Under the assumptions of triangular cross section channel and uniform stable flow, an analytical solution of the minimum ecological in-stream flow requirement （MEIFR） is deduced. Based on the analytical solution, th...Under the assumptions of triangular cross section channel and uniform stable flow, an analytical solution of the minimum ecological in-stream flow requirement （MEIFR） is deduced. Based on the analytical solution, the uncertainty of the wetted perimeter method is analyzed by comparing the two techniques for the determination of the critical point on the relationship curve between wetted perimeter, P and discharge, Q. It is clearly shown that the results of MEIFR based on curvature technique （corresponding to the maximum curvature） and slope technique （slope being 1） are significantly different. On the P-Q curve, the slope of the critical point with the maximum curvature is 0.39 and the MEIFR varied prominently with the change of the slope threshold. This indicates that if a certain value of the slope threshold is not available for slope technique, curvature technique may be a better choice. By applying the analytical solution of MEIFR in the losing rivers of the Western Route South-to-North Water Transfer Project in China, the MEIFR value via curvature technique is 2.5%-23.7% of the multi-year average annual discharge, while that for slope technique is 11%-105.7%. General conclusions would rely on the more detailed research for all kinds of cross-sections.展开更多
Examining the direct and indirect effects of climatic factors on vegetation growth is critical to understand the complex linkage between climate change and vegetation dynamics. Based on the Moderate Resolution Imaging...Examining the direct and indirect effects of climatic factors on vegetation growth is critical to understand the complex linkage between climate change and vegetation dynamics. Based on the Moderate Resolution Imaging Spectroradiometer(MODIS) Normalized Difference Vegetation Index(NDVI) data and meteorological data(temperature and precipitation) from 2001 to 2012, the trend of vegetation dynamics were examined in the Ziya-Daqing basins, China. The path analysis was used to obtain the information on the relationships among climatic factors and their effects on vegetation growth. It was found that the trends of growing season NDVI were insignificant in most plain dry land, while the upward trends were significant in forest, grass and dry land in Taihang Mountains. According to the path analysis, in 23% of the basins the inter-annual NDVI variation was dominated by the direct effect of precipitation, in 5% by the direct effects of precipitation and temperature, and in less than 1% by the direct effect of temperature or indirect effects of these two climatic factors. It indicated that precipitation significantly affected the vegetation growth in the whole basins, and this effect was not regulated by temperature. Precipitation increase(especially in July, August and September) was favorable to greenness enhancement. Summer temperature rising showed negative effect on plant productivity enhancement, but temperature rise in April was beneficial for the vegetation growth. When April temperature increases by 1℃, the onset date of greenness for natural vegetation will be 2 days in advance. There was a lag-time effect of precipitation or temperature on monthly NDVI for all land use types except grass.展开更多
College of Resources and Environment/Sino-Danish Center, Univers Beijing 100049, China nstitute of Geographic Sciences and ty of Chinese Academy of SciencesAbstract： Quantifying the contributions of climate change a...College of Resources and Environment/Sino-Danish Center, Univers Beijing 100049, China nstitute of Geographic Sciences and ty of Chinese Academy of SciencesAbstract： Quantifying the contributions of climate change and human activities to ecosystem evapotranspiration （ET） and gross primary productivity （GPP） changes is important for adaptation assessment and sustainable development. Spatiotemporal patterns of ET and GPP were estimated from 2000 to 2014 over North China Plain （NCP） with a physical and remote sensing-based model. The contributions of climate change and human activities to ET and GPP trends were separated and quantified by the first difference de-trending method and multivariate regression. Results showed that annual ET and GPP increased weakly, with climate change and human activities contributing 0.188 mm yr-2 and 0.466 mm yr-2 to ET trend of 0.654 mm yr-2, and -1.321 g C m-2 yr-2 and 7.542 g C m-2 yr-2 to GPP trend of 6.221 g C m-2 yr-2, respectively. In cropland, the increasing trends mainly occurred in wheat growing stage; the contributions of climate change to wheat and maize were both negative. Precipitation and sunshine duration were the major climatic factors regulating ET and GPP trends. It is concluded that human activities are the main drivers to the long term tendencies of water consumption and gross primary productivity in the NCP.展开更多
This study applies a hydroeconomic optimization method for water resources management in the highly water stressed Haihe River basin. A multi-objective, multi-temporal deterministic hydroeconomic optimization model ha...This study applies a hydroeconomic optimization method for water resources management in the highly water stressed Haihe River basin. A multi-objective, multi-temporal deterministic hydroeconomic optimization model has been built to quantify the economic trade-offs and reveal "minimum cost strategies" when reducing groundwater abstraction to sustainable levels. A complex basin representation, with ～140,000 decision variables is formulated where each decision variable represents a flow-path from a water source to a sink. Available water sources are runoff generated by the sub-basins upstream the nine major surface water reservoirs, the inter-basin transfers from Yellow River and South to North Water Transfer Project(SNWTP) and the natural groundwater recharge to the three main groundwater aquifers. Water demands, i.e. sinks, are aggregated for each model sub-basin in categories of the major agricultural users, domestic, industrial and ecological water demands. Each demand is associated with a curtailment cost and groundwater abstraction with a pumping cost. Groundwater overdraft is constrained in each model scenario, ranging from unlimited overdraft in the plain area groundwater aquifer to sustainable abstractions over an 8-year period. Inflow upstream Yuqiao reservoir, and the inter-basin transfers from SNWTP and Yellow River are identified as the water resources with the highest increase in average shadow prices when limiting groundwater overdraft. An increase in inflow shadow prices of 37.5% indicates that these water sources will be most valuable if sustainable groundwater abstraction should be achieved. The shadow prices of water sources reveal when and where in the Haihe River basin users are curtailed if water resources are managed in the most optimal way. Average shadow prices of 1.6 yuan/m3 for all surface water sources in the sustainable abstraction scenarios shows that overdraft can be avoided by curtailment of users with a willingness-to-pay ≤1.6 yuan/m3. The shadow prices of the existing surface water res-ervoirs represented in the model shows that no costs can be saved from expanding their capacities. Finally, the cost of achieving sustainable groundwater abstraction with present water resource availability is found to be minimum 8.2 billion yuan/year.展开更多
Evapotranspiration is one of the key components of hydrological processes. Assessing the impact of climate factors on evapotranspiration is helpful in understanding the impact of climate change on hydrological process...Evapotranspiration is one of the key components of hydrological processes. Assessing the impact of climate factors on evapotranspiration is helpful in understanding the impact of climate change on hydrological processes. In this paper, based on the daily meteorological data from 1960 to 2007 within and around the Aksu River Basin, reference evapotranspiration （RET） was estimated with the FAO Penman-Monteith method. The temporal and spatial variations of RET were analyzed by using ARCGIS and Mann-Kendall method. Multiple Regression Analysis was employed to attribute the effects of the variations of air temperature, solar radiation, relative humidity, vapour pressure and wind speed on RET. The results showed that average annual RET in the eastern plain area of the Aksu River Basin was about 1100 mm, which was nearly twice as much as that in the western mountainous area. The trend of annual RET had significant spatial variability. Annual RET was reduced significantly in the southeastern oasis area and southwestern plain area and increased slightly in the mountain areas. The amplitude of the change of RET reached the highest in summer, contributing most of the annual change of RET. Except in some high elevation areas where relative humidity predominated the change of the RET, the variations of wind velocity predominated the changes of RET almost throughout the basin. Taking Kuqa and Ulugqat stations as an example, the variations of wind velocity accounted for more than 50% of the changes of RET.展开更多
基金National Natural Science Foundation of China, No. 90211007 No.50279049+1 种基金 Knowledge Innovation Project of IGSNRR, CAS, No.CXIOG-A04-12 No.CX10G-E01-08
文摘Under the assumptions of triangular cross section channel and uniform stable flow, an analytical solution of the minimum ecological in-stream flow requirement （MEIFR） is deduced. Based on the analytical solution, the uncertainty of the wetted perimeter method is analyzed by comparing the two techniques for the determination of the critical point on the relationship curve between wetted perimeter, P and discharge, Q. It is clearly shown that the results of MEIFR based on curvature technique （corresponding to the maximum curvature） and slope technique （slope being 1） are significantly different. On the P-Q curve, the slope of the critical point with the maximum curvature is 0.39 and the MEIFR varied prominently with the change of the slope threshold. This indicates that if a certain value of the slope threshold is not available for slope technique, curvature technique may be a better choice. By applying the analytical solution of MEIFR in the losing rivers of the Western Route South-to-North Water Transfer Project in China, the MEIFR value via curvature technique is 2.5%-23.7% of the multi-year average annual discharge, while that for slope technique is 11%-105.7%. General conclusions would rely on the more detailed research for all kinds of cross-sections.
基金Under the auspices of National Natural Science Foundation of China(No.41471026,31171451)Strategic Science and Technology Program in the Thirteenth Five-Year Plan of Institute of Geographical Sciences and Natural Resources Research,Chinese Academy of Sciences(No.2012ZD003)
文摘Examining the direct and indirect effects of climatic factors on vegetation growth is critical to understand the complex linkage between climate change and vegetation dynamics. Based on the Moderate Resolution Imaging Spectroradiometer(MODIS) Normalized Difference Vegetation Index(NDVI) data and meteorological data(temperature and precipitation) from 2001 to 2012, the trend of vegetation dynamics were examined in the Ziya-Daqing basins, China. The path analysis was used to obtain the information on the relationships among climatic factors and their effects on vegetation growth. It was found that the trends of growing season NDVI were insignificant in most plain dry land, while the upward trends were significant in forest, grass and dry land in Taihang Mountains. According to the path analysis, in 23% of the basins the inter-annual NDVI variation was dominated by the direct effect of precipitation, in 5% by the direct effects of precipitation and temperature, and in less than 1% by the direct effect of temperature or indirect effects of these two climatic factors. It indicated that precipitation significantly affected the vegetation growth in the whole basins, and this effect was not regulated by temperature. Precipitation increase(especially in July, August and September) was favorable to greenness enhancement. Summer temperature rising showed negative effect on plant productivity enhancement, but temperature rise in April was beneficial for the vegetation growth. When April temperature increases by 1℃, the onset date of greenness for natural vegetation will be 2 days in advance. There was a lag-time effect of precipitation or temperature on monthly NDVI for all land use types except grass.
基金National Natural Science Foundation of China, No.41471026 National Key Research and Development Program of China, No.2016YFC0401402Acknowledgment We thank to all the data providers. We also appreciate editors and reviewers for their constructive comments and suggestions. Finally, the first author is grateful to the invaluable support received from doctoral student ZOU Yi.
文摘College of Resources and Environment/Sino-Danish Center, Univers Beijing 100049, China nstitute of Geographic Sciences and ty of Chinese Academy of SciencesAbstract： Quantifying the contributions of climate change and human activities to ecosystem evapotranspiration （ET） and gross primary productivity （GPP） changes is important for adaptation assessment and sustainable development. Spatiotemporal patterns of ET and GPP were estimated from 2000 to 2014 over North China Plain （NCP） with a physical and remote sensing-based model. The contributions of climate change and human activities to ET and GPP trends were separated and quantified by the first difference de-trending method and multivariate regression. Results showed that annual ET and GPP increased weakly, with climate change and human activities contributing 0.188 mm yr-2 and 0.466 mm yr-2 to ET trend of 0.654 mm yr-2, and -1.321 g C m-2 yr-2 and 7.542 g C m-2 yr-2 to GPP trend of 6.221 g C m-2 yr-2, respectively. In cropland, the increasing trends mainly occurred in wheat growing stage; the contributions of climate change to wheat and maize were both negative. Precipitation and sunshine duration were the major climatic factors regulating ET and GPP trends. It is concluded that human activities are the main drivers to the long term tendencies of water consumption and gross primary productivity in the NCP.
基金National Key Research and Development Program of China,No.2016YFC0401402National Natural Science Foundation of China,No.41471026
文摘This study applies a hydroeconomic optimization method for water resources management in the highly water stressed Haihe River basin. A multi-objective, multi-temporal deterministic hydroeconomic optimization model has been built to quantify the economic trade-offs and reveal "minimum cost strategies" when reducing groundwater abstraction to sustainable levels. A complex basin representation, with ～140,000 decision variables is formulated where each decision variable represents a flow-path from a water source to a sink. Available water sources are runoff generated by the sub-basins upstream the nine major surface water reservoirs, the inter-basin transfers from Yellow River and South to North Water Transfer Project(SNWTP) and the natural groundwater recharge to the three main groundwater aquifers. Water demands, i.e. sinks, are aggregated for each model sub-basin in categories of the major agricultural users, domestic, industrial and ecological water demands. Each demand is associated with a curtailment cost and groundwater abstraction with a pumping cost. Groundwater overdraft is constrained in each model scenario, ranging from unlimited overdraft in the plain area groundwater aquifer to sustainable abstractions over an 8-year period. Inflow upstream Yuqiao reservoir, and the inter-basin transfers from SNWTP and Yellow River are identified as the water resources with the highest increase in average shadow prices when limiting groundwater overdraft. An increase in inflow shadow prices of 37.5% indicates that these water sources will be most valuable if sustainable groundwater abstraction should be achieved. The shadow prices of water sources reveal when and where in the Haihe River basin users are curtailed if water resources are managed in the most optimal way. Average shadow prices of 1.6 yuan/m3 for all surface water sources in the sustainable abstraction scenarios shows that overdraft can be avoided by curtailment of users with a willingness-to-pay ≤1.6 yuan/m3. The shadow prices of the existing surface water res-ervoirs represented in the model shows that no costs can be saved from expanding their capacities. Finally, the cost of achieving sustainable groundwater abstraction with present water resource availability is found to be minimum 8.2 billion yuan/year.
基金National Key Basic Research Development Program of China No.2009CB421307 No.2010CB428404 National Natural Science Foundation of China No.41071024
文摘Evapotranspiration is one of the key components of hydrological processes. Assessing the impact of climate factors on evapotranspiration is helpful in understanding the impact of climate change on hydrological processes. In this paper, based on the daily meteorological data from 1960 to 2007 within and around the Aksu River Basin, reference evapotranspiration （RET） was estimated with the FAO Penman-Monteith method. The temporal and spatial variations of RET were analyzed by using ARCGIS and Mann-Kendall method. Multiple Regression Analysis was employed to attribute the effects of the variations of air temperature, solar radiation, relative humidity, vapour pressure and wind speed on RET. The results showed that average annual RET in the eastern plain area of the Aksu River Basin was about 1100 mm, which was nearly twice as much as that in the western mountainous area. The trend of annual RET had significant spatial variability. Annual RET was reduced significantly in the southeastern oasis area and southwestern plain area and increased slightly in the mountain areas. The amplitude of the change of RET reached the highest in summer, contributing most of the annual change of RET. Except in some high elevation areas where relative humidity predominated the change of the RET, the variations of wind velocity predominated the changes of RET almost throughout the basin. Taking Kuqa and Ulugqat stations as an example, the variations of wind velocity accounted for more than 50% of the changes of RET.
