Paper: Increased #drought severity tracks #warming in the United States’ largest river basin — Proceedings of the National Academy of Sciences #MissouriRiver

Map of the Missouri River drainage basin in the US and Canada. made using USGS and Natural Earth data. By Shannon1 – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=67852261

Click here to read the report. Here’s the abstract:

Across the Upper Missouri River Basin, the recent drought of 2000 to 2010, known as the “turn-of-the-century drought,” was likely more severe than any in the instrumental record including the Dust Bowl drought. However, until now, adequate proxy records needed to better understand this event with regard to long-term variability have been lacking. Here we examine 1,200 y of streamflow from a network of 17 new tree-ring–based reconstructions for gages across the upper Missouri basin and an independent reconstruction of warm-season regional temperature in order to place the recent drought in a long-term climate context. We find that temperature has increasingly influenced the severity of drought events by decreasing runoff efficiency in the basin since the late 20th century (1980s) onward. The occurrence of extreme heat, higher evapotranspiration, and associated low-flow conditions across the basin has increased substantially over the 20th and 21st centuries, and recent warming aligns with increasing drought severities that rival or exceed any estimated over the last 12 centuries. Future warming is anticipated to cause increasingly severe droughts by enhancing water deficits that could prove challenging for water management.

In much of the western United States (hereafter “the West”), water demand (i.e., the combination of atmospheric demands, ecological requirements, and consumptive use) is approaching or has exceeded supply, making the threat of future drought an increasing concern for water managers. Prolonged drought can disrupt agricultural systems and economies, challenge river system control and navigation, and complicate management of sensitive ecological resources. Recently, ample evidence has emerged to suggest that the severity of several regional 21st-century droughts has exceeded the severity of historical drought events; these recent extreme droughts include the 2011 to 2016 California drought and the 2000 to 2015 drought in the Colorado River basin.

Conspicuously absent thus far from investigations of recent droughts has been the Missouri River, the longest river in North America draining the largest independent river basin in the United States. Similar to California and the Upper Colorado River Basin, parts of the early 21st century have been remarkably dry across the Upper Missouri River Basin (UMRB). In fact, our assessment of streamflow for the UMRB suggests that the widespread drought period of 2000 to 2010, termed the “turn-of-the-century drought” by Cook et al., was a period of observationally unprecedented and sustained hydrologic drought likely surpassing even the drought of the Dust Bowl period.

Northern Hemisphere summer temperatures are now likely higher than they have been in the last 1,200 y, and the unique combination of recent anomalously high temperatures and severe droughts across much of the West has led numerous researchers to revisit the role of temperature in changing the timing and efficiency of runoff in the new millennium. Evidence suggests that across much of the West atmospheric moisture demands due to warming are reducing the effectiveness of precipitation in generating streamflow and ultimately surface-water supplies.

The waters of the Upper Missouri River originate predominantly in the Rocky Mountains of Montana, Wyoming, and Colorado, where high-elevation catchments capture and store large volumes of water as winter snowpack that are later released as spring and early summer snowmelt. This mountain water is an important component of the total annual flow of the Missouri, accounting for roughly 30% of the annual discharge delivered to the Mississippi River on average, but ranging between 14% to more than 50% from year to year, most of which is delivered during the critical warm-season months (May through September). Across much of the UMRB, cool-season (October through May) precipitation stored as winter snowpack has historically been the primary driver of streamflow, with observed April 1 snow-water equivalent (SWE) usually accounting for at least half of the variability in observed streamflow from the primary headwaters regions. However, since the 1950s, warming spring temperatures have increasingly driven regional snowpack declines that have intensified since the 1980s. By 2006, these declines amounted to a low snowpack anomaly of unusual severity relative to the last 800 y and spanned the snow-dominated watersheds of the interior West. A recent reassessment of snowpack declines across the West by Mote et al. suggests continued temperature-driven snowpack declines through 2016 totaling a volumetric storage loss of between 25 and 50 km3, which is comparable to the storage capacity of Lake Mead, the United States’ largest reservoir.

Here we examine the extended record (ca. 800 to 2010 CE) of streamflow and the influence of temperature on drought through the Medieval Climate Anomaly, with a focus on the recent turn-of-the-century drought in the UMRB. The role of increasing temperature on streamflow and basin-wide drought is examined in the UMRB over the last 1,200 y by analyzing a basin-wide composite streamflow record developed from a network of 17 tree-ring–based reconstructions of streamflow for major gages in the UMRB (Fig. 1) and an independent runoff-season (March through August) regional temperature reconstruction. We also explore the hydrologic implications (e.g., drought severity and spatial extent) and climatic drivers (temperature and precipitation) of the observed changes in streamflow across the UMRB and characterize shifts in the likelihood of extreme flow levels and reductions in runoff efficiency across the basin.

The Missouri River Basin and its subregions. The location of the Missouri River Basin within the continental United States (gray watershed, upper right) and the location of the five hydrologically distinct subregions (colored watersheds) that define the UMRB. Reconstructed gages used to develop the estimate of basin-wide mean annual streamflow are shown as triangles.

From The Washington Post (Darryl Fears):

For the first decade of the century, the Upper Missouri River Basin was the driest it’s been in 1,200 years, even more parched than during the disastrous Dust Bowl of the 1930s, a new study says.

The drop in water level at the mouth of the Missouri — the country’s longest river — was due to rising temperatures linked to climate change that reduced the amount of snowfall in the Rocky Mountains in Montana and North Dakota, scientists found.

The basin has continued to experience droughts this decade — in 2012, 2013 and 2017 — but their severity in comparison with historic drought is unknown. The “Turn-Of-The-Century Drought” study, published Monday in the Proceedings of the National Academy of Sciences, focused only on the 10 years after 2000.

“In terms of the most severe flow deficits, the driest years of the Turn-Of-The-Century-Drought in the [Upper Missouri River Basin] appear unmatched over the last 1,200 years,” the study said. “Only a single event in the late 13th century rivaled the greatest deficits of this most recent event.”

Researchers familiar with drought of this magnitude in the dry Southwest were surprised to find it in the Midwest…

“These findings show that the upper Missouri Basin is reflecting some of the same changes that we see elsewhere across North America, including the increased occurrence of hot drought” that’s more severe than usual, [Erika] Wise said.

The study is the latest to show how human-influenced climate change threatens to reshape the landscape by making naturally occurring drought far more severe.

Missouri River Basin

Journey to the top of the watershed — Platte Basin Timelapse

Click through to view the film (Carlee Koehler):

In June, a small team of PBT interns set out for the highest point in the Platte Basin watershed.

We had big intentions of catching 5-star media to fill in cracks for the Grays Peak scene in the upcoming PBT documentary featuring Mike and Pete’s 55-day, 1,300-mile journey across the watershed.

Grays and Torreys, Dillon Reservoir May 2017. Photo credit Greg Hobbs.

Grays Peak is the highest point in the Platte Basin watershed. The mountain, located west of Denver in the Front Range of Colorado, is ranked as the tenth-highest summit of the Rocky Mountains of North America. With the top reaching an elevation of 14,278 feet, it may be considered to some as quite a commitment to reach the top.

The beginning of the trip went as intended. We had the car loaded with all of our equipment and prepared a schedule that would allow us enough time to focus on what we needed to do, or so we thought.

After incidents of altitude sickness, a split hiking boot, bird invasions, and a major bear spray accident, we all accepted our humorous situation of what the trip turned into. We came back with quite the story for the rest of the PBT team. Nevertheless, we agreed the trip had been a successful one and after arriving back in Lincoln, made the best out of what we managed to capture.

The Platte River is formed in western Nebraska east of the city of North Platte, Nebraska by the confluence of the North Platte and the South Platte Rivers, which both arise from snowmelt in the eastern Rockies east of the Continental Divide. Map via Wikimedia.

Spring brings more fears for #MissouriRiver flooding — The Kirksville Daily Express

2019 Nebraska flooding. Photo Credit: University of Nebraska Lincoln Crop Watch

From The Kirksville Daily Express (Mike Genet):

A year after flooding battered the Missouri River’s levee system, inundating towns and farmland and causing multiple closures to the nation’s interstate highway system, early forecasts warn that more of the same could be on the way: above-normal rainfall, greater than normal spring runoff. A USA TODAY Network analysis delves into records of an aging system of nearly a thousand levees where nobody knows how many were damaged last year or how many were repaired…

The forecast is a veritable index of meteorological plagues: above-normal rainfall; greater than normal spring runoff; thoroughly saturated soils; and an aging system of nearly a thousand levees where nobody knows how many were damaged last year and in previous floods or how many were repaired.

The 855 levee systems throughout the Missouri River basin protect at least half a million people and more than $92 billion in property. Yet a USA TODAY Network analysis of Army Corps of Engineers’ records found at least 144 levee systems haven’t been fully repaired and that only 231 show an inspection date.

Of those, nearly half were rated “unacceptable,” which means something could prevent the levee from performing as intended or a serious deficiency was not corrected. Only 3.5% were deemed acceptable; the rest were found to be “minimally acceptable.”

U.S. levee systems map via the U.S. Army Corps of Engineers. Click on the map to go to the interactive website.

Only 231 of the levee systems show any inspection date. For 38, the most recent inspection date was more than five years ago.

In the Army Corps’ Kansas City district, for example, about 70 projects, spanning 119 levees that requested repair assistance, are eligible for funding, but that doesn’t mean they’ll be ready if the waters rise like they did last year.

“Some of them have been repaired, but from a total system perspective, I don’t think any of them are whole,” said Jud Kneuvean, the district’s chief of emergency management, who expects full levee rehabilitation and repair to take at least another year.

In the meantime, the extent and impacts of flooding will depend on when and where the rain falls…

The 2,300-mile Missouri River begins in southwestern Montana, where the Gallatin, Madison and Jefferson rivers converge near the community of Three Forks, before gathering water from 10 states and parts of two Canadian provinces to become the “Big Muddy,” North America’s longest river.

In recent years, more rainfall has been pouring into the Missouri River basin, raising questions about whether climate change is bringing worsening floods more often. Data from the National Oceanic and Atmospheric Administration dating back to 1895 shows record-setting rainfalls in the area occurring more often. Last year, for example, was the wettest on record in North Dakota, South Dakota and Minnesota.

All that water adds to the challenge faced by Corps policymakers, who juggle sometimes conflicting priorities that include maintaining navigation; managing the reservoir system to prevent flooding; providing farmers with irrigation and hydropower; protecting endangered species; and preserving recreational opportunities.

While the priority is protecting human life and safety, the Corps’ decision-making sometimes puts special interest groups at odds, and the agency remains embroiled in controversy over whether the engineering of the river exacerbates flooding.

Things came to a head last year when a bomb cyclone in March melted all the snow in Nebraska and Iowa at once and dumped tremendous rain, swelling not just the Missouri, but the Elkhorn, Platte, James and Big Sioux rivers.

The Niobrara River in Nebraska breached the Spencer Dam on March 14, sending a wall of water downstream and into the Gavins Point reservoir near Yankton, South Dakota. At the peak, water flowed into the reservoir at 180,000 cubic feet per second — nine times more than the normal average for March. Meanwhile water was coursing into the rivers downstream of the dam and the effects of all that water were felt in nearly every community downstream.

Two other big rain events occurred in May and September. When the Corps’ Kansas City district deactivated its emergency operations center in December, it had been open for 279 days, the longest period on record…

Construction of the higher levee is in the administrative and planning stages, with actual construction activity set for fall.

Most of the Missouri’s levees fall into one of two categories: either federally built and locally operated or locally built and operated. The Corps inspects — and helps pay to repair — only the levees maintained to federal standards that participate in the federal flood program.

That exception means no one has a full list of damaged levees still in need of repair.

The number of levees that aren’t regularly inspected doesn’t surprise Neal Grigg, an engineering professor at Colorado State University who chaired a Corps-appointed review panel after 2011 flooding.

In an ideal management system, every levee “would be under the responsibility of some authority that was responsible and had enough money and good management capability to do that,” Grigg said.

But that’s not realistic, he added, noting that the Corps has tried through a task force to get some organization to the levee systems along the river, but it’s problematic, in part, because there are so many conflicting interests.

A host of agencies are cooperating to repair levees, but the progress is slow, said Missouri farmer Morris Heitman, who serves on the Missouri River Flood Task Force Levee Repair Working Group.

In addition to the Corps, the Federal Emergency Management Agency, the state of Missouri, the USDA Natural Resources Conservation Service and a large number of local levee districts all work to repair levees.

“We’re trying to dance with different agencies,” Heitman told the University of Missouri Extension. “All these agencies have their own requirements and parameters, and we’re trying to coordinate those to build a secure system against the river.”

Fixes to the 144 levee systems listed in disrepair in the Corps’ Omaha and Kansas City districts are in various stages of completion, and some aren’t expected to be done for more than a year.

In the Omaha district that includes Nebraska and Iowa, “pretty much all of the levees were damaged in one way or another,” said the corps’ Matt Krajewski.

While almost all of the district’s levees that qualify for federal aid have been restored to pre-2019 flood heights, Krajewski said they don’t offer the same level of “risk reduction” because they need final touches such as sod cover and drainage structures to protect against erosion. The Corps hopes to complete those repairs this summer.

In the meantime, the Corps is working to prepare its flood storage capacity by releasing more water than normal from its dams.

“We’re being really aggressive with our releases and trying to maintain our full flood storage,” said Eileen Williamson, a Corps spokeswoman for the Northwestern region.

But the projections for spring runoff don’t look good and may limit how much the Corps can do.

In February, the runoff was twice the normal average, said Kevin Grode, with the Corps’ Missouri River Basin Water Management district.

The James River, a tributary that flows out of South Dakota, has experienced flooding since March 13 last year and that flooding is forecast to continue. Moderate flooding is expected along the Big and Little Sioux Rivers in South Dakota and Iowa, and possibly in Montana’s Milk River basin. A risk of minor to moderate flooding is forecast from Nebraska City to the river’s confluence with the Mississippi in St. Louis.

But it’s not just the spring runoff that’s a problem, Grode said. The forecast also calls for “above average runoff for every month in 2020.”

John Remus, chief of the Corps’ Missouri River Water Management Division, said during a March briefing that if those projections are realized, “the 2020 runoff will be the ninth highest runoff in 122 years of record keeping.”

In March, a three-man team with Montana’s Helena-Lewis and Clark National Forest set off on horseback for a 35-mile, five-day journey into the wild North Fork of the Sun River, a tributary of the Missouri River.

They rode horses for the first 12 miles. When they reached a foot of snow, they switched to skis and took turns breaking trail.

Greeted by a half inch of new snow each morning, higher and higher they skied, encountering snow depths of 19 inches, then 2 feet, 9 inches and finally, 3 feet, 3 inches.

Karl Wetlaufer (NRCS), explaining the use of a Federal Snow Sampler, SnowEx, February 17, 2017.

At each elevation, aluminum tubes with non-stick coating were stuck into the snow to collect core samples used to measure the depth and water content of the snowpack.

“The numbers are used for everything from dam control along the Missouri River to regulating the locks on the barges of the Mississippi,” said Ian Bardwell, the forest’s wilderness and trails manager, who led the snow survey expedition. “It just depends on what level you are looking at it from.”

As of Wednesday, mountain snowpack in the Missouri River basin in Montana was 112% of normal, said Lucas Zukiewicz, a water supply specialist with the Department of Agriculture’s Natural Resources Conservation Service in Montana.

In 2018, Montana’s April snowpack was 150% of normal, then 7 to 9 inches of rain over six days drenched the Rocky Mountain Front, inundating communities in its shadow. The Corps was forced to release water from the Fort Peck Dam spillway, a rarity, as a result of surging flows. Had that same thing happened last year, flooding in states downstream would have been even worse.

“With the way things are changing with our climate,” said Arin Peters, a senior hydrologist for the National Weather Service in Great Falls, Montana, “it’s probably a matter of time before something combines to create a big catastrophe downstream.”

Yet for this year, there may be some good news downstream from the Montana snowpack, at the Gavins Point Dam in Yankton.

Gavins Point is what’s known as a reregulation dam, its purpose to even the Missouri’s flow from the reservoirs upstream. Because Gavins Point wasn’t designed to hold floodwater, its gates had to be opened last year, sending a surge downstream after Nebraska and parts of South Dakota were hit with rain and the bomb cyclone.

In November and December, Gavins Point was still releasing water at a rate of 80,000 cubic feet per second — more than five times the average flow, and something that had never happened before, said Tom Curran, the dam’s project manager.

The good news? Releasing all that water through the winter left the mainstem dam system drained to its multipurpose zone, where it has capacity to absorb runoff while also fulfilling its other functions, including recreation and downstream barge traffic.

Created by Imgur user Fejetlenfej , a geographer and GIS analyst with a ‘lifelong passion for beautiful maps,’ it highlights the massive expanse of river basins across the country – in particular, those which feed the Mississippi River, in pink.

2020 #OgallalaAquifer Summit will take place March 31-April 1, 2020 in Amarillo, Texas

Here’s the release from Colorado State University (Jennifer Dimas):

The 2020 Ogallala Aquifer Summit will take place in Amarillo, Texas, from March 31 to April 1, bringing together water management leaders from all eight Ogallala region states: Colorado, Kansas, New Mexico, Nebraska, Oklahoma, Texas, South Dakota and Wyoming. The dynamic, interactive event will focus on encouraging exchange among participants about innovative programs and effective approaches to addressing the region’s significant water-related challenges.

“Tackling Tough Question” is the theme of the event. Workshops and speakers will share and compare responses to questions such as: “What is the value of groundwater to current and future generations?” and “How do locally led actions aimed at addressing water challenges have larger-scale impact?”

“The summit provides a unique opportunity to strengthen collaborations among a diverse range of water-focused stakeholders,” said summit co-chair Meagan Schipanski, an associate professor in the Department of Soil and Crop Sciences at CSU. “Exploring where we have common vision and identifying innovative concepts or practices already being implemented can catalyze additional actions with potential to benefit the aquifer and Ogallala region communities over the short and long term.”

Schipanski co-directs the Ogallala Water Coordinated Agriculture Project (CAP) with Colorado Water Center director and summit co-chair Reagan Waskom, who is also a faculty member in Soil and Crop Sciences. The Ogallala Water CAP, supported by the U.S. Department of Agriculture’s National Institute of Food and Agriculture, has a multi-disciplinary team of 70 people based at 10 institutions in six Ogallala-region states. They are all engaged in collaborative research and outreach for sustaining agriculture and ecosystems in the region.

Some Ogallala Water CAP research and outreach results will be shared at the 2020 Ogallala Summit. The Ogallala Water CAP has led the coordination of the event, in partnership with colleagues at Texas A&M AgriLife, the Kansas Water Office, and the USDA-Agricultural Research Service-funded Ogallala Aquifer Program, with additional support provided by many individuals and organizations from the eight Ogallala states.

The 2020 Summit will highlight several activities and outcomes inspired by or expanded as a result of the 2018 Ogallala Summit. Participants will include producers; irrigation company and commodity group representatives; students and academics; local and state policy makers; groundwater management district leaders; crop consultants; agricultural lenders; state and federal agency staff; and others, including new and returning summit participants.

“Water conservation technologies are helpful, and we need more of them, but human decision-making is the real key to conserving the Ogallala,” said Brent Auvermann, center director at Texas A&M AgriLife Research – Amarillo. “The emergence of voluntary associations among agricultural water users to reduce groundwater use is an encouraging step, and we need to learn from those associations’ experiences with regard to what works, and what doesn’t, and what possibilities exist that don’t require expanding the regulatory state.”

The summit will take place over two half-days, starting at 11 a.m. Central Time (10 a.m. MDT) on Tuesday, March 31 and concluding the next day on Wednesday, April 1 at 2:30 p.m. The event includes a casual evening social on the evening of March 31 that will feature screening of a portion of the film “Rising Water,” by Nebraska filmmaker Becky McMillen, followed by a panel discussion on effective agricultural water-related communications.

Visit the 2020 Ogallala summit webpage to see a detailed agenda, lodging info, and to access online registration. Pre-registration is required, and space is limited. The registration deadline is Saturday, March 21 at midnight Central Time (11 p.m. MDT).

This event is open to credentialed members of the media. Please RSVP to Katie.ingels@kwo.ks.gov or amy.kremen@colostate.edu

The Ogallala aquifer, also referred to as the High Plains aquifer. Source: National Oceanic and Atmospheric Adminstration

2020 #OgallalaAquifer Summit in Amarillo, #TX, March 31 – April 1, 2020 — The #Kansas #Water Office

Here’s the release from the Kansas Water Office (Katie Patterson-Ingels, Amy Kremen):

8-State Conversation to Highlight Actions & Programs Benefitting the Aquifer, Ag, and Ogallala communities

The 2020 Ogallala Aquifer Summit will take place in Amarillo, Texas, from March 31 to April 1, bringing together water management leaders from all eight Ogallala region states: Colorado, Kansas, New Mexico, Nebraska, Oklahoma, Texas, South Dakota and Wyoming. The dynamic, interactive event will focus on encouraging exchange among participants about innovative programs and effective approaches being implemented to address the region’s significant water-related challenges.

“Tackling Tough Questions,” is the theme of the event. Workshops and speakers share and compare responses to questions such as: “What is the value of groundwater to current and future generations” and “how do locally-led actions aimed at addressing water challenges have larger-scale impact?”

“The summit provides a unique opportunity to strengthen collaborations among a diverse range of water-focused stakeholders,” said summit co-chair Meagan Schipanski, an associate professor in the Department of Soil and Crop Sciences at CSU. “Exploring where we have common vision and identifying innovative concepts or practices already being implemented can catalyze additional actions with potential to benefit the aquifer and Ogallala region communities over the short- and long-term.”

Schipanski co-directs the Ogallala Water Coordinated Agriculture Project (CAP) with Colorado Water Center director and summit co-chair Reagan Waskom, who is also a faculty member in Soil and Crop Sciences. The Ogallala Water CAP, supported by the U.S. Department of Agriculture’s National Institute of Food and Agriculture, has a multi-disciplinary team of 70 people based at 10 institutions in 6 Ogallala-region states, engaged in collaborative research and outreach aimed at sustaining agriculture and ecosystems in the region.

Some Ogallala Water CAP research and outreach results will be shared at the 2020 Ogallala Summit. The Ogallala Water CAP has led the coordination of this event, in partnership with colleagues at Texas A&M AgriLife, the Kansas Water Office, and the USDA-Agricultural Research Service-funded Ogallala Aquifer Program, with additional support provided by many other individuals and organizations from the eight Ogallala states.

The 2020 Summit will highlight several activities and outcomes inspired by or expanded as a result of the 2018 Ogallala Summit. Participants will include producers, irrigation company and commodity group representatives, students and academics, local and state policy makers, groundwater management district leaders, crop consultants, agricultural lenders, state and federal agency staff, and others, including new and returning summit participants.

“Water conservation technologies are helpful, and we need more of them, but human decision-making is the real key to conserving the Ogallala,” said Brent Auvermann, Center Director at Texas A&M AgriLife Research – Amarillo. “The emergence of voluntary associations among agricultural water users to reduce ground water use is an encouraging step, and we need to learn from those associations’ experiences with regard to what works, and what doesn’t, and what possibilities exist that don’t require expanding the regulatory state.”

The summit will take place over two half-days, starting at 11:00 a.m. Central Time on Tuesday, March 31 and concluding the next day on Wednesday, April 1 at 2:30 p.m. The event includes a casual evening social on the evening of March 31 that will feature screening of a portion of the film “Rising Water,” by Nebraska filmmaker Becky McMillen, followed by a panel discussion on effective agricultural water-related communications.

Visit the 2020 Ogallala summit webpage to see a detailed agenda, lodging info, and to access online registration. Pre-registration is required, and space is limited. The registration deadline is Saturday, March 21 at midnight Central Time.

This event is open to credentialed members of the media. Please RSVP to Katie.ingels@kwo.ks.gov or amy.kremen@colostate.edu.

Ogallala Aquifer. This map shows changes in Ogallala water levels from the period before the aquifer was tapped to 2015. Declining levels appear in red and orange, and rising levels appear in shades of blue. The darker the color, the greater the change. Gray indicates no significant change. Although water levels have actually risen in some areas, especially Nebraska, water levels are mostly in decline, namely from Kansas southward. Image credit: National Climate Assessment 2018

@USFWS to start releases from Lake McConaughy on February 17, 2020 for the Platte River Recovery Implementation Program

Platte River Recomery Implemtation Program area map.

From The Kearney Hub:

The U.S. Fish and Wildlife Service, in coordination with the Platte River Recovery Implementation Program, plans to release water from Lake McConaughy to benefit downstream habitat used by threatened and endangered species.

Releases will start Monday and may continue through March 15…

USFWS, PRRIP and Central Nebraska Public Power and Irrigation District staff will coordinate the releases, monitor weather and runoff conditions, and be prepared to scale back or end releases if required to minimize the risk of exceeding flood stage.

Current expectations include:

Environmental account water traveling down the North Platte channel below Lake McConaughy will be increased by approximately 300 cubic feet per second to 700 cfs.

– The river will remain well below the designated flood stage of 6 feet at the city of North Platte.

– Flows downstream of North Platte are expected to be significantly below flood stage.

– Flows at Grand Island should be approximately 700 cfs, or less than 6 inches higher than current flows.

– In the Overton to Grand Island stretch, the river stage is expected to be less than 1 foot above normal levels for this time of year.

Report: #Groundwater Availability of the Northern #HighPlainsAquifer in #Colorado, #Kansas, #Nebraska, #SouthDakota, and #Wyoming — @USGS #OgallalaAquifer

Click here to download the paper. Here’s the executive summary:

The Northern High Plains aquifer underlies about 93,000 square miles of Colorado, Kansas, Nebraska, South Dakota, and Wyoming and is the largest subregion of the nationally important High Plains aquifer. Irrigation, primarily using groundwater, has supported agricultural production since before 1940, resulting in nearly $50 billion in sales in 2012. In 2010, the High Plains aquifer had the largest groundwater withdrawals of any major aquifer system in the United States. Nearly one-half of those withdrawals were from the Northern High Plains aquifer, which has little hydrologic interaction with parts of the aquifer farther south. Land-surface elevation ranges from more than 7,400 feet (ft) near the western edge to less than 1,100 ft near the eastern edge. Major stream primarily flow west to east and include the Big Blue River, Elkhorn River, Loup River, Niobrara River, Republican River and Platte River with its two forks—the North Platte River and South Platte River. Population in the Northern High Plain aquifer area is sparse with only 2 cities having a population greater than 30,000.

Droughts across much of the area from 2001 to 2007, combined with recent (2004–18) legislation, have heightened concerns regarding future groundwater availability and highlighted the need for science-based water-resource management. Groundwater models with the capability to provide forecasts of groundwater availability and related stream base flows from the Northern High Plains aquifer were published recently (2016) and were used to analyze groundwater availability. Stream base flows are generally the dominant component of total streamflow in the Northern High Plains aquifer, and total streamflows or shortages thereof define conjunctive management triggers, at least in Nebraska. Groundwater availability was evaluated through comparison of aquifer-scale water budgets compared for periods before and after major groundwater development and across selected future forecasts. Groundwater-level declines and the forecast amount of groundwater in storage in the aquifer also were examined.

Major Findings

  • Aquifer losses to irrigation withdrawals increased greatly from 1940 to 2009 and were the largest average 2000–9 outflow (49 percent of total).
  • Basin to basin groundwater flows were not a large part of basin water budgets.
  • Development of irrigated land and associated withdrawals were not uniform across the Northern High Plains aquifer, and different parts of the Northern High Plains aquifer responded differently to agricultural development.
  • For the Northern High Plains aquifer, areas with high recharge and low evapotranspiration had the most streamflow, and most streams only remove water from the aquifer.
  • Results of a baseline future forecast indicated that groundwater levels declined overall, indicating an overdraft of the aquifer when climate was about average and agricultural development was held at the same state as 2009.
  • Results of two human stresses future forecasts indicated that increases of 13 percent or 23 percent in agricultural development, mostly near areas of previous development, caused increases in groundwater pumping of 8 percent or 11 percent, and resulted in continued groundwater-level declines, at rates 0.3 or 0.5 million acre-feet per year larger than the baseline forecast.
  • Results of environmental stresses forecasts (generated from two downscalings of global climate model outputs) compared with the baseline forecast indicated that even though annual precipitation was nearly the same, differences in temperature and a redistribution of precipitation from the spring to the growing season (from about May 1 through September 30), created a large (12–15 percent) decrease in recharge to the aquifer.
  • For the two environmental stresses forecasts, temperature and precipitation were distributed about the same among basins of the Northern High Plains aquifer, but the amounts were different.
  • Citation

    Peterson, S.M., Traylor, J.P., and Guira, M., 2020, Groundwater availability of the Northern High Plains aquifer in Colorado, Kansas, Nebraska, South Dakota, and Wyoming: U.S. Geological Survey Professional Paper 1864, 57 p., https://doi.org/10.3133/pp1864.