Application Of Grey Prediction Model GM(1,N) In Groundwater Mineralization Of Cheng'an County In Handan City

Located in the south of Hebei Plain,Cheng'an is a typical agricultural zone,which has a great demand of water supply and a high demand of water quality.In order to meet the needs of agricultural life and economic development,deep groundwater in Cheng'an County has been severely overexploited for many years,leading to a series of geological environmental problems.And water quality changes are relatively serious in all of the geological environmental problems.Water quality changes are mainly reflected on changes of mineralization and hydrochemical types.Therefore,the simulated prediction and analysis of groundwater salinity in Cheng'an County will provide a basis for rational exploitation and protection of groundwater in Qiu County,which also promote the ecological restoration of groundwater in Handan Plain and alleviate the geological environmental problems.Choosing Cheng'an County of Handan City as the research area,this paper collects and sorts out the natural geography,social economy and local groundwater utilization of Cheng'an County.In the premise of understanding the basic data of water quality change,hydrogeological conditions and groundwater exploitation degree in the research area,two monitoring wells-Zhangzhuang and Zhang Xinzhuang,whose data collection are comprehensive in the area are selected.Taking groundwater mineralization degree as the target factor,the main influence factors,sucn as well water level,regional exploitation amount and regional rainfall are introduced,and then GM(1,N)grey prediction model is established based on MATLAB software,which can simulate and predict the solution.The monitoring data from 2010 to 2015 is used for simulation fitting,then predict the groundwater salinity value from 2016 to 2020,draw the simulation fitting curve of the model,make the trend line,and determine the fitting accuracy of the fitting curve.At the same time,GM(1,1)model and SPSS multiple linear regression prediction model are used to simulate the mineralization degree of Cheng'an County.The superiority and accuracy of GM(1,N)prediction model can be determined by comparison and analysis of the two models above.The final prediction result of the model is chosen as the prediction value for monitoring wells in the next few years.The results show that the GM(1,N)grey prediction model can be used to predict the mineralization degree of groundwater in Cheng'an County,and the fitting accuracy of monitoring wells is above 90 %,indicating that the model is feasible to predict the mineralization degree in Cheng'an County.Moreover,the relative error and root mean square error between the measured and simulated values in GM(1,N)model are smaller than GM(1,1)and SPSS multivariate linear regression prediction model,further demonstrating the accuracy and superiority of the model.The GM(1,1)model only reflects the evolution and development of mineralization over time.Although GM(1,1)has the advantage of less demand for statistical data,the mineralization of groundwater is affected by many factors,it can't reflect that groundwater salinity is the result of many factors.GM(1,N)model just makes up for the defect of GM(1,1),it can reflect the correlation between multiple factors and target factors.The measuring accuracy of GM(1,N)is higher and more practicalS.PSS multivariate linear regression uses SPSS software to simulate the study area.Compared with GM(1,N),the model is more suitable for the prediction of mid-long data series.GM(1,N)shows higher simulation accuracy in the case of data shortage in Cheng'an County.Using GM(1,N)model to predict the results shows that the mineralization value of the two monitoring wells is increasing year by year,indicating that Cheng'an County has been in a state of water resource shortage and is constantly evolving towards deterioration.Because Cheng'an County is located in the area where is no mountains and no rivers,it mainly relies on groundwater to support the development of industry and agriculture,resulting in rise in groundwater salinity year by year.Finally,the paper puts forward protection countermeasures against the water environment problems caused by groundwater overexploitation in this area.