关键词: 黄河, 水资源, 承受能力

Abstract:

Based on the data observed from 1919 to 1999, the paper systematically analyses temporal and spatial variations in both discharge and sediment load in the lower reaches of the Yellow River, reveals causes for its drying-up and a series of environment problems arising therefrom. A numerical simulation follows on water requirement of environment of the Yellow River catchment. The main points of them are as follows: (1) Water environment of taking fluvial systems as a link, as a part of the physical environment, is a basic condition of sustainable development of environment. Therefore the water resources of a catchment can not be sucked dry or exhausted. Its development intensity must be limited by environmental sustainability. (2) Drying-up of the lower Yellow River may give rise to a series of environment problems, such as flood, land desertification along the river region, soil salinization in delta area, pollution increase in the lower reaches and seas around the river mouth, and destruction of wetland ecosystem of the river mouth region. (3) An excess of water consumption and the inconsistency between the peak period diverting water and one of oncoming flow in the Yellow River catchment are the major and direct causes for drying-up of the lower Yellow River. From present relation of runoff yield to water consumption, it can be seen that the Yellow River with a trend of ephemeral river may be returned to a normal river by means of combined regulation of Xiaolangdi reservoir and others on the main Yellow River. (4) The Yellow River catchment tends to obvious drought recently. Its annual runoff flowing into sea decreased from 480.5×108 m3 (1950-1959) to 150.0×108 m³ (1986-1999). And the ratio of sediment output to input in the lower Yellow River correspondingly decreased from some 75% to less than 53%. So deposition seriously occurred in the river channel. To satisfy a need of sediment balance, the lower Yellow River must at least export sediment of 6×108 t a year into sea. And corresponding water demand exporting the sediment load is about 225×108 m³. Therefore there is a shortage of 75×108 m³ in water demand of environment. But viewing the problem from water saving potentiality of agricultural irrigation of the Yellow River catchment, present effective utilization ratio to water in irrigation by diversion of the Yellow River amounts to only 40-50%. If it will be raised to 70-80%, water saving in quantity will be over 85×108 m³ a year. And so merely this one can full the shortage of present environment water requirement. (5) The sustainability of catchment environment to development in water resources is also associated with its harnessing level. With gradually decreasing sediment yield due to soil and water conservation, and to give an outlet to the sediment load entering into the lower reaches of the Yellow River by means of various measures, such as strengthening dykes by warping, improving soil by warping and clearing situation in stream channel and so on, water demand exporting sediment load into sea can reduce, so the water resources to be able to supply utilization will gradually increase.

Key words: the Yellow River, water resources, sustainability