Studies on the mechanism of watershed hydrologic droughts based on the combined structure of typical karst lithologys : Taking Guizhou Province as a case
Hydrologic drought,which has become a typical natural phenomenon under the background of global climate change, is the continuation and development of the meteorologic and agricultural drought and is the ultimate and the most thorough drought. The lithology is an important substance of watershed underlying surfaces. The development of the landform and river system,and promote the formation of watershed water-storing space,which affects on the watershed water-storing ability and relates to the occurrence of hydrologic drought are controlled by the lithologic types and structures. We choose 40 typical sample areas in Guizhou Province, use the object-oriented classification technology to extract the remote sensing information of watershed lithologic types and use principal component analysis and grey theory to study the influence mechanism of the lithologic types and structures on hydrologic drought. This study shows that : 1) It has generally greater influence from the views of the lithologic types of factors on the hydrological drought,and the descending order of its influence degrees (associated degree) is K(0. 985)>Z(0. 96) >0(0. 924)>J(0. 922)>S(0. 806)>D(0. 788)>epsilon(0. 75) > C(0. 69)>Pt(0. 684)>P(0. 568)>T(0. 542) ; 2) The descending order (associated degree) of impacts of the principal component factors of lithologic types on hydrologic drought is Z_3(0. 48) >Z_4(0. 47) >Z_1(0. 44) >Z_5(0. 42) >Z_2(0. 39) ; 3) The descending order of impacts of the lithologic types of combinations on hydrologic drought is I、II>V、IV > III.