Chao River Research Articles

Estimation of daily actual evapotranspiration from remotely sensed data under complex terrain over the upper Chao river basin in North China

Daily actual evapotranspiration over the upper Chao river basin in North China on 23 June 2005 was estimated based on the Surface Energy Balance Algorithm for Land (SEBAL), in which the parameterization schemes for calculating the instantaneous solar radiation and daily integrated radiation were improved by accounting for the variations in slope and azimuth of land surface and terrain shadow in mountainous areas. The evapotranspiration (ET) estimated from satellite data in this study for the whole watershed ranges from 0 mm to 7.3 mm day−1 with a mean of 3.4 mm day−1, which was validated by Penman–Monteith approaches for water body and paddy land. The comparison of ET estimates for a wide range of land cover types reflected distinct mechanisms of energy partition and water removal of various land cover types, showing differences in the spatial distribution pattern of ET, which could be not only the reflection but also the driving force of advection and local circulation that may violate the surface energy balance equation in the vertical direction. The spatial variation in daily solar radiation and ET estimates under the complex terrain of forest land were elaborated and evaluated by exploring the relationship between ET estimates and elevations for wood land and grass land. In addition, the utility and limitations of SEBAL's applicability to watersheds with various land cover types and complex terrain were analysed.

Analysis on the phytoplankton and water quality in eastern and western Miyun Reservoir

密云水库被围堰隔为东、西两个库区．由于1999年以来华北地区的连续干旱，水库蓄水量迅速下降，两库区水体交换很少，相对稳定．2001年至2002年的调研结果显示，东库区比西库区BOD₅、TN、TP、Fe、浮游藻类细胞密度分别高出16．7%、40．2%、46．7%、161．1%和41．8%，TSI_m显示西库区的营养程度低于东库区，主要原因是:(1)西库区水体深于东库区，自净能力相对较强．(2)东库区以氮、磷为主的植物营养物的污染大于西库区；(3)由于潮河(东库区的主要入库河流)流域数座小铁矿的污染，东库区铁含量大于西库区．东库区水体中铁的浓度在适合浮游藻类生长的范围内，对浮游藻类，特别是蓝藻(Cyanophyta)的增殖有促进作用．有效地防治密云水库水体富营养化，应在统筹规划、分步实施的基础上，把防治的重点放在潮河流域．;The Miyun Reservoir could be separated into two parts by enclosing dam. The water quantity has been reduced rapidly due to dry climate since 1999. During 2001-2002 , the study on the water quality and the phytoplankton was carried out. The results were as follows:BOD₅ , TN, TP, Fe and cells density of phytoplankton in east region were 16.7% , 40. 2% , 46.7% , 161.1% , 41.8% higher than those in west part ;The water quality of west part was better than that of east region. The main causes of water quality difference between two reservoir parts were :( 1 ) The water depth and its buffer capability of west region was bigger than that of east part ;(2) The pollution in Chao river valley was more than it in Bai river valley;(3) Because of several iron mines'contamination, the iron concentration of east region was higher than that of west region, whereas the iron concentration of east part was suitable to phytoplankton growth, especially Cyanophyta. In order to control eutrophycation efficiently, we proposed an emphasis on Chao river valley basing on a carefully designed plan and step-by-step implementation.