Analysis On Lake Dynamics And Its Drivers In Hubei Province In The Past 40 Years

Lake dynamic change has been an important issue for regional environmental change, regional economic and sustainable development of ecological environment. Hubei province is known as the "province of thousands of lakes", due to the natural environmental changes and human activity’s interference, the problem of over exploiting, lake shrinking and the reduction of usable water resources were appeared, which have serious threats to the regional ecological environment and the sustainable development of social economy. Therefore, studying the spatial-temporal evolution of lakes in Hubei Province, and exploring the response mechanism between natural and human factors and lake change, has important reference value for promoting scientific management and planning and the sustainable use of lake resources.In this study, based on the improved water exponential model (MNDWI), with the help of visual interpretation, and GIS/RS technology is used, the lakes (larger than 0.1 km2) are extracted in Hubei Province in the year of 1975,1985,1995,2005 and 2014; and the lake spatial database is established with relevant attribute data of lakes; then the spatial-temporal evolution is analyzed. On this basis, the evolution mechanism of the lakes is discussed combine with the impact indicators of nature and human activities during 1971-2014. The main conclusions are as the follows:(1) The number of lakes larger than 0.1km2 is 1079,1591,1690,1940 and 1813 in the five times during 1975-2014, which shows a trend of first rapid growth and then slow or even declining. The total area of the lakes larger than 0.1 km2 are 4 449.81 km2, 4211.07 km2,3 889.74 km2,3548.74 km2 and 3422.53 km2, keeps decreasing in the five times, the magnitude of decrease first increased and then decreased. The total area of the lakes decreases about 1027.28 km2, account for about 23.09%. From the spatial distribution, the lakes shrink seriously in the Jianghan Plain; the problem of lakes shrinking is becoming better during 2005-2014.(2) Lake landscape shape index (LLSI) shows the trend of firstly increases and then decreases, the variation of the LLSI is a positive number during the two times in 1971-1995, which shows the degree of outside interference to the lakes is reducing, it does the opposite during the two times in 1995-2014. The total offset of lakes’ centroid is 33 km during 1971-2014 in Hubei province, the offset is the largest during 1985-1995, and it is reduced gradually. The lakes’centroid appears northwesterly migration from its spatial distribution, which further illustrates the problem of lake dwindling is more serious in southeastern area than that in the northwest area.(3) The indicators (annual average temperature, annual maximum temperature, minimum temperature and average annual evaporation) have an obvious rising tendency except the rainfall. The average annual rainfall is reduced most significantly during 2006-2014, which decreases 87.99mm relative to the average data of 1995-2005, reduced 8.12%; study area the average temperature increased by 1.38℃ during 1971-2014, and it increased significantly during 1996-2005, but it declined during 2006-2014. In the three indicators of human activity, The natural population growth rate shows obvious down trending of "S" type, from 12.79‰ in 1979 fall to 4.9%o in 2014, it is the most obvious during 1990-2000; the growth rate of GDP and urbanization rate have obvious fluctuations, the general trend is not very clear.(4) There is a high correlation between the indicators of temperature, evaporation and population and lakes area by comprehensive analyzing correlation and grey correlation degree. The total lake areas in the future two periods are predicted through a gray prediction model, the predicted value of total lake area in 2025 and 2035 were 3096.57 km2 and 2869.74 km2 respectively, the error rate of the model predicted values in each period are less than 0.6%, the prediction model has a high accuracy of prediction.The above data show that, the lake area in Hubei province presents the evolution trends of area decrease, fragmentation in nearly fourty yesrs; but this trend is becoming waning from the change of lake area and number in the four stages, which also indicates that the management and protection of lakes started to achieve some results in recent years. The climate shows the trend of warm and dry during the recent 45 years in Hubei province. Warming, reduced evaporation and the increased distractions due to the increase of population and are the main reasons caused lakes to shrink in Hubei province. The effect of climate factors is equally important to human activities on lake change.