全球智库信息集成服务系统

Nonpoint Source Pollution Management for Multipurpose Dam

Multipurpose dam has developed Korean economy by satisfying various water uses of industrial and residential areas. However, nonpoint source pollutants discharging to upper watersheds degraded water quality, increasing turbidity and algal bloom. We may face problems including unpleasant smell and taste, malfunctioning equipment and changing landscape.

Dam watersheds are mainly agricultural lands or mountains. Thus, these areas are characterized as distributed pollution sources while urban areas contain specific and concentrated pollution sources. Besides, it is hard to control nonpoint source once it outflows. Therefore, advanced countries are focusing on resource management system based on public education in managing agricultural nonpoint source pollution.

Generally, main pollution sources in dam watersheds in Korea are highlands, cultivated streambanks, stock farms, roads, and construction sites. To manage these main sources efficiently, following principles should be considered commonly: (1) to mitigate pollution through controlling sources; (2) to take advantages of surroundings as much as possible; (3) to prioritize water quality problems.

Specifically, highland cultivation should be controlled depending on its grade and altitude. Excessive organic chemicals such as fertilizer and pesticide can be exuded from the land, and the area is likely to be eroded by heavy rain. In the case of slope in 15% degree or more, prohibiting cultivation and restoring the surface is preferred to improving cultivation method in order to protect topsoil. Fallow, conservative cultivation, and covering can be alternatives for soil protection and reinforcement. In addition to these, construction of detour waterways and improvement of irrigation method can minimize the impact of runoff. For streambanks, it is the best way to prohibit cultivation. However, if the prohibition is not possible, potential pollution should be reduced with improved farming technique.

In the case of livestock farms, highly concentrated runoff can be generated. Management practices like roofing and waterway diversion are required to decrease total discharging volume and to prevent potential pollutants from entering rainwater. Following practices can be also considered to reduce the impact; to balance a whole farm, to treat livestock wastes, and to fence the area.

In forest, logging areas and roads are the major nonpoint sources. Especially, the roads should be managed continuously because those are easily disturbed. The surface can be conserved by covering with riprap and woodchip. However, if the roads are badly damaged or aged, pavement or reconstruction should be considered. Seeding, mulching, and vegetative covering can be also applied to protect fill and cut sides of the roads.

In construction activity, advanced permit system and management plan should be established to mitigate damage to waterbodies because a great amount of sediment are generated from the site.

After pollutants are discharged, decreasing or depositing them can contribute to delaying pollution expansion. Ponds, wetlands, vegetative waterways, and buffer strips will function to reduce and treat pollutant loads with other best management practices. Simultaneously, direct treatment can be implemented to control turbidity and algae in dam reservoir.

To manage nonpoint source pollution successfully, public involvement and education are fundamentals. The involvement can be achieved voluntarily or mandatorily and education will be helpful to achieve the goal economically when the knowledge is coherent with the economical drivers and regulations. Same programs will generate different results depending on socio-economic condition and natural properties of the region. Therefore, many trials and pre and post assessment of projects will result in better management measures.