USGS researcher Craig Allen stands on the edge of Mesa Alta, amid diverse forest and woodland in the uplands of northern New Mexico; note some recently dead ponderosa pine and Douglas-fir in the field of view. Forest drought stress is strongly correlated with tree mortality from poor growth, bark beetle outbreaks, and high-severity fire.

For hundreds of years, forests of piñon pine, ponderosa pine and fir trees have covered millions of acres of mesas, plateaus and mountains in the semi-arid southwestern United States. Like forests everywhere, they provide food and shelter for countless species and help anchor vital watersheds and soils of the region.

But their days may be numbered. Based on a new study co-authored by the USGS, projected climate change impacts suggest a grim picture for current forests in the U.S. Southwest.

Research led by A. Park Williams of the Department of Energy’s Los Alamos National Laboratory came to this conclusion by comparing the tree-ring record to climate data collected in the Southwest since the late 1800s. The researchers aligned some 13,000 tree-core samples with known temperature and moisture data, further blending in known historical events such as documented megadroughts that drove the ancient Pueblo Indians out of longtime settlements such as Mesa Verde, Colorado.

Worst Forest Drought Stress in 400 Years

What they found was this: since 2000, southwestern U.S. forests have experienced more drought stress than during any other period in more than 400 years. What’s interesting about this is that precipitation totals since 2000 haven’t been exceptionally low, but temperatures have been exceptionally high. These high temperatures have caused the atmosphere’s ability to evaporate water from soil and plants also to be exceptionally high.

Think of the atmosphere as a water-thirsty sponge: the warmer the air, the thirstier the sponge.  When the summers are too hot and dry, the trees lose much of the water that they otherwise would have used for growth. If this happens too often, trees become stressed and more vulnerable to disturbances like forest fires and bark beetle infestations.

Forest Growth Rates Predictable Using Climate Records            

When Williams and the other researchers, including USGS scientist and study co-author Craig D. Allen, compared southwestern tree-ring records to climate records, they found that southwestern forest growth rates can be predicted very effectively using just two climate variables: winter precipitation and summer-fall atmospheric evaporative demand.

The researchers were able to predict future forest growth rates using these climate and tree-growth relationships, combined with projections of future climate trends. The results: all climate models project warming to cause large increases in summer-fall atmospheric evaporative demand (thirstier sponge). No models project large increases in winter precipitation. If the climate models are correct, forest growth will decrease substantially in the coming decades primarily due to increasing drought stress from warmer growing season temperatures.

Tree Rings Link Past and Current Drought Stress

Drought and beetle-killed piñon pines in Walnut Canyon National Monument near Flagstaff, Arizona, amid a few surviving trees. Forest drought stress is strongly correlated with tree mortality from poor growth, bark beetle outbreaks, and high-severity fire.

The tree-ring records in the Southwest extend back in time for more than 1,000 years. This allowed the researchers to investigate how future forest drought-stress likely will compare to periods of major drought stress in the past. The tree-ring records indicate that two “megadrought” events, during the 1200s and again in the 1500s, occurred in the past 1,000 years. Past research has shown that both of these events probably coincided with widespread forest die-off in the Southwest. So, the researchers treat forest growth rates during those extreme megadroughts as a benchmark for drought conditions strong enough to cause widespread forest die-off. If warming occurs as rapidly as projected by climate models, forest drought-stress conditions are likely to exceed those historic megadrought conditions on a regular basis by the 2050s. In fact, the study forecasted that during the second half of this century, about 80 percent of years are projected to exceed those megadrought levels.

Williams says the current drought event, which began in 2000, demonstrates how close southwestern forests already may be to reaching drought-stress levels unprecedented in at least a millennium. The team concluded that forest drought stress during 4 of the past 13 years (about 30 percent), including 2011 and 2012, matched or exceeded megadrought-type levels. The only other 13-year periods when megadrought-type conditions were reached with such frequencies in the past 1,000 years were during the megadroughts themselves.

What’s Going to Happen to Southwestern Forests in the Future?

Sunset as seen through the smoke of a prescribed burn in the Jemez Mountains, New Mexico. The burn was conducted to restore fire as an ecosystem process and reduce hazardous tree densities and fuel loads due to more than 100 years of fire suppression. Foreground trees (Douglas-fir and aspen) were killed during the Cerro Grande fire in 2000. Forest drought stress is strongly correlated with tree mortality from poor growth, bark beetle outbreaks, and high-severity fire.

As trees become more stressed from increasingly hot, dry summers, eventually they will not be able to continue to grow in their current locations, and fires and beetle infestations will take an increasing toll. We can expect to see increased numbers of trees dying, with many not being replaced. Eventually, if warming trends continue as projected by state-of-the-art climate models, the current forests will give way to ecosystems more tolerant of prolonged, severe drought. This would mean substantial changes in forest species composition to more drought-tolerant trees, or even forest-replacing shrublands and grasslands.

The article, “Temperature as a potent driver of regional forest drought stress and tree mortality,” appears in the October 2012 Nature Climate Change. Authors are A. Park Williams (LANL), Craig D. Allen (U.S. Geological Survey), Alison K. Macalady (University of Arizona), Daniel Griffin (University of Arizona), Connie A. Woodhouse (University of Arizona), David M. Meko (University of Arizona), Thomas W. Swetnam (University of Arizona), Sara A. Rauscher (LANL), Richard Seager (Columbia University), Henri D. Grissino-Mayer (University of Tennessee), Jeffrey S. Dean (University of Arizona), Edward R. Cook (Columbia University), Chandana Gangodagamage (LANL), Michael Cai (LANL), Nate G. McDowell (LANL).

For More Information:

• Seeing the Forest and the Trees: USGS Scientist Links Local Changes to Global Scale

• Craig D. Allen Staff Page

• Western Mountain Initiative: Effects of Climate and Global Change on Western Mountains

• Climate Change: The Science of Impacts

• Haitian woman carrying supplies amid the destruction from the January 2010 Haiti earthquake.

September is National Preparedness Month, a time to highlight the threats posed by natural hazards and the importance for individuals and communities to be prepared.

Hurricane Isaac recently swept through the Gulf Coast, wildfires continue to ravage the west, and drought grips more than three quarters of the contiguous United States facing abnormally dry conditions. Natural hazards like these threaten lives and cause billions of dollars in damage every year throughout the nation. Sound science is essential for preparedness to natural hazards, guiding the best decisions to minimize their impacts.

USGS: Start with Science

The U.S. Geological Survey works with many partners to monitor, assess and conduct research on a wide range of natural hazards, providing policymakers and the public a needed understanding to enhance preparedness, response and resilience. USGS research includes earthquakes, volcanoes, landslides, wildfires, floods, droughts and extreme storms.

Earthquakes

Earthquakes pose a risk to more than 165 million people in 37 states. The USGS has created and provides information tools to support earthquake loss reduction, including hazard assessments, scenarios, comprehensive real-time earthquake monitoring and public preparedness handbooks.

Imagine if doctors had time to stop delicate procedures before an earthquake. And if emergency responders had a few extra moments to gear-up, airplane landings could be postponed, trains slowed, and people could move to safer locations. The USGS and its partners are helping to provide critical seconds of notification by developing a prototype Earthquake Early Warning System in the United States.

You can sign up to receive earthquake notices through the USGS Earthquake Notification System as well as USGS social media channels. Tips and suggestions for earthquake preparedness can be found on the Earthquake Country Alliance website and the USGS Prepare website. When you feel an earthquake, you can report your experience on the USGS “Did You Feel It?” website.

The Next Earthquake: Are You Ready?

Numerous states and countries will be participating in the next ShakeOut earthquake drill on Oct. 18, 2012. At 10:18 a.m., participants will “drop, cover and hold on.” This event offers citizens a chance to learn how to get better prepared and practice what to do when an earthquake happens in their community.

Shishaldin Volcano on Unimak Island, part of Izembek National Wildlife Refuge in Alaska.

This is the first year an official drill is being coordinated in the Southeast United States, and you can see a full list of participating locations at the ShakeOut website. Mark your calendar and sign up your family, school, business, or organization to join as well.

Volcanoes

When the violent energy of a volcano is unleashed, the results can be catastrophic. Lava flows, debris avalanches and explosive blasts have devastated communities. Noxious volcanic gas emissions have caused widespread lung problems. Airborne ash clouds from explosive eruptions have caused millions of dollars of aircraft damage and nearly brought down passenger flights.

Fortunately, volcanoes show signs of unrest hours, weeks and months before they erupt, and the USGS National Volcano Early Warning System is designed to detect these precursors. The USGS issues warnings and alerts of potential volcanic hazards – including ash fall forecasts – to responsible emergency-management authorities and those potentially affected. See current alerts and status for volcanoes in the United States.

Preparedness is increasingly important for the growing number of people that live, work, play and travel in volcanic regions. Learn more by visiting the USGS Volcano Hazards Program website and watching a video on USGS volcano science.

Landslides

Landslides occur in all 50 states and pose a risk to every citizen. Falling rocks, mudslides and debris flows can be deadly hazards, and we are still learning more about them. To protect communities from landslide hazards, USGS science is helping answer questions such as where, when and how often landslides occur, and how fast and far they might move.

For example, USGS scientists produce maps of areas susceptible to landslides and identify what sort of rainfall conditions will lead to such events. The USGS is working with the National Weather Service on a Debris Flow Warning System to help provide forecasts and warnings to inform community and emergency managers about what areas are at imminent risk of having a debris flow or mudslide.

For more information, watch a video about USGS landslide science, and visit the USGS Landslide Hazards Program website. Scientists at the USGS are also asking the public to help them track landslides and collect a more complete catalog of events. Report your landslide experiences and sightings at the new USGS “Did You See It?” website.

Wildfires

This landslide occurred in 2005 in La Conchita, California.

The USGS plays an integral role in preparing for and responding to wildfires. The USGS provides tools and information before, during and after fire disasters to identify wildfire risks and reduce subsequent hazards, while providing real-time geospatial support for firefighters during the events. For example, the USGS provides fire managers with up-to-the minute maps and satellite imagery about current wildfire extent and behavior throughout the nation.

The wildfire itself is a hazard, but once the smoke clears, the danger is not over. Secondary effects of wildfires, including erosion, landslides, invasive species and changes in water quality, are often more disastrous than the fire itself. As fires are contained, USGS scientists help to assess their aftermath to guide the re-building of more resilient communities and restoration of ecosystems.

Flooding, Storms and Drought

The USGS conducts real-time monitoring of the nation’s rivers and streams, providing officials with critical information for flood warnings and drought mitigation. If you want to know whether river levels are higher or lower than normal, visit USGS WaterWatch. You can also use USGS WaterAlert to receive texts or emails when water levels at a specific streamgage exceed certain thresholds.

During floods, USGS scientists measure water levels, river velocities and high water marks. The USGS and the National Weather Service work together to make flood inundation maps that show you exactly where the water will be – what yards, roads and buildings will be covered – and when a river or stream reaches a certain water level.

The USGS also studies coastal vulnerability and change from hurricanes and extreme storms, helping inform flood forecasts and evacuation warnings. Before, during and after major hurricanes or tropical storms affecting the United States, the USGS assesses the likelihood of beach erosion, overwash or inundation. Scientists also measure storm surge and monitor water levels of inland rivers and streams.

Unlike flooding, droughts often take a long time to begin to impact an area, sometimes festering for months or even years. USGS science contributes to the national Drought Monitor, which is the official report detailing drought conditions, as well as the National Weather Service’s Drought Outlook, which forecasts future drought.

More Information

Flooding hit record highs in in North Dakota and many other areas of the U.S. in 2011. For more on the floods of 2011: http://gallery.usgs.gov/videos/439

To learn more about National Preparedness Month, visit www.fema.gov/ or www.ready.gov.

The Arkansas River at Great Bend, Kansas, on July 13, 2012. Lying west of Isaac’s rain reach, the river was drier still on September 10.

More than three quarters of the contiguous United States still faces abnormally dry conditions in spite of scattered relief from rains generated by tropical storm system Isaac.  As seen on the U.S. Drought Monitor, exceptional drought — the worst category — persists in the very center of the nation from Nebraska south to Texas, east through Missouri and Arkansas to the Mississippi Valley. Much of Georgia is also in exceptional drought.

Drought: the slow but costly disaster

Drought is the nation’s most costly natural disaster, far exceeding earthquakes, tornados, hurricanes and floods. FEMA has estimated that the annual average cost of drought in the United States ranges from $6 to $8 billion. (By comparison, the annual costs of flooding are in the $2 to $4 billion range.) Unlike flooding, drought does not come and go in a single episode. Rather, it often takes a long time for drought to begin to impact an area, and it can fester for months or even years.

In order to reduce the impacts of drought, governments and managers rely on objective and unbiased scientific information about trends in streamflow, precipitation, and other factors that contribute to drought, so that they can understand where drought is occurring, how long it is likely to impact an area, and where drought is likely to strike next.

What about Isaac’s effects on the current drought?

The obvious question comes from both expert and casual observers: What difference did tropical system Isaac make in drought-stricken areas?

NOAA records show that Hurricane Isaac made landfall in southern Louisiana the evening of August 28 and then tracked north-northwest, losing its tropical character over Missouri on September 1 and then merging with another frontal zone to move on into the Ohio Valley. This NASA graphic of rainfall based on satellite measurements shows that Isaac’s rainfall was concentrated to the east of its tropical storm center. (100 mm is about 4 in. of rain.)

One week after Isaac officially dissipated (9/1), this real-time map of national stream flow from USGS WaterWatch  (below normal 7-day average streamflow compared to historical streamflow, updated 9/8) shows that streamflows have returned to normal or higher levels in the middle and lower Mississippi Valleys and the Ohio Valley where much of Isaac’s related precipitation fell.

However, while real-time streamflow levels from USGS WaterWatch are an essential aspect of measuring drought, stream and river conditions are not the only drought indicator.

Drought is a bigger concept than streamflow can show

The national Drought Monitor is the official report detailing drought conditions. This complex map service paints a fuller picture of drought than just stream flow information. In addition to relying heavily on USGS streamgage data, this map also incorporates soil moisture, agricultural information, satellite data, and precipitation.

The map — a joint product of NOAA, the U.S. Department of Agriculture, and the National Drought Mitigation Center — is prepared in consultation with scientists from several agencies, including the USGS. It portrays a comprehensive geographic assessment of areas experiencing drought, as well as the severity of drought.  This map has important economic significance because it is used by many states as the basis for declaring a drought emergency and requesting federal funding.

You can see that, according to the U.S. Drought Monitor (updated 9/4), extreme or severe levels of drought persist in parts of Arkansas, Missouri, Tennessee, Kentucky, Illinois, Indiana, and Ohio — states to which Isaac’s rains did come in varied amounts.

The next obvious question might be: Why didn’t Isaac make more of a difference in the drought?

That’s a complex inquiry that involves lots of issues like precipitation rates and volumes, water runoff, groundwater levels, and soil moisture. Let’s look for a broader answer in a story about accumulated precipitation deficit that’s no less true for its simplicity.

A Story of Drought: The Water Bank

USGS WaterWatch map of monthly-average streamflow for August 2012. Note how rain from Isaac accelerated the monthly average east of New Orleans.

It can be useful to think of drought as a water bank account held by Mother Nature. When it rains, Mother Nature makes a deposit into Earth’s water bank account. When it stops raining, Mother Nature is obliged to withdraw water from the soil and from vegetation for “payment” to the atmosphere; this is done through evapotranspiration. The longer she goes without making water deposits, the greater the amount of water that gets withdrawn from the soil, as well as from other storage accounts like lakes and reservoirs, and the greater her water deposits (i.e., precipitation) will have to be to bring the account back up to what it was before the drought started.

That’s essentially what’s going on when one huge storm system with its sudden rains seems to make little immediate difference in a drought. Mother Nature may have hit the million-dollar lottery with Isaac and is making big deposits into her terrestrial account. But she needs to make two or three more deposits like this to get back to the starting point of local average conditions of water deposits and withdrawals.

Looking ahead on drought

In addition to the U.S. Drought Monitor, which tracks current and historic drought conditions, every month the National Weather Service produces a Drought Outlook, with bi-weekly updates based primarily on precipitation forecasts.

The latest long-range report, released on September 6 and looking ahead to November 30, indicates that drought is likely to develop, persist, or intensify across much of the Great Plains (including Texas but not the Dakotas) and all or parts of the Rocky Mountain and Western states (excluding Arizona and Washington).

U.S. Seasonal Drought Outlook, Sept. 6 – Nov. 30. NOAA forecast.

Drought conditions are likely to improve in Louisiana, Alabama, the Dakotas, the upper Mississippi Valley, and the Ohio Valley. Arkansas, western Tennessee, and Georgia will see lesser degrees of improvement.

Links and resources

USGS WaterWatch

National Drought Monitor

NOAA Drought Outlook

Droughts of the Past

For local details and impacts related to drought, please contact your State Climatologist or Regional Climate Center.

Isaac’s floodwaters and impacts were measured using a variety of tools before, during and after the storm, including terrestrial and airborne lidar, acoustic Doppler and aerial photography

Mapping in 3-D: Terrestrial lidar and acoustic Doppler

USGS scientists mapped the Tangipahoa Dam using terrestrial lidar (video at right), or T-lidar and acoustic Doppler technology to capture multiple scans of different areas near the dam, showing the above and underwater topography. The dam was damaged during heavy rainfall in Hurricane Isaac and caused thousands of people downstream to be evacuated late last week.

These scans captured a clear view of two landslides on the dam’s downstream side. The larger of the two landslides occurred mostly underwater. While T-lidar provides a clear view of above ground features, scientists used acoustic Doppler techniques to conduct underwater measurements.

A 3-D terrestrial LiDAR scan of the Percy Quin Mississippi State Park Dam in McComb, Mississippi, taken Monday, September 3, 2012. The U.S. Geological Survey is using this new technology in select areas of Louisiana, Mississippi and Alabama to map impacts by Hurricane Isaac.

The first T-lidar scans took place Saturday, with more completed on Monday to assess whether additional movement of the landslides had occurred.  Monday’s scan showed little movement. This information and other data has been provided to the U.S. Army Corps of Engineers as they continue to address the dam’s structural risk and public safety.

T-lidar allows scientists to quickly generate 3-D maps of buildings, dams, levees and other structures, and can show areas of storm damage as well.  In a four-to-five minute scan, the instrument collects millions of topographic data points in a full 360-degree view to quickly produce highly accurate topographic information and can map areas up to two-thirds of a mile away.

Acoustic Doppler instruments are frequently used to measure stream or lake geometry and water velocity. An acoustic signal is bounced off the river or lake bottom and the amount of time required for the signal to return to the sensor provides a measurement of the distance to the bottom. In the Tangipahoa Lake application an acoustic Doppler instrument was used to map the underwater portion of the landslide area, and to determine the force of the water on the dam structure.

Isaac is the first storm in which USGS has used its terrestrial lidar capabilities to map urban flooding.

The view from above: aerial flight surveys and lidar showing coastal change

After the worst of the storm passed, USGS scientists began conducting aerial photography and elevation surveys of post-storm beach conditions along the Gulf Coast to document the impacts of hurricane surge, waves, and currents on beaches. Information obtained from these surveys allows scientists to measure changes to coastal environments.

Oblique aerial photography was collected this week from Isle Dernieres in Louisiana to Dauphin Island in Alabama.  Scientists compared these images with pre- storm images of the same location to illustrate the coastal changes and damage from Hurricane Isaac. Photo pairs of several locations are available online.

Photos from Dauphin Island indicated beach erosion and island overwash, furthering the erosion the island has seen during repeated storm events — Ivan, Katrina, Gustav and Isaac — that have led to the island’s increased vulnerability to future storms. This photo shows the effects that repeat hurricane waves and surge have had on Dauphin Island from 2004 -2008.

Some areas of the Chandeleur Islands in Louisiana experienced such extreme erosion from Isaac that only underwater shoals, or submerged shallow areas, remain. This erosion resulted in the disappearance of an oil-protection berm constructed following the BP oil spill.  Due to cumulative damage from previous storms like Hurricane Katrina, it remains in question whether this beach system will ever be able to fully recover from storm impacts.

Scientists are also conducting an airborne lidar survey of beach elevations to gather additional information in the most heavily impacted areas and to measure the amount of erosion.

Lidar, light detection and ranging, is an aircraft-based, remote-sensing technique that uses laser pulses to collect highly detailed ground elevation data. The photography and lidar data, as well as the coastal change analyses of these data, should be useful in mitigation and restoration efforts along the Gulf Coast shoreline. Data acquired will also be used to improve predictive models of future coastal impacts from severe storms and to identify areas vulnerable to extreme coastal change.

Flyover Shows Storm Damage and Marsh Dieback:

Another set of USGS aerial flight surveys flown this week used similar techniques to document vegetation and habitat change, and other ecological impacts and along coast and barrier islands post Isaac.

These flights examined areas from Wax Lake Delta, Louisiana, to Ship Island, Mississippi., and preliminary assessments suggest that Hurricane Isaac damaged coastal wetlands in a manner that is substantial, but not unprecedented. Damage to coastal wetland areas was evident throughout much of southeast Louisiana. The intensity of hurricane effects was most abundant in areas of upper Breton Sound, an area just to the south of the community of Braithwaite, which experienced devastating flooding.

The most prevalent effects of Hurricane Isaac observed were expansive wrack fields. Wrack is accumulated organic debris and trash that are transported and deposited by a hurricane’s surge. Wrack deposits from Hurricane Isaac were observed throughout southeast Louisiana, burying existing marsh areas and obstructing infrastructure, such as canals and railroads.

Large areas of marsh dieback, termed “brown marsh” or “sudden marsh dieback,” were observed in the Terrebonne and Barataria basins in Louisiana. Previous reports of sudden marsh dieback in the spring and summer of 2012, before Hurricane Isaac, indicate that the dieback in this area has been increasing over time and may be the result of a combination of other stressors. Evidence of vegetation stress, such as widespread discoloration, was also observed in areas that were directly impacted further to the east by hurricane storm surge. The browning and destruction in the marshes east of the Mississippi River in coastal Louisiana appear to be recent, indicating a more direct link to salinity and flooding stress associated with the Hurricane Isaac’s storm surge. The USGS will further investigate the recent history of sudden marsh dieback events in coastal Louisiana. Subsequent aerial surveys will be conducted to quantify the extent of brown marsh and to potentially separate the phenomenon of sudden dieback and the storm surge impacts.

Louisiana currently experiences more wetland loss then all other states in the U.S. combined. Coastal Louisiana has lost a wetland area the size of Delaware, equaling 1,883 square miles, over the past 78 years, according to a 2011 USGS National Wetlands Research Center study. For more information about NWRC’s hurricane research, visit http://www.nwrc.usgs.gov/hurricane/index.html. To view images collected during post-Hurricane Isaac reconnaissance flights, click on the Hurricane Isaac link. To learn more about marsh dieback or brown marsh, visit http://www.nwrc.usgs.gov/about/capabilities/brwnmrsh.htm.

Seeing the Surge: Collecting Sensors and Gathering High Water Marks

USGS field crews responded to the storm deploying 170 storm surge sensors and rapid deployment gauges along the Gulf coast between Mobile Bay in Alabama and Venice, Louisiana. Now those sensors are being collected and the data are being analyzed.

Surge elevations ranged from more than five feet in eastern Mississippi to nearly 11 feet west of Bay St. Louis.  Along the North Shore of Lake Pontchartrain, surge elevation ranged from six feet to over seven and a half feet near Madisonville, Louisiana.  The LaPlace area southwest of Lake Pontchartrain experienced over five feet of surge elevation, but the worst hit was the Plaquemines Parish area, where flooding continues to impede access to USGS sensors.  All data (provisional and subject to change upon review) are available via interactive mapper.

In addition to in measuring storm-tide, more than 75 independent high-water marks have been recorded to provide additional points between the sensors to document the extent and magnitude of storm surge from Isaac. Rains from Hurricane Isaac cause record flows on Mississippi streams. Inland flooding was recorded in Mississippi on the Wolf River, Black Creek and Wiggins. Three stations in southeastern Louisiana had the second highest peak stage of record ever recorded at these sites.  Bogue Chitto River near Bush, La. peaked at 19.82 feet on September 2^nd; Bogue Chitto River at Franklinton, La. also peaked on September 2^nd with a high-water mark of 22.13 feet; Tangipahoa River at Robert, La. peaked on September 1 with high water mark of 24.02 feet.

Over the next few days, USGS will send crews into the field to assess flooding, gather high water marks, and begin to collect and analyze data from storm surge sensors deployed prior to Hurricane Isaac’s landfall. USGS will also conduct aerial surveys along the Gulf’s coastline to photograph coastal change from the storm’s waves and currents.

USGS Flood Monitoring Network:

USGS boat launched during 2011 flood waters in Louisiana.

For more than 125 years, the USGS has monitored flow in selected streams and rivers across the U.S. through an extensive streamgaging network. More than 7500 streamgages throughout the U.S. provide real-time information of river and stream flow which is routinely used for water supply and management, monitoring floods and droughts, bridge and road design, determination of flood risk, and for many recreational activities.

Rising Floodwaters from Isaac:

Several southern states have experienced significant flooding as a result of rains from Hurricane Isaac.

Multiple USGS field crews from several states are recording high-water marks, collecting discharge measurements and obtaining water quality data in coastal and inland Alabama, Mississippi and Louisiana. This information is important because it is used by the National Weather Service to issue flood warnings, and the data is also used by emergency responders and planners to mitigate current and future flood hazards. These crews are being augmented by USGS staff from the Georgia Water Science Center. As the storm continues to move, crews from Illinois, Indiana, Kentucky, Missouri and Arkansas remain ready to address flooding along the storm’s track.

USGS field crews have also begun retrieving the 170 storm surge sensors and 17 temporary real-time gages that were deployed in response to Hurricane Isaac in locations where the storm has passed. Data from these sensors networks will be uploaded to the USGS Hurricane Storm Tide Sensor Map.  The sensors provide critical data for more accurate modeling and prediction capabilities and allows for improved structure designs and response for public safety.

Three dimensional (3D) topographic and bathymetric model of Yellowleaf Creek, AL.

New 3-D Mapping Technology to Measure Isaac’s Flooding

A new technology is being used by the USGS to map flooding in certain urban areas caused by the hurricane. Called terrestrial lidar, or T-lidar, this new capability is being deployed by scientists from the USGS to collect highly-detailed information in select population areas where the storm had the greatest impact in Louisiana, Alabama and Mississippi. The USGS has not previously used T-lidar for flood work.

Drought Persists in other parts of the U.S.

Although Isaac has brought significant precipitation in its wake, much of the country continues to be plagued by severe drought conditions. The U.S. Drought Monitor has provided the latest drought impacts for the states listed below. Real-time updates on the Nation’s drought conditions are available on the USGS drought homepage:

Dry, cracked streambed as a result of drought.

All of Wyoming is experiencing moderate drought, with 37 percent of the state comprising parts of the Cheyenne, North Platte, and Green River basins in extreme drought conditions.  More than 74 percent of Arkansas continues to be in extreme or exceptional drought conditions.  Colorado, Nebraska and Missouri all have 100 percent of the state in severe drought. Indiana is experiencing 97 percent of the state in severe drought. Moderate to below normal drought conditions cover the vast majority of the state of Georgia. Only the upper Tennessee basins and the Suwannee, Alapaha, and Ochlockonee River basins are in the normal range. In Kansas there are 56 USGS streamgages measuring zero water flow and in Oklahoma there are 22 gages currently measuring zero flow.

Access current flood and drought conditions across the country by visiting the USGS WaterWatch website.

Receive instant, customized updates about water conditions in your area via text message or email by signing up for USGS WaterAlert.

Drought conditions on the Arkansas River at Great Bend, Kansas on July 13, 2012. Photo by Nathan Sullivan, USGS.

Almost 80 percent of the contiguous United States is facing abnormally dry conditions right now. In fact, much of the lower half of the country is facing at least severe to extreme drought. To make matters worse, scientists are not expecting relief any time soon. In many of these areas, drought is predicted to continue to get worse.

Drought is the nation’s most costly natural disaster, far exceeding earthquakes, tornados, hurricanes and floods. FEMA has estimated that the annual average cost of drought in the United States ranges from $6 to $8 billion. (By comparison, the annual costs of flooding are in the $2 to $4 billion range.) Unlike flooding, drought does not come and go in a single episode. Rather, it often takes a long time for drought to begin to impact an area, and it can fester for months or even years.

Start with Science

In order to reduce the impacts of drought, governments and managers rely on objective and unbiased scientific information about trends in streamflow, precipitation, and other factors that contribute to drought, so that they can understand where drought is occurring, how long it is likely to impact an area, and where drought is likely to strike next.

Droughts can be subdivided into three types: meteorological, agricultural, and hydrologic drought. A meteorological drought begins with precipitation deficiency, high temperatures and winds, and low humidity. As soil moisture is reduced, plants and agriculture are stressed, leading to agricultural drought. When drought causes streamflow to be reduced, the result is a hydrologic drought.

You can view areas of low stream flow in real time at USGS WaterWatch. The map shows how current flows compare to what would be normal for a given time of year based on historical averages. Right now, almost the entire country is experiencing below normal conditions. The bright red coloring on the map indicates, for example, that flows in Georgia are especially low. While this map is an adequate real-time gauge for areas experiencing hydrologic drought, stream and river conditions are not the only drought indicator.

Drought conditions at Lake Hartwell, SC. Photo by Carol J. VanDyke, USGS (2011).

The national Drought Monitor is the official report detailing drought conditions, and this map paints a fuller picture of drought than just stream flow information. In addition to relying heavily on USGS streamgage data, this map also incorporates soil moisture, agricultural information, satellite data, and precipitation.

The map — a product of NOAA, the U.S. Department of Agriculture, and the National Drought Mitigation Center — is prepared in consultation with scientists from several agencies, including the USGS. It portrays a comprehensive geographic assessment of areas experiencing drought, as well as the severity of drought.  For example, when The Weather Channel reports on drought conditions in the country, they use the Drought Monitor map. This map also has economic significance, because it is used by many states as the basis for declaring a drought emergency and requesting federal funding.

In addition to the Drought Monitor, which tracks current and historic drought conditions, every month the National Weather Service produces a Drought Outlook, with bi-weekly updates based primarily on precipitation information. The latest report, released on July 5, indicates that drought is likely to develop, persist, or intensify across much of the Ohio and Tennessee Valleys, the Corn Belt region, the middle and lower Mississippi Valley, and much of the Great Plains.

How Does This Drought Compare to Past Droughts?

That’s a tough question, because the answer depends on a variety of factors: how you define drought, the specific parts of the country affected by drought, and the time of year.  However, the most extensive area of drought during the past century occurred in July 1934 during the dust bowl when 80 percent of the contiguous United States was in moderate to exceptional drought.  By comparison, the area in moderate to exceptional drought in June 2012 was 57 percent.  So the current drought, though severe, is not as extensive as that which occurred during the Dust Bowl era of the 1930s.

Additionally, as a nation we prepare better for today’s droughts, by using reservoirs more strategically and by putting other mechanisms in place to mitigate the impacts of drought. Most states have a plan to ensure there is enough water available when signs point to dry futures. For example, Virginia’s plan allows managers to issue emergency permits for water or even bring in water from elsewhere depending on drought severity. Other plans guide states in preparing for and proactively lessening drought. For example, Nebraska has a plan that includes incentives for water conservation, steps for awareness campaigns, protection of stream flows, and assessments of the most vulnerable areas.

While the Souris River is in the throes of record high flooding in Minot, N.D., O.C. Fisher Lake near San Angelo, Texas has been experiencing the exact opposite for a number of years now – a ground-cracking drought. These locations have more than their extreme water conditions in common. Though about 1,000 miles apart, these places are situated north and south of each other just west of the 100th meridian of longitude. Photo by Travis Dowell, USGS, June 23, 2011.

You can find out about low water levels in real-time with USGS WaterAlert. This USGS service allows you to automatically receive a text or email from a USGS streamgage when waters go below a certain threshold that you choose. Sign up for WaterAlert online by selecting a state, checking the “surface water” box, and clicking on your streamgage of choice.

Will Droughts Get Worse with Climate Change?

Drought is a normal component of our climate. Because of the way weather patterns work, there is always precipitation somewhere in the atmosphere and a lack of precipitation somewhere else. Certain areas are more prone to drought, but drought can happen anywhere.

While scientists agree that climate change will cause temperatures to continue to rise, changes to precipitation patterns are less certain. At the time, extrapolating these loose precipitation predictions to drought impacts is nearly impossible. Scientists agree that it is still very difficult to make generalized statements about how climate change will impact drought.

USGS Drought Information in Your State

While drought is affecting multiple states across the country, here is a glimpse at a few local impacts.

Oklahoma experienced a year of extreme heat and drought last year, due to high temperatures and precipitation deficits. Although precipitation has returned to near normal so far this year, Oklahoma is still in the grip of a hydrological drought. The USGS Oklahoma Water Science Center is working on multiple projects that provide reliable, impartial, and timely information to resource managers, planners, and other customers about drought. These federally-funded activities in Oklahoma emphasize regional assessments of surface-water and groundwater conditions, how natural processes and human activities affect those conditions through time, development of new tools and techniques for understanding complex hydrologic systems, effects of drought, and planning for drought.

The Colorado River runs dry on the U.S./Mexico border 2 miles below the Morelos Dam. Photo by Pete McBride, USGS, Jan 13, 2009

In Arkansas, streamflows across the state are about 10 – 50 percent of normal streamflow expected during this time of year. Some streams are exhibiting less than one percent of the normal streamflow expected. USGS scientists in Arkansas are studying the effects of climate on water levels, and have determined that long-term continuous monitoring is important to evaluating the effects of climate variability.

Western Texas continues to experience extreme drought, though winter and spring rains provided modest relief to the 2011 drought.   Although central Texas has gotten some recent rains, reservoirs are still well below capacity in many areas. Even with recent flooding in the Houston area , about 90% of the wells measured in the Gulf Coast Aquifer during the winter of 2011-12 showed water level declines. Additionally, statewide reservoir storage in 2011 was the lowest on record since 1978.

In Colorado streamflow in early July was below normal at more than 80 percent of the USGS long-term monitoring stations.  Record low flows were recorded at 23 of 127 long term monitoring stations. Severe hydrologic drought is primarily occurring in the upper Colorado River Basin, the upper Arkansas Basin, and parts of southwestern Colorado. The Rio Grande and South Platte Basins are experiencing moderate hydrologic drought while flows in the lower Arkansas Basin remain below normal.

In Kansas, USGS scientists are measuring the lowest flows since the 1950s for the Arkansas River, as well as several other rivers across the state. The North Fork of the Ninnescah River is running low enough that the creek temperature have hit 103 degrees.

USGS International Drought Science: Famine Early Warning Systems Network

The ability to grow crops in drought conditions is of high concern for many populations of the developing world. The Famine Early Warning Systems Network (FEWS NET), which is an activity of the U.S. Agency for International Development and its office Food for Peace, identifies populations with the most food insecurity, examining critical situations in which food aid will be needed. FEWS NET research was used to provide early warning of drought and the potential for the outbreak of famine conditions in Ethiopia and Kenya and Somalia in 2011. Another successful forecast was made in the spring of 2012 that helped motivate effective humanitarian responses in Kenya and Ethiopia.

The Vegetation Drought Response Index (VegDRI) incorporates satellite observations of vegetation to monitor at a finer spatial detail than other commonly used drought indicators.

FEWS NET also helps target more than $1.5 billion of assistance to more than 40 countries each year. As an implementing partner of FEWS NET, the USGS contributes remote sensing data and analyses to monitor and warn of impending drought and potential food insecurity, as well as providing scientific studies for informing adaptation to climate change. The FEWS NET program currently works in Africa, Asia, Central America, and Haiti, with the hope of expanding to global coverage in the near future.

Links and Resources:

• USGS WaterWatch
• National Streamflow Information Program
• Cooperative Water Program
• National Drought Monitor
• NOAA Drought Outlook
• Droughts of the Past

For local details and impacts related to drought, please contact your State Climatologist or Regional Climate Center

Young boys working in a newly cropped field in Africa.

Spring rains in the eastern Horn of Africa are projected to begin late this year and be substantially lower than normal.

From March–May, the rains are expected to total only 60 to 85 percentage of the average rainfall in this region. This is a significant deterioration compared to earlier forecasts.

Lower rain amounts would have significant impacts on crop production, rangeland regeneration for livestock, and replenishment of water resources.

This would put greater stress on the region, particularly Somalia which is still recovering from a famine declared last year, as well as Kenya and Ethiopia which also experienced a severe food crisis. An increase in food insecurity and in the size of the food insecure population is likely.

The State Department released a statement on this forecast and their intent to provide additional funding to aid refuges and drought-affected communities.

Famine Early Warning Systems Network

 The rainfall projections were completed by the Famine Early Warning Systems Network (FEWS NET), which helps target more than $1.5 billion of assistance to more than 40 countries each year. FEWS NET monitors high risk areas of the developing world with the most food insecurity, identifying critical situations in which food aid will be needed.

FEWS NET is sponsored and led by the U.S. Agency for International Development (USAID) Office of Food for Peace. Implementing partners include the U.S. Geological Survey (USGS), Chemonics International, Inc., National Aeronautics and Space Administration (NASA), National Oceanographic and Atmospheric Administration (NOAA), and the U.S. Department of Agriculture (USDA).

USGS Science

A herder moves cattle through a barren landscape in eastern Africa.

The USGS led the climate analysis for the recent FEWS NET rainfall projection.

“Rainfall projections were estimated by looking very closely at all the prior droughts from March–May since 1979 in the eastern Horn of Africa,” said USGS scientist Chris Funk, who led this research. “We found that sea surface temperatures in the western/central Pacific and the Indian oceans are key drivers of rainfall during that time period. So we compared sea surface temperatures from past years to March 2012, and developed an updated rainfall forecast for this spring season.”

Climate modeling analysis was done in collaboration with others, including Greg Husak and Joel Michaelsen with the Climate Hazards Group at the University of California, Santa Barbara, as well as Bradfield Lyon at The International Research Institute for Climate and Society. Lyon’s research identified the important role of the Pacific Ocean in recent droughts.

The USGS also contributes satellite remote sensing data and analysis of vegetation and rainfall to support FEWS NET activities throughout the world. Remote sensing from space allows scientists to provide rapid, accurate assessments of a broad range of environmental and agricultural conditions. A newly completed vegetation monitoring system allows FEWS NET analysts to track conditions across all of Africa in tremendous detail.

“The concerning picture that emerged from FEWS NET climate monitoring services was that despite the good rains of the past winter, the situation east Africa has deteriorated very rapidly, to a point that the water deficits and vegetation health looked as bad as this time last year,” said Funk.

Link between Sea Surface Temperatures and Rainfall

 As the globe has warmed over the last century, the Indian and central/western Pacific oceans have warmed particularly fast. USGS scientists found that the warming of these oceans affects rainfall over large areas of the Horn of Africa.

The resulting warmer air and increased humidity over the Indian and Pacific oceans produce more frequent rainfall over the oceans. The air then rises over the equatorial Indian and Pacific oceans, and flows westward, descending over Africa. Since the air has already lost moisture from rainfall over the oceans, this leads to decreased rain amounts in parts of eastern Africa. Trends toward increased frequency of drought that we are seeing now appear likely to continue into the future as warming continues.

“Essentially, our research has progressed to the point where we can recognize fairly well the climate patterns linked to the recent droughts, and we hope this helps identify potential bad seasons in advance to raise awareness,” said Funk.

More Information

Learn more about USGS science helping to save lives in Africa.

Listen to a podcast interview on FEWS NET and USGS research in Africa.

Young boys working in a newly cropped field in Africa.

In parts of eastern Africa, drought is of increasing concern, as poor families suffer from food shortages and the inability to grow crops and sustain livestock. Stunted growth in children due to malnutrition has also been linked to climate trends in Africa.

Drought conditions are expected to continue as global temperatures continue to rise and rainfall declines across parts of eastern Africa.

This poses increased risk to millions of people in Africa who currently face potential food shortages.

What’s being done to help?

The USGS is involved in a variety of research efforts to help understand current and future conditions in Africa, helping to inform plans to provide aid.

The Famine Early Warning Systems Network, or FEWS NET, is one endeavor that has already made great strides in helping to address this issue. FEWS NET helps target more than $1.5 billion of assistance to more than 40 countries each year.

FEWS NET examines the populations of the developing world with the most food insecurity, identifying critical situations in which food aid will be needed. These are populations whose livelihoods are typically tied to subsistence rain-fed agriculture and pastoralism.

FEWS NET is sponsored by the U.S. Agency for International Development (USAID) Office of Food for Peace and the USGS is actively involved.

FEWS NET at the United Nations Climate Convention

A USGS presentation on FEWS NET will be a featured side event on November 30, 2011, at the United Nations 17^th annual Conference of the Parties (COP-17) in Durban, South Africa. The convention’s purpose is to develop international agreements and a declaration of policies and practices for combating climate change and its impacts around the world.

A herder moves cattle through a barren landscape in eastern Africa.

Climate forecasts and remote sensing help spot future trouble

FEWS NET has developed its own climate services to provide decision makers with early identification of agricultural drought that might trigger food insecurity. Scientists use climate forecasts to develop forward-looking food security assessments that are based on expected agricultural outcomes for the season ahead.

Since networks of ground observation stations are often sparse or reported late in FEWS NET countries, satellite remote sensing of vegetation and rainfall fills in the gaps. Remote sensing from space allows for rapid, accurate assessments of a broad range of environmental and agricultural conditions. USGS scientists provide the technologies and expertise to support remote sensing for FEWS NET activities.

Early warning of famine in Somalia helps pre-position food supplies

On July 20, 2011, the United Nations declared parts of Somalia as a region of famine. The decision was supported by FEWS NET and USGS observational evidence of conditions in the area.

The declaration was the culmination of early warning communications encouraging — months before the crisis — that government and other agencies pre-position food and supplies in the region.

“None of the many uses of Earth-observing satellites is more vital — or has as much potential for prompting timely humanitarian intervention — as famine early warning,” said USGS Director Marcia McNutt. “Remote sensing from space allows USGS scientists to provide rapid, accurate assessments of a broad range of environmental and agricultural conditions.”

The eastern Horn of Africa, the continental region that encompasses Somalia, has experienced two consecutive seasons of very poor rainfall resulting in the worst drought in 60 years. Crops have failed, livestock deaths are widespread, and food prices are very high. While the rains this winter have been good, food prices remain high, and the food security situation remains insecure.

Stunted growth linked to malnutrition and climate change

Other USGS research is helping to identify the impacts of a changing climate on Africa’s people. Scientists recently discovered that malnutrition and dry hot living conditions are linked to stunted growth in Mali, West Africa.

USGS research found that Mali was becoming substantially warmer and a little bit drier. Scientists also knew that farmers and those who make a living raising sheep, cattle, goats, or camels were poor, and that stunted growth was occurring throughout Mali.

Scientists wondered if there could be a link between human health and increasingly warm and dry conditions.

To investigate, the USGS worked with the University of California, Santa Barbara, to study climate observations and demographic and health data. The Demographic and Health Survey program routinely compiles data from surveys in 90 countries to study trends in health and population. Scientists analyzed statistics on specific villages in Mali and found that there was a link between a warmer climate and increased stunting.

Population growth combined with the impacts of warming will further increase these health impacts.

Stunting was also linked to other factors, such as mother’s education and the water supply system. Women’s education, improved water supplies, and agricultural development could help to address malnutrition and stunting in Mali.

An article on this research was published in in the journal, Applied Geography, by San Diego State University, the University of California, Santa Barbara, and the USGS.

A Food Security Assessment in Somalia found severe impacts on livestock due to drought conditions.

Other studies underway

Other new research includes the discovery that the warming of the Indian and western Pacific oceans (which is linked to global warming) affects rainfall over large areas of the Horn of Africa. As the globe has warmed over the last century, the Indian Ocean and western Pacific have warmed especially fast.

The resulting warmer air and increased humidity over the Indian and western Pacific oceans produce more frequent rainfall in that region. The air loses its moisture during rainfall, and then flows westward and descends over Africa, leading to decreased rain in parts of eastern Africa. Trends toward increased frequency of drought that we are seeing now are likely to continue into the future as warming continues.

A few recent articles on this research were published in the journal, Climate Dynamics, by scientists with the USGS, the University of California, Santa Barbara, and Los Alamos National Laboratory. The most recent article concludes that global warming will lead to a decrease in rainfall during the summer monsoon season, from June to September, across southern Sudan, southern Ethiopia, and northern Uganda.  Another article concluded that eastern Africa, particularly Kenya and southern Ethiopia, will also have a significant decrease in rainfall during the long-rains season from March to June.

USGS scientists are working hard to translate these technical studies into reports for decision makers. To date, they have completed summary fact sheets focused on Sudan and Kenya.

Scientists also found that some regions, like northern Ethiopia, are not getting drier due to current warming temperatures. Rainfall varies dramatically across all of eastern Africa, with high mountainous areas typically receiving many times the rainfall received in low-lying areas. Therefore, agricultural growth in these climatically safe regions could help offset rainfall declines in other locations.

Start with science

Scientists are looking at clues and changes in nature to understand the impacts of global warming. In Africa, impacts are seen across the landscape — on farms and even in humans.

By starting with science, well-informed decisions can be made to help Africa as it faces drought, famine, and health concerns.

FEWS NET partners include the USAID, Chemonics International, the USGS, NASA, NOAA, and the USDA. The Geography Department at the University of California, Santa Barbara, is a partner to the USGS in this effort.

Want more information?

Listen to a podcast interview with USGS scientists as they discuss ongoing efforts to understand conditions in Africa.

Drought

The effects of drought are felt throughout the United States and the world, and USGS science has a prominent role in understanding the causes and consequences of this hydrological phenomenon.

Learn more