text: what are six problems of the yellow river?   the yellow river has special importance in the origins of the chinese civilization. it is referred to as "the mother river" and "the cradle of the chinese civilization" by chinese. traditionally, it is believed that the chinese civilization originated from the yellow river basin areas.  during the long history of china, the yellow river has been considered a blessing as well as a curse and has been nicknamed both "china's pride" (zhōngguó de jiāoào) and "china's sorrow" (zhōngguó de tòng). records indicate that, from 602 bc to present, the river's course made at least 5 major large-scale changes in direction and its levees were breached more than 1,500 times. a major course change that took place in 1194 took over the huai river drainage system throughout the next 700 years. the mud in the yellow river literally blocked the mouth of the huai river and left thousands homeless. the yellow river adopted its present course in 1897 after the final course change occurred in 1855. currently, the yellow river flows through jinan, capital of the shandong province and ends in the bohai sea.  the river gets its yellow color mostly from the fine-grained calcareous silts originated from the loess plateau which are carried in the flow. centuries of silt deposition and diking has caused the river to flow above the surrounding farmland, making flooding a critically dangerous problem. flooding of the yellow river has caused some of the highest death tolls in world history, with the 1887 huang he flood killing 900,000-2,000,000 and the 1931 huang he flood killing 1,000,000-3,700,000. in 1938, during the second sino-japanese war, the nationalist troops under chiang kai-shek broke the levees holding back the yellow river in order to stop the advancing japanese troops. the river at that time flooded a huge area and the floodwaters took some 500,000-900,000 lives.  another historic source of devastating floods was the collapse of upstream ice dams in inner mongolia with their accompanying sudden release of vast quantities of impounded water. there have been 11 such major floods in the past century, each causing tremendous loss of life and property. nowadays, explosives dropped from aircraft are used to break the ice dams before they become dangerous.  sometimes the yellow river is poetically called the zhuo liu (濁流), or the "muddy flow." the chinese expression "when the yellow river flows clear" is similar to the english expression "when hell freezes over."  some of the known flood defenses used in ancient times were the building of ditches, walls (dams), levees, and rebound channels to route floodwaters around a blockage. the main problem was that the solutions were local and sometimes the dams were too small and weak for the impact. if the river broke down the defenses, it would cause far more damage than if no levees had been built.  characteristics of the yellow river the yellow river is notable for the amount of silt it carries, amounting to 1.6 billion tons annually at the point where it descends from the loess plateau. if the river is running to the sea with sufficient volume, 1.4 billion tons are carried to the sea. in modern times, since 1972 when it first went dry, the river has gone dry in its lower reaches, from jinan to the sea, in most years, in 1997 for 226 days. the low volume of the river is due to increased demands on the river for use in irrigation which has increased by a factor of five since 1950. water diverted from the river by 1999 served 140 million people and irrigated 74000 km² of land. highest volume occurs during the rainy season, from july to october, when 60% of the volume of the river flows. water for irrigation, on the other hand, is needed between march and june. in order to capture excess water for use when needed and for flood control and electricity generation several dams have been built, but due to the hi