Abstract:

In this study,water samples from fourteen agriculture drainage ditches as well as from three critical check gates,two outlets of main channel of four lakes region in Hubei Province were collected and examined with six physicochemical parameters:electrical conductivity (EC),pH,dissolved oxygen (DO),chemical oxygen demand (COD),total nitrogen (TN),and total phosphorus (TP).Global positioning system (GPS) was used to determine the coordinates of sampling points.In order to identify the main pollution loading types of ditch water,the single factor pollution index was applied.Moreover,Nemero Index and the fuzzy comprehensive evaluation were used to judge the water quality grades,and then to characterize the water quality situation and the spatial variation features of water environment in this basin.The results indicated that DO and TN were 〖JP2〗the main polluting factors.And the proportion of agriculture〖JP〗 drainage ditches in slight pollution was about 7857%,among which 4286% points reached up to the standard requirement of class Ⅳ in《Surface Water Environment Quality Standard》（GB38382002）.This showed that the ditches were heavily polluted.The changing intensity of water pollution in agriculture drainage ditches was Jianli section (D03~D07)>the northern area of Honghu (D08~D09)>the west of Honghu county (D10~D12)>Jiangling and Qianjiang section (D01~D02)>the area of Datong Lake (D13~D14).In summary,the water quality in  main channel was much better than that in agriculture drainage ditches,the middle area was worse than the inferior segment in the aspect of water quality of agriculture drainage ditches.〖