The direct dumping of solid wastes into the rivers, discharge of industrial effluents together with direct discharge of domestic sewage have excessively polluted the major rivers Bagmati and Bish-numati. Groundwater a...The direct dumping of solid wastes into the rivers, discharge of industrial effluents together with direct discharge of domestic sewage have excessively polluted the major rivers Bagmati and Bish-numati. Groundwater along these river corridors is also affected from pollution of these rivers. Two major rivers: Bagmati and Bishnumati and shallow tube wells adjacent to these rivers were monitored for 2 years. Samples were analysed for the stable isotopes of hydrogen and oxygen (δD and δ18O) and selected physico-chemical parameters to investigate the possible interrelationship between river water and shallow groundwater along these river corridors. The physico-chemical values revealed that shallow groundwater and river water along the Bishnumati River corridor were heavily mineralized due to direct discharge of sewage wastes into this river. The isotope compositions of river water and shallow groundwater clustered together revealed possible interrelationship between them. Some of the isotopic compositions of groundwater and river water deviated below the Local Meteoric Water Line (LMWL) indicating that the water has undergone evaporation. The isotopic and chemical results suggested possible interrelationship between river water and groundwater. Fractional contribution of the river water to groundwater was calculated based on isotopic data using mass balance approach. Results showed that shallow groundwater SG1, along the Bagmati River corridor (in September 2013), was composed of approximately 30% - 40% Bagmati River water. Similarly, shallow groundwater SG5 of Bishnumati River corridor (in September 2013), was composed of approximately 45% - 50% river water. This result indicated that high portion of river water mixed-up with adjoining shallow groundwater along the river corridors. Further, the mix-up of the river water with groundwater can be harmful when rivers are polluted. These findings can be useful for a better understanding of hydrogeological processes at the river-aquifer interface and eventually benefit water management of the Kathmandu Valley in future.展开更多
Study on hydroclimatological changes in the mountainous river basins has attracted great interest in recent years. Changes in temperature, precipitation and river discharge pattern could be considered as indicators of...Study on hydroclimatological changes in the mountainous river basins has attracted great interest in recent years. Changes in temperature, precipitation and river discharge pattern could be considered as indicators of hydroclimatological changes of the river basins. In this study, the temperatures （maximum and minimum）, precipitation, and discharge data from 1980 to 2009 were used to detect the hydroclimatological changes in the Bagmati River Basin, Nepal. Simple linear regression and Mann-Kendall test statistic were used to examine the significant trend of temperature, precipitation, and discharge. Increasing trend of temperature was found in all seasons, although the change rate was different in different seasons for both minimum and maximum temperatures. However, stronger warming trend was found in maximum temperature in comparison to the minimum in the whole basin. Both precipitation and discharge trend were increasing in the pre-monsoon season, but decreasing in the post-monsoon season. The significant trend of precipitation could not be observed in winter, although discharge trend was decreasing. Furthermore, the intensity of peak discharge was increasing, though there was not an obvious change in the intensity of maximum precipitation events. It is expected that all these changes have effects on agriculture, hydropower plant, and natural biodiversity in the mountainous river basin of Nepal.展开更多
The Siwalik Belt is a frontal fold\|thrust belt of the Himalayas and composed of thick sequence of foreland basin sediments derived from the Himalayas during the last 15 to 17 million years.From this Miocene belt in t...The Siwalik Belt is a frontal fold\|thrust belt of the Himalayas and composed of thick sequence of foreland basin sediments derived from the Himalayas during the last 15 to 17 million years.From this Miocene belt in the central Nepal,we discovered exotic thrust packages of the Middle Proterozoic rocks,which has been regarded as the Siwalik Group or post\|collisional sediments correlatable with the Subathu or Murree Formation in India.The thrust belt,called the Bagmati Belt,is narrowly distributed in the Siwalik Belt,22km to the north of the Main Frontal Thrust (MFT or HFF) that is an active fault and considered to be the deformation front of the Himalayan orogen.The Main Boundary Thrust (MBT) which separates the Siwalik Belt from the Lesser Himalayan Belt runs 7km to the north of the thrust packages.Within the belt,tectonic slices of 400m to 1km in thickness are repeated three to five times due to thrusts,sandwiching a thin slice of the Siwalik beds.The thrust package consists of the pre\|Siwalik sedimetary rocks and sills of dolerite,and named as the Bagmati Group.The thickness is only about 800m due to tectonic repition by thrust,although the group has been considered to be a continuous sequence attaining 2200m in thickness.We divided the Bagmati Group into three formations,each of which shows an upward\|coarsening and thickening sequence of 200 to 350m in thickness.All sequence is composed of red\|brown orthoquartzite,pink quartzite,micaceous shale and thin sandstone interbed and rhythmite,mottled hematite and hematitic pisolite.We interpret that the Bagmati Group was deposited in shallow lacustrine and desert environments.展开更多
文摘The direct dumping of solid wastes into the rivers, discharge of industrial effluents together with direct discharge of domestic sewage have excessively polluted the major rivers Bagmati and Bish-numati. Groundwater along these river corridors is also affected from pollution of these rivers. Two major rivers: Bagmati and Bishnumati and shallow tube wells adjacent to these rivers were monitored for 2 years. Samples were analysed for the stable isotopes of hydrogen and oxygen (δD and δ18O) and selected physico-chemical parameters to investigate the possible interrelationship between river water and shallow groundwater along these river corridors. The physico-chemical values revealed that shallow groundwater and river water along the Bishnumati River corridor were heavily mineralized due to direct discharge of sewage wastes into this river. The isotope compositions of river water and shallow groundwater clustered together revealed possible interrelationship between them. Some of the isotopic compositions of groundwater and river water deviated below the Local Meteoric Water Line (LMWL) indicating that the water has undergone evaporation. The isotopic and chemical results suggested possible interrelationship between river water and groundwater. Fractional contribution of the river water to groundwater was calculated based on isotopic data using mass balance approach. Results showed that shallow groundwater SG1, along the Bagmati River corridor (in September 2013), was composed of approximately 30% - 40% Bagmati River water. Similarly, shallow groundwater SG5 of Bishnumati River corridor (in September 2013), was composed of approximately 45% - 50% river water. This result indicated that high portion of river water mixed-up with adjoining shallow groundwater along the river corridors. Further, the mix-up of the river water with groundwater can be harmful when rivers are polluted. These findings can be useful for a better understanding of hydrogeological processes at the river-aquifer interface and eventually benefit water management of the Kathmandu Valley in future.
基金supported by the Chinese Academy of Sciences (CAS),China,and TWAS,the Academy of Sciences for the Developing World,3240240226
文摘Study on hydroclimatological changes in the mountainous river basins has attracted great interest in recent years. Changes in temperature, precipitation and river discharge pattern could be considered as indicators of hydroclimatological changes of the river basins. In this study, the temperatures （maximum and minimum）, precipitation, and discharge data from 1980 to 2009 were used to detect the hydroclimatological changes in the Bagmati River Basin, Nepal. Simple linear regression and Mann-Kendall test statistic were used to examine the significant trend of temperature, precipitation, and discharge. Increasing trend of temperature was found in all seasons, although the change rate was different in different seasons for both minimum and maximum temperatures. However, stronger warming trend was found in maximum temperature in comparison to the minimum in the whole basin. Both precipitation and discharge trend were increasing in the pre-monsoon season, but decreasing in the post-monsoon season. The significant trend of precipitation could not be observed in winter, although discharge trend was decreasing. Furthermore, the intensity of peak discharge was increasing, though there was not an obvious change in the intensity of maximum precipitation events. It is expected that all these changes have effects on agriculture, hydropower plant, and natural biodiversity in the mountainous river basin of Nepal.
文摘The Siwalik Belt is a frontal fold\|thrust belt of the Himalayas and composed of thick sequence of foreland basin sediments derived from the Himalayas during the last 15 to 17 million years.From this Miocene belt in the central Nepal,we discovered exotic thrust packages of the Middle Proterozoic rocks,which has been regarded as the Siwalik Group or post\|collisional sediments correlatable with the Subathu or Murree Formation in India.The thrust belt,called the Bagmati Belt,is narrowly distributed in the Siwalik Belt,22km to the north of the Main Frontal Thrust (MFT or HFF) that is an active fault and considered to be the deformation front of the Himalayan orogen.The Main Boundary Thrust (MBT) which separates the Siwalik Belt from the Lesser Himalayan Belt runs 7km to the north of the thrust packages.Within the belt,tectonic slices of 400m to 1km in thickness are repeated three to five times due to thrusts,sandwiching a thin slice of the Siwalik beds.The thrust package consists of the pre\|Siwalik sedimetary rocks and sills of dolerite,and named as the Bagmati Group.The thickness is only about 800m due to tectonic repition by thrust,although the group has been considered to be a continuous sequence attaining 2200m in thickness.We divided the Bagmati Group into three formations,each of which shows an upward\|coarsening and thickening sequence of 200 to 350m in thickness.All sequence is composed of red\|brown orthoquartzite,pink quartzite,micaceous shale and thin sandstone interbed and rhythmite,mottled hematite and hematitic pisolite.We interpret that the Bagmati Group was deposited in shallow lacustrine and desert environments.
