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Hedeff I Essaid, Ph.D.

Hedeff Essaid is a Research Hydrologist with the USGS Water Resources Mission Area. 

My research has involved the analysis of field data and simulation of groundwater systems and watersheds to characterize water and chemical mass balances and to study the relative importance of different hydrologic processes and flow pathways.  The results of these studies provide an opportunity to compare and contrast groundwater transport, surface water-groundwater interactions and chemical fate in different hydrologic/environmental settings. This work has improved our understanding and quantification of processes and factors that control the magnitude and timing of environmental responses to contaminant loading and changing hydrology. I have used this approach to study: saltwater intrusion in layered coastal aquifer systems; the impact of heterogeneity and hysteresis on the distribution of crude oil at a spill site; the role of dissolution and biodegradation on the fate of hydrocarbon components in the subsurface; the impact of surface water-ground water interactions on stream flow, temperature, and water quality; the hydrology of natural and incised mountain meadows; and nutrient fate in diverse watersheds.


  • Stanford University, Ph.D., 1987, Hydrogeology
  • Stanford University, M.S., 1984, Hydrogeology
  • University of Baghdad, Iraq, B.S., 1978, Geology-Geophysics