Case Study Lake Dianchi

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Agricultural Non-point Source Water Pollution Caused Eutrophication of Dianchi Lake in China and Possible Solutions

Abstract: Eutrophication is a big problem around the world and especially in China where laws and regulations are not followed in rural areas. This is the case in Kunming, Yunnan, China at Lake Dianchi where eutrophication is the highest in the country. This case study will set up to study the effects of phosphate in the lake, the quantity of phosphate, and the possible source of the phosphate. From there the effects of plant and animal life will be discussed as well as the availability of water to be used for agriculture and potability of the water. Solutions will then be considered that can change the lake from eutrophic conditions to that of tropic ones.

Introduction: The intent of this case study is to determine the severity of eutrophication (being the over enrichment of nutrients in a body of water, can be phosphorus or nitrogen, phosphorus will be the focus of the Lake Dianchi study) in the Dianchi Lake and to postulate possible, viable and efficient solutions. The Dianchi Lake has received a lot of wastewater from 1988-2000[4]; this was a time of growing pollution to the lake and as time goes by it is only getting worse. Lake Dianchi is shown in figure 4.1 below as an aerial view in the blue. The main source of the pollutant is from agricultural runoff of the surrounding area of the lake. One thing to note is that phosphorus is one of the leading causes of eutrophication in the body of water, just above nitrogen. This pollution is due to national regulation not being met because of the isolation of the area from any big city or government. The reason the lake is becoming eutrophic is because inorganic fertilizers containing high amounts of phosphate are being used, causing the soil to have too much nutrients. The solutions provided will be ones that include national regulations and incentives and also natural solutions such as adding plants around the lake to absorb the pollutants.

Hypothesis: If the farmers in the area of the Dianchi lake cut back on their crop production, thus cutting back on fertilizer and pesticides, and the government subsidizes their loss from the social gain that will be acquired from the de-eutrophication of the lake, then the lake will return closer to its natural state and be an efficient solution.[2] If farmers are equipped with more “environmentally friendly” fertilizers and pesticides, then the lake will not be as eutrophic as it is today. If both of these proposals are met, then the state of the lake will be much less eutrophic.

Methodology: This case study will set out to study various other case studies and journal articles on the topic of eutrophication of the Dianchi lake and policy research on the issue. Graphs and models will be analyzed and shown to give real data and show the reality of the situation at Lake Dianchi. After the data is collected from these sources it will then be analyzed and possible solutions will be put forth.

Results and Analysis: There is a major consensus among the scientific community that the leading cause of eutrofication of Lake Dianchi is primarily due to the increase in phosphorus levels. The phosphorus levels have been on an increase, as studied, since 1988, as shown in Fig 2. The leading cause of this pollution, and of high phosphorus levels, is mainly due to agricultural use. This is because when the farmers use the fertilizer it increases their crop yield, thus increasing their income. A graph of this exact scenario can be seen in figure 4 which show that as one dollar is spent on fertilizer the dollar return is around 6 dollars. It is hard to pin point who is emitting how much pollutants because this is a problem of Non-point source pollution, which is discharged from the ground and diffused throughout the land and eventually ends up in the lake in a very scattered manner. Due to...
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