基于Landsat及ICESat和Hydroweb的太湖容积变化监测

为得到太湖长期动态变化过程,利用1975—2015年Landsat数据,基于归一化差异水体指数法(NDWI)和改进型归一化差异水体指数法(MNDWI)提取湖泊面积数据,并基于ICESat和Hydroweb数据提取太湖水位数据。将两者相结合,得到了太湖容积变化和水量平衡数据。据此,分析了太湖水位、面积和容积变化的规律和趋势,并对其影响因素进行了研究。结果表明,太湖面积和容积变化近40年来呈缓慢增长趋势,分别从1975年的2 320.07 km~2和-0.047 0 km~3增长到了2015年的2 341.06 km~2和0.275 9 km3,增长趋势不明显;太湖水位总体上呈波动变化趋势,水位从1975年的0.982 6 m变为2015年的1.135 9 m。因此,太湖水位与面积相关性中等(R2≈0.65),容积变化与面积和水位变化的相关性较高(R~20.85)。太湖水量平衡为正平衡且变化不大,为0.009 2 km~3。入湖水量的增加、年降雨量和年蒸发量的变化及政府"退地还湖"政策是导致太湖发生变化的主要原因。

ICESat/Hydroweb and Landsat data-based monitoring on volume variation of Taihu Lake

In order to obtain the long-term dynamic variation process of Taihu Lake and in accordance with the Landsat data from 1975 to 2015， the surface area of the lake is extracted based on the methods of the Normalized Difference Water Index （NDWI） and the Modified Normalized Difference Water Index （MNDWI）， while the water level of the lake is extracted according to the ICESat and Hydroweb data. By integrating both of them， the volume variation and the water balance data of the lake is obtained. On the basis of this， the water level， the surface area and the volume variation laws and trends are analyzed， and then their impacting factors are studied as well. The result shows that the variations of both the surface area and the volume of Taihu Lake in recent 40 years exhibit the trends of slow increases from 2 320.07 km2 and -0.047 0 km3 in 1975 to 2 341.06 km2 and 0.275 9 km3 in 2015 respectively with unobvious increasing trends， while the water level of the lake is generally presents a variation trend of fluctuation from 0.982 6 m in 1975 to 1.135 9 m in 2015. Therefore， a moderate correlation （R2≈0.65）is there between the water level and the surface area， meanwhile， a higher correlation （R2>0.85）is there between the volume variation and the variations of both the surface area and the water level. The water balance of Taihu Lake is positive with less variation， which is 0.009 2 km3. The increase of the inflow water amount， the variations of the annual precipitation and the annual evaporation as well as the policy of returning land to lake are the main factors to cause the variation of Taihu Lake.