基于Visual MODFLOW的洋河下游地下水向海输送研究

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基于Visual MODFLOW的洋河下游地下水向海输送研究摘要:本文通过系统分析研究区的自然地理与地质-水文地质条件,确定了研究区范围和边界条件,利用Visual MODFLOW软件建立了研究区地下水系统概念模型和数学模型,利用2001-2010年地下水动态观测资料对数值模型进行了识别和验证,运用识别验证后的模型对研究区地下水向胶州湾的排放量进行了模拟与分析。

结果表明:1)大气降水对地下水向海湾输送量影响较大,丰水年(2007年)地下水向海输送量高达28.38×106m3/a,而枯水年(2002年)地下水向海输送量仅为0.24×106m3/a;2)河水的渗透补给也对地下水向海湾输送量有影响;3)含水介质、含水层类型和含水层厚度岩性均对地下水向海湾输送量产生影响;4)海平面及海水的物理性质的变化也会影响地下水入海量。

关键词:洋河,地下水,数值模拟,SGD,Visual MODFLOW0.引言0. Introduction海底地下水排泄(Submarine groundwater discharge,SGD)是沿海地区海陆交互带普遍存在的一种自然作用过程(Burnett W C,Taniguchi M,Oberdorfer J.Measurement and significance of the direct discharge of groundwater into the coastal zone[J].Journal of sea research,2001,46(2):109-116),被广泛认为是地下水向海洋环境进行物质输送的重要途径(Burnett W C,Aggarwal P K,Aureli A,et al.Quantifying submarine groundwater discharge in the coastal zone via multiple methods[J].Science of the Total Environment,2006(367):498-543),其来源有陆源地下水和循环海水。

目前,越来越多的科学家认识到海底地下水排泄不仅仅是简单的地下水向海洋的输送,更重要的是大量的营养盐、污染物和其他化学物质随地下水输入海洋(郭占荣,黄磊,刘花台等.镭同位素示踪隆教湾的海底地下水排泄[J].地球学报,2008,29(5):647-652),影响近岸海水生态系统平衡。

目前,国内外对SGD的测量方法主要有:直接的原位测量、示踪技术和模型模拟(Burnett W C,Taniguchi M,Oberdorfer J.Measurement and significance of the direct discharge of groundwater into the coastal zone[J].Journal of sea research,2001,46(2):109-116)。

本文利用Visual MODFLOW软件建立数值模拟模型对海底地下水向海湾的输送量进行研究。

Submarine groundwater discharge(SGD)is an universal natural process in the coastal belts and has been recognized as an important pathway for material transport to the marine environment, the terrigenous groundwater and circulating water are its main source. Now, more and more scientists recognize that SGD is not only the groundwater transport to the marine, but a large number of nutrients, pollutants and other chemicals transport to the marine with the groundwater, and influence the coastal ecosystem balance. At present, the main measurements are direct suit measurement, tracing technology and model simulation. In this paper, we use the Visual MODFLOW to establish the numerical simulation model and research the conveying capacity of the SGD.1.洋河下游地区自然地理与地质-水文地质条件概况1. The natural geographic and geological-hydrogeological conditions in the Yang River downstream region1.1自然地理概况1.1 The natural geographic conditions洋河是一条独立入海的天然河道,位于山东青岛市,是青岛胶南市与胶州市的界河。

洋河有两个源头:主源南源起于胶南市洋河的吕家和金草沟一带,西源出自胶州市里岔乡陡岭前。

两源在张应镇洋河崖村汇流,自西向东,流经胶州市的张应、洋河、九龙、营海四镇,于营房镇王家滩村东注入胶州湾。

河道全长31km,流域面积303km2,河口宽85m。

据大村水文站观测,洋河多年平均径流量6100万m3,最大洪峰流量达608m3/s(尹明泉,李清平,郭玉强,袁西龙,冷梅.青岛市洋河下游水源地地下水调蓄开采资源评价[J].地质调查与研究,2008,32(3):222-228)。

The Y anghe River is an independent natural river, located in, Q ingdao, Shandong province, it is the boundary of Qingdao Jiaonan city and Jiaozhou city. The Y anghe River has two sources: the main source is from Lujia and Jin Caogou of Jiaonan City, the west is derived from the Tu Lingqian in Jiaozhou City. The two source confluence in Zhang Yingzhen, the Y anghe village, flow through Zhangying、Yanghe、Jiuling、Yinghai from west to East,and , flowing to the Jiaozhou City in Wang Jiatan villiage. The river’s full length is 31km, catchment area is 303km2, and mouth width is 85m. According to the Dacun hydrological observation station, the average annual runoff is 61000000m3, the maximum peak flow is 608m3/s.研究区(东经36°08′09″~36°05′43″,北纬119°59′51″~120°00′12″)位于胶州湾西部,属华北温带季风大陆型气候,但同时又受到海洋环境的直接调节,具有显著的海洋性气候特点。

多年平均气温12.2℃,极端高温37.4℃(1997年7月27日),极端低温-16.4℃(1931年1月10日)。

全年以8月份最热,平均气温25.1℃;l月份最冷,平均气温-1.2℃。

The study area(East 36°08′09″~36°05′43″,North 119°59′51″~120°00′12″)is located in western of Jiaozhou Bay, it is North temperate monsoon continental climate, but Influenced by the direct regulation of the marine environment, it has the remarkable characteristics of the maritime climate. The average annual temperature is 12.2℃, its extreme high temperature is 37.4℃(July 27,1997)and extreme low temperature is -16.4(January 10.1931)℃. August is the hottest month in a year, its average temperature is 25,1℃, and January is the coldest, its average temperature is -1.2℃.本区多年平均降水量686.1mm,降水量季节性变化十分明显,年内分布不均匀(见图1),降水量约有80%集中在汛期的四个月(6-9月份),特别是7、8月份。

多年平均蒸发量为972.4mm,蒸发量年内分布不均(见图1),全年中以5月份为最高,多年平均达180.1mm,以1月份最小,仅为54.9mm。

同时,本区年际蒸水量与蒸发量分布也不均,2001-2010年研究区的年降水量和蒸发量的变化见图2。

The average annual precipitation is 686.1mm in this area, the precipitation changes with the season obviously and distribute uneven in a year(Figure 1). There are about 80% precipitation concentrate in the 4 months of flood season(June to September), especially July and August. The average annual evaporation is 972.4mm, it distribute uneven in a year(Figure 1), it is most in May and up to 180.1mm, it is least in January and only 54.9mm. At the same time, the annual precipitation and evaporation distribute uneven, the annual precipitation and evaporation from 2001 to 2011 are shown in figure 2.图1 洋河下游地区多年月平均降水量和蒸发量Fig.1 Mean monthly precipitation and evaporation in the Y ang River watershed图2 2001-2010年洋河下游地区年蒸水量和蒸发量Fig.21.2地质-水文地质条件概况1.2 The geological-hydrogeological conditions据地质资料(宋明春,王沛成.山东省区域地质[M].济南:山东省地图出版社,2003),本区断裂构造较为发育,典型的为洋河断陷带:北部以铺集-大东郭断裂为界,南部以郝官庄断裂为界,向东进入胶州湾。