Impact Of Land Use Changes On Precipitation Infiltration Quantity In Jinan Spring Area

The calculation of precipitation infiltration quantity is one of the important contents of regional water resources evaluation.As a result of urbanization,the precipitation infiltration quantity has been greatly influnced by the changes of land use.Jinan is a tourism city which is famous for Baotu Spring.With the rapid development of social economy,and increasing of population,the urbanization extent of Jinan also rises.A series of human activities such as over-exploitation of groundwater has resulted in groundwater resources reducing,groundwater level falling,spring cutoff,and seriously damage of the natural balance of groundwater system in Jinan.Groudwater level dynamic observation data shows that the changes of karst water level and spring flow rate are closely related to precipitation.The continuous progress of the urbanization,along with the increase of area for construction,the area of impermeable or weakly permeable ground is increasing.The changes in landuse types mentioned above can result in the declinings of infiltration areas and infiltration quantity.This paper is funded by “Evolution trend of water resources in Jinan spring area”.On the basis of detail analysis of geological and hydrogeological conditions,3S technology is used to evaluate the precipitation infiltration quantity in Jinan spring area on the condition of land use/cover change.Main conclusions are as follows :1.Land use evolution in the study areaFrom 1985 to 2000,the cultivated land,surface water area and other land area showed a decreasing trend,and the construction land area showed a rapid growth trend,while the area of grassland changed little.From 2000 to 2015,the cultivated land,grassland forest and surface water area showed a decreasing trend,while the construction land and other types of land use showed an increasing trend.From 2015 to 2030,the changes of the cultivated land,grassland forest,surface water and the construction land area show the same trends.But the other types of land use area change a little.It indicates that urbanization has changed the type of land use/cover,construction land area rises and cultivated land and other vegetation cover land declines.2.Effects of land use on precipitation infiltration(1)Precipitation infiltration rate under different land use typesThere is a lack of plant interception and plant transpiration on the exposed ground.So the infiltration capacity is the strongest in the bare area,and the infiltration capacity of the vegetation cover area is the second,and the infiltration capacity of the water area and impermeable area is the weakest.(2)Interannual variation of water infiltration under land use/cover changesFrom 1985 to 2000,from 2000 to 2015,2015 ~ 2030,the average annual precipitation infiltration rate decreases by 5.27 mm,1.19 mm,3.44 mm.With the expansion of urbanization,the land use and land cover has changed,and the increase of area for construction land has led to the increase of impervious and weakly permeable ground in the area.The vegetation coverage area and exposed ground area show a decreasing trend,especially in the spring area of Jinan.The area of high amount of precipitation distributes in the urban area of Jinan in the northeastern region,so that the precipitation is directly distributed into the underground pipeline,which seriously affects the infiltration rate of precipitation.