天津滨海地区水库水质咸化机理分析及实验研究

【作者】 赵文玉；

【导师】 王启山；

【作者基本信息】 南开大学 ， 环境工程， 2006， 博士

【摘要】 天津市是个水资源极度匮乏的城市，水危机已成为制约天津市社会经济发展的重要因素。已经实施的引滦济津工程和引黄济津工程，为解决天津市水资源危机发挥了重大的作用。天津滨海地区的北大港水库作为引黄济津工程的调蓄水库，一直存在水质咸化的问题，限制了其作为饮用水源水库功能；正在实施的南水北调工程将是彻底解决天津市水资源危机的重要举措，拟将天津滨海地区的北塘水库设置为该工程配套的调蓄水库，经调查研究发现，北塘水库也存在水质咸化问题。因此，研究天津滨海地区水库水质咸化机理和水质咸化数学模型，进而研究水库水质咸化的防治措施，具有重大的理论意义和迫切的现实意义。从传质理论出发，根据天津滨海地区的自然地理和气候气象特点，结合天津滨海地区水库水质咸化的实际情况，全面地分析了天津滨海地区水库水质咸化的影响因素有盐碱土、咸化浅层地下水、气候气象条件(，包括风、蒸发、气温等)、大气沉降、海水入侵、库内底咸水的水质水量及水库水深(水位)等，其中主要的水质咸化机理是盐碱土和咸化浅层地下水的传质作用、蒸发量大于降雨量的蒸发浓缩作用、风的搅拌加快水质咸化速度的作用以及与水库水深相关的下渗压咸作用等。进行了盐碱土、咸化浅层地下水、水深、风、温度等主要因素对水库水质咸化影响的半定量的室内试验研究，探讨了它们对水库水质咸化影响的规律，得出如下结论：1)盐碱土和咸化浅层地下水的含盐量越高，上覆水体水质咸化速度越快；2)水深增加，水体水质咸化速度减慢；3)风的存在将加快水体水质咸化速度；4)温度越高，水体水质咸化速度越快。采用现场水质咸化模拟试验与实际数据的物料平衡相结合的方法，研究了天津滨海地区的北大港水库水质咸化机理与数学模型，并研究了北大港水库水质咸化防治措施，得出如下结论：1)由于风的扰动作用，北大港水库水质咸化模型为完全混合零维模型，即水质咸化程度只与时间有关，与空间点位无关；2)北大港水库库底盐碱土的传质作用是水质咸化的最主要因素，蒸发浓缩作用是次要因素；3)在研究期间，北大港水库水质咸化模型的数学表达式为零维线性模型，即水质咸化程度与时间成正比；4)防治北大港水库水质咸化主要的工程措施是加高围堤(库底高程不变，加大水深)、缩小水库面积(保证调蓄库容不变)，管理措施是蓄淡水前尽量排尽库内原存底咸水。采用对比的方法研究了天津滨海地区的北塘水库与北大港水库的水质咸化特点，用简化条件的理论推导方法研究了在传质与渗漏压咸共同作用下北塘水库水质咸化的数学模型，再结合北塘水库的实际情况研究讨论了各种因素对水库水质咸化的影响规律，最后研究了北塘水库水质咸化防治措施，得出如下结论：1)简化条件后推导出的在传质与渗漏压咸共同作用下的北塘水库水质咸化的数学模型，基本上符合北塘水库水质咸化的实测数据反映的趋势，即蓄水的前期水质咸化速度快，经过一段时间后，水的含盐量大体上保持不变；2)在前述理论模型的基础上，讨论了调蓄水深、非稳定渗流、围堤侧渗流、传质通量、初始盐度、蓄水过程及蒸发和降雨等因素对北塘水库水质咸化影响的规律；3)在上述研究和讨论的基础上，提出了北塘水库水质咸化防治的工程措施和管理措施，其中最有效的措施是采用加高围堤的方式增加北塘水库的库容，即库底高程不变，底面积不变，加大水深。更多还原

【Abstract】 The water resource is very insufficient in Tianjin city, which have become an important influencing factor to social and economic development. The project of Yellow River water transfer for Tianjin and the project of Luan-He water transfer for Tianjin have played important roles in solving the water shortage in Tianjin. As the storing reservoir of the project of Yellow River water transfer for Tianjin, Bei-Da-Gang reservoir in Tianjin Binhai Area has a problem of water salinization all long, which impacts its function as the drinking water source reservoir. The South-to-North Water Transfer Project, which is planning and carrying out for several years, will exhaustively solve the water crisis in Tianjin. The project need Bei-Tang reservoir in Tianjin Binhai Area as a storing reservoir. There also has a problem of water salinization of Bei-Tang reservoir after some researches. Therefore, the study on the reservoir water salinization mechanism and mathematical model in Tianjin Binhai Aera, and the study on the prevention and treatment measure for the reservoir water salinization, has significance in theory and practice.Based on the mass transfer theory, integrated with the characteristic of geography and weather in Tianjin Binhai Aera, combined with the reservoir water salinization, we roundly analyze and generalize the factors for reservoir water salinization as follows, saline soil, saline shallow groundwater, weather conditions (such as wind, evaporation and air temperature etc.), atmospheric deposition, sea water intrusion, water quality and quantity in reservoir bottom, and water depth in reservoir (water level) etc.. The main reservoir water salinization mechanisms are as follows, mass transfer of saline soil and saline shallow groundwater, and evaporation concentrating for evaporation over precipitation, and increase of water salinization speed owing to wind agitation, and percolation desalinization correlated with water depth in reservoir etc..We have done a lot of semi-quantitatively laboratory experiments to study the law of influence of reservoir water salinization about some main factors such as saline soil, saline shallow groundwater, water depth, wind and temperature. We drew some conclusions as follows: 1) if the salinity of saline soil or saline shallow groundwater is higher, the speed of water salinization is faster; 2) the speed of water salinization is slower when the water depth is greater; 3) wind can accelerate the speed of water salinization; and 4) when temperature is higher, the speed of water salinizatio is faster.We studied the water salinization mechanism and mathematical model of Bei-Da-Gang reservoir in Tianjin Binhai Aera by simulation experiment and mass balance of collected data interrelated with reservoir water salinization. Then we studied the prevention and treatment measure for water salinization of Bei-Da-Gang reservoir. Some conclusions were obtained as follows: 1) because of the agitation of wind, water salinization mathematical model can be described with complete mixing zero-dimension model, i.e. the degree of water salinization is not related with space but with time; 2) the mass transfer of the saline soil in the reservoir bottom is the most important factor for the reservoir water salinization and evaporation concentrating is secondary; 3) during the study period, the expression of reservoir water salinization mathematical model is linear model, i.e. the reservoir water salinity directs proportional to time; 4) the main engineering measure to control the water salinization of Bei-Da-Gang reservoir are building some higher reservoir banks and reducing the reservoir area under both the reservoir volume and the absolute altitude of the reservoir bottom remain changeless, and the management measure is draining the saline water in the reservoir by all means before storing fresh water.We compared the water salinization characteristics of Bei-Tang reservoir with those of Bei-Da-Gang reservoir. Through the methods of theoretical derivation by simplifying the factors, we inferred the water salinization mathematical model of Bei-Da-Gang reservoir under action of mass transfer together with percolation desalinization. Then we discussed the reservoir water sanilization influencing laws of some important factors consisting in Bei-Tang Reservoir. At last, we investigated the prevention and treatment measure for water salinization of Bei-Tang Reservoir. We achieved some results as follows: 1) the water salinization mathematical model, which is derived in theory, can basically explain the trend of the field test data in Bei-Tang reservoir, i.e. the speed of water salinization is faster in the beginning of storing water, then the water salinity keeps immobile on the whole; 2) Based on the theoretical model above, we discussed the reservoir water sanilization influencing laws of some important factors such as water depth, unsteady seepage, lateral seepage of reservoir bank, initial water salinity, the process of inflow and evaporation and precipitation etc.; 3) on the base of forementioned study, we put up some the engineering and management measures to reduce the water salinization in Bei-Tang reservoir, and the most effective measure is to implement a project, which is to increase the reservoir volume by increasing the height of reservoir bank under both the reservoir area and the absolute altitude of the reservoir bottom remain changeless.更多还原