Heavy storms have flooded parts of California, but the state has been unable to capture billions of gallons of water that are flowing unchecked into the ocean. Los Angeles is embarking on an ambitious new program to change that.
A team has developed a more accurate formula to calculate how much sediment a fluid can push across a granular bed, which could help engineers manage river restoration and coastal erosion. The key to the new formula comes down to the shape of the sediment grains.
Trapped sediment has robbed roughly 50,000 large dams worldwide of an estimated 13% to 19% of their combined original storage capacity, and total losses will reach 23% to 28% by 2050, UN research warns.
California has seen so much rain over the past few weeks that farm fields are inundated and normally dry creeks and drainage ditches have become torrents of water racing toward the ocean. Yet, most of the state remains in drought.
All that runoff in the middle of a drought begs the question — why can’t more rainwater be collected and stored for the long, dry spring and summer when it’s needed?
As a hydrogeologist at the University of California at Santa Cruz, I’m interested in what can be done to collect runoff from storms like this on a large scale. There are two primary sources of large-scale water storage that could help make a dent in the drought: holding that water behind dams and putting it in the ground.
Why isn’t California capturing more runoff now?
When California gets storms like the atmospheric rivers that hit in December 2022 and January 2023, water managers around the state probably shake their heads and ask why they can’t hold on to more of that water. The reality is, it’s a complicated issue.
California has big dams and reservoirs that can store large volumes of water, but they tend to be in the mountains. And once they’re near capacity, water has to be released to be ready for the next storm. Unless there’s another reservoir downstream, a lot of that water is going out to the ocean.
In more populated areas, one of the reasons storm water runoff isn’t automatically collected for use on a large scale is because the first runoff from roads is often contaminated. Flooding can also cause septic system overflows. So, that water would have to be treated.
You might say, well, the captured water doesn’t have to be drinking water, we could just use it on golf courses. But then you would need a place to store the water, and you would need a way to distribute it, with separate pipes and pumps, because you can’t put it in the same pipes as drinking water.
Putting water in the ground
There’s another option, and that’s to put it in the ground, where it could help to replenish groundwater supplies.
Managed recharge has been used for decades in many areas to actively replenish groundwater supplies. But the techniques have been gaining more attention lately as wells run dry amid the long-running drought. Local agencies have proposed more than 340 recharge projects in California, and the state estimates those could recharge an additional 500,000 acre-feet of water a year on average if all were built.
One method being discussed by the state Department of Water Resources and others is Flood-MAR, or flood-managed aquifer recharge. During big flows in rivers, water managers could potentially divert some of that flow onto large parts of the landscape and inundate thousands of acres to recharge the aquifers below. The concept is to flood the land in winter and then farm in summer.
Flood-MAR is promising, provided we can find people who are willing to inundate their land and can secure water rights. In addition, not every part of the landscape is prepared to take that water.
You could inundate 1,000 acres on a ranch, and a lot of it might stay flooded for days or weeks. Depending on how quickly that water soaks in, some crops will be OK, but other crops could be harmed. There are also concerns about creating habitat that encourages pests or risks food safety.
Another challenge is that most of the big river flows are in the northern part of the state, and many of the areas experiencing the worst groundwater deficits are in central and southern California. To get that excess water to the places that need it requires transport and distribution, which can be complex and expensive.
The idea is to siphon off some of that runoff and divert it to infiltration basins, occupying a few acres, where the water can pool and percolate into the ground. That might be on agricultural land or open space with the right soil conditions. We look for coarse soils that make it easier for water to percolate through gaps between grains. But much of the landscape is covered or underlain by finer soils that don’t allow rapid infiltration, so careful site selection is important.
One program in the Pajaro Valley encourages landowners to participate in recharge projects by giving them a rebate on the fee they pay for water use through a “recharge net metering” mechanism.
We did a cost-benefit analysis of this approach and found that even when you add in all the capital costs for construction and hauling away some soil, the costs are competitive with finding alternative supplies of water, and it is cheaper than desalination or water recycling.
Is the rain enough to end the drought?
It’s going to take many methods and several wet years to make up for the region’s long period of low rainfall. One storm certainly doesn’t do it, and even one wet year doesn’t do it.
For basins that are dependent on groundwater, the recharge process takes years. If this is the last rainstorm of this season, a month from now we could be in trouble again.
As parched California receives much needed rain and snow this winter, some local water officials are calling on state leaders to invest in new infrastructure projects that will store freshwater for inevitable dry times to come.
The worst megadrought in 1,200 years is devastating the water supply in the Western United States. It’s drying up the Colorado River basin, a major North American river system, while also depleting reservoirs and underground aquifers and forcing communities to make drastic cuts to their freshwater use.
Western states can no longer rely on snowmelt and rain to supply their communities in a drier, more arid landscape caused by climate change, say water experts.
Environmental groups have called for increased conservation efforts, such as pushing people to limit watering of ornamental lawns and upgrade to more efficient appliances. And they want officials to invest more in wastewater recycling or desalination projects. But some local water officials in California and across the West see a massive opportunity in storing rainwater in new or expanded reservoirs and groundwater aquifers.
Tackling nutrient pollution in the Gulf of Mexico is a big job, requiring coordination between dozens of states whose waters flow into the Mississippi. Although a 2011 U.S. Environmental Protection Agency memo set a framework for each state to reduce its nutrient load, it was up to the states to set their own policies in motion.
More than a decade on, critics have questioned the effectiveness of state nutrient reduction strategies, noting the still-massive hypoxic dead zones in the Gulf. In a new University of Illinois-led study, social scientists looked at the process states took to develop and implement their strategies, identifying key strengths and challenges that can inform other large-scale cooperative efforts.
A recently launched Franco-US satellite is on a mission to survey with unprecedented accuracy nearly all water on Earth’s surface for the first time and help scientists investigate its impact on Earth’s climate.
As water becomes increasingly scarce in the American West, a group of university and industry partners has been pursuing innovations in the largest use of this key resource: agricultural irrigation.
For almost five years, the Irrigation Innovation Consortium has supported industry-university collaboration to improve irrigation technologies, encourage their adoption and boost effective water management in agricultural and landscape contexts.
Nonpoint source pollution is the primary cause of the algae overgrowth that infiltrates eastern South Dakota lakes, rivers and ponds toward the end of every summer. The water’s pollution can be traced back to the runoff from agricultural land, which is filled with excessive nutrients from the fertilizer used to ensure a strong crop yield.
The resulting algae, often known as an “algae bloom,” can sometimes be harmful and have negative impacts on humans, wildlife, pets and livestock.
Tong Wang, an associate professor in the Ness School of Management and Economics at South Dakota State University and an SDSU Extension advanced production specialist, has spent the past few years gaining a better understanding of nonpoint source pollution, farmers’ perspectives on water pollution and solutions to the problem.
Her research paper, titled “Adopting cover crops and buffer strips to reduce nonpoint source pollution: Understanding farmers’ perspectives in the U.S. Northern Great Plains,” was published in the Journal of Soil and Water Conservation. Wang’s work was supported by a grant from the United State Department of Agriculture—National Institute of Food and Agriculture, Coordinated Agricultural Projects.