Spatio-temporal variation and driving factors of dissolved oxygen in surface water of typical watershed areas in Hubei Province

Dissolved oxygen(DO) is an important indicator to reflect the quality of surface water, and it is one of key parameters for carrying out accurate comprehensive management of watersheds. Automatic monitoring data of surface water from 200 water quality automatic monitoring stations in Hubei Province from 2021 to 2022 were collected to study the spatial-temporal variation characteristics of DO and perform cluster grouping. The driving factors of DO variations of sixteen watershed areas were analyzed quantitatively by correlation coefficient method and multiple linear regression, and some suggestions for watershed management were proposed. The results indicated that:(1) DO concentration of surface water in Hubei Province showed significant seasonal difference as winter>spring>autumn>summer. Moreover, there was a significant diurnal variation from May to October. (2) Sixteen watershed areas in Hubei Province were divided into low oxygen zone, medium oxygen zone and rich oxygen zone. The low oxygen zone was mainly concentrated on Sihu area and the lower reaches of Hanjiang River area, with low DO concentration and saturation and high frequency of low DO occurrence in summer. The rich oxygen zone was mainly concentrated in Qingjiang area and the upper reaches of Danku Reservoir area of the Hanjiang River, with supersaturation in summer. The other watershed areas were medium oxygen zone, with stable saturation at a high level. (3) In terms of influencing factors, the low oxygen zone was characterized by compound pollution, the rich oxygen zone was affected by aquatic plant activities, and the medium oxygen zone was affected by temperature. Based on the characteristics of DO changes in different watershed areas, from the perspective of overall coordination of "three water" (water environment, water resource, water ecology), systematic watershed management methods should be set in a graded and partitioned manner, namely strengthening pollution source and process control in the low oxygen zone, preventing and controlling the risk of water blooms in the rich oxygen zone, and strictly controlling the total discharge in the medium oxygen zone.