An investigation was conducted to study problems of determining a reasonable percentage for ecological water-use in the Haihe River Basin of China. Three key aspects for the ecological water requirement （EWR） were a...An investigation was conducted to study problems of determining a reasonable percentage for ecological water-use in the Haihe River Basin of China. Three key aspects for the ecological water requirement （EWR） were analyzed, involving i） the EWR for river system, ii） the EWR for wetlands and lakes, and iii） the EWR for discharge into the sea to maintain the estuary ecological balance of the Haihe River. The Montana method and related water level-flow relationships, and the statistic approach based on hydrological records were applied to estimate different components of EWR. The results showed that the total ecological water demand in the region, was about 3.47-14.56 billion m^3. Considering flow regime change and uncertainty, the ecological water demand could be estimated by the hydrological frequency approach. Preliminary analysis showed that for different annual runoff under the frequencies of 20%, 50%, 75% and 95%, the ecological water demand approached 12%-50%, 18%-74%, 24%-103%, 35%-148% and 16%-66%, respectively. By further analysis to balance ecological water-use and socioeconomic water-use, the rational percentage of ecological water-use was estimated as 35%-74%, that provides useful information to judge whether the allocation of water resources is reasonable, and was proved to be satisfactory by comparing with the practical condition.展开更多
Knowledge of the soil water characteristic curve is fundamental for understanding unsaturated soils.The objective of this work was to find scanning hysteresis loops of two fine textured soils at water potentials below...Knowledge of the soil water characteristic curve is fundamental for understanding unsaturated soils.The objective of this work was to find scanning hysteresis loops of two fine textured soils at water potentials below wilting point.This was done by equilibration over NaCl solutions with water potentials of-6.6 to-18.8 MPa at 25℃.When cycled repeatedly through a series of potentials in the range noted previously both soils exhibited a hysteresis effect.The experimental differences in water content between the drying and wetting soils at the same water potential were much too large to be accounted for by failure to allow sufficient time to attain equilibrium as predicted by the exponential decay model.The wetting versus drying differences were relatively small,however,at only 4 mg g-1 or less in absolute terms and about 3% of the mean of wetting and drying,in relative terms.Hysteresis should be a consideration when modeling biological and physical soil processes at water contents below the wilting point,where small differences in water content result in large potential energy changes.展开更多
Through the long-term plot studies on the precipitation distribution in the evergreen broad-leaved forest ecosystem in Hangzhou for two years, it was indicated that the pattern of precipitation distribution included l...Through the long-term plot studies on the precipitation distribution in the evergreen broad-leaved forest ecosystem in Hangzhou for two years, it was indicated that the pattern of precipitation distribution included larger amounts of penetration water and stemflow and a lower amount of interception water. The results revealed that the main factors to infulence the percentages of penetration and stemflow were the air temperature and the leaf area of the forest. The quantity of seepage through the litter layer was much larger than that through the soil layers which decreased sharply with soil depth. The output of water from the ecosystem by surface runoff and deep infiltration through the soil was much lower, only being 5.20 percent of the rainfall, while the water evapotranspiration loss was as large as more than 90 percent of it. The losses by the soil evaporation and plant evapotranspiration were the largest part of output in this forest ecosystem.展开更多
Chinese Forest Ecosystem Research Network, established in late 1950s and directly constructedand administered by the Science and Technology Department of State Forestry Administration of China,is a large ecology resea...Chinese Forest Ecosystem Research Network, established in late 1950s and directly constructedand administered by the Science and Technology Department of State Forestry Administration of China,is a large ecology research network focuses on long-term ecosystem fixed-observation. It embodies 15 sitesthat represent diverse ecosystems and research priorities, including 6 state-level sites. CFERN Officecoordinates communications, network publications, and research-planning activities. CFERN uses theadvanced ground and spatial observation technologies such as RS, GPS, GIS to study the structure,functional laws and feedback mechanism of Chinese forest ecosystem, as well as its effects on Chinassocial and economic development. The main tasks carried out by CFERN are: (1) construction of thedatabase on the structure and functions of Chinese forest ecosystem and its ecological environmentalfactors; (2) the database construction of forest resources, ecological environment, water resources andrelated social economy in both regional and national scales; (3) the establishment of an evaluation systemof forest ecological effects in Chinas main drainage areas; (4) the establishment of a forest environmentmonitoring network and a dynamic prediction and alarm system.展开更多
基金Project supported by the Natural Science Foundation of China (No. 50279049)the Knowledge Innovation Key Project of the Chinese Academy of Sciences (Nos. CX10G-E01-08 and KZCX2-SW-317)the National Challenging Program of Science and Technology of China (No. 2004BA610A-01).
文摘An investigation was conducted to study problems of determining a reasonable percentage for ecological water-use in the Haihe River Basin of China. Three key aspects for the ecological water requirement （EWR） were analyzed, involving i） the EWR for river system, ii） the EWR for wetlands and lakes, and iii） the EWR for discharge into the sea to maintain the estuary ecological balance of the Haihe River. The Montana method and related water level-flow relationships, and the statistic approach based on hydrological records were applied to estimate different components of EWR. The results showed that the total ecological water demand in the region, was about 3.47-14.56 billion m^3. Considering flow regime change and uncertainty, the ecological water demand could be estimated by the hydrological frequency approach. Preliminary analysis showed that for different annual runoff under the frequencies of 20%, 50%, 75% and 95%, the ecological water demand approached 12%-50%, 18%-74%, 24%-103%, 35%-148% and 16%-66%, respectively. By further analysis to balance ecological water-use and socioeconomic water-use, the rational percentage of ecological water-use was estimated as 35%-74%, that provides useful information to judge whether the allocation of water resources is reasonable, and was proved to be satisfactory by comparing with the practical condition.
文摘Knowledge of the soil water characteristic curve is fundamental for understanding unsaturated soils.The objective of this work was to find scanning hysteresis loops of two fine textured soils at water potentials below wilting point.This was done by equilibration over NaCl solutions with water potentials of-6.6 to-18.8 MPa at 25℃.When cycled repeatedly through a series of potentials in the range noted previously both soils exhibited a hysteresis effect.The experimental differences in water content between the drying and wetting soils at the same water potential were much too large to be accounted for by failure to allow sufficient time to attain equilibrium as predicted by the exponential decay model.The wetting versus drying differences were relatively small,however,at only 4 mg g-1 or less in absolute terms and about 3% of the mean of wetting and drying,in relative terms.Hysteresis should be a consideration when modeling biological and physical soil processes at water contents below the wilting point,where small differences in water content result in large potential energy changes.
基金Project supported by the Laboratory of Material Cycling in Pedosphere, Institute of Soil Science, Chinese Academy of Sciences.
文摘Through the long-term plot studies on the precipitation distribution in the evergreen broad-leaved forest ecosystem in Hangzhou for two years, it was indicated that the pattern of precipitation distribution included larger amounts of penetration water and stemflow and a lower amount of interception water. The results revealed that the main factors to infulence the percentages of penetration and stemflow were the air temperature and the leaf area of the forest. The quantity of seepage through the litter layer was much larger than that through the soil layers which decreased sharply with soil depth. The output of water from the ecosystem by surface runoff and deep infiltration through the soil was much lower, only being 5.20 percent of the rainfall, while the water evapotranspiration loss was as large as more than 90 percent of it. The losses by the soil evaporation and plant evapotranspiration were the largest part of output in this forest ecosystem.
文摘Chinese Forest Ecosystem Research Network, established in late 1950s and directly constructedand administered by the Science and Technology Department of State Forestry Administration of China,is a large ecology research network focuses on long-term ecosystem fixed-observation. It embodies 15 sitesthat represent diverse ecosystems and research priorities, including 6 state-level sites. CFERN Officecoordinates communications, network publications, and research-planning activities. CFERN uses theadvanced ground and spatial observation technologies such as RS, GPS, GIS to study the structure,functional laws and feedback mechanism of Chinese forest ecosystem, as well as its effects on Chinassocial and economic development. The main tasks carried out by CFERN are: (1) construction of thedatabase on the structure and functions of Chinese forest ecosystem and its ecological environmentalfactors; (2) the database construction of forest resources, ecological environment, water resources andrelated social economy in both regional and national scales; (3) the establishment of an evaluation systemof forest ecological effects in Chinas main drainage areas; (4) the establishment of a forest environmentmonitoring network and a dynamic prediction and alarm system.
