- 期刊
A Special River System: Review of Okawango Delta
摘要
The Okavango Delta is one of the largest inland deltas in the world. It was formed by the Okavango River injected into the Kalahari Desert. During this period, most of the river's water was lost through evaporation due to drought. It is located in northern Botswana and covers an area of about 15,000 square kilometers. It was formed by the Okavango River injected into the Kalahari Desert. Most of the water is lost through evaporation and transpiration. Approximately 11 cubic kilometers of water irrigates 15,000 km2 of land each year, and the excess water will flow into Lake Engami. This delta can be divided into three parts: 1) permanent swamp; (2) seasonal swamp, when seasonal floods occur, the area will grow vegetation; (3) the remaining part is forest and grassland (Wilson, 1973). This delta is actually a very huge alluvial fan with an area of about 40,000 km2. Among them, 9,000km2 is a permanent wetland (perennial wetland), and 14,000km2 is a seasonal wetland (seasonal wetland). The radial length of its central axis exceeds 150km, and the area of rivers, lakes, sandbars, seasonal wetlands and permanent wetlands included is 22,000km2. The reason for the formation of the Okavango Delta is an unresolved problem. For decades, different scholars have discussed this from different aspects and angles, but it has been difficult to achieve a completely convincing effect. To a large extent, the reason for its formation is very complicated, and it is the final result of the interaction of many factors, and the reason for the formation of Okavango's river model is very different from the current traditional understanding of the river model. For example, in the traditional sense, it is generally believed that the formation of the channel pattern is mainly related to the way the river transports the sediments. The bottom transport generally forms a braided river, the mixed transport generally forms a meandering river, and the suspended transport generally forms a direct-flow river, but Okavango Breaking this model, different types of sediment transport methods can form meandering rivers, and the current research hotspots in academic circles are concentrated on the transition mode from meandering rivers to braided rivers, which is also common in nature. Type, but Okavango's river course changes from meandering river to direct-flow river, which is very different from our usual change of river course mode. Many scholars have conducted a lot of research work from different angles and put forward many different explanations, but they have not been able to achieve satisfactory results. The reasons for the formation of the Okavango Delta, the type of river channel, the mode of river transition, and the nature and characteristics of the delta are all different from our current views on deltas, fan deltas, and river channels. Studying the Okavango Delta can help us Breaking through the traditional understanding of these issues has brought us many new inspirations. This article mainly collects more than 20 foreign literatures on Okavango in the past 30 years. Based on the research results of domestic and foreign scholars and meandering rivers, Okavango Delta is a typical meandering river delta. Combining the idea of ＂combining the present and discussing the ancient＂, conducts research on the Okavango Delta, summarizes previous research results and progress, and systematically summarizes these documents, briefly reviews the overall research status and existing problems, and points out that the current urgent need The issue of in-depth research is expected to arouse the interest and attention of domestic scholars in the study of Okavango.