Tianjin Binhai Area Reservoir Water Salinization Mechanism Analysis And Experimental Research

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.