## 1 Introduction  
Lakes are essential fresh water bodies, which are not only vital resource for human life and productive activities, but also play an important role in the biogeochemical and hydrological cycles. The water-surface area variations of lakes are regulated by water inputs (_i.e._, precipitation, surface inflow, groundwater inputs) and water outputs (_i.e._, evaporation, surface outflow, groundwater outputs). Moreover, the water inputs and outputs are affected by anthropogenic activities. Agriculture, industry and other human activities mainly affect the water-surface areas of lakes via land use change [1,2]. Due to climate change and anthropogenic activities, many inland lakes in China have undergone dramatic changes in both number and area during the past 30 years. Two-hundred forty-three lakes have disappeared and 60 lakes newly formed in this time period, respectively [3]. For example, the rapidly rising temperature has accelerated glacier melt throughout almost the entire Tibetan Plateau, which causes the rapid lake expansion in this region [4, 5, 6, 7, 8]. Moreover, the number of vanished lakes in the middle and lower reaches of the Yangtze River accounts for 40% of total loss of lakes in China, which is mainly attributed to human activities such as exploitation of fisheries, reclamation of land and construction of water conservancy [9]. In particular, the construction and operation of the Three Gorges Dam (TGD) exert large influence on downstream lakes, making it a hot issue in the middle and lower reaches of the Yangtze River.  
Honghu Lake, located in the mid-lower reaches of the Yangtze River, is the seventh largest freshwater lake in China. As the largest lake among thousands of water bodies in the Jianghan Plain, Honghu Lake plays an irreplaceable role in regional irrigation for agriculture, fisheries, and upstream flood drainage [10]. The extreme climate events (_i.e._, flood and drought) are so frequent in the mid-lower reaches of the Yangtze River that the water-surface area of Honghu Lake can change greatly on both short and long time scales due to precipitation and temperature anomalies. Especially since the 1950s, Honghu Lake has been separated from the Yangtze River by several sluice gates, and hardly been modulated by upstream of Yangtze River [11]. From this point, Honghu Lake area has decreased dramatically, which is mainly caused by excessive human activities mainly including reclamation and aquaculture [12]. According to previous studies [13], the quantitative impacts of climate change and human activities on Honghu Lake area variations are controversial, which is also the focus of this paper.  
Previous studies have investigated water-surface area variations of Honghu Lake based on remote sensing images, but they are subjected to low measurement frequency and resolution [13,14]. Besides, there are many challenges to quantitatively estimate impacts of each driving force on lake area variations, especially for human activities due to lack of comprehensive and reliable data. For example, [PERSON] _et al_. [13] only use fishery production data to analyze the influence of human activities on the water-surface area variations of Honghu Lake. In this paper, the longer times series of high resolution (30 m) Landsat and HJ-1 A/B images from 1990s to 2013 is used, which is more suitable to extract the seasonal and inter-annual changes in water-surface area of Honghu Lake. In addition, the area of dryland agriculture, paddies and aquaculture ponds, accounting for a major portion of land use data in 1990, 2000 and 2010, are used to analyze the impacts of human activities. The quantitative impacts of climate change and human activities on Honghu Lake obtained in this study will provide helpful reference for local water resource management, ecologic environment protection, and a better understanding of climate change.