We live in a warming world. And we often characterize that warming through metrics of temperature. But that’s only a sliver of the story. Another sliver, and perhaps a more consequential one, of the story is the connected increase in atmospheric moisture.
Recent months have brought us—yet again—real-world examples of what these increases in moisture can bring.
To say it’s been a wet year in the mid-Atlantic is an understatement. Through August, that is to say, before Florence, we were already working on the wettest year on record, or close to it, in much of the region.
January-through-August precipitation ranks for the contiguous United States. The darkest green areas saw record high precipitation for that eight-month period. The medium green indicates places with Jan-Aug precipitation in the top ten percent of history. The lightest green shade indicates areas with precipitation totals in the top one-third of history. The period of record dates back to 1895. From NCEI’s US State of the Climate report for August 2018.
Once Florence’s rains are factored into the end-of-September analyses, we’ll see much more dark green in the Southeast and mid-Atlantic.
What does that have to do with warming? Taken individually, not a lot. But taking the larger history into context, this is a continuation of a signal we’ve seen in recent decades, especially east of the Rockies: it’s getting wetter. 2018’s rank as the wettest year on record (to date) for parts of the East just reinforces this trend.
So, what does that have to do with warming? Again, it’s complicated, because precipitation is the end result of several atmospheric ingredients and processes, but to oversimplify: a warmer atmosphere can hold more water vapor, and an atmosphere with more water vapor can make more precipitation.
But the bigger and more consequential change we’ve seen is how much rain can and does fall in an event. I’m going to call that “Big Rain” as shorthand. What I mean by “event” is something meteorological in scale, lasting a day or two or maybe three.
I should stop here, as an aside, and say there are a multitude of ways to define “Big Rain.” One way that the National Climate Assessment has chosen is to define Big Rain as the top 1% of daily totals from the reference period of 1961-90.
This indicator shows the increase or decrease of the amount of annual rainfall that comes in the form of very heavy precipitation. For this indicator, very heavy precipitation refers to events in the top 1% of those occurring during the reference period of 1961-90. From the National Climate Assessment Climate Science Special Report, and the US Global Change Research Program’s Indicator Platform.
By this indicator, most of the country has seen dramatic increases in Big Rain. You can learn more about this indicator here.
By NCEI’s Climate Extremes Index—another way to diagnose changes in Big Rain—it’s increasing, too. Component 4 of the CEI is dedicated to one-day rainfall totals. That trend is up, with a bullet.
NCEI’s Climate Extremes Index Component 4 shows how much of the US was subject to greater than normal proportion of precipitation derived from extreme 1-day precipitation events. The increase in recent years means that more of the US is subject to increased very heavy one-day precipitation.
How is that tied to warming? The same way: a warmer atmosphere can hold more water vapor and an atmosphere with more water vapor can make more precipitation. And the warmer it gets, the higher the theoretical “Big Rain” events can get. That’s playing out in the data, pretty much any way you look at it.
These two trends—wetter conditions overall, and bigger Big Rain—are exemplified in this plot for Wilmington, NC. This plot, often called a “Haywood Plot,” shows the cumulative precipitation for about 70 years at Wilmington. Each line on the graph shows a year’s progression in total precipitation. The driest five years are plotted in brown; the wettest years in mint, with 2018 highlighted in light NOAA blue.
This Haywood plot for precipitation at Wilmington, NC shows how each year’s cumulative precipitation played out. The 2018 precipitation (through September 16) is in the thick, blue line. The other four years that make up the five wettest on record (with 2018) are shown in mint, while the five driest years are shown in brown. The other years are shown as grey. 2018 became the wettest year on record at Wilmington with more than 100 days left in the year. Haywood plots are often included in the supplemental materials associated with NCEI’s monthly US State of the Climate reports.
Look at 2018. Even before Florence, Wilmington was experiencing the wettest year-to-date on record, with the blue line outpacing its “rivals” in the field. Florence’s totals pushed that line into—literally—uncharted territory. Even if no rain were to fall in the next 100 days, 2018 will be the wettest year on record at Wilmington by almost a foot.
But what’s more interesting, looking beyond this year’s data, are the spikes. Each of those five wettest years has a large spike in September or October. And each of those spikes—indicating a huge increase in precipitation over the span of just a day or two or three—came courtesy of a named storm. Specifically, 2005’s Ophelia, 2016’s Matthew, and 1999’s Floyd, which made landfall in the region, and 2015’s Joaquin, whose moisture was entrained into massive rains over the Carolinas.
The other years don’t have these huge spikes. Sure, it’s kind of intuitive that the years with the biggest spikes would have the highest totals, but what’s not so obvious is all five of those years have happened in the last 20 years. The previous 50 years? Not so much.
And that brings us back to hurricanes and tropical storms, or “tropical cyclones” for short. We’ve long known that generally speaking, warmer means more intense storms and more potential rainfall, but the latest piece of knowledge on tropical cyclones is that they appear to be slowing down, for reasons that aren’t entirely clear.
Why does that matter? Slower storms can dump more rain on a place, and when that place is coastal land, it can bring catastrophic flooding. We definitely saw this with Harvey and Florence.
These factors—an atmosphere more laden with water vapor making more rain, and making more rain in larger doses, and the change in forward speed of tropical cyclones—are connected to our very real observations of more precipitation. It’s something we’ll need to build for, warn for, and work on.
Ivanhoe Reservoir, in the headwaters of the Fryingpan RIver basin. Photo: Brent Gardner-Smith/Aspen Journalism
From email from Reclamation (James Bishop):
Releases from Ruedi Dam to the Fryingpan River are scheduled to decrease from 350 to 300 cubic feet per second on Monday, September 24 at 8 a.m.
This release rate maintains “fish water” deliveries to the 15-mile Reach for endangered fish species. Routine updates to follow. Feel free to contact me with any questions at jbishop@usbr.gov or by phone at 970-962-4326.
Click here to go to the Colorado River Water Conservation District website:
Our 15th Annual Water Seminar, “Risky Business on the Colorado River” was held on September 14th, 2018 in Grand Junction, Colorado.
We heard from speakers with Southern Nevada Water Authority, the Utah Division of Water Resources, a member of the Board of the Colorado Water Conservation Board, the Colorado River District and others as they discussed current conditions on the river and how water is managed.
The headwaters of the Rio Grande River in Colorado. Photo: Brent Gardner-Smith/Aspen Journalism
From the New Mexico Political Report (Laura Paskus):
Right now, New Mexico’s largest reservoir is at about three percent capacity, with just 62,573 acre feet of water in storage as of September 20.
Elephant Butte Reservoir’s low levels offer a glimpse of the past, as well as insight into the future. Over the past few decades, southwestern states like New Mexico have on average experienced warmer temperatures, earlier springs and less snowpack in the mountains. And it’s a trend that’s predicted to continue.
“There was no spring runoff this year. We started this year at basically the point we left off at last year,” says Mary Carlson, a spokesperson for the U.S. Bureau of Reclamation, which operates Elephant Butte Dam, just north of the town of Truth or Consequences. The federal agency runs the Rio Grande Project, which stores water that legally must be delivered downstream to the Elephant Butte Irrigation District, the state of Texas and Mexico.
Drought has moved around the U.S. Southwest since the late 1990s, and last winter’s dismal snowpack broke records in the headwaters of the Rio Grande. Without runoff this spring, by February reservoir levels around the state—including at Elephant Butte—were as high as they were going to be this year. “We had some help from the monsoons,” Carlson says, “but not as much as we wanted, where we wanted.”
Many spots around New Mexico reveal signs of drought and climate change, whether it’s the puny flows of the Rio Grande, the fire-ravaged forests of the Jemez Mountains or the crispy rangelands of the northeast. But Elephant Butte Reservoir offers perhaps the starkest reminder that keeping up with the changing climate may require questioning long-held ideas of how water is managed and shared, how we think about rivers and reservoirs and even, who we consider our friends or foes.
Farmers ‘dealing with La Nada’
For farmers in southern New Mexico, this year “really stung,” says Gary Esslinger, manager of Elephant Butte Irrigation District, or EBID. This year, he explains, less than 45,000 acre-feet of water flowed via the Rio Grande into Elephant Butte. That’s the lowest recorded inflow since the dam was built in the early 20th century.
“There was virtually no snowpack runoff, and whatever there was didn’t get to Elephant Butte,” he says. “The Middle Rio Grande, that river was drying up way too early.”
Beginning in early April, when the state’s largest river is usually running high with snowmelt, it began to dry south of Socorro and upstream of the reservoir…
Watching the reservoir empty out this year makes farmers feel like they are running out of water, he says. At the same time, they’re uncertain about how long their groundwater supplies will last, even though the district tries to monitor groundwater levels and has hired a full-time groundwater specialist.
“We’re not cratering; it’s not Doomsville yet,” he says. “But we’ve got to find another source.” People can pray for rain and snow, he says, but the challenge is finding a long-term, consistent water source. And western states, including New Mexico, don’t have that.
“Everybody’s thinking, ‘Well, climate change is really happening,’ and I think we need to change the way we’re thinking. We keep looking for improvement in the West,” he says.
With improvement unlikely, Esslinger says he’s started considering more radical solutions—like whether western states could share the cost of a canal that would move water from the East, from someplace like the Mississippi River. “People think I might be crazy, but I think we should start looking at it,” he says. “I don’t think we can continue to keep playing this game of predicting and forecasting: we need to find some water and get it over here to the West.”
Farmers face other challenges, too, including the growing expense of pumping groundwater and an “insurmountable” number of regulations, he says. It’s also hard to find workers to hand-pick crops like chile and onions, thanks to changes in immigration policy.
CNHP Wetland Ecologists Joanna Lemly and Sarah Marshall hold a wetland soil core taken from Todd Gulch Fen at 10,000 feet in the Colorado Rockies. The dark, carbon-rich core is about 3 feet long. Living plants at its top provide thermal insulation, keeping the soil cold enough that decomposition by microbes is very slow. William Moomaw, Tufts University, CC BY-ND
Sand Creek in Aurora.
Map of the Roaring Fork River watershed via the Roaring Fork Conservancy
Here’s the release from the Environmental Protection Agency (Lisa McClain-Vanderpool):
Colorado Natural Heritage Society and Colorado State University-Natural Heritage Program will provide invaluable resources to Roaring Fork and Aurora watershed stakeholders
EPA has awarded $575,333 in wetlands grants to two programs in Colorado to survey, assess, map and provide technological tools such as smart phone applications.
“The data these projects generate are important to understanding, protecting and restoring wetlands in the state of Colorado,” said Darcy O’Connor, Assistant Regional Administrator of the Office of Water Protection. “Supporting decision making with solid scientific data is the wise approach to wetlands protection.”
Colorado Natural Heritage Society was awarded $221,250 to survey and assess critical wetlands in the Roaring Fork watershed in western Colorado. This project proposes to conduct a prioritized survey and assessment for critical wetlands within the Roaring Fork Watershed. The primary goal is to provide stakeholders, including private landowners with scientifically valid data on the condition, rarity, location, acres, and types of wetlands within the watershed.
Colorado State University’s Colorado Natural Heritage Program (CNHP) was awarded $221,250 for the 5th phase of CNHP’s wetlands database including vegetation classification, floristic quality assessment, a wetland restoration database and updates to the Colorado Wetlands Mobile App. The CNHP will revise Colorado’s wetland and riparian vegetation classification and floristic quality assessment, and create a Colorado wetland and stream restoration database.
The CNHP was also awarded $132,833 to assess critical urban wetlands in the city of Aurora, Colorado. CNHP will update the National Wetland Inventory mapping and conduct field-based wetland assessments in the greater Aurora area. Water quality data will also be collected at these sites. The goal is to create useful products for local land managers, land owners and community members.
EPA has awarded over $2.5 million in wetlands grant funding for 11 projects across EPA’s mountains and plains region of the West (Region 8). Healthy wetlands perform important ecological functions, such as feeding downstream waters, trapping floodwaters, recharging groundwater supplies, removing pollution, and providing habitat for fish and wildlife.
Wetlands Program Development Grants assist state, tribal, local government agencies, and interstate/intertribal entities in building programs that protect, manage, and restore wetlands and aquatic resources. States, tribes, and local wetlands programs are encouraged to develop wetlands program plans, which help create a roadmap for building capacity and achieving long-term environmental goals.
In 2018, SWSI is being updated using the latest information and will it serve as the technical mainframe for the revisions of the Colorado Water Plan and the Basin Implementation Plans. SWSI 18 will provide parameters that will help plan revision teams consider a variety of scenarios based on climate variance, existing supply and demands, and population growth. This will help these teams make the revised plans, maps that truly guide Colorado and the basin’s water future.
Want to know more? Visit the Colorado Water Conservation boards website at http://cwcb.state.co.us/Pages/CWCBHome.aspx or join in the Rio Grande Basin Roundtable meetings which are held the second Tuesday of each month at the San Luis Valley Water Conservancy District, 623 Fourth Street in Alamosa. Meetings begin at 2 pm. Also visit http://www.rgbrt.org.
