The impact of water is everywhere you look in Yosemite, particularly in the spring when the waterfalls are in full flow! (I must confess that I'm a little behind in the blog as we were in Yosemite in late April to see this wonderful spectacle).
But all this water is not just for Yosemite's benefit. The snow and rain that falls here also plays a critical role in providing water to California once it flows out of the park. Just to stress the importance here, California produces over one third of the country's vegetables and two thirds of the country's fruits and nuts. This is done with extensive irrigation, with more than 60 percent of the water for this coming from the Sierra Nevada, of which Yosemite is a part.
Yosemite National Park have a hydrology programme in cooperation with the US Geological Survey, the Merced Irrigation District, and Hetch Hetchy Water and Power. This involves monitoring water quantity and quality to provide information for drought management, park planning, and long-term hydrologic trends and possible ecological impacts.
This is not a new thing for Yosemite. The importance of this water source for the park and the state has meant that river gauges have been in use for many decades, producing valuable long-term records of monitoring data. The Happy Isles Bridge gauging station on the Merced River, shown below, has been recording since 1915. As well as quantity, park scientists assess water quality along the Merced and Tuolumne Rivers, which together drain the entire park.
Most precipitation falls as snow, accumulating during the winter. As spring temperatures rise, the melting snow increases stream and groundwater levels, temporarily flooding meadows, providing a key water influx for plants and animals.
However, Northern California is predicted to warm (3-6°C) by 2100. This would lower annual snowpack volume and cause earlier melting, resulting in longer, drier summers with less water in rivers, streams, and aquifers.
It is essential in this changing world that we continue to study hydrology, and as engineers it is a vital part of any project that will utilise or manage water resources, to ensure sustainable solutions are found.
