Study On The Characteristics Of Water Environment And Its Effect In Irrigation Area

The Sanjiang Plain is also known as the Sanjiang Lowland.After the three major rivers of Heilongjiang,Wusuli River and Songhua River converge and alluvially form a fertile land.It is an important commodity grain production base in China.Due to the important agricultural production tasks,the region has been subjected to high-intensity development,resulting in a serious decline in soil fertility.In order to increase yield and increase profits,local farmers have used a large amount of chemical fertilizers and groundwater resources.After rainfall,evaporation,runoff,infiltration and other water activities,some point source pollution and non-point source pollution have been caused.Under this background,this paper selected sixteen typical riversides in the core area of grain production in the hinterland of the Sanjiang Plain as the research base,and evaluated its surface water environment quality,groundwater environment quality,and the overall water environment quality of the irrigation area to explore its internal relationships.And use scenario analysis to study the future development of water environment in the study area.And study the optimal coordination of agricultural water resources in irrigation areas under water environment constraints.The main research contents and conclusions are as follows:1)By sampling and experimenting the surface water quality indicators in the study area,the constructed AMFO-PPE model was used to evaluate the surface water quality.The results showed that in addition to the Jixian Irrigation District,the overall quality of surface water and water environment in other irrigation districts is good,and the irrigation districts with relatively poor water quality are mainly distributed in the central and western regions.Its spatial distribution is related to the river network density in the irrigation area,and the area with high river network density has better relative water quality.By analyzing the performance of the AMFO-PPE model,RAGA-PPE model,FA-PPE model and NIM,the Spearman rank correlation coefficient of the AMFO-PPE model is 0.968.Next,10 irrigation districts are randomly selected and repeated 25 times.The Spearman rank correlation coefficient is 24.079.The calculated discrimination value of AMFOPPE model is 1.09875.Although the NIM discrimination is 1.14205,the NIM standardized score curve distribution is not reasonable.It shows that the AMFO-PPE model has certain advantages in terms of stability and reliability in surface water environmental quality assessment.2)By sampling and experimenting the groundwater water quality indicators in the study area,the constructed AMFO-PPE model was used to evaluate the groundwater water quality.The distribution space of groundwater grades in the sixteen irrigation areas showed a trend of better conditions in the east than in the west.The results showed that the overall condition of surface water and water environment is poor in other irrigation areas except the toad irrigation area.From the measured index values,the content of Fe and Mn indicators significantly exceeded the standard.After consulting the literature,it was found that the local pore water contains a large amount of organic matter,which can dissolve iron-manganese minerals in the water body.By analyzing the performance of the four models,the Spearman rank correlation coefficient of the AMFO-PPE model is 0.998.Next,10 irrigation districts are randomly selected and repeated 25 times.The Spearman rank correlation coefficient is 24.366.The calculated discrimination value of AMFO-PPE model is 1.18358.Although the NIM discrimination is 1.21836,the NIM standardized score curve distribution is not reasonable.It shows that the AMFO-PPE model has certain advantages in terms of stability and reliability in groundwater and water environmental quality assessment.3)The R cluster and variation coefficient method were used to screen the water environment indicators of the irrigation area.The selected indicators were used to evaluate the water environment quality of the irrigation area using the constructed AMFO-PPE model.The results showed that the overall quality of surface water and water environment is poor in other irrigation areas except the toad-pass irrigation area.Spatial distribution of water quality is better in the west,north and east,and poorer in the south-central.According to the analysis of the results and the quality of surface water environment and groundwater environment,it can be found that the correlation between the water environment quality and groundwater quality in the irrigation area is greater than the other two,showing a strong correlation.By analyzing the performance of the four models,the Spearman rank correlation coefficient of the AMFO-PPE model is 0.973.Next,10 irrigation districts are randomly selected and repeated 25 times.The Spearman rank correlation coefficient is 24.409.The calculated discrimination value of AMFO-PPE model is 1.15267.Although the NIM discrimination is 1.17080,the NIM standardized score curve distribution is not reasonable.It shows that the AMFOPPE model has certain advantages in terms of stability and reliability in the evaluation of water environmental quality in irrigation districts.4)By selecting the four driving factors of the proportion of cultivated land area,precipitation,canal infiltration replenishment coefficient,and fertilizer application per unit area,multiple regression equations and scenario analysis methods were used to predict the future development of the study area according to the survey.The results showed that continuing to develop in accordance with current trends,the water environment in the study area is showing a trend of improvement.By reducing the increase in the proportion of cultivated land area or reducing the amount of fertilizer applied per unit area,the local water environment quality is improving,but the trend is still not obvious.5)By constructing a multi-objective optimization model and using the cuckoo algorithm to solve,the water environment quality index of the irrigation area is used as a constraint to optimize the allocation of agricultural water resources in the irrigation area.The results show that due to the constraints of the water environment constraints,it plays a certain role in protecting local water resources and can reduce the use of water resources.At the same time,it also has a certain restrictive effect on local agricultural production,and provides methods and suggestions for local waterenvironmental protection and agricultural water resources utilization.