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 The availability of freshwater is one of the most critical environmental issues of our time.
Modern society depends on rivers, lakes, wetlands, and groundwater to provide water for irrigation, industry and household use. Changes in water availability or water quality – caused by climate change or human practices – could have serious consequences on human health and welfare.
SAGE works to improve our understanding of freshwater systems in a changing world. We use extensive field data, computer models, and satellite images to examine the impact of natural processes and human activities on freshwater supplies.
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Understanding Freshwater Systems – Rivers, Lakes and Wetlands
The Earth's freshwater systems, as sources of potable water, hydroelectric power and food, are of great importance to human society.
Our research is focused on the linkages between climate, land cover, and the behavior of whole watersheds – including lakes, wetlands, rivers and groundwater systems. In particular, we are interested in how land use and variations in climate can affect the availability and quality of fresh water resources. In order to help answer these questions, we are developing new computer modeling tools to examine the impact of human activities on freshwater supplies across the globe.
Recent efforts have been focused on the THMB (Terrestrial Hydrology Model with Biogeochemistry) model (formerly known as HYDRA), which simulates the flow of water through groundwater systems, rivers, lakes and wetlands. THMB is one of the few hydrological models that simulate the complete freshwater system.
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LANDSAT image showing shrinking of Aral Sea (a fresh water lake)
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We are currently working to understand the effects of management practices, artificial structures, and land use changes on the water cycle. We continue to improve the modeling tools, and test them against field data and satellite measurements.
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African Water Resources
Lake Chad is disappearing.
The lake has shrunk by over 95% – from 25,000 km2 to 1,200 km2 – in just the last three decades. SAGE scientists are examining the causes of this massive lake decline, including losses from drought and irrigation.
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Recently, our work has expanded to include other portions of Africa – including the Nile River in Sudan, the Niger River in West Africa and the Okavango River in southern Africa. Our goal is to understand how important water resources of these regions are affected by increasing agriculture and by year-to-year variations in climate.
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Freshwater of the Upper Midwest
The Upper Midwest has some of the most valuable freshwater resources in the world – including the Great Lakes and the Mississippi River.
Despite this abundance of freshwater, the region still experiences major problems with water supply. Floods and droughts are common occurrences, causing major economic disruptions.
SAGE scientists are working to understand how changes in climate and land cover over the Upper Midwest may impact the behavior of freshwater systems, and the availability of water in coming decades.
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Missouri River LANDSAT 1992
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Missouri River LANDSAT 1993 flood
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Nitrogen Pollution in the Mississippi Basin
Large amounts of nitrogen are finding their way into the freshwater systems of the Mississippi basin.
Through massive increases in fertilizer runoff and industrial pollution, nitrogen levels in surface water and groundwater has been increasing dramatically in the last several decades. In our groundwater, excess nitrogen poses a significant health risk to humans. Too much nitrogen can also degrade the quality of freshwater and marine ecosystems, as in the case of the Gulf of Mexico “Dead Zone” near the mouth of the Mississippi.
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Space shuttle photo of the Mississippi delta at New Orleans. The green area is the muddy water of the Mississippi mixing with the clearer waters of the Gulf of Mexicio
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We are investigating the whole cycle of nitrate pollution in freshwater, including the effects of fertilizer use, climate, and water cycling. By identifying where pollution is occurring now, we may be able to predict which areas could be susceptible in the future.
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Freshwater Systems of the Amazon
The Amazon is one of the most amazing and important rivers on the planet.
In terms of river flow, the Amazon is the largest river system on Earth: the other largest 9 rivers combined do not equal the discharge of the Amazon. The freshwater systems – including the complex of tributary streams and wetlands – of the Amazon play an important role in regulating the Earth’s hydrologic cycle, as well as providing habitats to unique plants and animals.
The Amazon is also changing dramatically. Over the last few decades, increasing population and development pressures have led to large areas of deforestation in the Amazon – mostly along the southeastern portion of the basin. In the coming years and decades, rates of deforestation are likely to increase as more roads are built through the core of the forest, and international markets continue to drive a demand for agricultural and forest products.
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Amazon Basin outlined in red
the Amazon River (J. Cardille)
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At SAGE, we are working closely with scientists in Brazil and the United States to improve our understanding of this remarkable system. SAGE scientists are involved in the international LBA (Large Scale Atmospheric Biosphere Experiment in Amazonia) experiment, which is examining the climate, ecology and water systems of the Amazon region. In this project, we are evaluating how increased human management, deforestation, and climate influence the area’s ecosystems and freshwater systems.
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