|LIN Huan,XU Xiuli,ZHANG Qi.Relationship of the water supply and drainage in a typical wetland of Lake Poyang. J. Lake Sci.2017,29(1):160-175. DOI:10.18307/2017.0118
|湿地水分在地下水含水层-土壤-植物-大气界面的运移和转换是维持能量和营养物平衡的重要环节，水分运移是湿地生态水文过程研究的关键.数值模型模拟已成为水分运移研究的重要手段，然而限于复杂的湿地自然条件及有限的监测手段，部分界面水分通量连续动态变化数据的获取及定量化工作较为困难，目前应用数值模拟法于湿地水分运移研究的案例仍不多见.本文以鄱阳湖典型湿地为研究区，构建垂向一维数值模型，阐释了湖泊水位显著季节性变化条件下，湿地水分在不同界面的传输过程，量化了湿地水分的补排关系.结果表明：（1）界面水分通量季节性差异大，降雨入渗地面和根系层水分渗漏均对降雨变化响应敏感，主要集中在4-6月，分别占年总量（1450和1053 mm）的65%和73%.土面蒸发和植物蒸腾年总量为176和926 mm，土面蒸发主要受气候条件影响，植物蒸腾还与植物生长特征有关，均集中在7-8月，分别占年总量的30%和47%.深层土壤向浅层根系层的水分补给集中发生在地下水浅埋时段-68月，占年总量（609 mm）的76%；（2）湿地植物根系层水分补排受鄱阳湖水位季节性波动影响显著.除丰水期（7-9月）主要补给为深层土壤水外，退、枯、涨水期的主要补给均为降水入渗.涨水期（4-6月）和枯水期（12-3月）的主要排泄为根系层水分渗漏，丰水期以植物蒸腾排泄为主，退水期（10-11月），土面蒸发与植物蒸腾为主要排泄，且比重相当.本文定量了鄱阳湖典型湿地不同界面水分连续交换关系，区分了土面蒸发和植物蒸腾，辨析了各界面水分的主要影响因子，研究结果有助于深入理解水分在湿地生态系统地下水含水层-土壤-植物-大气界面的相互作用机制，认识湖泊洲滩湿地水量平衡，为揭示湖泊水情变化对湿地生态的可能影响提供依据，为湿地生态水文过程研究提供重要方法和理论参考.
|关键词: 土壤水 根系层 水分补排过程 鄱阳湖湿地 GSPAC系统 HYDRUS模型
|Relationship of the water supply and drainage in a typical wetland of Lake Poyang
LIN Huan1,2, XU Xiuli1,2, ZHANG Qi1
1.Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, P. R. China;2.University of Chinese Academy of Sciences, Beijing 100049, P. R. China
|Water movement within the groundwater-soil-plant-atmosphere continuum (GSPAC) plays an important role in maintaining energy and nutrient balance in wetland, and water movement is a key to wetland eco-hydrological process. Numerical simulation is an important method for the study of water movement. However there are few examples of numerical simulation on water movement in wetlands, due to the limitation of complicated natural conditions and restricted monitoring methods. In this paper, a typical wetland in Lake Poyang was selected as a study area. One-dimensional vertical numerical model was used to investigate the water movement process through different interfaces and to quantify relationship of the water supply and drainage. The results showed that, (1) the water fluxes through interfaces were in a significant seasonal variation. The rainfall infiltration and the soil water drainage were sensitive to rainfall, which mainly occurred during April and June, taking 65% and 73% of the annual amount (1450 and 1053 mm), respectively. The soil evaporation and vegetation transpiration were related to climatic conditions and the character of plant growth, which were highest in July-August, taking 30% and 47% of their annual amount (176 and 926 mm), respectively. The upward fluxes from deep soil into root zone mainly occurred in June-August, accounting for 76% of the annual amount (609 mm). (2) The water supply and drainage in plant root zone of the wetland were strongly influenced by the seasonal changes of water level of the Lake Poyang. The main water supply of the root zone is rainfall infiltration except for the high water level period (July-September), in which the upward flow from deep soil is the major water source. In the rising water level (rainy seasons of April-June) and low water level (December-March) periods, the main drainage way is via deep leakage. In the high water level period, the vegetation transpiration is the major water discharge. In lake water level recession period, soil water drainage is mainly via vegetation transpiration and soil evaporation. Our study quantified the water transformation relationship through different interfaces in the typical wetland in Lake Poyang and differentiated the soil evaporation and vegetation transpiration. The results help to better understand the water movement in the GSPAC system and the water balance of lake wetlands, which are essential for lake and wetland managements.
|Key words: Soil water plant root zone water supply and drainage process Lake Poyang wetland GSPAC system HYDRUS model