Hydraulic Efficiency Assessment of Correctives Measures to Reverse Seawater Intrusion
Date: Feb. 21, 2007
Place: Aerospace 355
Time: 4:00 p.m.
Dr. Elena Abarca
Hydrogeology Group, Dept. of
Geotechnical Engineering & Geosciences,
School of Civil Engineering, Technical University of Catalonia, Barcelona, Spain
Biography
Dr. Abarca received her PhD degree in 2006 from the Department of Geotechnical Engineering and Geo-Sciences at the Technical University of Catalonia, Barcelona, Spain. Her PhD dissertation titled "Seawater intrusion in complex geological environments" was completed under the supervision of Professors Jesús Carrera and Xavier Sánchez-Vila. Her research interests include seawater intrusion management and urban hydrogeology. She recently received the prestigious Fulbright fellowship award to pursue her post-doctoral studies in USA.
Website: http://www.h2ogeo.upc.es/English/People/elena.abarca.html
Abstract
Hydraulic Efficiency Assessment of Correctives Measures to Reverse Seawater Intrusion
Freshwater injection to create seawater intrusion barriers is often considered a waste of resources. It is generally believed that most of the injected water flows seawards and, thereby, it is lost. However, we present here a field case that contradicts this extended belief.
The main aquifer of the Llobregat delta suffers a severe seawater intrusion problem. Water authorities have sought advice to optimally design corrective measures that allow both maintaining the current pumping regime and restoring the water quality of the aquifer. To address this issue we determine the hydraulic efficiency of different corrective measures. This hydraulic efficiency is computed by the shadow prices obtained using a linear programming optimization method that constrains heads at several control points. In the case of the freshwater injection barrier this efficiency is higher than one, which implies that by injecting water near the shore, not only can we recover the amount of water that has been injected but extract even more resources. This result reflects that, in this case, the protective effect of the barrier is as relevant or more than the sole increase of available water caused by injection.
Once the efficiency is determined, a non-linear optimization method is used to design the optimal injection regime to restore the water quality of the aquifer. Chloride concentration constrains are used in this case to determine the optimal injection rate in the studied corrective measures.
