浅谈大连水土流失与生态环境问题 英语

Discussion on the issue of water loss and soil erosion and ecological environment
of Dalian
In recent years, Dalian is faced with serious water loss and soil erosion due to the reduction of forest vegetation, climate change, heavy rain disaster and so on, which has a serious negative effect to the ecological environment and industrial and agricultural production of the region. In this paper, we will discuss the reasons, hazards and preventive measures of water loss and soil erosion of Dalian.
1. The hazards of water loss and soil erosion and its impact on the ecological environment
The main factors caused the water loss and soil erosion of Dalian are the geographic location, geology and geomorphology, climate conditions and improper human economic activities. The water loss and soil erosion not only undermines the ecological environment, affects the local economic construction, but also causes great loss of people's life and property.
The water loss and soil erosion makes plenty of fertile lands washed away. As per estimates, the area of the water loss and soil erosion of Dalian reaches 7 million acres. The annual amount of sediment loss is equal to stripping 2 mm ground of the city. Long-term rainfall, large volume of runoff, torrential flood make the water loss and soil erosion heavier, many hills bald, some farmland scoured out ditch. These make the soil thinner, the nutrients of the soil lost seriously. We lost a lot of fertile lands for the above reasons. During the period of flash floods, the debris flow along with a large amount of sand boulders makes the valley bottom and riverbed high, the fairways blocked, the farmland harmed, which determines the basis of industrial and agricultural production.
The water loss and soil erosion not only affects agricultural production, but also increases the annual sediment load of several major rivers. Due to the water loss and soil erosion, the riverbed is elevated and the waterways are blocked. In Dalian port, the workers have to dredge mud of 990 thousand cubic meters annually to dredge the waterways. It will cost 4,755 thousand yuan every year.1
The water loss and soil erosion causes the lose of a lot of water of the soil. The other side of the hazard of the water loss and soil erosion is causing drought and aeolian sandy soil. Basically there is no big sandstorm in the Xiyang Commune of Fu County of Dalian at the initial stage of liberation. However, in recent years, due to the
1Wenyuan Nan, Northen Forest--Ecological Environment of Grassland and the Changes of National Culture[M], National Press, 2011.
water loss and soil erosion, Tanjia Unit existed 800 acres of shifting sand dunes. And it's extended by a speed of 200 meters every year. In the early sixties, there were more than 80 houses of 20 households inundated by sand dunes. When the people of the whole unit entered the commune, they have more than 7000 acres farmlands, while now they only have 4200 acres. The water loss and soil erosion destroys the soil fertility, causing sand hazard. What's even more serious is that the farmland itself suffers devastating harm, which exacerbating the flood hazards. The soil trenches formed by the flood erosion and scour reach 9966.2The average area of each soil trench is 7.8 acres. In total, they lost more than 70 thousands acres fertile lands. The water loss and soil erosion has not yet been fully controlled, so that the soil trenches of the water loss and soil erosion area of this region are still active. Some gully networks develop quite fast. Not only the soil which became waste valleys can't be planted, but also we need to pay a high price even if planting trees or seeds because of the dilapidated soil.
The destruction of the forest vegetation is one of the main factors causing water loss and soil erosion. Due to the reduction of forest vegetation and the cutting down of all the forests in some areas, the bare slopes of the hills and downlands are full of small clay and large boulders in the long-term impact of the monsoon. The mudslides formed during heavy rain, along with a large number of of boulders strikes the downstream rocks, cottages, farmland, roads, bridges and the water conservancy facilities with a high flow rate, and even blocks the riverway, which composes a serious hazard to the downstream construction.
2.The main reasons of the water loss and soil erosion and the ecological unbalance
There are many factors caused the water loss and soil erosion and the ecological unbalance in this region. In general they can be divided into two categories, one is the natural geographical and climatic factors, the other is the human factors. University of Missouri confirmed by experiments,"continuous cropping of the corn will reduce 50% loss of soil compared with the nudation. The rotation of corn, wheat, clover will reduce 86% loss of soil further".3
2.1 Natural geographical and climatic factors
Dalian is located at latitude 38° 43 'N ~40° 10' N, longitude 120 ° 58'E ~123 °31'E, in the monsoon. There is less rainfall in winter and spring in Dalian affected by
2Dalian Statistical Yearbook, 2011.
3Bevier, Soil Physics[M], Agricultural Press, 1983.
the monsoon. The drought happens frequently. For example, Within forty days from early April to early May, 1980, the precipitation is less than 5mm, while the evaporation is more than 200mm. According to the meteorological data records, during the sixteen years from 1967 to 1982, there is 10 years of summer drought.4 The precipitation is decreasing, while the evaporation is growing, resulting in groundwater levels declining.
In summer, Dalian is often attacked by typhoons or heavy rain. From 1956 to 1980, The typhoon which influences Dalian is up to 30 times. And the frequency of typhoon has a growing trend year by year. The average annual precipitation is about 600 to 800 mm, and 60 to 70% of which is concentrated in the summer.
The amount and distribution of rainfall is one of the basic factors of water loss and soil erosion. In the growing season of crop, a long period of little rain or no rain will lead to drought or partial drought, while too concentrated rainfall will form a flood, the water loss and soil erosion and so on. The heavy rain often cause flash floods, which leads to huge flood.
This region is a part of Liaodong hills. There are high mountains, middle mountains and low mountains, and many hills and downlands. The terrain of Dalian gradually increases from south to north, the highest mountain is the Buyun Mountain of Zhuanghe(about 1130 meters). This terrain feature of Dalian provides rich water resources, at the same time constitutes extensive and intricate inclined plane to various types of erosion.
The soil in the sloping land without vegetation or with less forest vegetation is seriously eroded. Once meeting heavy rain, the soil will easily form a sheet erosion and gully. The role of forest vegetation of sluggish water and protecting the soil is lost due to excessive deforestation. Therefore, the slopes with serious forest vegetation destruction suffer heavier water loss and soil erosion, and increase flood volume and peak flow within a certain range.
2.2 Human factors
Human beings develop and utilize land resources and natural resources. The results have both positive and negative aspects. The inappropriate economic activity of the people is the main factors causing the water loss and soil erosion because of lacking of the concept of water and soil conservation and ecology, against the order of nature. Before liberation, the forest area of Dalian is more than 6 million acres, the
4Dalian Statistical Yearbook, 2011.
forest coverage rate is more than 40%. Due to the deforestation without plan and fires, by 1981, the forest area has decreased by over one million acres, the forest coverage rate dropped to 17.5%. The destruction of the forest vegetation led to a huge loss of water and soil, heavier floods, frequent drought, irrigation diversion difficulties, being vulnerable to the threat of drought. Coupled with inappropriate measures of agricultural production, it causes soil erosion hazards.
3.Keep the water and soil to create a new ecological balance
Affected by the water loss and soil erosion, the farmlands of Dalian decrease, the fertility of soil declines, natural resources damage seriously, ecological environment deteriorates markedly. In order to reduce water loss and soil erosion, restore the ecological balance, change the vicious cycle to be a virtuous circle, coordinate the ecological balance and economic benefits, we should establish good grass ecosystem with the overall concept and structure of ecosystem. For this purpose, we should do the following work.
3.1 Grow vegetation vigorously to keep soil and water
Good forest vegetation and grass can ease the influence of climate, topography, soil to erosion. Generally speaking, the annual soil loss of soil with good turf is less than 1 ton/acre. Vegetation canopy has the function of retention the erosion of raindrops on soil. Therefore, we need to carry out activities of planting trees and grass vigorously, develop various types of plantation.
3.2 Crop rotation to maximize reduce soil erosion
The slopes of hills and downlands should be planted by turf and crop, or turf-corn rotation. This will maximize reduce soil erosion, so that the situation of water loss and soil will get better control.
3. 3 The engineering measures of controlling water loss and soil erosion
There are a variety of measures to do soil and water conservation, such as governing slope engineering, small water projects and so on so forth. According to the situation of Dalian, the government should proceed small water projects in close connection with soil and water conservation, such as reservoirs. The governing slope engineering should be regarded as the main task of Dalian. At last, the sloping characteristics should be changed to reduce the speed of runoff.
In short, to govern the water loss and soil erosion of Dalian, people should take appropriate measures and methods, such as growing vegetation vigorously, crop rotation, increasing water conservancy facilities and so on.
Reference
[1]Wenyuan Nan, Northen Forest--Ecological Environment of Grassland and the Changes of National Culture[M], National Press, 2011.
[2]Bevier, Soil Physics[M], Agricultural Press, 1983.
[3]Research institution of soil of Dalian, Soil Knowledge[M],Shanghai People Press, 1986.
[4]Dalian Statistical Yearbook, 2011.。