Better dam planning strategies

This is a map showing combined effect of current and future dams. Credit: McGill University

When dams are built they have an impact not only on the flow of water in the river, but also on the people who live downstream and on the surrounding ecosystems. By placing data from close to 6,500 existing large dams on a highly precise map of the world's rivers, an international team led by McGill University researchers has created a new method to estimate the global impacts of dams on river flow and fragmentation.

Among their findings, published online today in Environmental Research Letters: 48% of the world's river volume is moderately or severely affected by dams today -- and that figure would nearly double if all dams planned or under construction are completed in the future.

"Over the past 60 years, a myriad of dams have been built either to provide hydroelectric power, or for irrigation purposes, or as flood protection," says Bernhard Lehner, a professor in McGill University's Department of Geography and the research director of the project. "The construction of large dams then slowed down for the last 20 years as we became more aware of their negative effects on people and ecosystems. But now, with fears about how climate change may affect water flows in the future, the goal of creating reservoirs is once more appealing, and dam construction is on the rise."

The new research was made possible by the team's development of a global river map with unprecedented resolution and detail, showing all waterways of the world from small creeks to the largest of rivers, accounting for a cumulative river length of 48.3 million km -- and by a new map of future dam locations assembled by colleagues at the Leibniz-Institute of Freshwater Ecology and Inland Fisheries in Berlin.

The key components of the team's dam assessment method are two indices that describe river fragmentation and river regulation.

The river fragmentation index (RFI) is a measure of the way that a river's natural flow path (also known as its connectivity) has been disrupted by the creation of dams or by barriers that allow for the transfer of water between basins or towards irrigation areas, for example.

The river regulation index (RRI) is a measure of the proportion of the river water that can be stored in reservoirs, and thus affects the natural fluctuation and properties of river flow downstream.

By combining these two indices, the researchers have arrived at a way of assessing the impact of any existing or planned dam. So, for example, the Danube is severely impacted by fragmentation effects but is relatively weakly affected in terms of flow regulation due to many dams with relatively small reservoirs. The Murray-Darling basin in southern Australia, by contrast, is only weakly affected by fragmentation, but is heavily impacted by flow regulation, due to fewer but larger reservoirs.

"Not all dams are equal," says Günther Grill, a postdoctoral fellow in McGill University's Department of Geography and the lead author on the paper. "Our research assumes that it is not only the size of a dam but also where it is placed along the river that makes a difference. So depending on whether a dam is high up in the mountain headwaters or further down close to the delta, if it is on the main stem of the river or on a small tributary, all of these factors will have varying effects on the rivers and their surrounding ecosystems."

Researchers at the University of Minnesota's Institute on the Environment and the University of Wisconsin's Center for Limnology also contributed to the study.

Some dam and river facts:

There are 6,374 large dams already in existence and 3,377 planned or proposed large dams to be built by 2030.

Currently 48% of the world's river volume is moderately or severely affected by either flow regulation or fragmentation or both.

Assuming that all the dams that are planned or under construction are completed, this number would almost double to 93%, largely due to multiple dams being planned for major tributaries in the Amazon Basin.

Other large rivers that are currently rather free-flowing but on which large dams are planned are the Mekong River in Southeast Asia and the Amur River in Russia.

Source: McGill University

Protect the world's deltas, experts urge

The Atchafalaya River delta meets the Gulf of Mexico. The view is upriver to the northwest. Credit: Photo courtesy A. Belala/U.S. Army Corps of Engineers

Extensive areas of the world's deltas -- which accommodate major cities such as Shanghai, Dhaka and Bangkok -- will be drowned in the next century by rising sea levels, according to a Comment piece in this week's Nature. In the article, Dr. Liviu Giosan, a geologist with the Woods Hole Oceanographic Institution (WHOI), and colleagues call for maintenance efforts to be started now to avert the loss of vast expanses of coastline, and the consequent losses of ecological services, economic and social crises, and large-scale migrations.

The authors state the problems start upstream: deltas are built from sediments deposited at the mouths of rivers, but dams and river engineering have lowered rates of sediment flow. The Nile and the Indus, for example, carry 98 percent and 94 percent less mud respectively than they did 100 years ago. At the coast, rising seas resulting from warmer global temperatures are eroding delta plains, increasing the chance of flooding. Coastal lands lower than a meter in elevation will be inundated within a century.

Lack of quantitative knowledge of basic delta processes is hindering efforts to develop maintenance strategies for deltas, the authors say. At the same time, the role of healthy marshes in coastal processes needs to be more fully understood. Giosan and colleagues call for river sediment flows to be restored, and natural land-building methods to be exploited in delta plains under worldwide monitoring programs coordinated and guided by United Nations committee of experts.

Source: Woods Hole Oceanographic Institution

Colorado River Delta greener after engineered pulse of water

Water being released from Morelos Dam in the first environmental release of water to the Colorado River Delta. The Minute 319 pulse flow of water started March 23, 2014 and ended May 18, 2014. Credit: Rebecca Lester, Deakin University, Australia

The engineered spring flood that brought water to previously dry reaches of the lower Colorado River and its delta resulted in greener vegetation, the germination of new vegetation along the river and a temporary rise in the water table, according to new results from the binational team of scientists studying the water's effects.

The experimental pulse flow of water was the result of a U.S.-Mexico agreement called Minute 319.

"The pulse flow worked," said Karl W. Flessa, co-chief scientist for the Minute 319 Science Team. "A small amount of water can have a big effect on the delta's ecosystem."Starting March 23, 2014, and ending May 18, approximately 105,392 acre-feet (130 million cubic meters) of water was released into the dry river bed below Morelos Dam, which straddles the U.S.-Mexico border just west of Yuma.

"The groundwater was recharged, vegetation got greener than previous years and the water helped germinate new native vegetation," said Flessa, a University of Arizona professor of geosciences. "As a bonus, the river reached the sea."

In addition, people living along the river benefited, he said.

"People in the communities along the river were just overjoyed to see their river again," he said. "When the surface water was there, people celebrated. Kids who'd never seen water in the river before got to splash in it."

The science team includes more than 21 scientists from universities, government agencies and nongovernmental organizations from both Mexico and the U.S, including the UA, the Universidad Autónoma de Baja California, the U.S. Geological Survey, the U.S. Bureau of Reclamation, The Nature Conservancy, the Tucson-based Sonoran Institute and the Ensenada-based Pronatura Noroeste.

Flessa will present the team's findings at his talk, "The Science and Policy of the First Environmental Flows to the Colorado River Delta," on Dec. 18 as part of the American Geophysical Union's annual meeting in San Francisco.

Although most of the water soaked into the ground in the 37 miles (60 km) below the dam, the river's surface flow reached areas farther downstream that had been targeted for restoration. The increase in groundwater revived vegetation along the entire 83-mile (134 km) route to the sea.

By comparing Landsat 8 satellite images from August 2013 with those from August 2014, team members calculated a 23 percent increase in the greenness of riparian zone vegetation.
Although the groundwater did eventually recede, the surface water caused the germination of new willows and cottonwoods. Those plants germinate after natural spring floods, and their roots can grow fast enough to keep up with the receding water table.

The surface water reached the restoration sites prepared by the Sonoran Institute and Pronatura Noroeste and helped establish native vegetation.

"So long as the roots get down into the permanent water table, then you have established a new bunch of trees that will then live for 20, 30, 40 years," Flessa said. "Those trees will attract birds."

The scientists already observed an increase in the numbers of birds, he said.
Learning where the newly germinated plants survived past the first summer will help the researchers figure out where ecosystem restoration will do the most good using the least amount of water, he said.

"The water that soaked into the ground is also good for the farmers," Flessa said. "It raises the water table and they pump that water -- so this isn't just about trees and birds."
The team will continue to monitor the lower Colorado River Delta's vegetation and hydrological response to the pulse flow, including the long-term effect on groundwater. They will also study how the new vegetation affects both resident birds and those migrating along the Pacific Flyway.

The five-year program to monitor the environmental results of the pulse flow is being supported by government agencies and environmental groups in both countries, under the auspices of the International Boundary and Water Commission.

The Minute 319 pulse flow is part of a five-year agreement (2012-17) adopted by the International Boundary and Water Commission, under the framework of a 1944 U.S. -- Mexico treaty that governs water allocations on the Colorado River between the two countries.

The agreement provides multiple benefits for Colorado River water users in both countries, including environmental flows to the delta. Minute 319 identifies criteria for sharing of future water shortages and surpluses between the two countries, allows storage of Mexican water in Lake Mead and supports improvements to Mexican irrigation infrastructure.
"Another pulse flow would require a new agreement, because Minute 319 calls for only one pulse flow within the five-year term of the minute," Flessa said. "We hope the results of this pulse flow encourage the negotiators to make this happen again."

Source: University of Arizona

Laser from a plane discovers Roman goldmines in Spain

These are ancient goldmines in the Eria river valley, with channels and reservoirs for exploitation. The model generated with LiDAR data (left) allows these structures to be located on aerial photos (right). Credit: J. Fernández Lozano et al.

Hidden under the vegetation and crops of the Eria Valley, in León (Spain), there is a gold mining network created by the Romans two thousand years ago, as well as complex hydraulic works, such as river diversions, to divert water to the mines of the precious metal. Researchers from the University of Salamanca made the discovery from the air with an airborne laser teledetection system.

Las Médulas in León is considered to be the largest opencast goldmine of the Roman Empire, but the search for this metal extended many kilometres further south-east to the Erica river valley. Thanks to a Light Detection and Ranging (LiDAR) laser system attached to an aircraft, the ancient mining works of the area and the complex hydraulics system used by the Romans in the 1st century BC to extract gold (including channels, reservoirs and a double river diversion) have been discovered.

"The volume of earth exploited is much greater than previously thought and the works performed are impressive, having achieved actual river captures, which makes this valley extremely important in the context of Roman mining in the north-east of the Iberian Peninsula," as Javier Fernández Lozano, geologist at the University of Salamanca and co-author of this study published in the Journal of Archaeological Science, said.

The specialists consider that the systems for the transport and storage of water were copied from those already existing in North Africa, where the Egyptians had been employing them for centuries. Some details of the methodology used appear in texts such as those of the Pliny the Elder, the Roman procurator in charge of overseeing mining in Hispania.

"We have established that the labour that went into extracting the resource until its exhaustion was so intensive that after removing the gold from surface sediments, operations continued until reaching the rocks with the auriferous quartz veins underneath," explains Fernández Lozano.

The researcher stresses that the real discoverer was the LiDAR technology: "Unlike traditional aerial photography, this airborne laser detection system allows the visualisation of archaeological remains under vegetation cover or intensely ploughed areas."

From aircraft or drones
LiDAR comprises a laser sensor which scans the ground from an aircraft or drone with geographical references provided by GPS ground stations. The data obtained is represented by point clouds, which are processed with a piece of software to construct a cartographic model where the forms are identified, such as old reservoirs or channels.

This technology was developed by NASA in the sixties to analyse the retreating sea ice in the Arctic and composition of the oceans. Since then their use has been extended to topography, cadastral mapping, geology and archaeology. According to the authors, the study of Roman mining in the Eria valley is the first piece of 'geo-archaeology' performed with LiDAR in Spain.

"Our intention is to continue working with this technique to learn more about mineral mining in the Roman Empire and clear up any mysteries such as why Rome abandoned such a precious resource as gold from one day to the next," concludes the researcher.

Source: Plataforma SINC

The Severe drought is causing the western US to rise like a spring uncoiling

Maps of GPS points in the western United States, with blue indicating a drop and yellow-red reflecting a rise.
Credit: Image courtesy of University of California - San Diego

The severe drought gripping the western United States in recent years is changing the landscape well beyond localized effects of water restrictions and browning lawns. Scientists at Scripps Institution of Oceanography at UC San Diego have now discovered that the growing, broad-scale loss of water is causing the entire western U.S. to rise up like an uncoiled spring.

Investigating ground positioning data from GPS stations throughout the west, Scripps researchers Adrian Borsa, Duncan Agnew, and Dan Cayan found that the water shortage is causing an "uplift" effect up to 15 millimeters (more than half an inch) in California's mountains and on average four millimeters (0.15 of an inch) across the west. From the GPS data, they estimate the water deficit at nearly 240 gigatons (62 trillion gallons of water), equivalent to a six-inch layer of water spread out over the entire western U.S.

Adrian Borsa, an assistant research geophysicist at Scripps Institution of Oceanography, UC San Diego.

Results of the study, which was supported by the U.S. Geological Survey (USGS), appear in the August 21 online edition of the journal Science.

While poring through various sets of data of ground positions from highly precise GPS stations within the National Science Foundation's Plate Boundary Observatory and other networks, Borsa, a Scripps assistant research geophysicist, kept noticing the same pattern over the 2003-2014 period: All of the stations moved upwards in the most recent years, coinciding with the timing of the current drought.
Agnew, a Scripps Oceanography geophysics professor who specializes in studying earthquakes and their impact on shaping Earth's crust, says the GPS data can only be explained by rapid uplift of the tectonic plate upon which the western U.S. rests (Agnew cautions that the uplift has virtually no effect on the San Andreas fault and therefore does not increase the risk of earthquakes).

For Cayan, a research meteorologist with Scripps and USGS, the results paint a new picture of the dire hydrological state of the west.

"These results quantify the amount of water mass lost in the past few years," said Cayan. "It also represents a powerful new way to track water resources over a very large landscape. We can home in on the Sierra Nevada mountains and critical California snowpack. These results demonstrate that this technique can be used to study changes in fresh water stocks in other regions around the world, if they have a network of GPS sensors."

The study was supported by USGS National Earthquake Hazards Reduction Program

Source: University of California - San Diego