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A Better Forecast for Projecting Water Supplies
A Better Forecast for Projecting Water Supplies

Dr. Hamid Moradkhani is a technician working behind the scenes of a challenge faced by resource managers here and around the world: how to be sure there’s enough water to meet demands as populations swell and weather patterns shift as the climate changes.

The winter of 2014 left much of the American West sunny and water starved while the Midwest and Eastern regions endured prolonged periods of extreme cold and record snowfall. Forecasters at the National Oceanic and Atmospheric Administration (NOAA) recently issued an official El Niño watch that could bring damaging droughts to Australia, South Africa, and large swaths of the northern US. To avoid the costly consequences of extreme and exceptional drought conditions, water resource managers around the world are taking a close look at what they have, what they can expect from future precipitation, and how they’re going to meet the demand of urban and rural populations, commerce, industry, agriculture, and ecosystems.

Dr. Moradkhani is a civil engineer, Associate Professor at PSU, and expert in hydrology, hydraulics, and water resource systems. He works with government agencies, concerned stakeholders, and fellow researchers here and abroad assessing, integrating, and enhancing models that forecast seasonal water supplies and predict droughts. He, his collaborators, and students use methods such as remote sensing, climate downscaling, Monte Carlo statistical analysis, multi-model combination and optimization, and parallel computing to characterize the state of hydrologic systems and minimalize uncertainties in hydrologic forecasting. The effects of flux in hydrologic systems and uncertainties in climate and hydrologic modeling lead to inaccurate water supply projections that could have devastating consequences for whole regions. Dr. Moradkhani provides resource managers with improved tools that produce better data by mitigating the effects of uncertainties.

Here in the Northwest, Dr. Moradkhani is working with the Bonneville Power Administration (BPA) and the Institute for Sustainable Solutions at PSU on a study assessing the climate change impacts on the hydrology of the Columbia River Basin (CRB). The CRB is the central hub for water flowing out of parts of Oregon, Washington, Nevada, Idaho, Wyoming, Montana, and British Columbia. The social, economic, and environmental vitality of the region depends on the fragile water cycle that feeds the CRB. Could climate change alter or otherwise disturb this system? And if so, what might happen to the water supply that nourishes the Pacific Northwest?

Using data from the coupled ocean-atmosphere general circulation model (CMIP5)—a long-range projector of future weather patterns—in conjunction with three hydrologic forecasting models, Dr. Moradkhani and his team will assess the climate change impacts on streamflow over the entire CRB, an area comprising the entire Columbia River and its roughly 113 tributaries. When complete, this project will provide a hydrologic model for watersheds throughout the CRB and a detailed set of projections that take into account the possible effects of climate change on streamflow. The study will also expand our understanding of the relationships between climate and hydrology and how they influence water supply and drought conditions all of which will help the BPA and others manage freshwater supplies for society and the environment.

“The aim of this project,” said Dr. Moradkhani, “is to reduce the uncertainties that are embedded in models we’re already relying on. Generally, those making projections rely on a single model. So if you use multiple climate models, different downscaling procedures, and if you consider different condition scenarios for the next hundred years, what’s going to happen to the strength of the projection? We think we’ll see great improvements.”

Dr. Moradkhani is taking a similar approach in another project with the aim of producing better water supply projections. Resource managers typically feed data on monthly precipitation, the amount of water contained in snowpacks, and past observations into whichever hydrologic model they’re using to forecast seasonal water supplies. But not all forecasters use the same models and methods to derive results from the data, meaning not everyone arrives at the same supply projections. According to Dr. Moradkhani, agencies like the National Weather Service Northwest River Forecast Center and the National Resource Conservation Service meet regularly, compare their numbers, and come to a consensus on an ‘official’ projection.

Obviously this approach doesn’t hold to the principles of objective scientific rigor. One or more projections could turn out to be closer to actuality than the consensus. In order to achieve an objective streamflow forecast, these agencies and the NOAA have partnered with Dr. Moradkhani on a study that proposes to optimize models used by the agencies involved and test whether the optimized multi-model, multi-institutional forecast can outperform the individual models. The study is scheduled to wrap up in the summer of 2014. Papers and presentations highlighting the study’s results will follow.

“The techniques we’ve developed to improve water supply forecasting are not just useful here in the Northwest, they’re applicable around the world,” Dr. Moradkhani noted. “With our methods, we can improve the forecasts made by water managers, which will help them prepare for times when supply is low. The point of our work is to promote and increase sustainability in times of drought and climate change.”

Nationwide, the winter of 2014 left as many as 30 states experiencing some level of drought intensity—from abnormally dry conditions in states like Hawaii, Alaska, and Main, to what the National Drought Mitigation Center labels as ‘Exceptional Drought’ in areas of Central Texas, Colorado, and the Nation’s most agriculturally productive region, California’s San Joaquin Valley. With populations and demands rapidly increasing in lockstep, managing freshwater resources is a must. Here at Portland State University and in places like the CRB, the upper Colorado River Basin, the Klamath River Basin, and elsewhere around the world, Dr. Moradkhani is working with research sponsors and partners to improve our ability to predict when freshwater resources will be abundant and scarce so that as demand rises, supplies will be there to meet it.

For more information about Dr. Moradkhani, including a mini-biography, other research projects, publications, and courses, visit his personal website at: 

Authored by Shaun McGillis
Posted April 1, 2014