California’s Tulare Lake, in the southern San Joaquin Valley, has reappeared in satellite photos after last winter’s heavy rains, reports The Guardian.
Tulare was once the largest freshwater lake west of the Misissippi River; it would appear seasonally fed by rainfall and snowmelt. By 1920, water in the basin had been diverted for agricultural irrigation and other uses, and the lakebed was converted to cropland and pastures. The “ghost lake” reappears occasionally in extremely wet years with lots of rain or snowmelt, with significant flooding in 1969 and 1983. The basin is now home to about 4 million people.
The agricultural centre of the state is still dealing with the consequences of the wet winter weather. Extensive flooding has already caused widespread damage, leading to evacuations and loss of livestock and crops.
The area is expected to experience significant snowmelt as temperatures rise leading into the summer. According to a statement by the state’s Department of Water Resources (DWR), as of May 16, the snowpack in the southern Sierra was 443% of the normal level for this time of year, similar to the levels in 1969 and exceeding the levels in 1983, posing continued flood risks in the San Joaquin Valley. The increased snowpack will result in sustained high flows in the Tulare basin until July.
To mitigate the flood risks, water managers have redirected flows to fill ponds to allow water to seep underground and replenish depleted aquifers. The DWR is providing assistance to local flood control districts and water storage districts responsible for managing the flood response and diverting water.
Additionally, there are calls for a more permanent revival of Tulare Lake as an environmental resource, as well as proposals to divert more water into the historic lakebed to alleviate overflows upstream and protect the communities in the area.
The drought in the Western U.S. might be finally ending after more than 3 years, though the wet conditions have not replenished the region completely. The effects on groundwater can take longer to alleviate, in part because of years of overdraft.
According to Chad Hecht, a meteorologist with the Center for Western Weather and Water Extremes at the University of California San Diego’s Scripps Institution of Oceanography, California’s Sierra Nevada has about double its normal snowpack, and some locations have experienced more than double the number of strong atmospheric rivers it typically sees. A key feature in the California water cycle, atmospheric rivers are air currents that carry huge amounts of water vapour from the tropics to the U.S. West Coast, as much as 20 Mississippi Rivers on average. Half of California’s water supply comes from atmospheric rivers.
The upper Colorado River Basin also has a healthy snowpack this year, which will bring relief to the basin, though it has been depleted by climate change and water overuse. But it takes more than one or two good water years to fill Lake Mead and Lake Powell, which hit record low levels last summer and are key for water supplies in the Colorado River Basin.
