| The lake eutrophication question has already caused the extensive concern in recent years, lake eutrophication and bloom of algal tha issue world most loud problem that lake faces. Dianchi lake that plays an important role in the economic development of Kunming faces the same problem too. Because of the influence of the human activity, pore water receives serious pollution, seem more and more important through the nutrition load of entering the lake of groundwater, especially played facilitation to the eutrophication of the lake water body. The main reason of eutrophication of lake is excessive nitrogen, inward-remittance of phosphorus. According to mechanism this, whom lake take mainly in the administration of eutrophication " accuse of other source" and measure that " make a reduction of endogenous " in the past, but the lake eutrophication question is not lightened fundamentally, In order to control the environment, the mechanism that look for Dianchi lake to degradate, better understanding nutriment permeates through the law of the lake through the groundwater, find out the reason why the eutrophication of lake produces, this text proceeds with basin pore water of Kunming (because pore water is buried shallowly, high degree of pollution), come, probe into it enter lake water yield and N, P nutrition load carried to lake water body contribution of eutrophication, offer the scientific basis for the groundwater amount of lake entered and determination of N carried, P nutrition load of basin of Dianchi lake. This text synthesizes the investigations of domestic and international relevant contents, utilize more popular basin pore water of Kunming of Visual Modflow software simulation domestic and internationally and enter lake flux and N, P load. Through studying, draw the following conclusion:1)Survey the situation of the materials over the years according to the pore water water level monitoring point in the basin, combine groundwater water level dynamic characteristic and their influence terms of change, study region groundwater change dynamic characteristic divide following 3 type into within the year: Rainfall type, exploiting type and irrigating type. From edge of basin to the centre, dynamic change of water level reduces the groundwater. West of the basin, north bank groundwater water level has demonstrated the course slowly lifting in the past 20 years. And it is influenced that the groundwater is still exploited near edge of east of basin and southern Chenggong, the water levelpresents the downward trend. Because of enormous change that land utilize, so as to study region enter one relative wet season since the 1990s, and the increase of rainfall is the basic reason lifted wholly in basin pore water water level of Kunming.2)Simulation Kunming when the underground rivers of basin, use and commonly recognized Visual Modflow (visual groundwater flow model) extensively in the world. It is a square net of 52X44 (little equilibrium land) that the model is dispersed on the level, the size of each net is 500×500 m~2; Hang down the upward dispersed foundation stratum rock, hydrogeological structure, holing in the section and carrying on detailed analysis of studying area, it is five layers to be dispersed in the imitating area: The first layer is soil layer of earth, thick 1.5m; The second layer glues the soil layer, thick 7.5m for flour sand quality; The third layer is powder sand layer, thick 3m; The fourth layer is stone soil layer of gravel, thick 5m; Fifth for being weak water glue soil layer completely, regarded as relative water barrier, bottom border the non- horizontal border. The thickness change of water-bearing stratum is 3-17m. In order to reduce the complexity of simulation, the earth's surface water body impact on groundwaters such as river,etc. in it last basin this research (MODFLOW software can be imitate the river after being melted generally), mainly consider the long-term water table change trends and impact on groundwater of rainfall. This model regards the lake as a part of the water-bearing stratum, set up the water-bearing stratum of the area of the lake as unit dose with high penetrance, set up, for make flood peak border terms, input area of lake namely water level of lake as known border terms into reach the model. Bondary uses the control of water level, the circle uses and observes the moon average water level materials of the monitoring materials over the years of the well as border terms outside the simulation region, the water level of Dianchi lake adopts the moon average water level materials over the years, the initial condition adopts the water level of January of 1984.3) This text tentative calculated groundwater discharge flux to lake of the north of basin of Kunming basin .The groundwater discharge flux to lake is 6.5×10~6-6.9×10~6m~3/a. Compared with flow 665 millionm~3/a of foot-path of the earth's surface it, it is the flow of foot-path of the earth's surface percent 0.98-1.04; The nitrogen, phosphorus carried by it enters the range of the lake quantity in 27.13t-406.26t/a, 1.84t-10.04t/a separately, it compares with nitrogen, phosphorus amount 14155t/a, 1486t/a that the rainwash carries, the nitrogen that the groundwater carries, phosphorus amount of lake entered are that the nitrogen,phosphorus that the rainwash carries enters 0.2-2.8 of the lake quantity, separately 0.12-0.67. This research has filled in the blank of quantitative research of the amount of lake entered in the basin research of Kunming, content and method studied in abundant basin groundwater of Kunming are that the determination of entering the lake flux of salt of nutrition is offered scientific basis in the basin groundwater in Dianchi lake.4)An analysis result of underground rivers: It is simpler that the benefit of the basin groundwater of Kunming arranges the relation, in this model, precipitation is a main factor of influencing the field of underground rivers, in different seasons, groundwater water level line or to move on the bank to lake always, the movement to study into region result that precipitation influence mainly. The precipitation changed with change of time, therefore lines of water level such as the groundwater in the studying area,etc. were moved with time dynamically too. Particularly, the increase of the precipitation will cause the corresponding rising of the groundwater water level. Lines of water level such as the groundwater,etc. will be moved to the lake; On the contrary, turn towards on the bank and move.5)The main supply amount of the groundwater is the atmospheric precipitation in the simulation of model, the changing the total trend every year of precipitation rises. The amount of lake entered of groundwater, N, P nutrition load presents the downward trend, on its reason, mainly because the simulation region is in the site of Kunming, the land use change greatly in the most recent 13 years, the construction land, forest meadow and field are increase; The cultivated land, not land of use are in the reduction. Combine with Kunming in recent years because of the underground pipe network and completion on road surface of cement, precipitation enters the quantity of oozing the supply groundwater and reduces because of this too. So, the groundwater discharge flux to the lake reduce Correspondingly. |
