The Revised Universal Soil Loss Equation （RUSLE） was applied to assess the spatial distribution and dynamic properties of soil loss with geographic information system （GIS） and remote sensing （RS） technologies. ...The Revised Universal Soil Loss Equation （RUSLE） was applied to assess the spatial distribution and dynamic properties of soil loss with geographic information system （GIS） and remote sensing （RS） technologies. To improve the accuracy of soil-erosion estimates, a new C-factor estimation model was developed based on land cover and time series normalized difference vegetation index （NDVI） datasets. The new C-factor was then applied in the RUSLE to integrate rainfall, soil, vegetation, and topography data of different periods, and thus monitor the distribution of soil erosion patterns and their dynamics during a 3o-year period of the upstream watershed of Miynn Reservoir （UWMR）, China. The results showed that the new C-factor estimation method, which considers land cover status and dynamics, and explicitly incorporates within-land cover variability, was more rational, quantitative, and reliable. An average annual soil loss in UWMR of 25.68, 21.04, and 16.8o t ha-1 a-1 was estimated for 1990, 2000 and 2010, respectively, corroborated by comparing spatial and temporal variation in sediment yield. Between 2000 and 2010, a 1.38% average annual increase was observed in the area of lands that lost less than 5 t ha-1 a^-1, while during 1990-2000 such lands only increased on average by o.46%. Areas that classified as severe, very severe and extremely severe accounted for 5.68% of the total UWMR in 2010, and primarily occurred in dry areas or grasslands of sloping fields. The reason for the change in rate of soil loss is explained by an increased appreciation of soil conservation by developers and planners. Moreover,we recommend that UWMR watershed adopt further conservation measures such as terraced plowing of dry land, afforestation, or grassland enclosures as part of a concerted effort to reduce on-going soil erosion.展开更多
This paper focuses on analysis of salinity distribution along Red River and its main branches to determine and limit effects of salinity intrusion under variable scenarios for outlet discharge from upstream reservoirs...This paper focuses on analysis of salinity distribution along Red River and its main branches to determine and limit effects of salinity intrusion under variable scenarios for outlet discharge from upstream reservoirs and the tidal magnitude under global climate change effects. The effect of outlet discharge from upstream reservoirs, which generates flow in droughty months, is considered as upstream input condition for salinity intrusion. The sea level rising phenomenon is represented by scenarios according to prediction of the Intergovernmental Panel on Climate Change （IPCC）. The lateral flow and the rainfall in dry season are neglected in the process of simulation. MIKE 11, ID river model software by DHI （Danish Hydraulic Institute）, is used to simulate the processes of salt water intrusion from the river mouths to the upstream of the river in consideration the effect of the Sea Level Rise phenomenon and the operation of existing reservoirs and those under construction. The results indicate that salinity intrusion length from river mouth depends on the estuary characteristics, discharges from upper reservoirs and tidal phases （low and high tides）. With the safe salinity concentration for agriculture and livestock is 4 psu, the study shows that the length of intruded salt in Red River is about 40km from the river mouth, in otherwise, the effect of salinity intrusion in Thai Binh river is negligible. The Sea Level Rise phenomenon has inconsiderable affects on salinity intrusion processes in Red River System. The influence of outlet discharges from upstream reservoirs has also negligible affects on prevent salinity intrusion from the sea. According to the results of the study, reasonable water resources utilization and appropriate reservoir operation approaches in the drought will be studied to protect the crop and aquaculture from salinity intrusion.展开更多
基金supported by the National Natural Science Foundation of China (Grant No.41101399)the open fund of State Key Laboratory of Remote Sensing ScienceJointly Sponsored by the Institute of Remote Sensing Applications of Chinese Academy of Sciences and Beijing Normal University,China
文摘The Revised Universal Soil Loss Equation （RUSLE） was applied to assess the spatial distribution and dynamic properties of soil loss with geographic information system （GIS） and remote sensing （RS） technologies. To improve the accuracy of soil-erosion estimates, a new C-factor estimation model was developed based on land cover and time series normalized difference vegetation index （NDVI） datasets. The new C-factor was then applied in the RUSLE to integrate rainfall, soil, vegetation, and topography data of different periods, and thus monitor the distribution of soil erosion patterns and their dynamics during a 3o-year period of the upstream watershed of Miynn Reservoir （UWMR）, China. The results showed that the new C-factor estimation method, which considers land cover status and dynamics, and explicitly incorporates within-land cover variability, was more rational, quantitative, and reliable. An average annual soil loss in UWMR of 25.68, 21.04, and 16.8o t ha-1 a-1 was estimated for 1990, 2000 and 2010, respectively, corroborated by comparing spatial and temporal variation in sediment yield. Between 2000 and 2010, a 1.38% average annual increase was observed in the area of lands that lost less than 5 t ha-1 a^-1, while during 1990-2000 such lands only increased on average by o.46%. Areas that classified as severe, very severe and extremely severe accounted for 5.68% of the total UWMR in 2010, and primarily occurred in dry areas or grasslands of sloping fields. The reason for the change in rate of soil loss is explained by an increased appreciation of soil conservation by developers and planners. Moreover,we recommend that UWMR watershed adopt further conservation measures such as terraced plowing of dry land, afforestation, or grassland enclosures as part of a concerted effort to reduce on-going soil erosion.
文摘This paper focuses on analysis of salinity distribution along Red River and its main branches to determine and limit effects of salinity intrusion under variable scenarios for outlet discharge from upstream reservoirs and the tidal magnitude under global climate change effects. The effect of outlet discharge from upstream reservoirs, which generates flow in droughty months, is considered as upstream input condition for salinity intrusion. The sea level rising phenomenon is represented by scenarios according to prediction of the Intergovernmental Panel on Climate Change （IPCC）. The lateral flow and the rainfall in dry season are neglected in the process of simulation. MIKE 11, ID river model software by DHI （Danish Hydraulic Institute）, is used to simulate the processes of salt water intrusion from the river mouths to the upstream of the river in consideration the effect of the Sea Level Rise phenomenon and the operation of existing reservoirs and those under construction. The results indicate that salinity intrusion length from river mouth depends on the estuary characteristics, discharges from upper reservoirs and tidal phases （low and high tides）. With the safe salinity concentration for agriculture and livestock is 4 psu, the study shows that the length of intruded salt in Red River is about 40km from the river mouth, in otherwise, the effect of salinity intrusion in Thai Binh river is negligible. The Sea Level Rise phenomenon has inconsiderable affects on salinity intrusion processes in Red River System. The influence of outlet discharges from upstream reservoirs has also negligible affects on prevent salinity intrusion from the sea. According to the results of the study, reasonable water resources utilization and appropriate reservoir operation approaches in the drought will be studied to protect the crop and aquaculture from salinity intrusion.
