| Qaidam Basin is an important strategic location which has unique advantages in resources with the potential economic value of mineral resources about 16.27 trillion yuan. With the implementation of national economic construction and the large-scale development of western region in China, the State Council will take Qaidam Basin as a national circulating economy experiment area. Although Qaidam Basin is facing good opportunities for development, the lag of groundwater exploration work and water supply projects becomes a bottleneck of economic and social development in Haixi State. To provide information of water resources and environmental geology for governments at all levels and major projects and to solve the long-term contradiction between supply and demand of daily life and production, rational development and utilization of groundwater resources has become the most important task at present. Mahai industrial zone(in Mahai Basin) is located in the northern margin of the Qaidam Basin with many salt lakes, rich mineral resources associated with many rare elements such as lead, zinc, gold, silver, lithium, boron, magnesium, coal, potassic fertilizer, glauber salt, oil and other 11 kinds of mineral deposits. The mineral reserves are huge and high grade, and located along the highway and railway, so the development prospect is extremely broad. In Mahai Basin, industrial water consumption of metal mineral areas, coal mining area and salt lake industrial zone is 2775×10~4m~3/a, and agricultural water consumption of Mahai Farm is 2200×10~4m~3/a. But Mahai Basin is short of water resources due to dry climate, strong evaporation and little rainfall, and large-scale development and utilization of water resources will destroy ecological environment, so economic development, water resources development and utilization and environmental protection are mutually restricted. To ensure economy sustainable development and ecological environment of Mahai Basin, it is bound to provide scientific water resources development and utilization plan.Hydrogeological conceptual model of Mahai Basin is established according to hydrogeological investigation and field drilling using a portable drill which is to study boundary conditions quantitatively and qualitatively. Numerical simulation model of Mahai Basin is established applying Visual MODFLOW software. Then the model is calibrated based on the fit degree of calculated values and observation results of groundwater level, and at the same time, hydrogeological parameters are inferred. This model which is identified and verified and can reflect the real hydrogeology is used to assess groundwater resources:(1) Analyse groundwater recharge and discharge of Mahai Basin through groundwater balance calculation;(2) Calculate groundwater allowable exploitation using numerical method considering changes of wetland area, springs flux, evaporation flux and groundwater downstream discharge flux and pumping ability of water pumps after groundwater withdrawal;(3) Design groundwater source field plan and verify its feasibility and rationality through model;(4) Simulate and analyse the feasibility of establishing a reservoir.Through simulation, calculation and analysis, it can conclude that, for current situation, groundwater recharge flux is 12420×104 m~3/a, groundwater discharge flux is 11111×104 m~3/a, groundwater allowable exploitation is 5475×10~4m~3/a and designed groundwater withdrawal of groundwater source field A and B is each 2737.5×10~4m~3/a, for average condition, groundwater recharge flux is 11097×104 m~3/a, groundwater discharge flux is 10760×104 m~3/a, groundwater allowable exploitation is 4380×10~4m~3/a and designed groundwater withdrawal of groundwater source field A and B is each 2190 x 10~4m~3/a. If a reservoir(intake 2.057 m~3/s) was built in Mahai Basin, for average condition, the wetland area would decrease by 39.67%, far more than the rate under the condition of groundwater allowable exploitation, which means that the construction of a reservoir(intake 2.057 m~3/s) would have serious impact on ecological environment. |
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