Nima Ehsani

Water Scientist

Investigating the impact

of climate change and

anthropogenic disturbances

on the terrestrial water cycle

Impact of Climate Change on the Function of Existing Dams and the Hydrological Implications for the Northeastern United States


Twenty year average (2080-2099) of projected changes in monthly precipitation and temperature under RCP4.5 and RCP8.5, relative to the average of 1950-1999.

Natural precipitation and runoff variability highly impact the availability of water. There is a spatial and temporal disparity between natural water supply and human demand. Construction of dams is a strategy to reduce this spatiotemporal inconsistency. The cumulative environmental and economic effects of dams remain largely unexplored at the regional and global scales as a result of the lack of reliable methods for simulating operation of dams. This pushes scientists to look into precipitation and local runoff values as measures for the availability of water, or to analyze annual river flows where impacts of dams are mostly negligible. In this work a general reservoir operation scheme is used to quantify the impacts of operation of more than 11000 dams on the hydrology of New England and the Northeastern United States. Climate change Impacts on water availability in the region, and also changes in the magnitude and timing of flow extremes have been compared to the contemporary conditions.


Water, energy and food are inextricably linked. Water is an input for producing agricultural goods in the fields and along the entire agro-food supply chain. Energy is required to produce and distribute water and food: to pump water from groundwater or surface water sources, to power tractors and irrigation machinery, and to process and transport agricultural goods. Agriculture is currently the largest user of water at the global level, accounting for 70% of total withdrawal. The food production and supply chain accounts for about 30% of total global energy consumption.

There are many synergies and trade-offs between water and energy use and food production. Using water to irrigate crops might promote food production but it can also reduce river flows and hydropower potential. Growing bioenergy crops under irrigated agriculture can increase overall water withdrawals and jeopardize food security. Converting surface irrigation into high efficiency pressurized irrigation may save water but may also result in higher energy use. Recognizing these synergies and balancing these trade-offs is central to jointly ensuring water, energy and food security.

The global community is well aware of food, energy and water challenges, but has so far addressed them in isolation, within sectoral boundaries. At the country level, fragmented sectoral responsibilities, lack of coordination, and inconsistencies between laws and regulatory frameworks may lead to misaligned incentives. If water, energy and food security are to be simultaneously achieved, decision-makers, including those responsible for only a single sector, need to consider broader influences and cross-sectoral impacts. A nexus approach to sectoral management, through enhanced dialogue, collaboration and coordination, is needed to ensure that co-benefits and trade-offs are considered and that appropriate safeguards are put in place.

Source: World Water Development Report 2014