Studies On The Lake Evolution And Its Water Storage Capacity In Jianghan Plain Based On LUCC

As a natural barrier,the lake plays an important role in resisting flood disaster in the lake area and ensuring the safety of flood control.However,due to the changes of natural environment and the activities of human development and utilization,the problems such as over-exploitation of water resources,deterioration of water quality,lake shrinking and lake sedimentation,have a significant impact on the water storage capacity of lakes,threat to the property security of lake masses seriously,and is not conducive to the sustainable development of social economy.This paper takes the Jianghan Plain as the study area,and takes the Landsat TM remote sensing image and the land use database of Jianghan Plain as data source.First,the overall characteristic of land use and land cover change in the study area is analyzed.Then,based on the normalized difference water index model(NDWI),and combined with artificial visual interpretation,the data of the lake surface area with the area of more than 0.1km2 in 1990,1995,2005,2010 and 2015 were extracted respectively,and the collected lake attribute data were also used to establish the lake database of Jianghan Plain,so as to analysis the spatial and temporal evolution of lakes in Jianghan Plain from 1990 to 2015.On the basis of this,combined with the spatial and temporal variation of natural and human activities from 1990 to 2015,the lake evolution mechanism under the influence of various driving factors was discussed.Finally,the lake water storage capacity evaluation model was established to estimate the lake water storage capacity in different periods.The main conclusions are as follows:(1)From the whole research period,the trend showed that the cultivated land and unused land continued to decrease,water area and construction land continued to increase,while forest land and grassland show fluctuated from 1990 to 2015.Among of which the area of cultivated land,woodland and unused land decreased by 2200.12km,2.8 km2 and 23.08km2 respectively,while the construction land,water area and grassland area increased by 1036.03km,1169.54km2 and 20.45km2 respectively.From the point of the rate of change,especially the decrease of cultivated land,the increase of water and construction land is more prominent.The construction land is the fastest growing,followed by water and grassland growth is slow,the average annual growth rate is 1.75%,1.11%and 0.57%respectively.The average annual reduction rates of cultivated land,woodland and unused land is 0.40%,0.01%and 0.43%respectively,for that the unutilized land was the fastest,the second was the cultivated land,and the forest land was the slowest,but the reduction of cultivated land was much larger than unused land and woodland,and is about 95 times of the unused land.(2)The number of lake patches in the Jianghan Plain that area more than 0.1km2 is 563,482,424,473,417 and 469 in the six periods from 1990 to 2015,respectively.In addition to the slight increase in 2005,the number of lake patches show rapid decrease in the early period,while the decrease rate slowed down of the late overall,and the number of lake patches decreased by 94,and the rate of decline is 16.70%.The total area of lakes in the study area is 1631.19 km2,1523.26 km2,1464.85 km2,1505.99 km2,1440.41 km2 and 1503.34 km2 respectively,and the total area of lakes continued to decrease early,the latter part of the slow increase in the trend.In the past 25 years,the total area of lake had decreased 127.85 km2,and the rate of decline is 7.84%.From the point of spatial distribution,the distribution of the lake area in the range of 0-50 meters play the dominate role,and the total area is between 1363.42 km2 and 1507.62 km2,accounting for about 92%to 95%of the total area of the lake.From 1990 to 2015,the overall deviation of the lake centroid of Jianghan Plain is 5.49km,showing increases at first and then decreases,and among of which the offset lake centroid is the largest between 2005 and 2010.(3)About the three natural factors,the annual rainfall and annual actual evaporation showed a trend of fluctuation decrease,while the annual mean temperature showed the trend of fluctuation increase,slightly.In particular,the average annual rainfall in the study period was 1291.89mm,among of which the average annual rainfall in the period of between 1990 and 2001 is 1418.61mm,while the average annual rainfall in the period of between 2002 and 2015 is 1183.28mm,decreasing 235.33mm compared with the previous period.The annual average temperature is 16.60?,and the average annual temperature between 1990 and 2002 had increased by 1.91 ?,while the average annual temperature in 2003-2015 had increased by only 0.38?.Among the three indicators of human activity,the natural growth rate of population showed a downward trend as a whole,from 14.30‰ in 1990 to 4.91 ‰ in 2015,showing a trend of rising slowly after a sharp decline.The growth rate of urbanization fluctuated sharply from 1990 to 2001,and then showed a steady trend from 2002 to 2015.The growth rate of economic growth fluctuated sharply and the overall development trend was not obvious.The results of correlation analysis show that the three factors of rainfall,population growth and urbanization rate have the most significant effect on the change of lake surface area.(4)A series of factors that influenced the water storage capacity of lake,such as the terrain of lake bottom,the depth of lake water,the area of lake,the connectivity of river and lake,etc.But because of the particularity of the lake formation in Jianghan Plain,the lake water storage capacity is closely related to the lake area,so the relationship between lake surface area and lake water storage capacity model was constructed.The total adjustable water storage capacity of Jianghan Plain is 47.80×108m3-55.09×108m3 in the study period,and with the decreasing of the surface area of the lake in Jianghan Plain,the adjustable water storage capacity of the lake show the trend of decreasing overall,but the difference of change rate is large between the different years.So far,there are many researches on the evolution of lakes at home and abroad,but there are few studies on the impact of lake evolution on flood control capacity from the perspective of flood control and disaster reduction.By constructing lake water storage capacity evaluation model,a large-scale lake regulation function evaluation of the study is also lacking,this study can make up for such gaps.This study can provide reference for the study of flood control capacity of regional lake,and can provide scientific guidance for flood of lake control construction in Jianghan Plain and Hubei Province as a whole.