Towards No Regrets Hydrology: Including Climate Variability and Change in Design and Operation of Water Resources Projects
James S. McDonnell Distinguished University Professor Professor of Civil and Environmental Engineering Princeton University
Juan B. Valdés
Former Director of the National Science Foundation (NSF) Science and Technology Center SAHRA (Sustainability of Semi-Arid Regions and Riparian Hydrology)
Professor, University of Arizona
José D. Salas
Professor of Civil & Environmental Engineering
Colorado State University
Given that the purpose of Bank’s engagement in water projects is to help client countries in their development efforts, a common denominator includes growth and poverty alleviation in an environmentally sustainable manner. Water plays an important role in achieving that purpose. There is, however, wide agreement in the scientific literature and the science community that greenhouse gases (GHG) are having a significant impact in the Earth’s climate. This is confirmed by instrumental evidence and results from mathematical models. There is also consensus in that climate change will “intensify the hydrologic cycle”, i.e. causing changes in the frequency of events, changes in the magnitude of events, and changes in the seasonal dynamics of events.
Simulation and forecasting of hydrological variables have been important components in planning, design, operation and management of water resources systems for several decades. However, in recent years some of the basic hydrologic models, assumptions, and procedures underlying the estimation of extreme values, stream flow sequences and other design parameters have been questioned because of concerns related to climate variability and change and that the traditional approach of using past observations to mimic the future may not be the most appropriate course of action.
Advances in the preparation of a HEF Technical Note (first working draft for discussion is attached) describing efforts towards accounting for climate change and variability in design and operation of water resources projects will be presented and discussed. These impacts vary greatly from region to region and are also different accordingly to the ecosystem where they take place as well as with the objectives of the project under consideration. Because of that the Technical Note is organized around the study of four case studies reflecting different conditions in hydrologic regimes as well as different controlling hydrologic variables: Caroni River Basin (Venezuela); Verde Basin (Arizona, USA); Central Kenya; and Wetlands of Florida (USA).
It is expected that this discussion would be of interest to Bank project team members involved in operations dealing with water resources projects. Specifically, to those that are interested in practical ways to face new hydrologic design challenges imposed by climate variability and change. Namely, those involved in the estimation of design floods, monthly flow sequences and the impacts on the water balance in the ecosystems. It is expected that practitioners involved in the design and operation of water resources projects will find it useful.