Impact Of Agricultural Activities On Groundwater Environment In West Liaohe River Plain

The West Liaohe Plain located in the eastern part of Inner Mongolia Autonomous Region.The whole plain is an important agricultural production base in the autonomous region,known as"Inner Mongolia Granary"because of its thick soil and abundant water resources,which is convenient for irrigation and agricultural machinery operation.In order to meet the demand of agricultural irrigation water,a large amount of groundwater is exploited in West Liaohe Plain.The exploitation of groundwater driven by agricultural irrigation is increasing.At the same time,the application of chemical fertilizers and pesticides has an important impact on groundwater quality and poses an increasingly serious threat to the groundwater environment.Therefore,identifying and diagnosing the impact of agricultural activities on groundwater quantity,water level and quality change is particularly critical and important,and has important theoretical significance for coordinating the contradiction between agricultural production and groundwater deterioration.The climatic and meteorological conditions,hydrogeological conditions,farmland irrigation and groundwater development and utilization in Kerqin and Kailu counties are representative of the West Liaohe Plain.Therefore,this paper takes Kerqin and Kailu counties in Tongliao City as typical research areas,and briefly describes the physical geography and agricultural situation of the two areas.Mann-Kendall trend test and grey relational degree calculation are carried out on groundwater level data by using MATLAB,and the contribution degree of agricultural activity factors to groundwater environmental impact is calculated by using pursuit projection model;the distribution maps of groundwater depth,ion concentration and factor score are made by using ArcGIS software;and the groundwater level is drawn by Origin.Groundwater ion concentration curve with time and linear fitting curve between agricultural activity factors and groundwater burial depth;factor analysis of groundwater ion concentration data using SPSS.The research conclusions are as follows:?1?The groundwater level in Horqin District and Kailu County shows a downward trend between 2005 and 2015,and the time of abrupt change of groundwater level in these two areas is from 2009 to 2010through catastrophe analysis.The relationship between annual precipitation and annual exploitation and groundwater level change in the two areas is studied quantitatively by using grey correlation degree method.It is concluded that the influence degree of agricultural exploitation on groundwater level in Horqin area is higher than that of precipitation on groundwater level,and that the influence degree of precipitation on groundwater level in Kailu county is higher than that of agricultural exploitation on groundwater level.The degree of influence.?2?Groundwater ion concentration in Horqin area decreases gradually from east to west,while that in Kailu County,located in the west of Horqin area,decreases gradually from west to east.The overall analysis shows that the ion concentration decreases from east to west at the junction of the two places.The seasonal variation of ion concentration in groundwater was seasonal.The seasonal variation characteristics of NH₄⁺-N,SO₄^2-concentration and COD content were spring>summer>autumn,and the concentration or content increased in winter.The seasonal variation characteristics of Ca²⁺,Mg²⁺,NO₃^--N and TP concentration were summer>spring>autumn,and the seasonal variation characteristics of Na+concentration increased in winter.Spring>Autumn>Winter>Summer;K⁺,Cl^-concentration did not show strong seasonal characteristics,and the content of NO₂^-was very low,and did not show seasonal characteristics.The factor analysis method of SPSS was used to identify the main influencing factors of groundwater in the two areas,F₁ was the Migration-Enrichment of groundwater,F₂ and F₃ were the influencing factors of agricultural and industrial activities,and F₄ was the primary environmental geological factor.?3?The groundwater depth change in Horqin and Kailu counties has a strong correlation with agricultural planting structure,crop yield,vegetable and melon planting area and yield,and the amount of chemical fertilizer,especially nitrogen fertilizer,has a certain correlation with the change of"three nitrogen"content in groundwater.The weights of factors of agricultural activities on groundwater environmental impact are calculated by using the pursuit projection model,which can provide certain data and theoretical reference for the construction of groundwater environmental assessment system,the adjustment of agricultural planting structure and the development of agricultural water-saving technology.