水的颜色

Much like the sky, rivers are rarely painted one color. Rivers around the world appear in shades of yellow, green, blue, and brown—and subtle changes in the environment can alter their colors.

就像天空一样，河流很少被涂成一种颜色。世界各地的河流呈现出黄色、绿色、蓝色和棕色的色调——环境的细微变化会改变它们的颜色。

New research shows the dominant color has changed in about one-third of large rivers in the continental United States over the past 35 years.

新的研究表明，在过去35年中，美国大陆约三分之一的大型河流的主要颜色发生了变化。

The figure above shows data from a map of river color for the contiguous United States. The rivers are colored as they would approximately appear to the human eye. The map was built from 234,727 images collected by Landsat satellites between 1984 and 2018. The dataset includes 67,000 miles (100,000 kilometers) of waterways of at least 200 feet (60 meters) wide.

上图显示了来自美国毗连河流颜色地图的数据。河流的颜色与人眼所见的大致相同。该地图是根据地球资源卫星在1984年至2018年期间收集的234,727张图像构建的。该数据集包括67,000英里（100,000公里）、至少200英尺（60 米）宽的水域。

While is not unusual for rivers to change colors over time due to fluctuations in flow, concentrations of sediments, and the amount of dissolved organic matter or algae in the water, scientists have found that the most extreme changes often occur near man-made reservoirs. Around 56 percent of rivers were dominantly yellow over the course of the investigation, and 38 percent were dominantly green.

虽然由于流量、沉积物浓度以及水中溶解的有机物或藻类的数量的波动，河流会随着时间的推移而改变颜色并不罕见，但科学家们发现，最极端的变化通常发生在人造水库附近。在调查过程中，大约56%的河流以黄色为主，38%以绿色为主。

Want more? Read Amazing Earth: Satellite Images from 2021

想要了解更多？阅读惊人的地球：2021 年的卫星图像

Image Credit: NASA Earth Observatory image by Joshua Stevens, using data courtesy of Gardner, J., et al. (2020).

影像来源：NASA Earth Observatory image by Joshua Stevens, using data courtesy of Gardner, J., et al. (2020).