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We used multiyear Greenhouse Gases Observing Satellite (GOSAT) dry air, column-integrated CO 2 (XCO 2) retrievals (2010-2013) to evaluate urban and local-scale CO 2 emissions over East Asia and examined whether GOSAT XCO 2 captures the impact of strong local CO 2 emissions over South Korea, an East Asian downwind region with high atmospheric aerosol loading and strong summer monsoons. We chose a region in western Mongolia (upwind region) as the XCO 2 background, and estimated XCO 2 enhancements in South Korea to gauge local and regional emissions. We found that the cold season (November-February) was better suited for estimating XCO 2 enhancements of local emissions due to the summer monsoon and stronger transboundary impacts in other seasons. In particular, we focused on three local GOSAT XCO 2 footprints (about 10.5 km in diameter) in South Korea: the Seoul Metropolitan Area (SMA), the Gwangyang Steelworks and Hadong power plants (GYG), and the Samcheonpo power plants (SCH). The range of XCO 2 enhancement was 7.3-10.7 ppm (14.1-21.3 mg m −3 in standard temperature and pressure (STP)). By estimating other important contributions to XCO 2 enhancements such as the XCO 2 latitudinal gradients and Chinese fossil fuel combustions, we estimated the net enhancements caused mainly by local CO 2 emissions in the range of 4.2-7.6 ppm (8.1-14.7 mg m −3 in STP) These high enhancements imply that large point source contributions are an important factor in determining these enhancements, even if contributions are also made by broaderscale emissions. Additionally, differences in net XCO 2 enhancements and trends between GYG (+ 4.2 ppm (+ 8.2 mg m −3 in STP),-0.2 ppm year −1 (-0.4 mg m −3 year −1 in STP)) and SCH (+ 7.6 ppm (+ 14.9 mg m −3 in STP), + 1.3 ppm year −1 (+ 2.6 mg• m −3 year −1 in STP)) indicate that these closely located footprints (approximately 26 km apart) are separable. These results will be useful in evaluating and reducing uncertainties in regional and local anthropogenic greenhouse gas (GHG) emissions over East Asia.

This paper presents an optimal control model of integrated watershed management in the presence of a dam. Management efforts focus on upstream soil conservation, reservoir‐level sediment removal, and downstream damage control from water pollution. Increased soil conservation potentially benefits farmers and also has the external benefit of reducing sediment accumulation in the reservoir. Sediment is released downstream of the reservoir using the hydrosuction sediment removal system (HSRS). This sediment release extends reservoir life and provides nutrients to downstream farmers who then use less fertilizer. Also included in the functions of the dam manager are the provision of water to downstream farms, the control of instream flow to mitigate downstream damages from water pollution, and the use of water treatment to meet quality standards for water supplied directly from the reservoir to residential users. An illustrative application of the model to Lake Aswan, located between Egypt and Sudan, indicates substantial benefits from far‐sighted behavior and cooperation across all agents. Moving from the baseline case that reflects the status quo to the socially optimal solution increases watershed net present value by more than $500 billion. Other scenarios with varying types of collaboration among the agents are also explored. Interestingly, while decisions with respect to soil conservation do impact the welfare of upstream farmers, the benefits to reservoir management and agriculture in Egypt are modest compared to benefits Egypt gets from improved control of instream flow. Also, subject to technical limits, increasing reservoir life through practice of HSRS is economically desirable.

No abstract

An empirical framework for assisting with water quality management is proposed that relies on open-source hydrologic data. Such data are measured periodically at fixed water stations and commonly available in time-series form. To fully exploit the data, we suggest that observations from multiple stations should be combined into a single long-panel data set, and an econometric model developed to estimate upstream management effects on downstream water quality. Selection of the model's functional form and explanatory variables would be informed by rating curves, and idiosyncrasies across and within stations handled in an error term by testing contemporary correlation, serial correlation, and heteroskedasticity. Our proposed approach is illustrated with an application to the Nakdong River basin in South Korea. Three alternative policies to achieve downstream BOD level targets are evaluated: upstream water treatment, greater dam discharge, and development of a new water source. Upstream water treatment directly cuts off incoming pollutants, thereby presenting the smallest variation in its downstream effects on BOD levels. Treatment is advantageous when reliability of water quality is a primary concern. Dam discharge is a flexible tool, and may be used strategically during a low-flow season. We consider development of a new water corridor from an extant dam as our third policy option. This turns out to be the most cost-effective way for securing lower BOD levels in the downstream target city. Even though we consider a relatively simple watershed to illustrate the usefulness of our approach, it can be adapted easily to analyze more complex upstreamdownstream issues.