Hydrogeological Characteristics Of Shallow Groundwater Caused By Wenchuan Earthquake With A Case Study Of Moutuo Area

In the paper, we consider the area of Mutuo village, Mao County as an example.hydrogeological characteristics of shallow groundwater and groundwater system andmountain ecosystem affected by the “5.12”earthquake are analyzed by the flowvelocity of DC charging method means test and leakage test. And some conclusionsare showed as follows:The earthquake changed the groundwater storage and hydrodynamic migrationcharacteristics in the study area, and changed the conditions of recharge, runoff anddischarge of groundwater. Because the earthquake caused the groundwater diversionsand occlusion of the dominant channel, the springs of the study area has formed a newdominant channel, which thus changed the source of the supply of springs’ rechargeand flow conditions, resulted in the phenomenon of the spring flow is smaller andeven drying after the earthquake, meanwhile, the dynamical feature of the springswere changed, hydrogeological characteristics of the area correspondingly gotchanged, too.After the "512" earthquake, the groundwater flow system of the study area waschanged, while a new local groundwater flow system was formed. Regionalgroundwater flow system is recharged by atmospheric precipitation, verticalinfiltration of irrigation, and the mountain bedrock fracture water, then thegroundwater flow moves to the river horizontally. The local groundwater flow systemof the head water, the groundwater accepts recharge which forms the groundwaterflow and migrates to the downstream. On the dense layer formed by earthquakes, theconditions of the flow are changed, which results in the changes of the flows, a part ofwhich excrete in spring form and another part by penetrating through the dense layer,continue to recharge the down streams. In the local groundwater flow system of thelower course, the recharge sources of the groundwater comes from the atmospheric precipitation and the upstream penetration, and excrete by the springs, then transformsfor the surface water, and then converges to the Minjiang River. Overall speaking, thegroundwater system of the study area is relatively complete, and the shallowgroundwater flow system is affected by topography, which mainly converges from thePiedmont recharge area to the river discharge area, a new recharge and dischargechannel is developed in seismic action.Due to the change of the size of the earthquake accumulation lithology particle isbigger, the structure is looser, and the coefficient of permeability is larger, andbecause of the larger porosity, combined with the slope’s changes, the conditions ofthe slope groundwater storage and transport are changed, while the soil moisture isalso changed; after the earthquake, the secondary geological disasters occurredfrequently, leading to the crushed stones and gravels covering as well as the soilcontent decreased. All of them are the reasons that change the shallow aquiferstructure, and the growth and recovery of the plants is affected, at last, a great impacton the self-recovery of the mountain ecosystems in the study area is caused.