| Heifangtai terrace is located in Yanguoxia Town,Yongjing County,Gansu Province,China.Because of the long-term use of agricultural irrigation with flooding irrigation,the groundwater level of the terrace has been rising continuously,which has caused hundreds of Loess landslides,known as "modern landslide natural laboratory".The occurrence of a large number of landslides has seriously restricted the local economic development.At present,scholars at home and abroad have done a lot of research on the infiltration mechanism and landslide mechanism of irrigation water in Heifangtai terrace,but they neglected the influence of different crop irrigation zones on the distribution characteristics of groundwater.Most of the prevention and control proposals are to change irrigation methods and establish drainage facilities,without fully considering the influence of the source of groundwater recharge,i.e.the planting structure and distribution characteristics of crops on groundwater.Therefore,this paper studies the relationship between crop irrigation characteristics and groundwater distribution characteristics based on crop non-uniform irrigation.Firstly,the multi-stage high spatial resolution remote sensing images of Heifangtai area are collected,and based on field investigation,the object-oriented remote sensing image classification method is used to extract the crop planting data of Heifangtai terrace for many years.Then,the characteristics of crop irrigation are obtained by using KDE,and the proportion of various types of crop irrigation in Heifangtai area is analyzed to determine the causes.And then the main factors of high irrigation area are compared and analyzed between crop irrigation characteristics and water level monitoring data and inversion of groundwater distribution characteristics by ERT.Then,the Heifangtai terrace landslide database is established and the temporal and spatial evolution law is analyzed.Finally,taking groundwater distribution as the link point,the influence of groundwater distribution characteristics on the evolution of landslide is studied,and the farming is illustrated on the side.The effect of irrigation characteristics on Landslide Evolution provides a basis for scientific planting in Heifangtai area in the later stage.Through the research,the main conclusions of this paper are as follows:?Using object-oriented multi-level rule remote sensing image classification method,14 high spatial resolution remote sensing images in Heifangtai terrace were extracted for crops.The planting characteristics of maize,wheat and vegetables in Heifangtai terrace from 2010 to 2017 were obtained.The results showed that different types of crops in Heifangtai terrace had different planting heat zones,wheat was mainly planted in the north,Maize were planted in the West and north,vegetables are mainly planted in the middle and east.Although the single irrigation amount of each type of crop is not very different,the annual irrigation times are quite different,specifically vegetable > wheat > maize,which ultimately leads to the existence of four high irrigation areas in the terrace,and vegetables are the main influencing factors.?The monitoring data of groundwater level show that the groundwater level in Heifangtai area rises unevenly,and the rising rate in the middle of the terrace is higher than that at the edge of theterrace.The distribution of groundwater level obtained by inversion of more than 50 ERT profiles with a cumulative length of 38 km in Heifangtai terrace shows that the groundwater level in Heifangtai area is unevenly distributed and there are three vaults of groundwater level.?Comparing the crop irrigation characteristics and groundwater distribution characteristics in Heifangtai terrace from 2014 to 2017 estimated by KDE,it is found that the high irrigation area is in good agreement with the vault of groundwater level,indicating that the uneven irrigation of crops affects the uneven distribution of groundwater.?A database of Heifangtai landslide was established from 1972 to 2019.The results show that there are 82 landslides in Heifangtai area,including 8 landslides in Fangtai area and 74 landslides in Heitai area.Which had caused 215 landslides.Among them,there are 14 loess-bedrock slide with 21 landslides;39 loessslides with 106 landslides;6 loess flow with 17 landslides;23 Loess flowslides with 72 landslides.?According to the time span of crop extraction,the temporal and spatial evolution of Dangchuan section in Heifangtai is analyzed.The results show that the landslide in Dangchuan section undergoes a process of transformation from loeddslide to loess flowslide in time distribution.In spatial distribution,the loess flowslide in Dangchuan section develops from west to East.The cumulative rise of groundwater is the main factor for the frequent occurrence of landslides and the change of slope types in recent years in the Dangchuan section.The distribution characteristics of groundwater affect the overall development of loess flowslide in the Dangchuan section from west to east.?The characteristics of crop irrigation affect the distribution of groundwater level,while the characteristics of groundwater level affect the development and evolution of landslides,that is,the characteristics of crop irrigation can affect the evolution of landslides.Based on the research results,some suggestions are put forward for the adjustment of crop irrigation mode,planting structure and industrial structure in Heifangtai to slow down the further occurrence of landslides in this area. |
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