Water Quantity And Water Quality Characteristics Of Xiangjiang River Basin

Xiangjiang is the "Mother River" of Hunan Province,which is the main source of domestic water,agricultural irrigation water,drinking water,industrial water,sewage and shipping and so on.With the development of economy,the water quantity of Xiangjiang basin is uneven and the water resource pollution is more and more serious,which affects the ecological environment of Xiangjiang River Basin,and causes more water resources problems.Therefore,it is significant to study the water quantity,water quality and ecological environment of Xiangjiang River Basin in Xiangjiang.In this study,2011?2015 Xiangjiang River main stream upstream(Yongzhou hydrological station,HengYang Railway Station),middle(Zhuzhou hydrological station,Xiangtan hydrological station,Changsha hydrological station)and downstream(Yueyang hydrological station)water quantity and water quality data of long-term observations and self monitoring as the basis,analyzed the change characteristics of water quantity and water quality,water quality comprehensive evaluation and fuzzy mathematics method is used to map overlap method,discusses the present situation of ecological environment of Xiangjiang basin and puts forward protection measures.The conclusions are as follows:(1)Xiangjiang water characteristics:annual precipitation of 1200?1400 mm,with an average annual runoff of 3100.04 m3/s,with an average annual water level of M,with an average annual evaporation of 656 mm,with an average annual sediment load of 1.14 × 107t.The upper middle and lower reaches of the precipitation had no significant difference(P ? 0.01),the same trend,irregular unimodal,uneven distribution of rainfall during the year,the rainy season accounted for most of the annual rainfall.There was significant difference between the lower and upper and middle reaches.There was a positive correlation between rainfall and runoff and water level.(2)The sediment concentration in the upper reaches of the river is small,and the bed load is mainly granular,and the sediment concentration in the middle reaches of the river is gradually increased,reaching 0.1?0.2 kg/m3,and the suspended sediment is mainly composed of particles.The uneven time of precipitation and the uneven space of runoff increase the risk of flooding in Xiangjiang basin.(3)Xiangjiang water quality index of physical and chemical characteristics:from the time point of view,the middle reaches of the ammonia nitrogen(NH3N)concentration is higher than that of upstream and downstream,but decreased significantly in 2012,of which 2012?2013 years decreased most significantly,the decline rate of 19%.In the year of the change,the 4?11 concentration in the month of NH3N changed little,which was lower than 1.00 mg/L,and the concentration of NH3N increased in May,in the year of July and in the year of,which indicated that there was a certain influence on the concentration of ammonia nitrogen.The concentration of TP in the upper reaches of the 2011?2013 showed an upward trend in 2013,and the highest concentration of 0.09 mg/L occurred in the year of 2013.In the year of,the concentration began to decline sharply in the year to the end of the year,and the concentration of TP was only 0.03 mg/L in the upper reaches of the year of 66.66%.Changes in the year,from 4 to June in the middle and lower reaches of the average concentration of TP higher than in other months,this is mainly because of the increasing precipitation intensity associated with frequent agricultural activities,resulting in a large number of phosphorus with surface runoff in Xiangjiang caused.The TP concentration in the middle reaches the highest value in November,when the Xiangjiang river basin is in the low water period,Xiangjiang is mainly affected by point source pollution,and the concentration of TP in the middle reaches is higher than other places.The permanganate index(CODmn)decreased gradually from around 2013.One of the most obvious is the upstream 2013?2015 and downstream 2014?2015 years,the upper reaches of the average decline rate of 12%decline;downstream decline rate of 17%.The CODmn of the Xiangjiang river basin is between 1.425?3.001 mg/L,the level is in the surface water environment quality standard II class and above,conforms to the water quality standard.The pH value of pH showed a downward trend during the period from 2011 to 2015,and the pH value of the upper and lower reaches increased firstly and then decreased steadily after 2014.The pH values were stable between 7.5 and 8,and the overall change was not significant.The dissolved oxygen(DO)mainly affects the water purification capacity,from the perspective of space,the dissolved oxygen concentration decreased in 6?8 months,the upper reaches of Xiangjiang River downstream water purification capacity than high,weak middle water purification capacity.(4)To evaluate the water quality in Xiangjiang,150 indicators measured,because the pH value of the dimensionless,not the classification,the 120 index for grading most of the II class,accounting for 48%of the total;individual factor pollution in III index,accounting for 16%of the total,the main pollution indicators or CODmn I index and NH3N;which accounted for 34%of the total;in 2011 and 2014 in Hengyang section of NH3N concentration in the surface water environmental quality index belongs to V type water,accounting for 2%of the total.On the whole,the Xiangjiang river water quality there are still some problems,although compared to the previous pollutants have eased,but some areas pollution is still serious,especially in the middle reaches of the region,if we don't pay more attention,the Xiangjiang river water quality deterioration may exist.