鄱阳湖水位-淹水面积关系不确定性的分析

湖泊淹水范围的时空变化特征往往决定了湖泊湿地的景观结构和功能。鄱阳湖是我国最大淡水湖,水位和淹水范围的季节变化悬殊,鄱阳湖淹水特征对研究鄱阳湖湿地生态系统的结构与功能都具有显著意义,过去很多研究关注鄱阳湖水位-淹水面积关系,不同的研究者得到的水位-淹水面积关系各有差异,表现出一定的不确定性。利用多时相的卫星遥感影像提取的鄱阳湖水面面积的基础上,结合鄱阳湖长时间序列的水位观测资料,探讨鄱阳湖水位-淹水面积关系不确定的原因。研究结果表明:(1)尽管鄱阳湖水面面积与水位表现分段线性关系,但在相同水位条件下,鄱阳湖水面面积表现出较大的不确定性;(2)鄱阳湖水位表现南高北低的空间异质性格局,随着水位增加,鄱阳湖水位的空间异质性降低,并且水面坡降具有季相性,相同水位下退水期的水面坡降大于涨水期的水面坡降;(3)受洲滩地形和"堑秋湖"渔业方式的影响,相同水位下退水期出露洲滩中子湖泊的水面范围大于涨水期中子湖泊水面范围;(4)此外,鄱阳湖采砂显著改变采沙场的湖盆地形,从而改变低水位下的主要采沙场的淹水范围。综上所述,鄱阳湖水位-淹水面积关系的不确定性除了受湖盆地形、"五河"来水、长江顶托等自然原因,还有采砂和堑秋湖渔业方式等人类活动的原因。

ANALYSIS OF THE RELATIONSHIP BETWEEN WATER LEVEL AND NATURAL WATER SURFACE IN POYANG LAKE

The spatial and temporal variations of inundation extent for a lake have a great influence on landscape structure and function of wetland ecosystems. Poyang Lake is the largest freshwater lake in China. Poyang Lake wetland is a very important wetland in the world for biodiversity conservation. It is very important to measure accurately the water surface dynamics of the Poyang Lake. In this paper, the scatterplot between lake water level and MODIS-derived inundation area of the Poyang Lake was used as a starting point, and the uncertainty of inundation areas with lake water levels was discussed. The results showed that:(1) Although a significant linear relationship was found between water level and inundation area for the Poyang Lake, the water surface area shows uncertainty. (2) Water level in Poyang Lake is higher in the south and lower in the north when lake water level is low, and the spatial heterogeneity of water level was decreasing with increasing lake level. (3) Water level slope in Poyang Lake in the time period of water withdrawal was greater than that in flood period. (4) Affected by fishery practice of dish-shaped sublakes, the water surface area of the sublakes in water withdrawal period is greater than that in flood period. Sand mining also changed the water extent around the sandpits when in low lake level. Therefore the inundation extent for Poyang Lake was affected by topography of lake basin, water discharge from the tributaries in Poyang Lake watershed, and the backwater effect of the Yangtze River, as well as by human activities such as sand mining and fishing practice with levees.