Based on the investigation and analysis of protection and restoration of aquatic ecosystems in rivers and lakes of China, the ideas and measures of restoring aquatic ecosystems were proposed to build healthy aquatic e...Based on the investigation and analysis of protection and restoration of aquatic ecosystems in rivers and lakes of China, the ideas and measures of restoring aquatic ecosystems were proposed to build healthy aquatic ecosystems of rivers and lakes in China, such as setting scientific and clear goals, improving the standard adopted by wastewater treatment plants, controlling sources of pollutants and intercepting pollutants, collec- tion of blue-green algae, water transfer, dredging, reducing the quantity of blue-green algae, restoring reed wetlands on a large scale, combing dredging and base raise of restored reed wetlands, making full use of microorganisms, and implementing effective management, technology integra- tion and innovation.展开更多
The Xianshuihe-Anninghe fault extends SE–S and constitutes the southeastern margin of the Tibetan Plateau.However,the Dadu River which is associated with the fault does not flow following the path,but makes a 90º...The Xianshuihe-Anninghe fault extends SE–S and constitutes the southeastern margin of the Tibetan Plateau.However,the Dadu River which is associated with the fault does not flow following the path,but makes a 90ºturn within a distance of 1 km at Shimian,heading east,and joins the Yangtze River,finally flowing into the East China Sea.Adjacent to the abrupt turn,a low and wide pass near the Daqiao reservoir at Mianning separates the N–S course of the Dadu River from the headwater of the Anning River which then flows south into the Yunnan Province along the Anninghe fault.Therefore,many previous studies assumed southward flow of the paleo-Dadu River from the Shimian to the Anning River.However,evidences for the capture of the integrated N–S paleo-Dadu-Anning River,its timing,and causes are still insufficient.This study explored the paleo-drainage pattern of the Dadu and Anning Rivers based on bulk mineral and geochemical analyses of the large quantities of fluvial/lacustrine sediments along the trunk of the Dadu and Anning Rivers.Similar with sands in the modern Dadu River,the Xigeda sediments also exhibit a granitoid affinity with the bulk major mineral compositions of quartz(>50%),anorthite(about 10%),orthoclase(about 5%),muscovite(about 5%),and clinochlore(about 4%).Correspondingly,bulk major elements show high SiO_(2),with all samples>60%,and some of them>70%,low TiO_(2)(≤0.75%),P_(2)O_(5)(≤0.55%),FeO*(≤5%),and relatively high CaO(1.02%–8.51%),Na_(2)O(1.60%–2.52%),and K_(2)O(2.17%–2.71%),with a uniform REE patterns.Therefore,synthesizing all these results indicate that these lacustrine sediments have similar material sources,which are mainly derived from its course in the Songpan-Ganzi flysch block,implying that the paleo-Dadu originally flowed southward into the Anning River and provided materials to the Xigeda ancient lake.The rearrangement of the paleo-Dadu River appears to be closely related to the locally focused uplift driven by strong activities of the XianshuiheXiaojiang fault system.展开更多
Based on 2022 and 2023 hydrometric data and satellite images (Sentinel 2022, SPOT 2010), this study aims to present the Nokoué Lake and its channels’ re-cent hydromorphological characteristics. Integrating flow,...Based on 2022 and 2023 hydrometric data and satellite images (Sentinel 2022, SPOT 2010), this study aims to present the Nokoué Lake and its channels’ re-cent hydromorphological characteristics. Integrating flow, tributary morphology, and topography data determined specific power values along the axes studied. The values obtained range from 2.69 to 12.92 W/m2 for Ouémé River and 2.46 to 10.99 W/m2 for Sô River. The resulting water erosion on banks and bottoms is of linear, areolar, or gully and claw types. Lake bathymetry varies from -0.5 to -2.6 m (low flow period) and -1 to -4 m;in the Ouémé, Sô, and Totchè rivers, it varies from -5 m to -7 m, reaching -10 m at the Cotonou channel entrance (flood period). Bathymetric profiles reveal varied “U”, “V” and “Intermediate” bottom morphologies, influenced by erosion/sedimentation processes and human activities. The flow facies identified are lentic in the northern tributaries and lotic in the Cotonou and Totchè canals. Spatial analysis identified nine (09) thematic classes. In 2022, the surface area of the water body has increased from 274 km2 at low water to 280 km2 at high water, whereas in 2010 (a recent year of exceptional flooding), the surface area was 270 km2 at low water and 277 km2 at high water. Significant changes in land use are observed between 2010 and 2022. The floodplain area decreased slightly, from 421 km2 in 2010 (year of exceptional flooding) to 419 km2 in 2022. The evolution of land use shows a progressive expansion of the urban environment to the detriment of the natural environment. In the medium to long term, this trend could threaten the hydromorphological balance and even the existence of this important lagoon ecosystem.展开更多
The Qaidam Basin(QB)is a concentrated distribution area and chemical industrial bases of salt lakes in China.Lakes in the QB have been expanding during the past 20 years.Rapid lake expansion resulted in some considera...The Qaidam Basin(QB)is a concentrated distribution area and chemical industrial bases of salt lakes in China.Lakes in the QB have been expanding during the past 20 years.Rapid lake expansion resulted in some considerable scientific issues on the protection of salt lake resources and infrastructure,and monitoring of hydrological processes at the lake-basin scale.Although the spatial-temporal trends of lake changes on the Qinghai-Tibet Plateau(QTP)have been well documented,the underlying influencing mechanism and hydrogeological implications of rapid lake changes in the QB are not well understood.Three lakes in the northern QB were selected to investigate lake water level fluctuations on different time scales based on extensive in-situ monitoring and satellite observations.The influencing mechanism and hydrogeological implications of rapid changes of terminal lakes were discussed in combination with the reported increasing precipitation rate and mass balance of glaciers in the northern QTP.Results reveal the following:(1)the fluctuation pattern of Sugan Lake was asynchronous and out of phase with that of Xiao Qaidam and Toson lakes during the monitoring period;(2)Sugan Lake water rose gradually,and the rise interval was from late April to early July.In contrast,Xiao Qaidam and Toson lakes took on a rapid and steep rise,and the rise intervalwas from late July to September;(3)the influencing mechanisms for rapid lake fluctuations are controlled by different factors:glacier and snow melting with increasing temperature for Sugan Lake and increasing precipitation for Xiao Qaidam and Toson lakes;(4)in accordance with different intervals and influencing mechanisms of rapid lake expansions in the QB,hydrological risk precaution of lakes and corresponding river catchments was conducted in different parts of the basin.This study provided an important scientific basis for assessing the hydrological process and hydrological risk precaution,and protection of salt lake resources along with rapid lake expansions in the arid area.展开更多
This article deals with assessment of changes in ice cover duration and maximum ice cover thickness for the last three decades compared with the previous period by the example of observation data for 28 hydrometric st...This article deals with assessment of changes in ice cover duration and maximum ice cover thickness for the last three decades compared with the previous period by the example of observation data for 28 hydrometric stations on rivers and 10 hydrological stations on lakes. Estimations of homogeneity and trends of long term serious of above mentioned rivers and lakes ice regime characteristics for three time periods were carried out using Student and Fisher criteria. Assessment of changes in ice regime characteristics for the period 1980-2010 compared with the period of stationary climate (from the beginning of observations until 1979) using two methodological approaches was made. The results can be used for solving problems of economy branches adaptation in case of rivers and lakes used in winter conditions.展开更多
This article is concerned with assessment of changes in two critical characteristics of lake and river ice regime, namely ice cover duration and maximum ice thickness, in the period from the beginning of the 80s to th...This article is concerned with assessment of changes in two critical characteristics of lake and river ice regime, namely ice cover duration and maximum ice thickness, in the period from the beginning of the 80s to the present, which is characterized by higher temperatures in the Northern Hemisphere compared with the previous period. The above ice regime characteristics are often limiting factors in winter operation of lakes and rivers (navigation, hydraulic construction works in cold period, construction of ice roads etc.). Assessment of changes in ice characteristics of lakes and rivers has been made for 52 river and five lake gauging sites of the Asian part of Russia (APR) using long-term observation data from the Russian observing network. Long-term series of the above characteristics were divided into two periods: from 1955 to 1979 (the period of stationary climate) and from 1980 to 2014 (non-stationary climate) and assessed from the point of view of their homogeneity and trend significance by Student’s t-test. The research has found that at most of the sites in the APR, both ice cover duration and maximum ice thickness decreased during non-stationary climate period compared with the previous one. The greatest quantitative changes have occurred in the Eastern Siberia (average net decrease in ice cover duration amounted to 7 days.decade-1 and in maximum ice thickness-20 cm.decade-1) and in the Amur River basin (7 days.decade-1 and 17 cm.decade-1 respectively).展开更多
With China's economic development and population growth,China's ecological environment continues to deteriorate.The comprehensive ecosystem restoration of the Shichuan River aims to build an ecosystem containi...With China's economic development and population growth,China's ecological environment continues to deteriorate.The comprehensive ecosystem restoration of the Shichuan River aims to build an ecosystem containing"mountains,rivers,forests,farmland,lakes and grass"by determining scientific and reasonable thickness of foreign soil,pollution restoration,ecological reconstruction,safeguard measures,etc.It brings new vitality to local ecological environment remodeling and economic development.展开更多
In this paper,15 rivers and 10 lake reservoirs in the Liaohe River basin were taken as research objects. Based on six indexes: satisfaction situation of ecological water demand,standard-reaching rate of water quality ...In this paper,15 rivers and 10 lake reservoirs in the Liaohe River basin were taken as research objects. Based on six indexes: satisfaction situation of ecological water demand,standard-reaching rate of water quality in water function area,eutrophication index of lakes and reservoirs,longitudinal connectivity of rivers,reserve rate of important wetlands and status of important aquatic habitat,water ecological conditions of main rivers and lakes in the basin were evaluated. The results showed that the rivers with better ecology were mainly distributed in east mountainous area of Liaoning,such as the upper reaches of the Hunhe River and the Taizi River;the problems of water pollution,ecological water shortage and habitat shrinkage were widespread in the Liaohe River basin,and the situation of water ecological security in the Liaohe River basin still faced great pressure.展开更多
The report of the 19th National Congress of the Communist Party of China stated that it was necessary to establish and practice the concept that lucid waters and lush mountains are invaluable assets,treat the ecologic...The report of the 19th National Congress of the Communist Party of China stated that it was necessary to establish and practice the concept that lucid waters and lush mountains are invaluable assets,treat the ecological environment as life,and coordinate the management of mountains,rivers,forests,farmlands,lakes and grasslands.In recent years,China has organized a series of pilot projects for the ecological protection and restoration of mountains,rivers,forests,farmlands,lakes and grasslands,breaking the boundary between administrative divisions,departmental management and ecological elements,and implementing conservation and restoration oriented towards the improvement of ecosystem services,so as to solve the problem of the lack of overall planning for ecological protection and restoration projects and the separated management of ecological elements.This study systematically elaborated the theoretical basis and connotation characteristics of ecological protection and restoration of mountains,rivers,forests,farmlands,lakes and grasslands.It proposed the implementation path of ecological protection and restoration project of mountains,rivers,forests,farmlands,lakes and grasslands by taking the water source conservation area of Beijing-Tianjin-Hebei as a case,so as to provide reference for the implementation and decision-making management of ecological protection and restoration projects in various regions.展开更多
CAO Yu is famous for having been one ofChina’s greatest contemporary dramatists, butfew people know that Qianjiang is his home-town. Similarly, the Jianghan Oilfield is knownnationally as one of China’s ten major oi...CAO Yu is famous for having been one ofChina’s greatest contemporary dramatists, butfew people know that Qianjiang is his home-town. Similarly, the Jianghan Oilfield is knownnationally as one of China’s ten major oilfields. Whatis not widely known is that it is also located inQianjiang.展开更多
Taihu Lake is one of the five biggest lakes in China. Surface water samples from 26 sampling sites of Taihu Lake were collected. Furthermore wet chemical analysis (CODCr and BOD5) and measurement of three dimensiona...Taihu Lake is one of the five biggest lakes in China. Surface water samples from 26 sampling sites of Taihu Lake were collected. Furthermore wet chemical analysis (CODCr and BOD5) and measurement of three dimensional excitation-emission matrix (3DEEM) spectra in the laboratory have been conducted. Using parallel factor analysis (PARAFAC) model, three components of colored dissolved organic matter (CDOM) have been identified successfully, based on the analysis of 3DEEM data. The characteristics of the three components also have been described by comparing them to some components of CDOM, identified in earlier researches. Meanwhile, spatial variations of concentration for the three components in Taihu Lake have been analyzed, and the result indicates that the concentration of component 1 depends more on the situation of wastewater pollution and can be used as the indicator of wastewater pollution. The relationship between the concentrations of the three components and results of the wet chemical analysis show that none of the three components can be used as indicators of gross organic matter in water. However, the concentrations of all the three components have obvious linear relationships with the BOD5 value, especially for component 1 (r = 0.72878). Finally, the potential applications of the composition analysis based on 3DEEM and PARAFAC model in water quality monitoring have been illuminated.展开更多
Many moraines formed between Daduka and Chibai in the Tsangpo River valley since Middle Pleistocene. A prominent set of lacustrine and alluvial terraces on the valley margin along both the Tsangpo and Nyang Rivers for...Many moraines formed between Daduka and Chibai in the Tsangpo River valley since Middle Pleistocene. A prominent set of lacustrine and alluvial terraces on the valley margin along both the Tsangpo and Nyang Rivers formed during Quaternary glacial epoch demonstrate lakes were created by damming of the river. Research was conducted on the geological environment, contained sediments, spatial distribution, timing, and formation and destruction of these paleolakes. The lacustrine sediments 14C (10537±268 aBP at Linzhi Brick and Tile Factory, 22510±580 aBP and 13925±204 aBP at Bengga, 21096±1466 aBP at Yusong) and a series of ESR (electron spin resonance) ages at Linzhi town and previous data by other experts, paleolakes persisted for 691±305 kaBP middle Pleistocene ice age, 75-40 kaBP the early stage of last glacier, 27-8 kaBP Last Glacier Maximum (LGM), existence time of lakes gradually shorten represents glacial scale and dam moraine supply potential gradually cut down, paleolakes and dam scale also gradually diminished. This article calculated the average lacustrine sedimentary rate of Gega paleolake in LGM was 12.5 mm/a, demonstrates Mount Namjagbarwa uplifted strongly at the same time, the sedimentary rate of Gega paleolake is more larger than that of enclosed lakes of plateau inland shows the climatic variation of Mount Namjagbarwa is more larger and plateau margin uplifted more quicker than plateau inland. This article analyzed formation and decay cause about the Zelunglung glacier on the west flank of Mount Namjagbarwa got into the Tsangpo River valley and blocked it for tectonic and climatic factors. There is a site of blocking the valley from Gega to Chibai. This article according to moraines and lacustrine sediments yielded paleolakes scale: the lowest lake base altitude 2850 m, the highest lake surface altitude 3585 m, 3240 m and 3180 m, area 2885 km2, 820 km2 and 810 km2, lake maximum depth of 735 m, 390 m and 330 m. We disclose the reason that previous experts discovered there were different age moraines dividing line of altitude 3180 m at the entrance of the Tsangpo Grand Canyon is dammed lake erosive decay under altitude 3180 m moraines in the last glacier era covering moraines in the early ice age of late Pleistocene, top 3180 m in the last glacier moraine remained because ancient dammed lakes didn't erode it under 3180 m moraines in the early ice age of late Pleistocene exposed. The reason of the top elevation 3585 m moraines in the middle Pleistocene ice age likes that of altitude 3180 m. There were three times dammed lakes by glacier blocking the Tsangpo River during Quaternary glacial period. During other glacial and interglacial period the Zelunglung glacier often extended the valley but moraine supplemental speed of the dam was smaller than that of fluvial erosion and moraine movement, dam quickly disappeared and didn't form stable lake.展开更多
On the basis of the Taihu water resources assessment, an analysis of the importance and rationality of the water diversion from the Yangtz,e River to Taihu Lake in solving the water problem and establishing a harmonio...On the basis of the Taihu water resources assessment, an analysis of the importance and rationality of the water diversion from the Yangtz,e River to Taihu Lake in solving the water problem and establishing a harmonious eco-environment in the Taihu Basin is performed. The water quantity and water quality conjunctive dispatching 'decisi"ofi-makifig support system, which ensures flood control, water supply and eco-aimed dispatching, is built by combining the water diversion with flood control dispatching and strengthening water resources monitoring and forecasting. With the practice and effect assessment, measures such as setting the -integrated basin management format, further developing water diversion and improving the hydraulic engineering projects system and water monitoring system are proposed in order to maintain healthy rivers and guarantee the development of the economy and society in the Taihu Basin.展开更多
Gezhouba hydroproject was impounded and put into operation in 1981. In order to analyse the impact on the downstream river course, Jingjiang Hydrologic and Water Resources Survey Bureau of Changjiang Water Resources C...Gezhouba hydroproject was impounded and put into operation in 1981. In order to analyse the impact on the downstream river course, Jingjiang Hydrologic and Water Resources Survey Bureau of Changjiang Water Resources Commission has conducted prototype observation on the Yichang-Chenglingji river stretch. On basis of the observed data, the change in river regime and scour-sedimentation evolution and water surface profile below the dam are analysed systematically. The results show that the scouring of downstream river course mainly stretches from Yichang to Ouchikou, mainly occurring in 1980~1987; the scourring mainly takes place in the river channel and the water surface profile drops significantly in dry season,but not quite in high flood season.展开更多
Under increasing anthropogenic pressure,species with a previously contiguous distribution across their ranges have been reduced to small fragmented populations.The critically endangered Yangtze finless porpoise(Neopho...Under increasing anthropogenic pressure,species with a previously contiguous distribution across their ranges have been reduced to small fragmented populations.The critically endangered Yangtze finless porpoise(Neophocaena asiaeorientalis asiaeorientalis),once commonly observed in the Yangtze River-Poyang Lake junction,is now rarely seen in the river-lake corridor.In this study,static passive acoustic monitoring techniques were used to detect the biosonar activities of the Yangtze finless porpoise in this unique corridor.Generalized linear models were used to examine the correlation between these activities and anthropogenic impacts from the COVID-19 pandemic lockdown and boat navigation,as well as environmental variables,including hydrological conditions and light levels.Over approximately three consecutive years of monitoring(2020–2022),porpoise biosonar was detected during 93%of logged days,indicating the key role of the corridor for finless porpoise conservation.In addition,porpoise clicks were recorded in 3.80%of minutes,while feeding correlated buzzes were detected in 1.23%of minutes,suggesting the potential existence of localized,small-scale migration.Furthermore,both anthropogenic and environmental variables were significantly correlated with the diel,lunar,monthly,seasonal,and annual variations in porpoise biosonar activities.During the pandemic lockdown period,porpoise sonar detection showed a significant increase.Furthermore,a significant negative correlation was identified between the detection of porpoise click trains and buzzes and boat traffic intensity.In addition to water level and flux,daylight and moonlight exhibited significant correlations with porpoise biosonar activities,with markedly higher detections at night and quarter moon periods.Ensuring the spatiotemporal reduction of anthropogenic activities,implementing vessel speed restrictions(e.g.,during porpoise migration and feeding),and maintaining local natural hydrological regimes are critical factors for sustaining porpoise population viability.展开更多
As significant evidence of permafrost degradation,thermokarst lakes play an important role in the permafrost regions by regulating hydrology,ecology,and biogeochemistry.In the Sources Area of the Yellow River(SAYR),pe...As significant evidence of permafrost degradation,thermokarst lakes play an important role in the permafrost regions by regulating hydrology,ecology,and biogeochemistry.In the Sources Area of the Yellow River(SAYR),permafrost degradation has accelerated since the 1980s,and numerous thermokarst lakes have been discovered.In this paper,we use Sentinel-2 images to extract thermokarst lake boundaries and perform a regional-scale study on their geometry across the permafrost region in the SAYR.We also explored the spatiotemporal variations and potential drivers from the perspectives of the permafrost,climate,terrain and vegetation conditions.The results showed that there were 47,518 thermokarst lakes in 2021 with a total area of 190.22×106 m^(2),with an average size of 4,003.3 m^(2).The 44,928 ponds(≤10,000 m^(2))predominated the whole lake number(94.1%)but contributed to a small portion of the total lake area(28.8%).With 2,590 features(5.9%),small-sized(10,000 to 100,000 m^(2))and large-sized lakes(>100,000 m^(2))constituted up to 71.2%of the total lake area.Thermokarst lakes developed more significantly in warm permafrost regions than in cold permafrost areas;74.1%of lakes with a total area of 119.6×106 m^(2)(62.9%),were distributed in warm permafrost regions.Most thermokarst lakes were likely to develop within the elevation range of 4,500~4,800 m,on flat terrain(slope<10°),on SE and S aspects and in alpine meadow areas.The thermokarst lakes in the study region experienced significant shrinkage between 1990 and 2021,characterized by obvious lake drainage;the lake numbers decreased by 5418(56.1%),with a decreasing area of 58.63×106 m^(2)(49.0%).This shrinkage of the thermokarst lake area was attributable mainly to the intensified degradation of rich-ice permafrost thawing arising from continued climate warming,despite the wetting climatic trend.展开更多
Accurate winter wheat identification and phenology extraction are essential for field management and agricultural policy making. Here, we present mechanisms of winter wheat discrimination and phenological detection in...Accurate winter wheat identification and phenology extraction are essential for field management and agricultural policy making. Here, we present mechanisms of winter wheat discrimination and phenological detection in the Yellow River Delta(YRD) region using moderate resolution imaging spectroradiometer(MODIS) time-series data. The normalized difference vegetation index(NDVI) was obtained by calculating the surface reflectance in red and infrared. We used the Savitzky-Golay filter to smooth time series NDVI curves. We adopted a two-step classification to identify winter wheat. The first step was designed to mask out non-vegetation classes, and the second step aimed to identify winter wheat from other vegetation based on its phenological features. We used the double Gaussian model and the maximum curvature method to extract phenology. Due to the characteristics of the time-series profiles for winter wheat, a double Gaussian function method was selected to fit the temporal profile. A maximum curvature method was performed to extract phenological phases. Phenological phases such as the green-up, heading and harvesting phases were detected when the NDVI curvature exhibited local maximum values. The extracted phenological dates then were validated with records of the ground observations. The spatial patterns of phenological phases were investigated. This study concluded that, for winter wheat, the accuracy of classification is 87.07%, and the accuracy of planting acreage is 90.09%. The phenological result was comparable to the ground observation at the municipal level. The average green-up date for the whole region occurred on March 5, the average heading date occurred on May 9, and the average harvesting date occurred on June 5. The spatial distribution of the phenology for winter wheat showed a significant gradual delay from the southwest to the northeast. This study demonstrates the effectiveness of our proposed method for winter wheat classification and phenology detection.展开更多
Carbon dioxide(CO_(2))emissions from aquatic ecosystems are an important component of the karst carbon cycle process and also a key indicator for assessing the effect of karst carbon sinks.This paper reviewed the CO_(...Carbon dioxide(CO_(2))emissions from aquatic ecosystems are an important component of the karst carbon cycle process and also a key indicator for assessing the effect of karst carbon sinks.This paper reviewed the CO_(2)partial pressure(pCO_(2))and its diffusion flux(FCO_(2))in karst surface aquatic ecosystems,mainly rivers,lakes,and reservoirs,and their influencing factors summarized the methods for monitoring CO_(2)emissions in karst aquatic ecosystems and discussed their adaptation conditions in karst areas.The pCO_(2)and FCO_(2)decreased in the order of rivers>reservoirs>lakes,and the values in karst lakes were eventually significantly lower than those in global lakes.The pCO_(2)and FCO_(2)of karst aquatic ecosystems had patterns of variation with diurnal,seasonal,water depth and hydrological cycles,and spatial and temporal hetero-geneity.The sources of CO_(2)in karst waters are influenced by both internal and external sources,and the key spatial and temporal factors affecting the CO_(2)emissions from karst rivers,lakes,and reservoirs were determined in terms of physicochemical indicators,biological factors,and bio-genic elements;additionally,the process of human activity interference on CO_(2)emissions was discussed.Finally,a conceptual model illustrating the impacts of urban devel-opment,agriculture,mining,and dam construction on the CO_(2)emissions at the karst surface aquatic ecosystem is presented.Meanwhile,based on the disadvantages existing in current research,we proposed several important research fields related to CO_(2)emissions from karst surface aquatic ecosystems.展开更多
The analysis of the 3 stages' (1988,1996,2000) variation of land-cover is performed according to Thematic Mapper (TM) and Enhancement Thematic Mapper(ETM) satellite image by combining ground GIS database with G...The analysis of the 3 stages' (1988,1996,2000) variation of land-cover is performed according to Thematic Mapper (TM) and Enhancement Thematic Mapper(ETM) satellite image by combining ground GIS database with GPS field collected data in the area of Xiaowan-Dachaoshan Reservoirs of Lancangjiang River cascaded Hydropower Area. Consequently, the land-cover is divided into five subclasses, namely water, paddy field and wetland, bare dryland and sparse shrub, secondary forest and density forest. The result showed that the areas of bare land, upland and secondary forest decreased in 1988-1996, whereas from 1996 to 2000, water body and density forest keep invariability while the areas of paddy field and wetland, bare dryland and sparse scrub increasing and the area of secondary forest decrease; Features of reciprocal transformation between density forest and other type of land-cover had two points, i.e. secondary forest, bare dryland and sparse shrub converted to density forest; and density forest converted to secondary forest and paddy field and wetland. It reflects the dynamic variation of density forest; the area which slope less than 8° and greater than 15° shows bigger variation, however, less change in 8°-15°.展开更多
Groundwater is an important water resource in Haihe River basin,North China.The number of aquifers that appear to be declining under conditions of groundwater overdraft is increasing.To effectively manage the water re...Groundwater is an important water resource in Haihe River basin,North China.The number of aquifers that appear to be declining under conditions of groundwater overdraft is increasing.To effectively manage the water resources,there is a strong scientific need to analyze the net use of this important water resource and to quantify the water rights allocation for improved understanding of the future water展开更多
文摘Based on the investigation and analysis of protection and restoration of aquatic ecosystems in rivers and lakes of China, the ideas and measures of restoring aquatic ecosystems were proposed to build healthy aquatic ecosystems of rivers and lakes in China, such as setting scientific and clear goals, improving the standard adopted by wastewater treatment plants, controlling sources of pollutants and intercepting pollutants, collec- tion of blue-green algae, water transfer, dredging, reducing the quantity of blue-green algae, restoring reed wetlands on a large scale, combing dredging and base raise of restored reed wetlands, making full use of microorganisms, and implementing effective management, technology integra- tion and innovation.
基金financially supported by the Natural Science Foundation of China(41941016,42072240,41830217)Ministry of Science and Technology of China(2019QZKK0901,2021FY100101)+2 种基金Key Special Project for Introduced Talents Team of the Southern Marine Science and Engineering Guangdong Laboratory(GML2019ZD0201)China Geological Survey(DD20221630)Special Fund of the Institute of Geophysics,China Earthquake Administration(DQJB20B21).
文摘The Xianshuihe-Anninghe fault extends SE–S and constitutes the southeastern margin of the Tibetan Plateau.However,the Dadu River which is associated with the fault does not flow following the path,but makes a 90ºturn within a distance of 1 km at Shimian,heading east,and joins the Yangtze River,finally flowing into the East China Sea.Adjacent to the abrupt turn,a low and wide pass near the Daqiao reservoir at Mianning separates the N–S course of the Dadu River from the headwater of the Anning River which then flows south into the Yunnan Province along the Anninghe fault.Therefore,many previous studies assumed southward flow of the paleo-Dadu River from the Shimian to the Anning River.However,evidences for the capture of the integrated N–S paleo-Dadu-Anning River,its timing,and causes are still insufficient.This study explored the paleo-drainage pattern of the Dadu and Anning Rivers based on bulk mineral and geochemical analyses of the large quantities of fluvial/lacustrine sediments along the trunk of the Dadu and Anning Rivers.Similar with sands in the modern Dadu River,the Xigeda sediments also exhibit a granitoid affinity with the bulk major mineral compositions of quartz(>50%),anorthite(about 10%),orthoclase(about 5%),muscovite(about 5%),and clinochlore(about 4%).Correspondingly,bulk major elements show high SiO_(2),with all samples>60%,and some of them>70%,low TiO_(2)(≤0.75%),P_(2)O_(5)(≤0.55%),FeO*(≤5%),and relatively high CaO(1.02%–8.51%),Na_(2)O(1.60%–2.52%),and K_(2)O(2.17%–2.71%),with a uniform REE patterns.Therefore,synthesizing all these results indicate that these lacustrine sediments have similar material sources,which are mainly derived from its course in the Songpan-Ganzi flysch block,implying that the paleo-Dadu originally flowed southward into the Anning River and provided materials to the Xigeda ancient lake.The rearrangement of the paleo-Dadu River appears to be closely related to the locally focused uplift driven by strong activities of the XianshuiheXiaojiang fault system.
文摘Based on 2022 and 2023 hydrometric data and satellite images (Sentinel 2022, SPOT 2010), this study aims to present the Nokoué Lake and its channels’ re-cent hydromorphological characteristics. Integrating flow, tributary morphology, and topography data determined specific power values along the axes studied. The values obtained range from 2.69 to 12.92 W/m2 for Ouémé River and 2.46 to 10.99 W/m2 for Sô River. The resulting water erosion on banks and bottoms is of linear, areolar, or gully and claw types. Lake bathymetry varies from -0.5 to -2.6 m (low flow period) and -1 to -4 m;in the Ouémé, Sô, and Totchè rivers, it varies from -5 m to -7 m, reaching -10 m at the Cotonou channel entrance (flood period). Bathymetric profiles reveal varied “U”, “V” and “Intermediate” bottom morphologies, influenced by erosion/sedimentation processes and human activities. The flow facies identified are lentic in the northern tributaries and lotic in the Cotonou and Totchè canals. Spatial analysis identified nine (09) thematic classes. In 2022, the surface area of the water body has increased from 274 km2 at low water to 280 km2 at high water, whereas in 2010 (a recent year of exceptional flooding), the surface area was 270 km2 at low water and 277 km2 at high water. Significant changes in land use are observed between 2010 and 2022. The floodplain area decreased slightly, from 421 km2 in 2010 (year of exceptional flooding) to 419 km2 in 2022. The evolution of land use shows a progressive expansion of the urban environment to the detriment of the natural environment. In the medium to long term, this trend could threaten the hydromorphological balance and even the existence of this important lagoon ecosystem.
基金Supported by the Second Tibetan Plateau Scientific Expedition and Research Program(No.2019 QZKK 0805)the National Natural Science Foundation of China(No.U 21 A 2018)the Foundation of Department of Qinghai Science&Technology(No.2020-ZJ-T 06)。
文摘The Qaidam Basin(QB)is a concentrated distribution area and chemical industrial bases of salt lakes in China.Lakes in the QB have been expanding during the past 20 years.Rapid lake expansion resulted in some considerable scientific issues on the protection of salt lake resources and infrastructure,and monitoring of hydrological processes at the lake-basin scale.Although the spatial-temporal trends of lake changes on the Qinghai-Tibet Plateau(QTP)have been well documented,the underlying influencing mechanism and hydrogeological implications of rapid lake changes in the QB are not well understood.Three lakes in the northern QB were selected to investigate lake water level fluctuations on different time scales based on extensive in-situ monitoring and satellite observations.The influencing mechanism and hydrogeological implications of rapid changes of terminal lakes were discussed in combination with the reported increasing precipitation rate and mass balance of glaciers in the northern QTP.Results reveal the following:(1)the fluctuation pattern of Sugan Lake was asynchronous and out of phase with that of Xiao Qaidam and Toson lakes during the monitoring period;(2)Sugan Lake water rose gradually,and the rise interval was from late April to early July.In contrast,Xiao Qaidam and Toson lakes took on a rapid and steep rise,and the rise intervalwas from late July to September;(3)the influencing mechanisms for rapid lake fluctuations are controlled by different factors:glacier and snow melting with increasing temperature for Sugan Lake and increasing precipitation for Xiao Qaidam and Toson lakes;(4)in accordance with different intervals and influencing mechanisms of rapid lake expansions in the QB,hydrological risk precaution of lakes and corresponding river catchments was conducted in different parts of the basin.This study provided an important scientific basis for assessing the hydrological process and hydrological risk precaution,and protection of salt lake resources along with rapid lake expansions in the arid area.
文摘This article deals with assessment of changes in ice cover duration and maximum ice cover thickness for the last three decades compared with the previous period by the example of observation data for 28 hydrometric stations on rivers and 10 hydrological stations on lakes. Estimations of homogeneity and trends of long term serious of above mentioned rivers and lakes ice regime characteristics for three time periods were carried out using Student and Fisher criteria. Assessment of changes in ice regime characteristics for the period 1980-2010 compared with the period of stationary climate (from the beginning of observations until 1979) using two methodological approaches was made. The results can be used for solving problems of economy branches adaptation in case of rivers and lakes used in winter conditions.
文摘This article is concerned with assessment of changes in two critical characteristics of lake and river ice regime, namely ice cover duration and maximum ice thickness, in the period from the beginning of the 80s to the present, which is characterized by higher temperatures in the Northern Hemisphere compared with the previous period. The above ice regime characteristics are often limiting factors in winter operation of lakes and rivers (navigation, hydraulic construction works in cold period, construction of ice roads etc.). Assessment of changes in ice characteristics of lakes and rivers has been made for 52 river and five lake gauging sites of the Asian part of Russia (APR) using long-term observation data from the Russian observing network. Long-term series of the above characteristics were divided into two periods: from 1955 to 1979 (the period of stationary climate) and from 1980 to 2014 (non-stationary climate) and assessed from the point of view of their homogeneity and trend significance by Student’s t-test. The research has found that at most of the sites in the APR, both ice cover duration and maximum ice thickness decreased during non-stationary climate period compared with the previous one. The greatest quantitative changes have occurred in the Eastern Siberia (average net decrease in ice cover duration amounted to 7 days.decade-1 and in maximum ice thickness-20 cm.decade-1) and in the Amur River basin (7 days.decade-1 and 17 cm.decade-1 respectively).
文摘With China's economic development and population growth,China's ecological environment continues to deteriorate.The comprehensive ecosystem restoration of the Shichuan River aims to build an ecosystem containing"mountains,rivers,forests,farmland,lakes and grass"by determining scientific and reasonable thickness of foreign soil,pollution restoration,ecological reconstruction,safeguard measures,etc.It brings new vitality to local ecological environment remodeling and economic development.
基金Supported by the National Water Resources Protection Plan of the Ministry of Water Resources。
文摘In this paper,15 rivers and 10 lake reservoirs in the Liaohe River basin were taken as research objects. Based on six indexes: satisfaction situation of ecological water demand,standard-reaching rate of water quality in water function area,eutrophication index of lakes and reservoirs,longitudinal connectivity of rivers,reserve rate of important wetlands and status of important aquatic habitat,water ecological conditions of main rivers and lakes in the basin were evaluated. The results showed that the rivers with better ecology were mainly distributed in east mountainous area of Liaoning,such as the upper reaches of the Hunhe River and the Taizi River;the problems of water pollution,ecological water shortage and habitat shrinkage were widespread in the Liaohe River basin,and the situation of water ecological security in the Liaohe River basin still faced great pressure.
文摘The report of the 19th National Congress of the Communist Party of China stated that it was necessary to establish and practice the concept that lucid waters and lush mountains are invaluable assets,treat the ecological environment as life,and coordinate the management of mountains,rivers,forests,farmlands,lakes and grasslands.In recent years,China has organized a series of pilot projects for the ecological protection and restoration of mountains,rivers,forests,farmlands,lakes and grasslands,breaking the boundary between administrative divisions,departmental management and ecological elements,and implementing conservation and restoration oriented towards the improvement of ecosystem services,so as to solve the problem of the lack of overall planning for ecological protection and restoration projects and the separated management of ecological elements.This study systematically elaborated the theoretical basis and connotation characteristics of ecological protection and restoration of mountains,rivers,forests,farmlands,lakes and grasslands.It proposed the implementation path of ecological protection and restoration project of mountains,rivers,forests,farmlands,lakes and grasslands by taking the water source conservation area of Beijing-Tianjin-Hebei as a case,so as to provide reference for the implementation and decision-making management of ecological protection and restoration projects in various regions.
文摘CAO Yu is famous for having been one ofChina’s greatest contemporary dramatists, butfew people know that Qianjiang is his home-town. Similarly, the Jianghan Oilfield is knownnationally as one of China’s ten major oilfields. Whatis not widely known is that it is also located inQianjiang.
基金Project supported by the Knowledge Innovation Project of ChineseAcademy of Sciences (No. KGCX2-SW-111).
文摘Taihu Lake is one of the five biggest lakes in China. Surface water samples from 26 sampling sites of Taihu Lake were collected. Furthermore wet chemical analysis (CODCr and BOD5) and measurement of three dimensional excitation-emission matrix (3DEEM) spectra in the laboratory have been conducted. Using parallel factor analysis (PARAFAC) model, three components of colored dissolved organic matter (CDOM) have been identified successfully, based on the analysis of 3DEEM data. The characteristics of the three components also have been described by comparing them to some components of CDOM, identified in earlier researches. Meanwhile, spatial variations of concentration for the three components in Taihu Lake have been analyzed, and the result indicates that the concentration of component 1 depends more on the situation of wastewater pollution and can be used as the indicator of wastewater pollution. The relationship between the concentrations of the three components and results of the wet chemical analysis show that none of the three components can be used as indicators of gross organic matter in water. However, the concentrations of all the three components have obvious linear relationships with the BOD5 value, especially for component 1 (r = 0.72878). Finally, the potential applications of the composition analysis based on 3DEEM and PARAFAC model in water quality monitoring have been illuminated.
基金supported by Project No.1212011120185 sponsored by China Geological Survey
文摘Many moraines formed between Daduka and Chibai in the Tsangpo River valley since Middle Pleistocene. A prominent set of lacustrine and alluvial terraces on the valley margin along both the Tsangpo and Nyang Rivers formed during Quaternary glacial epoch demonstrate lakes were created by damming of the river. Research was conducted on the geological environment, contained sediments, spatial distribution, timing, and formation and destruction of these paleolakes. The lacustrine sediments 14C (10537±268 aBP at Linzhi Brick and Tile Factory, 22510±580 aBP and 13925±204 aBP at Bengga, 21096±1466 aBP at Yusong) and a series of ESR (electron spin resonance) ages at Linzhi town and previous data by other experts, paleolakes persisted for 691±305 kaBP middle Pleistocene ice age, 75-40 kaBP the early stage of last glacier, 27-8 kaBP Last Glacier Maximum (LGM), existence time of lakes gradually shorten represents glacial scale and dam moraine supply potential gradually cut down, paleolakes and dam scale also gradually diminished. This article calculated the average lacustrine sedimentary rate of Gega paleolake in LGM was 12.5 mm/a, demonstrates Mount Namjagbarwa uplifted strongly at the same time, the sedimentary rate of Gega paleolake is more larger than that of enclosed lakes of plateau inland shows the climatic variation of Mount Namjagbarwa is more larger and plateau margin uplifted more quicker than plateau inland. This article analyzed formation and decay cause about the Zelunglung glacier on the west flank of Mount Namjagbarwa got into the Tsangpo River valley and blocked it for tectonic and climatic factors. There is a site of blocking the valley from Gega to Chibai. This article according to moraines and lacustrine sediments yielded paleolakes scale: the lowest lake base altitude 2850 m, the highest lake surface altitude 3585 m, 3240 m and 3180 m, area 2885 km2, 820 km2 and 810 km2, lake maximum depth of 735 m, 390 m and 330 m. We disclose the reason that previous experts discovered there were different age moraines dividing line of altitude 3180 m at the entrance of the Tsangpo Grand Canyon is dammed lake erosive decay under altitude 3180 m moraines in the last glacier era covering moraines in the early ice age of late Pleistocene, top 3180 m in the last glacier moraine remained because ancient dammed lakes didn't erode it under 3180 m moraines in the early ice age of late Pleistocene exposed. The reason of the top elevation 3585 m moraines in the middle Pleistocene ice age likes that of altitude 3180 m. There were three times dammed lakes by glacier blocking the Tsangpo River during Quaternary glacial period. During other glacial and interglacial period the Zelunglung glacier often extended the valley but moraine supplemental speed of the dam was smaller than that of fluvial erosion and moraine movement, dam quickly disappeared and didn't form stable lake.
基金supported by the Innovation Programmes of the Ministry of Water Resources (Grant No. SCXC2002-09)
文摘On the basis of the Taihu water resources assessment, an analysis of the importance and rationality of the water diversion from the Yangtz,e River to Taihu Lake in solving the water problem and establishing a harmonious eco-environment in the Taihu Basin is performed. The water quantity and water quality conjunctive dispatching 'decisi"ofi-makifig support system, which ensures flood control, water supply and eco-aimed dispatching, is built by combining the water diversion with flood control dispatching and strengthening water resources monitoring and forecasting. With the practice and effect assessment, measures such as setting the -integrated basin management format, further developing water diversion and improving the hydraulic engineering projects system and water monitoring system are proposed in order to maintain healthy rivers and guarantee the development of the economy and society in the Taihu Basin.
文摘Gezhouba hydroproject was impounded and put into operation in 1981. In order to analyse the impact on the downstream river course, Jingjiang Hydrologic and Water Resources Survey Bureau of Changjiang Water Resources Commission has conducted prototype observation on the Yichang-Chenglingji river stretch. On basis of the observed data, the change in river regime and scour-sedimentation evolution and water surface profile below the dam are analysed systematically. The results show that the scouring of downstream river course mainly stretches from Yichang to Ouchikou, mainly occurring in 1980~1987; the scourring mainly takes place in the river channel and the water surface profile drops significantly in dry season,but not quite in high flood season.
基金supported by Science and Technology Service Network Initiative Program of the Chinese Academy of Sciencesthe National Natural Science Foundation of China (41806197)the Exploratory Program of the Natural Science Foundation of Zhejiang Province (ZX2023000154)。
文摘Under increasing anthropogenic pressure,species with a previously contiguous distribution across their ranges have been reduced to small fragmented populations.The critically endangered Yangtze finless porpoise(Neophocaena asiaeorientalis asiaeorientalis),once commonly observed in the Yangtze River-Poyang Lake junction,is now rarely seen in the river-lake corridor.In this study,static passive acoustic monitoring techniques were used to detect the biosonar activities of the Yangtze finless porpoise in this unique corridor.Generalized linear models were used to examine the correlation between these activities and anthropogenic impacts from the COVID-19 pandemic lockdown and boat navigation,as well as environmental variables,including hydrological conditions and light levels.Over approximately three consecutive years of monitoring(2020–2022),porpoise biosonar was detected during 93%of logged days,indicating the key role of the corridor for finless porpoise conservation.In addition,porpoise clicks were recorded in 3.80%of minutes,while feeding correlated buzzes were detected in 1.23%of minutes,suggesting the potential existence of localized,small-scale migration.Furthermore,both anthropogenic and environmental variables were significantly correlated with the diel,lunar,monthly,seasonal,and annual variations in porpoise biosonar activities.During the pandemic lockdown period,porpoise sonar detection showed a significant increase.Furthermore,a significant negative correlation was identified between the detection of porpoise click trains and buzzes and boat traffic intensity.In addition to water level and flux,daylight and moonlight exhibited significant correlations with porpoise biosonar activities,with markedly higher detections at night and quarter moon periods.Ensuring the spatiotemporal reduction of anthropogenic activities,implementing vessel speed restrictions(e.g.,during porpoise migration and feeding),and maintaining local natural hydrological regimes are critical factors for sustaining porpoise population viability.
基金supported by the Natural Science Foundation of Qinghai Province,China(No.2021-ZJ940Q)the Open Project of State Key Laboratory of Plateau Ecology and Agriculture,Qinghai University(No.2022-ZZ-02)。
文摘As significant evidence of permafrost degradation,thermokarst lakes play an important role in the permafrost regions by regulating hydrology,ecology,and biogeochemistry.In the Sources Area of the Yellow River(SAYR),permafrost degradation has accelerated since the 1980s,and numerous thermokarst lakes have been discovered.In this paper,we use Sentinel-2 images to extract thermokarst lake boundaries and perform a regional-scale study on their geometry across the permafrost region in the SAYR.We also explored the spatiotemporal variations and potential drivers from the perspectives of the permafrost,climate,terrain and vegetation conditions.The results showed that there were 47,518 thermokarst lakes in 2021 with a total area of 190.22×106 m^(2),with an average size of 4,003.3 m^(2).The 44,928 ponds(≤10,000 m^(2))predominated the whole lake number(94.1%)but contributed to a small portion of the total lake area(28.8%).With 2,590 features(5.9%),small-sized(10,000 to 100,000 m^(2))and large-sized lakes(>100,000 m^(2))constituted up to 71.2%of the total lake area.Thermokarst lakes developed more significantly in warm permafrost regions than in cold permafrost areas;74.1%of lakes with a total area of 119.6×106 m^(2)(62.9%),were distributed in warm permafrost regions.Most thermokarst lakes were likely to develop within the elevation range of 4,500~4,800 m,on flat terrain(slope<10°),on SE and S aspects and in alpine meadow areas.The thermokarst lakes in the study region experienced significant shrinkage between 1990 and 2021,characterized by obvious lake drainage;the lake numbers decreased by 5418(56.1%),with a decreasing area of 58.63×106 m^(2)(49.0%).This shrinkage of the thermokarst lake area was attributable mainly to the intensified degradation of rich-ice permafrost thawing arising from continued climate warming,despite the wetting climatic trend.
基金supported by the National Natural Science Foundation of China (41471335, 41271407)the National Remote Sensing Survey and Assessment of Eco-Environment Change between 2000 and 2010, China (STSN-1500)+2 种基金the National Key Technologies R&D Program of China during the 12th Five-Year Plan period (2013BAD05B03)the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA05050601)the International Science and Technology (S&T) Cooperation Program of China (2012DFG22050)
文摘Accurate winter wheat identification and phenology extraction are essential for field management and agricultural policy making. Here, we present mechanisms of winter wheat discrimination and phenological detection in the Yellow River Delta(YRD) region using moderate resolution imaging spectroradiometer(MODIS) time-series data. The normalized difference vegetation index(NDVI) was obtained by calculating the surface reflectance in red and infrared. We used the Savitzky-Golay filter to smooth time series NDVI curves. We adopted a two-step classification to identify winter wheat. The first step was designed to mask out non-vegetation classes, and the second step aimed to identify winter wheat from other vegetation based on its phenological features. We used the double Gaussian model and the maximum curvature method to extract phenology. Due to the characteristics of the time-series profiles for winter wheat, a double Gaussian function method was selected to fit the temporal profile. A maximum curvature method was performed to extract phenological phases. Phenological phases such as the green-up, heading and harvesting phases were detected when the NDVI curvature exhibited local maximum values. The extracted phenological dates then were validated with records of the ground observations. The spatial patterns of phenological phases were investigated. This study concluded that, for winter wheat, the accuracy of classification is 87.07%, and the accuracy of planting acreage is 90.09%. The phenological result was comparable to the ground observation at the municipal level. The average green-up date for the whole region occurred on March 5, the average heading date occurred on May 9, and the average harvesting date occurred on June 5. The spatial distribution of the phenology for winter wheat showed a significant gradual delay from the southwest to the northeast. This study demonstrates the effectiveness of our proposed method for winter wheat classification and phenology detection.
基金supported by the National Natural Science Foundation of China(42163003)the Project of Talent Base in Guizhou Province(No.RCJD2018-21).
文摘Carbon dioxide(CO_(2))emissions from aquatic ecosystems are an important component of the karst carbon cycle process and also a key indicator for assessing the effect of karst carbon sinks.This paper reviewed the CO_(2)partial pressure(pCO_(2))and its diffusion flux(FCO_(2))in karst surface aquatic ecosystems,mainly rivers,lakes,and reservoirs,and their influencing factors summarized the methods for monitoring CO_(2)emissions in karst aquatic ecosystems and discussed their adaptation conditions in karst areas.The pCO_(2)and FCO_(2)decreased in the order of rivers>reservoirs>lakes,and the values in karst lakes were eventually significantly lower than those in global lakes.The pCO_(2)and FCO_(2)of karst aquatic ecosystems had patterns of variation with diurnal,seasonal,water depth and hydrological cycles,and spatial and temporal hetero-geneity.The sources of CO_(2)in karst waters are influenced by both internal and external sources,and the key spatial and temporal factors affecting the CO_(2)emissions from karst rivers,lakes,and reservoirs were determined in terms of physicochemical indicators,biological factors,and bio-genic elements;additionally,the process of human activity interference on CO_(2)emissions was discussed.Finally,a conceptual model illustrating the impacts of urban devel-opment,agriculture,mining,and dam construction on the CO_(2)emissions at the karst surface aquatic ecosystem is presented.Meanwhile,based on the disadvantages existing in current research,we proposed several important research fields related to CO_(2)emissions from karst surface aquatic ecosystems.
文摘The analysis of the 3 stages' (1988,1996,2000) variation of land-cover is performed according to Thematic Mapper (TM) and Enhancement Thematic Mapper(ETM) satellite image by combining ground GIS database with GPS field collected data in the area of Xiaowan-Dachaoshan Reservoirs of Lancangjiang River cascaded Hydropower Area. Consequently, the land-cover is divided into five subclasses, namely water, paddy field and wetland, bare dryland and sparse shrub, secondary forest and density forest. The result showed that the areas of bare land, upland and secondary forest decreased in 1988-1996, whereas from 1996 to 2000, water body and density forest keep invariability while the areas of paddy field and wetland, bare dryland and sparse scrub increasing and the area of secondary forest decrease; Features of reciprocal transformation between density forest and other type of land-cover had two points, i.e. secondary forest, bare dryland and sparse shrub converted to density forest; and density forest converted to secondary forest and paddy field and wetland. It reflects the dynamic variation of density forest; the area which slope less than 8° and greater than 15° shows bigger variation, however, less change in 8°-15°.
文摘Groundwater is an important water resource in Haihe River basin,North China.The number of aquifers that appear to be declining under conditions of groundwater overdraft is increasing.To effectively manage the water resources,there is a strong scientific need to analyze the net use of this important water resource and to quantify the water rights allocation for improved understanding of the future water