and the MRB decreased significantly due to climatic variation and human activities from 1960 to 2005. The climate elasticity method is widely used to quantitatively separate the impacts of climatic variation and human activities on streamflow. One of the uncertainties of the method is that the impacts of changes in precipitation and potential evapotranspiration on streamflow are separated with the assumption that they are independent. However, precipitation and potential evapotranspiration are not totally independent. Aridity index, as the ratio between potential evapotranspiration and precipitation, could be considered as the representative indicator of climatic variation. In this study, the sensitivity of streamflow to aridity index is evaluated to assess the impact of climatic variation on streamflow in the DRB and the MRB. The result shows that streamflow in the MRB is more sensitive to climatic variation than that in the DRB. However, the effective impact of aridity index on streamflow is the product of the sensitivity and the change rate of aridity index. The attribution results show that change in aridity index contributed 68.8 % of the decrease in streamflow in the DRB while it contributed 31.5 % of the decrease in streamflow in the MRB. This indicated that the impact of climatic variation was the main reason of decrease in streamflow in the DRB while human activities such as increasing water consumption and land use change were the main reasons of decreasing streamflow in the MRB.

An Artificial Neural Network Method for Vegetation Cover Retrieval with “Beijing-1” Microsatellite Data

Beijing-1 is a new type of earth observation satellite which is lunched by China.An Artificial Neural Network(ANN) method for vegetation cover retrieval with Beijing-1 in Miyun Reservoir basin has been developed in this paper,and then the result was compared with the traditional regression analysis method and the NDVI method for dimidiate pixel model.It demonstrates that for vegetation cover retrieval in mountainous areas,ANN has the advantage of precise simulation of non-linear transmission over traditional methods,especially for case mountainous vegetation information which traditional methods usually fail.

LUCC and its impact on run-off yield in the Bai River catchment--upstream of the Miyun Reservoir basin

The Miyun Reservoir is the most important drinking water source for Beijing-the capital of China with a population of more than 16 million. Since the 1980s, the inflow to the reservoir has been decreasing, which seriously threatens the security of water use in Beijing. Our goal was to analyze the impact of land use and cover change (LUCC) on run-off yield in the upstream of the Miyun Reservoir. In this study, the Soil andWater Assessment Tool (SWAT) was used to simulate the impacts of LUCC on the run-off yield in the Bai River catchment-upstream of the Miyun Reservoir basin in northern China. The investigation was conducted using two 6-year historical streamflow records: from 1986 to 1991 and from 2000 to 2005. A split sample procedure was used for model calibration and validation. The data from 1986 to 1988 and from 2000 to 2002 were used for calibration, while those from 1989 to 1991 and from 2003 to 2005 for validation. The SWAT calibration was based on monthly measured discharge at Zhangjiafen station at the catchment outlet from Bai River catchment. Additionally, the influence of LUCC on the surface run-off was distinguished from that of climate change on the surface runoff through SWAT scenarios modeling, the two-way analysis of variance (ANOVA), and the rainfall-run-off double-mass analysis in the Bai River catchment. We found that the SWAT model could be used successfully to accurately simulate run-off yield and different LUCC patterns affecting water quantity in this catchment. During calibraion for the two periods the simulated monthly run-off satisfactorily matched the observed values, with the Nash-Sutcliffe coefficient > 0.9 and 0.7 and a coefficient of determination of 0.9 and 0.65 at the outlet station (Zhangjiafen station), while during validation for the two periods the obtained values were 0.85, 0.65 and 0.9, 0.65, respectively. During the period of 1986-91, both the SWAT scenarios modeling and the analysis of the two-way ANOVA method showed that LUCC and climate change had some impact on run-off, and the impact of climate change was more significant than that of LUCC. Compared with the period during 1986-91, the run-off yield in the period during 2000-05 significantly decreased. The obtained results from the rainfall-run-off double-mass analysis indicate that since 1998 LUCC has had an increasing influence on the run-off, while the response of the run-off to rainfall has been decreasing. Since 1998, the LUCC has been a major driving force for run-off change in Bai River catchment.