Hydrochemical assessment of groundwater from shallow aquifers in parts of Wadi Al Hamad, Madinah, Saudi Arabia
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ORIGINAL PAPER
Hydrochemical assessment of groundwater from shallow aquifers in parts of Wadi Al Hamad, Madinah, Saudi Arabia Obaid Aziz Alharbi 1 & Oumar Allafouza Loni 1 & Faisal K. Zaidi 2
Received: 24 August 2016 / Accepted: 20 December 2016 # Saudi Society for Geosciences 2017
Abstract The present study was carried out in the Mulaylih area which forms a part of Wadi Al Hamad in the Madinah Province of Saudi Arabia. Thirty groundwater samples from agricultural farms were collected and analyzed for various physio-chemical parameters including trace elements. The area is occupied by the Quaternary alluvium deposits which form shallow unconfined aquifers. Evaporation and ion exchange are the major processes which control the major ion chemistry of the area. The extreme aridity has results in high total dissolved solid values (average of 9793.47 mg/l). Trace element concentrations are low and are mainly attributed to geogenic sources (silicate weathering). Na-Cl groundwater type is the main hydrochemical facies found in the area. The waters are found to be oversaturated with calcite/aragonite and dolomite. The average nitrate concentration was found to be 134.10 mg/l and is much higher than the WHO recommended limit of 50 mg/l in drinking water. Their high values are mainly associated with the application of N-fertilizers on the agricultural farms. The average fluoride concentration in the study was found to be 1.54 mg/l. The relation between F and Cl and Cl and Na reveals that the fluoride concentrations are mainly attributed to geogenic sources. A comparison of the groundwater quality with the Saudi drinking water standards shows that the water is unfit for drinking. The high salinity and sodicity of the groundwater make it unfit for irrigation. Principal component analysis resulted in extraction of four
* Faisal K. Zaidi [email protected] 1
King Abdulaziz City for Science and Technology, Riyadh, Saudi Arabia
2
SGSRC, Geology and Geophysics Department, College of Science, King Saud University, Riyadh, Saudi Arabia
principal components accounting for 79.5% of the total data variability and supports the fact that the natural hydrochemical processes (evaporation and ion exchange) control the overall groundwater chemistry. Keywords Wadi Al Hamad . Mulaylih . Evaporation . Ion exchange . Saturation indices . Principal component analysis
Introduction Groundwater forms the most important source of water supply in arid regions including Saudi Arabia. Water stored in the deep-seated sedimentary aquifers in the Arabian platform and renewable groundwater in the fractured/weathered Precambrian basement and shallow alluvial aquifers located in the Arabian shield (Al-Shaibani 2008) form the main sources of groundwater supply in the country. Shallow alluvial aquifers, restricted to the major valleys (locally termed as wadis) form an important source of water supply in the Arabian shield and the western and southwestern coastal plains. The high temperatures coupled with the low and erratic nature of rainfall results in
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