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Abstract
The Effect of Hilti Recharge Dam in Batineh Area (Oman) on the Quality of Groundwater Using GIS
Track: Water Resources
Author(s): William Bajjali
The government of Oman decided to build 17 dams at various locations to store floodwaters and use them to replenish the shallow groundwater that had been affected by the salt intrusion. Hilti/Salahi dam is one of the dams, which was built in the Batina area for this purpose. The dam is one of the oldest and longest dams that have been built. The effective capacity and length of the dam are 0.55 million cubic meters (MCM) and 9 km respectively.
GIS was used to analyze and interpret the quality of groundwater and characterize the most susceptible locations for recharge along the groundwater flow path downstream of the Hilti/Salahi dam.
The ArcGIS Spatial Analyst extension was used for this study. To carry out the study various hydrogeological features, groundwater wells, and chemical parameters were georeferenced and integrated into the GIS system.
Two major parameters, salinity and nitrate, were used as an input function to characterize the hydrochemistry and quality of the groundwater along the flow path from the recharge area to the coast of Oman. Two color-coded maps representing the TDS (salinity) and NO3 were created. Each map demonstrates the distribution and describes the level of each parameter downstream of the dam.
The TDS and Nitrate concentration of the groundwater wells have been taken as an indicator to verify if the Hilti/Salahi dam is playing a role in replenishing the groundwater and improving its quality.
The maps show that significant variations occur in groundwater chemistry for the TDS and NO3 concentrations. The elevated salinity values at various well locations along the coast of Oman are attributed mainly to salt intrusion. The high salinity of the wells located far from the coast is due to re-irrigation. The high nitrate concentration in all the wells is attributed to anthropogenic sources--mainly septic tanks and inorganic fertilizer sources.
The output results of the analysis showed that the majority of the groundwater wells downstream of the dam have improved in their quality in terms of salinity and nitrate concentration . Little improvement of the quality was observed for the groundwater wells, which are located further from the dam and closer to the seacoast.
The GIS was able to detect a hidden relationship related to the nitrate concentration in the groundwater wells located along the coast and the wells located a little bit further from the coast.
The GIS techniques demonstrate how the dam is an excellent facility to capture the runoff water and use it for recharging the groundwater. It also provides significant environmental information that could be used to manage the groundwater resources and enhance its recovery from the floodwater stored in the dam during the rainy season. The produced GIS color-coded map could also be used as a key factor in the public awareness to promote the value of groundwater.
William Bajjali
University of Wisconsin at Superior
Biology & Earth Science
Belknap & Catlin P.O.Box 2000
Barstaw Hall, Room 106-A
Superior , WI 54880
USA
Phone: (715) 394-8056
Fax: (715) 394-8418
E-mail: wbajjali@facstaff.uwsuper.edu