A decade of variation of COD in the Changjiang River (Yangtze River) and its variation trend analysis

Abstract

The average annual value of COD (chemical oxygen demand) fluxes of the Changjiang River (Yangtze River) and its main tributaries in the past decade (i.e., 1991-2000), has been evaluated. Based on the data from the Datong Hydrological Station (DHS), it was found that the Dongting Lake drainage basin contributed the greatest water discharge (35.8%) and COD flux (48.3%) among the main tributary drainage basins, followed by the Poyang Lake drainage basin with the contributions of 15.4% and 19.3% respectively. By the end of the year of 2000, COD flux in the Changjiang River rose by almost 45% relative to that in the year of 1991, reaching about 1941000 ton/a at DHS. Statistical analysis revealed that industrial wastewater discharge, as well as COD in it, was found decreasing in the same period, due to the gradual reinforcement of environmental management. Moreover, correlation analysis indicated that non-point pollution from agriculture and increasing discharge of domestic sewages caused by rapid growth of population along the Changjiang River drainage valley should be responsible for the high COD. Furthermore, with the current trend of population growth and agricultural development in this basin, water quality of the Changjiang River, in terms of COD level, is going to deteriorate in the near future. Thus, the rational applications of fertilizers and pesticides in agriculture and the proper treatment of domestic sewages before they are discharged would be the most concerned controlling parameters.

Experimental Research on Preventing Root-Stones Loss with Tetrahedron-Like Concrete Penetrating Frames

“…The concrete triangular pyramid belongs to a deformation body of concrete tetrahedron, which can maintain three feet to cling to the riverbed surface in any case. It has the advantage of good stability, good anti-erosion and good energy dissipation action, and its size can be calculated and determined according to the local conditions of water flow and river bed [3]. The large scale experiment was carried out in Nanguotou and Madu dangerous projects in 1997～1998, and the test block is 98.3cm high, the top part of foot has the diameter of 30cm, the volume of 0.27m 3 and the weight of 648kg.…”

“…During the period of production operation of water and sediment regulation in 2007, other parts of dam 15 have been in greater danger, and the volume of emergency repair stones is 1176m 3 , and the total investment is 201,500 yuan, but the dam sections protected by tetrahedron-like concrete penetrating frames are without danger.…”

Assessing the Impact of Vegetation Variation, Climate and Human Factors on the Streamflow Variation of Yarlung Zangbo River with the Corrected Budyko Equation

“…Liu et al [16] found that both climate and land use changes can lead to runoff change trends in the YZR. Wang et al [17] used the trend analysis and wavelet analysis methods to analyze the annual runoff change trend in Yangcun and Nuxia stations on the YZR from 1970 to 2012. The results showed that runoff presented an insignificant growth trend.…”

The Numerical Simulation of Aerated Cavity Length and Negative Pressure on Stepped Spillway Combined with Y-Shape Asymmetrical Flaring Gate Pier

“…Morever,which give full play to the energy dissipation rate advantage for small unit overcurrent on stepped spillway to solve the energy dissipation problem [1] . Aeration can be effectively reduced cavitation damage, the buildings of flow with high head are generally set the aerator, prompting water aeration, thus reduced cavitation damage [2] . Take advantage of transverse contraction and vertical diffusion of asymmetric flaring gate pier and form a sheet longitudinally opened water tongue and aerated cavity between the stepped surface and the free jet which can realize fully aerated.…”