南水北调来水对漳卫新河口的可能影响及生态需水分析

中国北部地区面临严重的缺水问题，而南水北调工程将在一定程度上缓解人民的生活用水问题，同时南水北调来水在一定程度上也将对受水地区生态产生积极作用。特别是随着入海水量的相应增加，河口生态系统将得到一定的改善。但目前关于河口生态系统需水的研究还不多，基于河口生态稳定阈值分析的更少，对河口生态恢复工作还缺少相应的理论支持。这些都不利于河口生态系统的可持续发展。本文应用河口－海岸－海洋模型（ECOMSED）模拟漳卫新河河口及附近海域的水环境状况，分析在不同来水情景下河口海域盐度的扩散分布情况，特别是南水北调来水对河口盐度分布的影响。同时，根据生态系统稳定性阈值原理及关键物种理论，查阅渤海湾鱼类对盐度的适应情况，特别是主要鱼类在产卵育幼期对河口咸淡水区域的依赖程度及对盐度的要求，确定适宜的盐度范围。并结合模型模拟结果，分析不同来水情景下漳卫新河河口的鱼类适宜盐度面积及分布。研究结果表明，在现状来水条件下，枯季漳卫新河河口的鱼类适宜盐度面积仅为1.87平方公里，且基本沿岸分布；雨季为2.63平方公里，南水北调来水后汛期相应的面积能增加4.00平方公里。同时根据来水量与鱼类适宜盐度面积的相关关系曲线，分析得出，天然来水条件下，维持漳卫新河河口生态系统稳定所需要的入海流量约为90m?/s左右，这与历史流量水平基本相一致。

Possible impacts of South-to-North Water Diversion to estuaries and estuarine ecological water demand

Water scarcity is one of the most serious constraints to economic development and threats to the populations in the north of China. South-to-North Water Transfers is designed to meet the developing water requirements of Northern China. It also benefits ecology of water-receiving area, especially for the estuaries of these areas, because the diversion increases freshwater input. However, researches on ecological water demand of estuary especially it based on ecological equilibrium threshold limit are insufficient. This leads to lack of theory supports for ecological restoration of estuary, which is a main obstacle for sustainable development of estuary ecosystem. This paper simulates ecological conditions of Zhangwei New River estuary with ECOMSED model and analyzes salinity distributions in this area with different freshwater discharges, particularly of the South-to-North Water Transfers scenario. Simultaneously, according to ecological threshold theory and key species theory, we consult and analyze the accommodation of Bohai fishes to the salinity, especially at their spawning season or larva stage. Then with model simulation results, the suitable habitat areas and their distribution for fishes are calculated. The results show that at current freshwater input scenario, the suitable habitat area for fishes in Zhangwei New River estuary is only 1.87 km? and almost distributes along the coast in dry season. In wet season, it is about 2.63 km?. However, when South-to-North Water Transfers projects divert waters, the area can increase to 4.00 km?. We also draw the curve between freshwater inputs and suitable habitat areas, which gives results that for the historical water input, ecological water demand of estuary can be guaranteed, but current water discharge is not enough for estuary ecosystem without diversion conduction. We estimate that as Zhangwei New River estuary, with river mouth of 300m width, its minimum ecological water demand is about 15m?/s, and suitable ecological water demand is about 90m?/s.