| With the development of regional economic and society,the problems about water has been coming into attention around the world,a series of serious problems,such as water scarcity,heavily water pollution,increased water disasters and so on,has become increasingly prominent.As the resident basic material security of living and production,once the water environment has problems,these will have wide covering range,serious impact and of long duration the negative effects,meanwhile,the problems of water environment would severely threaten the water ecosystem security,becoming a huge obstacle for the sound development of regional social economic and virtuous circle of environmental system.Recently,the water environment and ecological problems of river basins has been attracting the attention from scholars.At home and abroad,mass progresses have been obtained in theory and practice of water environment change and water ecosystem security.Lots of researches show that the water ecosystem suffers serious damage is mainly due to the water environment change,which affect the ability of the biosphere to sustain life.The study in this paper breached the traditional evaluation research of water environment change and water ecosystem security,selecting the representative factors of water environment in the study area and screening out the indexes can fully explain the characteristics of water ecosystem,and then improved the traditional research methods,established mathematical model,in-depth analyzing the impact of water environment change on the water ecosystem security in the temporal and spatial scales.The could provide technical support and theoretical basis for the improvement of the regional water environment and the protection of the water ecosystem,and supply scientific basis and practical reference for the water resources sustainable development and utilization of Songhua river basin water environment governance and water ecosystem protection.In this paper,Songhua river basin in Harbin(from Sanjiazi to Daliangzi)was chosen as the study area,and the daily flow monitoring data within the study area derived from Songhua river Harbin hydrological station(Laowantou station)between 2005 and 2014 as the basic data;the linear tendency estimate model,the cumulative departure method and the Mann-Kendall nonparametric test method were used to analyze the intra-annual and inter-annual variation characteristics of basin flow.6 indexes of dissolved oxygen,potassium permanganate index,chemical oxygen demand(COD),five-day biochemical oxygen demand(BOD5)and ammonia nitrogen and fecal coliform,which appear more often in industry and agriculture,were selected to explore the water’s quality variation laws of two water functional areas of Songhua river basin in Harbin in recent ten years with the methods of the linear tendency estimate model,the Spearman rank correlation test analysis and the Mann-Kendall nonparametric test method.Principal component analysis and factor analysis were used to study the structure of the monitoring data of each water quality indexes in the study area,finding out the water environment typical pollutant in the study area.The specific pollutant water zone assimilative capacity of two secondary water function zones,contaminants landscape recreational water area and East River bridges sewage control area in Songhua River Harbin,respectively represented by Second Water Source and Cement Plant.Taking the social and economic factors such as the urban population,per capita income,GDP,the output value of primary industry,secondary industry output value,the tertiary industry output value from 2005 to 2014 as the driving force,the correlational analysis method was employed to conduct the driving force analysis to the change of each water environment factor in the study area.The change trend of the water environment factors in the next 5 years(2015-2019)in the study area was forecasted using the time series analysis method.The indexes monitoring data from 2005 to 2014 gained from Songhua river Harbin hydrological station was selected to analyze the hydrological change trend in time dimension.For the differences of regional in study area,5 indexes that can fully reflect the hydrology,water quality,biology,basin geomorphology,human disturbance of study area was screened out,calculating the weight of each index,namely hydrology,water quality,biology,habitat and human activity based on the improved AHP method.Combined with the present situation of research area,the security state of water ecosystem from 2005 to 2014 in the study area was evaluated using the fuzzy math method.Water depth,flow velocity,dissolved oxygen,potassium permanganate index,chemical oxygen demand(COD),five-day biochemical oxygen demand(BOD5),ammonia nitrogen and fecal coliform was selected as the water environment factors,the structure indexes of phytoplankton and zooplankton species’ community having change indicative function for water ecosystem as the water ecosystem factors,and the Spearman rank correlation coefficient was made use of to seek the correlation of water environment change and water ecosystem change,analyzing the influence of water quantity,water quality and assimilative capacity on the water ecosystem qualitatively and quantitatively.The relationship between specific pollutant and the structure of phytoplankton and zooplankton species’ community was analyzed with the monadic regressive analysis,exploring its impact on the water ecosystem,and according to the measured data in the study area,the comprehensive state early warning of the water ecosystem was made with the hierarchical fuzzy comprehensive evaluation method.On the strength of the water environment change characteristics and the water ecosystem security features in the study area,the study in-depth analyzed the impact of water environment change on the water ecosystem security of the study area.For the water environment and water ecosystem of the study area,some specific measures were proposed about water environment management and protection of water ecosystem.Though the study,we can get the conclusions:(1)The result of water quantity analysis in the study area shows that the index non-uniform coefficient,fully adjustable coefficient and concentration in the study area have a great relationship from 2005 to 2014.In the past ten years,the mean flow of the study area in each quarter all shows an increasing trend on the whole,and the range of the largest is the autumn,followed by summer.The river inflow in the study area is mainly the flow increase in summer and fall.The years of 2005-2008 is dry season,2009-2011 the medium season and 2012-2014 the abundant season.The average annual amount of flow in the study area has an increasing trend on the whole from 2005 to 2014,and it can be forecast that the average annual amount of flow will decline during 2015 and 2019.(2)The analysis of water quality shows that,in the last ten years of 2005-2014,the chemical oxygen demand of two-water sources monitoring station significantly declines,and the content of ammonia and nitrogen has a sharp significant declining trend;the chemical oxygen demand and the content of ammonia-nitrogen at the section of cement plant also have a sharp significant declining trend as a whole.It can be predicted that the dissolved oxygen content will shows an obvious increasing trend at the two monitoring sections of two-water sources and cement plant from 2015 to 2019.The content of the rest indexes at the two monitoring sections all declines on the whole,in which the potassium permanganate index and the content of fecal coliform bacteria are more obvious.(3)The analysis of specific pollutant shows that,the specific pollutants at the two monitoring sections of two-water sources and cement plant are the five-day biochemical oxygen demand and the fecal coliform;the pollution indexes associated to five-day biochemical oxygen demand mainly include the permanganate index and the chemical oxygen demand,and the pollution indexes associated to fecal coliform are ammonia-nitrogen and dissolved oxygen.(4)The analysis of the assimilative capacity and driving force shows that,on condition that the study area maintains its normal water quality objectives,the dissolved oxygen content at the monitoring sections of two-water sources has a significant correlation with the urban population;and both the chemical oxygen demand concentration and the ammonia nitrogen concentration have significant correlation with per capita income,GDP,primary industry output value,the secondary industry output value and the tertiary industry output value,of which the secondary industry output value is more prominent.(5)The analysis of change features on water level and aquatic life factor of water ecosystem in study area from 2005 to 2014 show that,the water level changes more gentle in nearly a decade,and the minimum value of aquatic species,water biomass and aquatic life abundance occurres in 2012,and the maximum value occurres in 2013.(6)Hydrology,water quality,biology,habitat,human activities were selected to establish the safety evaluation index system of water ecosystem in the study area,and the weight of each index was calculated based on the improved AHP method.The result shows that the hydrological regime has played an extremely important role in the safety of the water ecological system in the study area,the human activities comes second,while the water quality,the biology and the rivers feature have little influence.(7)The hydrology security value comes down from 2005 to 2014;water quality and biology decreases first and then increases;habitat has a certain stability,and its security value is higher;the influence of human activity has been increasing year by year,especially in 2011-2014,whose security rating lies at a more dangerous state.(8)The analysis on the impact of water quantity on the water ecosystem security shows that,the main water quality factor affecting the community structure of the phytoplankton is the water depth in spring and summer,while the flow rate in fall;for the zooplankton,it is the water depth in spring and summer,he flow rate in summer and fall.(9)The analysis on the impact of water quality on the water ecosystem security shows the analysis results of water ecosystem security caused by water quality showed that:for the phytoplankton,the chemical oxygen demand and fecal coliform are two main water quality factors which affecting community structure during spring,summer and fall;while for the zooplankton,the dissolved oxygen,ammonia-nitrogen and iron ion wre the main water quality factors.(10)The analysis on the impact of specific polluant on the water ecosystem security shows that,in Songhua River in Harbin,both the five-day biochemical oxygen demand and the fecal coliform have a significant effect on the community structure of the phytoplankton and the zooplankton.Regression analysis results are consistent with the spearman correlation.(11)The analysis on the impact of assimilative capacity on the water ecosystem security shows that,in spring,summer and fall,what affects the community structure of the phytoplankton is the chemical oxygen demand assimilative capacity value,and for the zooplankton,they are the ammonia-nitrogen and the iron ion.(12)The pre-warning result of water ecosystem security shows that,from 2005 to 2014,the comprehensive safety evaluation value of water ecological system in study area ranges from 0.49 to 0.65.The water ecological security level in study area ranges between general and better,and the pre-warning status in study area ranges between light alarm and relatively safe state from 2015 to 2019,the pre-warning discrimination safety evaluation value of water ecological system in study area ranges from 0.54 to 0.58,the water ecological security level in study area ranges between general and better,the pre-warning status in study area ranges between light and safe alarm.Recently,the downward trend of pre-warning status in Songhua River has come into control,but the water environment in study area has not returned to safe status,the recovery and the protection work of water ecosystem still need to last for a long time.(13)Based on the current situation analysis and prediction results of future trend of the change of water environment and water ecology system safety in study area,the water environmental improvement countermeasures were mainly proposed from pollution control,watershed dredging,aeration reoxygenation,purification of ecological floating bed,promoting the pollution control,strengthening environmental monitoring and other aspects.The water conservation measures were mainly proposed from improving waterfront green,ecological treatment of riparian,restoration of aquatic vegetation,construction of water ecological restoration scheme,improving the protection of ecological compensation mechanism and other aspects. |
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