基于Visual Modflow的洪湖石码头--小港剖面地下水数值模拟

Groundwater numerical simulation at Shimatou-Xiaogang section of Honghu region by means of Visual Modflow

随着三峡大坝的分期蓄水的逐步实施，显著改变坝下水文状况，必然改变长江中下游地下水与长江之间的关系，从而对中下游地区的生态造成影响．为定量研究洪湖地区地下水与长江之间的补排关系以及地下水与长江的交换量，为三峡工程对中下游地区的生态影响评价提供依据，采用Visual Modflow模拟洪湖地区石码头小港剖面的地下水动态，为三峡工程的生态影响提供确实依据．在模拟过程中考虑长江水位变化、降水入渗补给、潜水蒸发以及地下水头的初始值可能对模拟造成的影响，使用River、Recharge、Evpotranspiration模块分别模拟河流、降水入渗补给和潜水蒸发．使用2001年～2003年的螺山水位数据、小港监测站的气象数据及地下水每日观测数据对模型进行调校．调校后，模型整体洪差下降到0．16m，误差均方根下降至0．639m．利用模型分别对2004年～2006年地下水位进行预测，预测误差为02629m，误差均方根为0．864m．模拟显示一年中地下水补给长江的天数为146d，时间为每年的12月中旬至第2年的4月底；长江补给地下水的平均天数为220d，时间为5月初至12月中旬．模拟估算出研究区内平均每年长江对地下水的单宽补给量为37．92m^3，在研究区1551m的长江干堤上，长江每年向研究区补给地下水水量为58819．09m^3．

With the Three Gorge Projects was used in 2003, it changes the hydrological condition of downstream of Yangze River and influence the relation between underground water and river, and then affect the ecological system of region of downstream of Yangze River. For revealing the relation between underground water and river, this article uses the Visual Modflow to establish a groundwater numerical model, and then it is used to simulate the groundwater flow in ShiMaTou-Xiao Gang section of Honghu region. Several factors are taken into account, which include the water level of Yangze River, precipitation, evaporation and the initial head. River, precipitation and evaporation are modeled by River modular, Recharge modular and Evpotranspiration modular respectively. After established, it is calibrated by the observed data from 2001 to 2003. The average error decreases to 0.16m and the Root Mean Squared of the error decreases to 0. 639m. The result shows that the average error is 0. 629 and the Root Mean Squared of the error is 0. 864m when it is used to predict the water level of groundwater from 2004 to 2006. Furthermore, it shows that the number of the day during which the underground water recharge to the Yangze River is 146 days while the number of the day during which the Yangze River recharge to the underground water is 220 days. Beside, the supply that the Yangze River to underground water at one kilemeter is 37.92 m^3 the longth of Yangze River within the research region is; 1 551m, so the total amount that Yangze River recharge to the underground water is 58 819.09 m^3.