Evaluation status and problems of groundwater resource potential in Yunnan Province

Yunnan Province is located in the southwest of China,bordering Vietnam,Laos and Myanmar,with a total area of 394,000 km2. The mountainous area of Yunnan Province accounts for about 94% of the total land area.The terrain is high in the northwest and low in the southeast,descending in a ladder form from north to south.The highest point is the Kawagbo peak of Meili snow mountains at the border between Yunnan and Tibet,with an altitude of 6，740 m.The lowest point is at the intersection of the Nanxi river and Honghe river in Hekou county,with an altitude of 76.4 m.The distance between the two points is about 900 km as the crow flies,with height difference over 6，000 m.The general topography of Yunnan is bounded by the Yuanjiang and Yunling mountains,which are divided into two parts.The eastern part is the central Yunnan red bed and the eastern Yunnan karst plateau,with an average elevation of about 2，000 m.Here landform is gentle rolling mountains,low mountains and hills,among which karst faulted basins are prevail.The western part is the longitudinal valley of the Hengduan mountains,with an elevation of about 3,000-4,000 m.It consists of the Gaoligong mountains,Nu mountains and Yunling mountains and the Nu river,Lancang river and Jinsha river,forming a "Three parallel rivers" landform wonder.In the south,the Hengduan mountains and valleys are remaining,with gentle terrain in general,and the river valley is gradually broad. In the border areas in the south and southwest,the terrain is low and gentle,hosting many wide valley basins,generally about 800-1,000 m above sea level,and some sections are lower than 500 m.Yunnan has generally a subtropical plateau monsoon climate,with distinct dry and rainy seasons.Due to the specific geographical conditions,the formation of water resources in space and time distribution is uneven,resulting frequent drought in winter and spring.Regional hydrogeological surveys show that the average runoff of groundwater in the province is 74.274 billion m3?a-1,and the allowable yield of groundwater is about 19.035 billion m3?a-1.Groundwater resources have the characteristics of wide distribution,stable dynamics and excellent water quality,which play an irreplaceable role in daily and drought-resistant water supply.Groundwater resource potential refers to the amount of the allowable yield of groundwater that can be available for expansion under the condition of groundwater exploitation and utilization.The specific value is，the difference between the amount of allowable yield of groundwater resources in the evaluation area or aquifer and the amount of actual exploitation.The purpose of this paper is to accurately evaluate groundwater resource potential in Yunnan Province for the development and utilization of groundwater resources including science planning,protection and management,and provide guidance,in-depth investigation,and evaluation.Our analysis builds on the system science theory,historical analysis,the principle and method of hydrogeology and water balance analysis,abundant groundwater resources investigation data,and dynamic monitoring data.We evaluate and analyze the development and problems of groundwater resources potential in Yunnan Province.In a systematic investigation of the history and present situation,the groundwater resource potential evaluation methods and results are reviewed.The utilization rate of groundwater resources is 30.32%-51.49% in intermountain basins where the cities above country level are located,and that in the vast mountainous area is 9.63%-30.0%.The current status quo of groundwater resource potential is about 13.448 billion m3?a-1.At present,the basic hydrogeological survey is in the general survey stage,and there are still large gaps in the northwest and west Yunnan,so the evaluation results of the provincial and regional groundwater resource potential only reach the accuracy of inference and prediction. For the first time, the main problems are analyzed systematically,such as poor understanding of water resources and the environmental system,incomplete evaluation contents and standards,and insufficient monitoring and forecasting of water quality and water quantity,which lays a good foundation for a new round of water resources investigation and evaluation.