1.1. Background and motivation
1.1.1. Water problematics of the Lake Soyang watershed
Chapter 1
Synopsis
1.1. Background and motivation
1.1.1. Water problematics of the Lake Soyang watershed
In 2009, the Republic of Korea (hereinafter referred to as South Korea) implemented its National Strategy for Green Growth by adopting the first of its Five-Year Plans for Green Growth. The National Strategy for Green Growth is a stimulus package in response to the financial and economic crisis that erupted in late 2008, and is the most comprehensive environmental plan that South Korea has implemented since its establishment in 1948 (UNEP, 2010). The concept of green growth, as advanced by the South Korean government, consists of three elements (Committee on Green Growth, 2014):
the virtuous cycle of the environment and the economy,
improving the quality of life and the green revolution of daily life, and
establishing a national standing corresponding with international expectations.
In the short-term, the strategy aims at stimulating job creation and revitalizing the economy.
In the mid- and long-term, it aims at achieving the sustainable management of the nation’s natural resources and mitigating climate change and its environmental impacts. In this sense, the strategy is also a response to the current and predicted environmental challenges faced by South Korea (UNEP, 2010). Due to the increasing urbanization and industrialization of the country, to the high population density, to the highly mountainous topography and to the highly seasonal precipitation regime, the South Korean environment and natural resources have been under pressure. For example, the United Nations defined South Korea as a water
hotspot in terms of flood frequency and projected that, in terms of water availability, the Seoul Capital Area will be under very severe water stress by 2050 (< 500 m3 of freshwater per person per year; WWAP, 2012). In recent decades, the pressure on the environment and natural resources has been exacerbated by changes in the South Korean climate, namely an above-world-average increase in surface temperature, a substantial increase in the frequency of heavy rainfall events, and a substantial increase in the intensity of these events, which are predicted to intensify until at least 2100 (Jung et al., 2002; Ministry of Environment, 2015;
NIER, 2010). These changes could potentially have considerable, negative impacts on the nation’s water resources in terms of water flow, balance and quality (Bae et al., 2008; Kim et al., 2011; Park et al., 2010). To prevent and mitigate these potential impacts, the South Korean government has implemented a series of measures (Ministry of Environment, 2015).
One of these measures is the Four Major Rivers Restoration Project, which was implemented through the first Five-Year Plan of the National Strategy for Green Growth. This project revolved around five core tasks (Ministry of Environment and Korea Environment Institute, 2009):
securing water supply,
flood control,
water quality improvement and ecosystem restoration,
development of spaces for cultural and leisure activities, and
regional development around the four major rivers.
One of these four major rivers is the Han River, of which the basin is considered the heart of South Korea due to its population and the ecosystem services it provides to the population (WWAP, 2009). A major tributary of the Han River is the Soyang River, which flows within the Lake Soyang watershed and is the main tributary of Lake Soyang. The provision of water from the Lake Soyang watershed is a highly valued ecosystem service by a significant proportion of the South Korean population, as Lake Soyang is one of the main sources of freshwater for the Seoul National Capital Area. The watershed provides additional services, such as soil erosion prevention, plant production, flood regulation, carbon uptake, irrigation, fish habitat, recreation and weather regulation (Kang and Tenhunen, 2010). The Lake Soyang watershed is a good example of a socio-ecological system, where agricultural production and the provision of high-quality water to downstream regions are highly valued and desired, but sometimes opposed (Raskin et al., 1997). In recent decades, water problematics have emerged
Chapter 1 − Synopsis
3 from the aforementioned climate changes and changes in land use and land cover (Park et al., 2010). These problematics have been threatening the provision of ecosystem services by the Lake Soyang watershed. The Four Major Rivers Restoration Project targeted these problematics and furthered progress towards the sustainable management of water.
Nevertheless, the achievement of this goal and the completion of the core tasks of this project require additional progress (Kang and Park, 2015; Lah et al., 2015). Although this doctoral project was not an official contribution to the Four Major Rivers Restoration Project, its results should provide accurate and relevant information for the sustainable management of water in the Lake Soyang watershed.
In recent decades, increasing trends of sediment load, nutrient load, and consequent turbidity and eutrophication of Lake Soyang have been observed (Cho et al., 1991; Kim and Jung, 2007; Kim et al., 1995; Kim et al., 2001). These trends are related to increasing rates of soil erosion and non-point source pollution within the watershed (Park et al, 2010). The development of agriculture in highland areas of the watershed has been a major factor in the increase in sediment load. In these areas, steep slopes prevail and a change in land cover from forest to agricultural field concurrent with the tilling of the land is usually followed by a substantial increase in the average rate of soil erosion (Yang et al., 2010). In addition, the high levels of fertilizer application practiced in the watershed and the production of animal manure result in the massive input of nutrients to the system, and ultimately to Lake Soyang and downstream regions (Kim et al., 2001). The transport of sediment and nutrients from agricultural areas to water bodies of the watershed is greatly enhanced by the occurrence of surface runoff during heavy rainfall events (Park et al, 2010). The precipitation intensity of typhoon- and East Asian summer monsoon (EASM)-related events can easily exceed the infiltration capacity of agricultural soils, resulting in the substantial production of surface runoff. In fact, most the inputs of sediment and nutrients to water bodies occur during and shortly following rainfall events of the EASM (Jo et al., 2010; Kim et al., 2000; Park et al., 2011). Figure 1.1 depicts the hypothesized processes of Lake Soyang and highlights the seasonality of these inputs.
Figure 1.1. Hypothesized hydrological and chemical processes of Lake Soyang over an annual cycle (from Peiffer et al., 2012).
Although the bulk of the sediment and nutrient inputs to Lake Soyang originates from agricultural non-point sources, most of the water input to the lake originates from forested catchments, as more than 90% of the Lake Soyang watershed is covered by forests (KFS, 2010). In this sense, the water balance and quality of Lake Soyang are tightly linked to the hydrological processes occurring within these catchments. From a scientific point of view, an important question to be answered is: How are the hydrological and chemical processes within the Lake Soyang watershed coupled to the Lake Soyang internal chemical processes influencing water quality? This doctoral project aimed at providing a part of the answer by studying some of the hydrological processes occurring within typical forested catchments of the watershed. This project was realized with the conviction that understanding and assessing these processes are pre-requisites to providing suggestions and guidelines for the sustainable management of water in the Lake Soyang watershed.
Chapter 1 − Synopsis
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