Sunday, March 25, 2018
4:00 – 5:00 p.m.
Auditorium between Bldg. 4&5, Level 0, Room 0215
Human influences on flood and drought risk across scales
Bio
Prof. Justin Sheffield is Professor of Hydrology and Remote Sensing at the University of Southampton. He spent 16 years at Princeton University in the US before returning to the UK in 2016, carrying out fundamental and applied research on large-scale hydrology and its interactions with climate variability and change. He has published extensively on hydrological extremes, climate change, and hydrological processes from catchment to global scale. He has also pioneered work on the application of research to natural hazards impacts reduction and water and food security, particularly in developing regions, including the production of monitoring and prediction systems. He has received a number of awards including the Prince Sultan Bin Abdulaziz International Prize for Water in 2014 for research work on drought monitoring and prediction, and the Plinius Medal of the European Geosciences Union in 2013 for outstanding multi-disciplinary research and applications in hydrological hazards. Most recently he was named as the 2019 Robert E. Horton Lecturer in Hydrology by the American Meteorological Society for advancing hydrologically coherent analyses of drought across time and space scales, and for pioneering the development of integrated drought monitoring tools for food-insecure countries.
Abstract
Human activities can play a significant role in modifying the terrestrial hydrological cycle, through water management, agriculture and power generation. This can translate into changes in the severity of floods and droughts, either locally or as a cumulative effect downstream. We quantify the impact of human activities on flood and drought severity over the US using a large-scale water resources model, PCR-GLOBWB, which includes representation of reservoirs, surface water and ground water abstractions, and water use for irrigation, livestock, industry and municipal activities. We run model experiments with and without individual activities to show the relative contribution of water abstraction and return flows to explain how each human activity contributes to enhancing or mitigating hydrological floods and droughts. The results indicate a complex spatial pattern of mitigation and enhancement of drought severity across the US, with mostly mitigation in the east and enhancement in the central and western US. In the lower Mississippi and Central Valley of California, extensive irrigation appears to mitigate drought severity by up to 60-80%, through enhanced return flows. This is driven mostly by renewable groundwater abstraction. On the other hand, pumping of non-renewable groundwater in the southern High Plains leads to enhancement of drought severity. In comparison, flood severity is mostly enhanced by human activities but to a lesser magnitude than for drought. The impact of local activities on floods and droughts tends to accumulate downstream, although in some regions this switches from exacerbation to mitigation, creating a complex pattern of downstream impacts. This approach to integrated hydrological modeling enables attribution of different human impacts to altering risk, which in turn helps policy-makers better evaluate long-term policy development for assessing potential water infrastructure investments and operations in mitigating droughts and floods.