Empirical study on ecological environment early warning of water source area

The main eco-environmental problems in water source areas are soil erosion, non-point source pollution, geological disasters, less cultivated land per capita and high population density. The comprehensive evaluation of the ecological environment in the water source area shows that the quality of the ecological environment in this area is in a general state, and the ecological environment will deteriorate in a short time. To carry out early warning research of water sources, it is necessary to accurately grasp the current situation of ecological environment security in the study area, predict and evaluate its ecological environment security, predict the spatial and temporal distribution and harm degree of unsafe state, and put forward preventive measures.

5.6. 1 early warning technical route

The technical route of eco-environmental early warning is the same as that of eco-environmental quality evaluation. Through on-the-spot investigation, data collection, literature review and expert consultation, the index system and evaluation criteria are established, the judgment matrix of different levels of indicators is established, the consistency of the judgment matrix is tested and revised, the quantitative scores of individual indicators at all levels are determined, the quantitative scores of each subsystem are determined, and the total scores of regional environmental quality (including current and predicted values in different periods) are determined. According to the evaluation results, the early warning degree and countermeasures are put forward.

5.6.2 Determination of Early Warning Period and Data Collection

This study selected three early warning periods, that is, now, 20 10 and 2020, in order to cooperate with the "Eleventh Five-Year Plan" and the medium and long-term development plan of social and economic development.

Existing data are based on Nanyang Economic Statistics Yearbook (calendar year), Danjiangkou Reservoir Area and Upstream Water Pollution Prevention and Control Plan (2003), Nanyang Ecological Function Zoning (2002) and Nanyang Environmental Bulletin (calendar year) compiled by Nanyang Environmental Protection Bureau. Nanyang Water Resources Bulletin (calendar year) compiled by Nanyang Water Resources Bureau, Danjiangkou Reservoir Area and its upstream water and soil conservation plan (2003), Investigation of Non-point Source Pollution in South-to-North Water Diversion Project compiled by Nanyang Agriculture Bureau (2004), Proposal of Natural Forest Protection Project in the Middle Route of South-to-North Water Diversion Project compiled by Nanyang Forestry Bureau (2004), and the coordination of land use and ecological environment construction in Nanyang City.

The data sources of 20 10 and 2020 are obtained by trend extrapolation based on historical statistical data.

5.6.3 Determination of forecast years of ecological factors (20 10 and 2020)

The present situation value is directly calculated by the score calculated in the fourth chapter of ecological environment quality evaluation, and the weight is directly obtained by the index weight established earlier. The data of 20 10 and 2020 are obtained by trend extrapolation based on the statistical data of Nanyang city over the years. Through the analysis of 23 eco-environmental quality indicators in this study area, the ecological indicators representing the natural environment background, such as average annual rainfall, annual accumulated temperature ≥ 10℃, dryness (k), runoff depth, slope, cutting intensity, soil texture, frequency of drought and flood, flood threat and soil erosion modulus, can be considered as constants, and their scores remain unchanged. Ecological indicators such as groundwater abundance, the ratio of water area to wetland area, per capita cultivated land, population density, geological disasters, soil erosion area, surface water quality grade, fertilizer and pesticide application intensity. Generally, it shows a worsening trend, and the score shows a decreasing trend; Effective irrigation area ratio, forest coverage rate, soil organic matter, cultivated land area ratio, sewage discharge intensity and so on have changed in a good direction, but there has been little overall change in the near future. Therefore, the ecological environment early warning index score of water source area is shown in Table 5.2.

Table 5.2 ecological environment early warning index score of water source area

sequential

5.6.4 Analysis of Early Warning Results

Combined with the actual situation of ecological environment in the study area and the changing trend of statistical data over the years, the changing trend of various ecological factors in the water source area was analyzed, and the forecast scores of 20 10 and 2020 were obtained respectively according to the trend extrapolation method, and the comprehensive ecological environment scores of 20 10 and 2020 were calculated by weighted summation. The calculation results show that the ecological environment in the study area is in a reverse evolution trend, and its final score is reduced from the current 5.2 1 to 4.97 in 20 10 and 4.87 in 2020, and the ecological environment is in a deteriorating trend, which should be warned.

Although the people's governments at all levels in the water source area have done a lot of work and achieved certain results, the ecological environment in the water source area is still deteriorating. If practical measures are not taken to protect the ecological environment, it will inevitably affect the smooth implementation of the Middle Route Project of South-to-North Water Transfer. The water source area belongs to the backward area of economic development. Xichuan County, where the reservoir area and canal head are located, is a national poverty-stricken county, and the income of the people in the reservoir area is lower than the average level of Nanyang City and Henan Province. Zhongshan and low hills each account for nearly one-third of the water source area, and cultivated land is scarce. In addition, the immigrants in the early stage of Danjiangkou Reservoir construction have not been properly resettled, and the relocation phenomenon is serious. The heightening of Danjiangkou Dam will add 6.5438+0.32 million mu of flooded farmland, which will make the contradiction among local people more acute. With the continuous growth of population and the increase of population density, the pressure on people and land is more prominent, and the phenomenon of excessive land reclamation cannot be contained. The monitoring of water quality in the water source area shows that nitrogen and phosphorus in the water exceed the standard, mainly due to the extensive use of pesticides and fertilizers, sparse vegetation in the low hills around the reservoir area, excessive reclamation of barren hills and slopes by the people in the reservoir area, and serious soil erosion. The non-point source pollution in the reservoir area is caused by the loss of fertilizers with soil and water. In addition, the progress of returning farmland to forests in the reservoir area is slow, and the forest coverage rate and soil erosion control rate are not high. There are no domestic sewage treatment plants and domestic garbage treatment plants in the counties and major towns around the reservoir area, and pollutants are directly discharged into rivers, causing water pollution. The mine environment in the water source area is harsh and geological disasters continue to occur. Mining has caused water and soil pollution in the water source area, so it is urgent to control the mine environment.

The research shows that in the next 15 years, the ecological environment quality of water source areas will be in a general state, and the ecological environment will show a reverse evolution trend, and the deterioration speed can not be ignored. Although the overall compound ecological environment is in a relatively balanced stage under the buffering force and bearing capacity of the natural environment, ecological problems will appear and ecological disasters will occur from time to time. From the warning interval division table of ecological environment early warning, it can be seen that the early warning situation is approaching from moderate early warning to severe early warning, and the general state of ecological environment quality is transitioning to bad state.