湖泊科学   2017, Vol. 29 Issue (1): 160-175.  DOI: 10.18307/2017.0118. 0

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LIN Huan, XU Xiuli, ZHANG Qi. Relationship of the water supply and drainage in a typical wetland of Lake Poyang. Journal of Lake Sciences, 2017, 29(1): 160-175. DOI: 10.18307/2017.0118.
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2016-01-29 收稿
2016-04-21 收修改稿

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(1: 中国科学院南京地理与湖泊研究所流域地理学重点实验室, 南京 210008)
(2: 中国科学院大学, 北京 100049)

Relationship of the water supply and drainage in a typical wetland of Lake Poyang
LIN Huan 1,2, XU Xiuli 1,2, ZHANG Qi 1
(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)
Abstract: 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.
Keywords: Soil water    plant root zone    water supply and drainage process    Lake Poyang wetland    GSPAC system    HYDRUS model

1 试验区及野外数据观测 1.1 试验区概况

 图 1 试验区地理位置 Fig.1 Location of the study area
1.2 观测方法与数据获取

 图 2 试验区联合观测系统布设 Fig.2 Joint observation system at the study area
2 典型湿地GSPAC系统水分垂向运移模型的构建 2.1 模型概化

 图 3 湿地GSPAC系统水分垂向运移概念模型 Fig.3 Conceptual model of water vertical movement in wetland GSPAC system

 ${R_{{\rm{in}}}} + G-D-{E_{\rm{a}}}-{T_{\rm{a}}} = \mathit{\Delta }W$ (1)

2.2 数值模型的构建

2.2.1 模型原理与数学描述

 $\frac{{\partial \theta }}{{\partial t}} = \frac{\partial }{{\partial z}}\left[{K\left( \theta \right)\left( {\frac{{\partial h}}{{\partial z}} + 1} \right)} \right] -S\left( {z, t} \right)$ (2)

 $\theta \left( h \right) = \left\{ \begin{array}{l} {\theta _{\rm{r}}} + \frac{{{\theta _{\rm{s}}}- {\theta _{\rm{r}}}}}{{{{\left[{1 + {{\left| {\alpha h} \right|}^n}} \right]}^m}}}\;\;\;\;h < 0\\ {\theta _{\rm{s}}}\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;h \ge 0 \end{array} \right.$ (3)
 $K\left( \theta \right) = {K_{\rm{s}}}S_{\rm{e}}^{1/2}{\left[{1-{{\left( {1-S_{\rm{e}}^{1/m}} \right)}^m}} \right]^2}$ (4)
 ${S_{\rm{e}}} = \frac{{\theta-{\theta _{\rm{r}}}}}{{{\theta _{\rm{s}}}-{\theta _{\rm{r}}}}}$ (5)

 $S\left( {z, t} \right) = \alpha \left( h \right)\gamma \left( z \right){T_{\rm{p}}}$ (6)

 $\alpha \left( h \right) = \frac{1}{{1 + {{\left( {h/{h_{50}}} \right)}^\mathit{p}}}}$ (7)

2.2.2 边界条件和初始条件

2.2.3 输入数据

 图 4 地下水位埋深日变化 Fig.4 `Diurnal variation of the groundwater depth
 图 5 降雨、太阳辐射、气温和湿度等气象数据的日变化 Fig.5 Diurnal variations of rainfall, solar radiation, temperature and humidity

2012年12月-2013年11月期间，年降雨量为1718 mm，主要集中在4-6月，占年总量的66 %；年太阳辐射总量为3836.92 MJ/m2，7-8月太阳辐射量最大，达到979.11 MJ/m2；气温年内呈单峰型变化，日平均气温的最高值出现在7月，最低值出现在1月；湿度在54.3 % ~98.7 %范围内变化.

 $r\left( z \right) = \left\{ \begin{array}{l} 317/{L_{\rm{R}}}\;\;\;\;\;\;0\;{\rm{cm}} \le z \le 10\;{\rm{cm}}\\ \;{\rm{85/}}{\mathit{L}_{\rm{R}}}\;\;\;\;\;\;\;\;10\;{\rm{cm}} \le \mathit{z} \le 40\;{\rm{cm}}\\ {\rm{12}}{\rm{.4/}}{\mathit{L}_{\rm{R}}}\;\;\;\;\;\;40\;{\rm{cm}} \le z \le 80\;{\rm{cm}} \end{array} \right.$ (8)
2.2.4 模型参数

 图 6 脱湿条件下土壤水分特征曲线 Fig.6 The soil water characteristic curves in dehumidification experiments

 ${A_i} = \frac{{\Delta y/y}}{{\Delta {x_i}/{x_i}}}$ (9)

2.3 模型率定

 $RMSE = \sqrt {\frac{1}{N}\sum\limits_{i = 1}^N {{{\left( {{S_i}-{O_i}} \right)}^2}} }$ (10)
 $RE = \sum\limits_{i = 1}^N {{S_i}} /\sum\limits_{i = 1}^N {{O_i}-1}$ (11)
 $R = \sum\limits_{i = 1}^N { \le \left( {{S_i}-\bar S} \right)\left( {{O_i}-\bar O} \right)} /\sqrt {\sum\limits_{i = 1}^N {} {{\left( {{S_i}-\bar S} \right)}^2}/\sum\limits_{i = 1}^N {{{\left( {{O_i} - \bar O} \right)}^2}} }$ (12)

3 结果与分析 3.1 土壤含水量的参数敏感性分析

3.2 模型率定结果

 图 7 土壤含水量模拟值与实测值的对比 Fig.7 Comparison of observed and simulated soil water contents

3.3 GSPAC系统界面水分运移规律分析

 图 8 湿地GSPAC界面的日水分通量变化 Fig.8 Diurnal variation of water fluxes in wetland GSPAC interfaces

(1) 大气-植物界面水分通量

(2) 大气-土壤界面水分通量

(3) 根系层底部界面水分通量

(4) 根系层土壤水分变化

3.4 土壤水分补排过程分析

 图 9 不同水文时段根系层土壤水的补排关系 Fig.9 Supply and drainage relationships of root zone in different water level stages

4 讨论

5 结论

6 参考文献