US-Egypt Cooperative Research: Improved Hydrogeophysical Assessment of Recharge Beneath Ephemeral Streams and Applications in Arid Areas

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0322548 FerreDescription: This award is for support of a joint research project by Dr. Paul Ferre, Department of Hydrogeology and Water Resources, University of Arizona, Tucson, Arizona and Dr. Hesham El-Kaliouby, Department of Geology and Geophysics, the National Research Center, Cairo, Egypt. The purpose of the research is: 1) to apply nondestructive, geophysical methods to monitor changes in water storage throughout the vadose zone beneath an ephemeral stream; 2) to determine the temporal relationships between streambed infiltration, subsurface redistribution, and recharge; and 3) to describe these relationships in a manner that will allow for improved representation of streambed recharge in hydrologic models. The two scientists will develop field geophysical methods for quantifying recharge beneath ephemeral streams. This data set will provide a unique opportunity to calibrate a transient unsaturated flow model through a thick vadose zone, leading to improved understanding of water movement beneath ephemeral streams. Measurements will be collected with noninvasive surface time domain electromagnetic instrument. A simplified conceptual model of streambed recharge will be developed based on interpretations of the field measurements with numerical models. This description of the subsurface hydrology of arid regions is critical to define the spatial and temporal distributions of recharge for use in sustainable development planning. Scope: The sustainable development of arid and semi-arid regions can be achieved only through the establishment of a sustainable water budget at the basin scale, which depends on an improved, quantitative understanding of recharge. For many semi-arid environments, recharge beneath ephemeral streams dominates total recharge; however, this topic has received little study. One of the most difficult challenges facing a quantitative study of recharge beneath ephemeral streams is the need to make accurate, detailed hydrologic measurements to depths in excess of 50 meters. Current methods of measuring the water content or matric potential have limited depth resolution and maximum depths of practical measurement, while profiling the hydraulic conductivity from measurements on soil cores is time consuming and expensive. As a result, existing methods are incapable of monitoring these properties over the entire thickness of the deep vadose zones that are typical in arid and semi-arid regions. The significance of this work lies in the convergence of hydrology and geophysics leading to critical measurements that cannot currently be made to quantify recharge. This work should lead to a more efficient water planning that can be achieved with these improved recharge estimates. Funding for this project is provided by the Office of International Science and Engineering and the Division of Earth Sciences.