The Study On Numerical Model Of Groundwater Flow And Urban Water Supplement Safety In The City Of Hohhot

Recently,water crisis has been a problem along with rapid development of industry and a lack of awareness of water resources protection in all parts of our country.Therefore,issues related to water supply safety caused by the water crisis,which has severely restricted the city construction and development,attract extensive attention these days.Hohhot,the capital of Inner Mongolia located in northeast Hetao Plain,is one of the most developed cities in Inner Mongolia but also one of the cities suffering serious water shortage in northern China.Before 2007,urban water supply of Hohhot mainly depended on groundwater pumping.Since 2007 the project of diverting water from Yellow River to Hohhot has been supplying water for the city,and the supply capacity reaches to 10?16×104m3/d.At the present time,the annual withdrawal of groundwater resources in Hohhot is up to 2.48×108m3,and the water resources from Yellow River is up to 5840×104m3.This study was in combination with the project-Numerical Simulation of Groundwater Resources for Hetao Plain,the sub subject of the project-Investigation and Evaluation for Groundwater Resources and Environment Issues in Hetao Plain carried out by the China Geological Survey and Department of Land and Resources of Inner Mongolia.After collecting investigation data of groundwater resources in the study area and synthetically analyzing local hydrogeological conditions and sources and sinks,we used the groundwater modeling software GMS and ModFlow2005 to construct a groundwater flow model for the study area.By analyzing a two-year water budget of the study area,we obtained the result that in the Hetao Plain accumulated reduced amount of groundwater was 4964.15×104m3,average annual discharge was 3.36×108m3/a,average annual recharge was 3.86×108m3/a,and average annual withdrawal rate was 1.99×108m3/a.Through sorting out and analyzing current urban water supply information of Hohhot,we were informed that there were two major urban water supply crises in Hohhot in recent years.First,if the study area was in consecutive dry years,according to the predicted water budget,we could obtain the result that the difference value between recharge and discharge was 0.97×108m3/a,which showed a negative balance and the groundwater table dropping obviously.When the precipitation rises to average annual value,even the groundwater system still stay in a negative balance,the decline of groundwater table would stop.Second,if we assume that the groundwater supply from Yellow River was stop for some unexpected reason,the emergency water supply,which would be used to meet city's water needs,may make a small drop of groundwater table in the study area.This emergency water supply not only meet the principle of groundwater table control,but also ensure the city' water supply.Finally,we synthetically analyzed that the groundwater resources in the study area could guarantee the water supply safety of the study area.However,groundwater protection measures should be taken to help recover the groundwater resources after the emergency groundwater pumping.