Predicting climate change impact on the water supply

Soumya Sagarik | 02 Feb 2016 | Comments

Climate change, while always present, has not really been a matter of concern for water managers and hydrologists. Major changes in climate have typically taken place in intervals of thousands of years, and consequently the flow of surface water has been assumed to be stationary.

However, reports from the Intergovernmental Panel on Climate Change have shown increases in the Global Mean Surface temperature since the late 19th century and increases in greenhouse gasses over the last two decades. These rapid changes in climate deviate from long-held historical conditions, and have the potential to dramatically impact our water resources.

Whether caused by natural processes or human activities, the average temperature in the US has increased by about 2˚F over the last 50 years. By the end of the century, global average temperatures are projected to increase 2.5˚- 11.5˚F (depending on future levels of heat-trapping greenhouse gases). Projected changes in our long-term climate are expected to precipitate more frequent extreme events such as heat waves, heavy downpours, infectious diseases, drought and flooding, affecting many aspects of life throughout the US and the world. Regional and seasonal precipitation patterns are likely to change and rainfall will become more concentrated into heavy events with longer, hotter dry periods in between.

There is now stronger evidence for substantial and wide-ranging impacts of climate change on water resources, coastal systems, and ecosystems on land and in the ocean—which will no doubt, impact our agriculture and water supply. Climate change has already altered and will continue to alter the water cycle, affecting where, when, and how much water is available for all uses. The production of several crops, such as wheat and maize, has been impacted by climate change over the past several decades. Resulting economic losses due to extreme weather events have also increased globally.

So, climate change has deservingly gained the attention of water managers and hydrologists, and needs to be examined in order to develop infrastructure and systems that can adapt to these changed conditions. Climate change intensifies the hydrological process, while quickly changing hydrology may lead to gaps between what we’ve designed our infrastructure projects to do, and what is actually required to meet our long-term needs. When predictive data is lacking and our knowledge is incomplete, it creates a technical challenge in providing clients reasonable estimates for projects, especially when related to water resource management and risks. Therefore it’s easy to see why improvements in forecasting technologies are being closely followed by hydrologists and climatologists.

It’s increasingly critical that water managers understand the links between climate variability and hydrology. By understanding the relationship climate change has across various locations, we start to see patterns that help us bridge the gap and plan for sustainability. The solution doesn’t arrive from addressing global climate change, because different parts of the earth can respond differently to the same climate indicators. There may be differences in intensity, time frames and influences of local factors involved, and these changes may come in gradual trends or abrupt shifts. Making data more regionally applicable, therefore, is key.

Numerous studies have found links between pre-defined climate indexes (such as the El Nino Southern Oscillation) and climate phenomenon in various regions. And while pre-defined indices are currently the prime choice for water managers to predict future hydrologic patterns, a study I’d recently worked on for my thesis at UNLV, using entire oceanic sea surface temperatures, drew new regional correlations.

By evaluating the link between sea surface temperatures, atmospheric pressures and continental US seasonal streamflows, new regions not seen previously in standard indices were identified. Pacific and Atlantic Ocean climatic variability showed a greater correlation with spring-summer streamflow compared to the summer season streamflow, and atmospheric pressures were found to have a more pronounced effect on US seasonal streamflows compared to sea surface temperatures. The contributions from this research are significant, helping build a better understanding of the changes in streamflows and relationships with oceanic-atmospheric variability across regions.

While there is more to discover, the findings from this study lay the foundation for developing predictive techniques that may assist water managers in planning and preparing for the effects of climate change on water resources. As the climate changes, so must we—and by carefully studying the relationships found in nature, we’ll find new answers.