Methods of EMergy analysis (a scientifically based measure of wealth with units of solar emjoules [sej]) are explained and illustrated, using the economy of Thailand and two proposed darns on the Mekong River. Thailand's EMergy/$ ratio is near the world average (3.46 . 10(12) sej/$), its EMergy per capita ratio (2.98 . 10(15) sej/capita) is low compared to developed economies (that of the United States is 29.3 . 10(15) sej/capita), and its EMergy balance of payments is negative (the EMergy in exports is almost twice the EMergy in imports), The calculated net yield ratios of the proposed dams were sensitive to the treatment of sediments. The analysis yielded high net yield ratios (12.3/1 and 20.3/1) if sediments were not included, but yielded ratios of only 1.4/1 and 1.3/1 if sediments were included. If the two dams were constructed as a cascade, the combined net yield ratio was 2.5/1 (sediments included). If compared to conventional fossil fuels as a primary source of energy to the economy, the net yield ratio of the electricity generated from the two-dam cascade expressed as fossil fuels was 7.4/1.
