Rivers and streams runs in dry state. Learn more…
Tuesday, 22nd June 2021
The water flowing from surface rivers and streams effectively transport sediments, organic matter, and nutrients from slopes and land areas to downstream lakes, reservoirs, and oceans. The rivers and streams (hereinafter collectively referred to as streams) along the way provide important resources for our communities and support a rich and complex ecosystem. In this case, very annual streams (flowing throughout the year) are crucial. However, since the surface water source of non-perennial streams is not as reliable as perennial plants, there is less research on them compared with perennial plants. In Nature, Messager provided a much-needed estimate of the total proportion of the world's river network, calculated by length, not perennial, and they found that most of them fall into this category.
The author reports that 51% to 60% of the world’s rivers do not flow for at least one day each year, and 44% to 53% of the world’s river lengths are dry for at least one day. 30 days) per year. Their model indicates that non-perennial streams flow out of all climates and biomes on all continents. The model also shows that 95% of the river network in hot and dry regions, which account for 10% of the world's land area, is drying up every year. Surprisingly, even parts of major rivers like the Niger in West Africa are expected to dry up in these arid regions. In these locations, the widespread prevalence of non-perennial streams highlights how even discontinuous streams can significantly affect the quantity and quality of available water. The results emphasize the need for more detailed regional and local scale perennial and non-perennial flow maps, and the need for more research on how non-perennial rivers affect overall water availability and quality.
Small upstream rivers (rivers without tributaries) account for 70-80% of the length of global rivers, similar to the total length of the finger is much longer than the length of the palm. The model by Messager and his colleagues predicts that even in the wettest areas, such as the Amazon basin and parts of central Africa and Southeast Asia, up to 35% of these source streams stop flowing at some point in the year. However, it should be noted that upstream rivers are monitored by relatively few flow meters, which are often located in larger perennial rivers downstream. Therefore, the model can provide highly uncertain estimates for the upstream area of ??the river network.
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Lack of river flow data is a common problem in source modeling, and data collection is being implemented to fill this knowledge gap. For example, France has developed the National Astronomical Observatory (ONDE) network, which complements the national current measurement network but focuses on the source of streams. However, these procedures are expensive and require a large investment of resources. For the more common non-perennial rivers, the river indicator is also scarce. For example, in Messager and colleagues' analysis, there are no meters in non-perennial streams in Argentina; only one in New Zealand; 10 in the Pacific Northwest of the United States, and on a 250-meter network. To improve the mapping of perennial and non-perennial river models, low-cost field observations will be required, along with the development of high-resolution remote sensing technologies, which often detect, or at least predict, the surface flow of rivers.
The analysis by Messager and colleagues provides strong quantitative confirmation of the universality of non-perennial rivers. Their results indicate that fundamental changes are needed in the science and management of rivers and streams, of which non-perennial streams have been largely ignored. In arid regions, the predominance of non-perennial rivers may be the main driver of water availability and quality. In areas where human-developed services are not easily accessible, ecosystem services (such as running water in streams) are used to meet basic needs and will determine the well-being and prosperity of the people in the area to some extent. Therefore, the new findings clarify the need for global accounting for perennial and non-perennial flows.
In addition, changes in river distribution will have a profound impact on global and continental carbon and biogeochemical cycles 6 and on the survival of river-dwelling organisms, including many endangered species. Therefore, the predominant global reference points for perennial and non-perennial rivers are essential to assess the impact of future climate-related distribution changes and land-use changes. Finally, regional and local river models are needed, as well as better data on the source and non-perennial parts of the river network to further increase the value of the global model.
The News Talkie Bureau
Source:
Nature.com