Research On The Basic Characteristics And Changes Of China’s Inland Water Body From 1984 To 2015

Water bodies(WBs),such as lakes,ponds,wetlands,and impoundments provide essential ecosystem services to human societies.WB distribution,size and aboundance in China have undergone great changes over the past three decades,resulting from the land use and land cover change.However,the spatial distribution,size-abundance characteristics,and contemporary changes of WBs in China,particularly of small WBs(less than 1 km2 in area),have not been well characterized and understood due to the data availability,which has become a bottleneck problem for the utilization and sustainable management of China’s water resources.Here,we delineate China into 11 large regions primarily following the watershed boundaries from prrevious studies(Yangtze river basin(YTR),Yellow river basin(YR),Pearl river basin(PR),Southeast river basins(SER),Southwest river basin(SWR),Tibetan plateau basin(TP),Northwest river basins(NWR),Songhua river basin(SHR),Liao river basin(LR),Hai river basin(HR),and Huai river basin(HuR)).We used unprecedented data layers derived from all Landsat images available between 1984 and 2015 to understand the overall characteristics and changes of WBs between two epochs(i.e.,1984-1999 and 2000-2015)in China.The main conclusions are as follows:(1)China has a total of 1 544 116 individual WBs(>0.001km2)with an area of 132 662 km2.The abundance of WBs(>1 km2)is estimated to be 6 821 in our study,which 1.2 times the previous highest estimate and 1.7 times the lowest estimate.The total area of WBs(>1 km2)is estimated to be 123 342 km2 in our study,41 to 63%larger than the previous estimates.(2)At regional scale,Surface WBs are distributed unevenly across regions,the Yangtze River Basin has the largest number of WBs(538 462),and the Liaohe River Basin has the smallest number of WBs(35 372).The largest area of WBs is Yangtze River Basin(37 297 km2),the mixmum area of WBs is in the Southeast Rivers region(1 803 km2).(3)The size-abundance relationships in China conform to the power law with a Pareto coefficient of-0.835,similar to-0.85 reported for the contiguous United States(CONUS),but higher than that for the world in 2016(-1.054).At a regional scale,the Pareto coefficient in the Tibetan Plateau basin(TP)is-0.662,the highest among all regions,signifying a higher fraction of large WBs in the TP compared to other regions.In contrast,the scaling exponent in the Pearl River basin(PR)basin is-0.941,the lowest among all regions,representing a relatively higher share of small lakes.(4)The shoreline fractal dimension(SFD)derived from dimensional analysis(log perimeter-log area analysis)also conform to the power law scaling,and the SFD in China is 1.254.The highest SFD is 1.321 in PR,indicating the WBs in this regions larger altered by human activities.The lowest SFD is 1.178 in TP,indicating the WBs are less affected by human activities.(5)Over the past three decades,a total of 5 197.09 km2 or 3.92%of WB area in China disappeared(absolutely decreased),meanwhile,a total of 9 040.26 km2 were converted from nonwater surfaces into WBs(absolutely increased),corresponding to 6.81%of the total WB area.WBs experienced 5 737.18 km2 of net increase across China and 53.9%of the WBs remain unchanged nationwide.(6)The widespread co-existence of disappearance of existing and emergence of new WBs across China,which presented great difference.The WBs change most occurred in the Yangtze River Basin(WBs change showed huge fluctuation primarily due to human activities)and Tibetan Plateau(WB area showed great expansion largely caused by ice/glacier melting)during the two epoches.Overall,our results shows surface WBs are distributed unevenly across regions in China.The relationship of WBs size-abundance and perimeter-area conform to the power scaling law,and the scaling exponent shows great differences at regional scale under the influence of climate and land use patterns.WB change in China are also uneven across regions in China,which resulted from the various land use activities across regions.Our results highlight the importance of using appropriate long-term satellite data to reveal the true properties and dynamics of WBs over large areas,which is essential for developing scaling theories,scaling many hydrological and biogeochemical processes(e.g.,the carbon cycle)and understanding the relative impacts of human activities and climate change on water resources in the world.