Assessment of well performance criteria and aquifer characteristics using step-drawdown tests and hydrogeochemical data, west of Qena area, Egypt

作者：Abdalla Fathy^*; Moubark Karem

来源：Journal of African Earth Sciences, 2018, 138: 336-347.

DOI：10.1016/j.jafrearsci.2017.11.023

• Step drawdown
• Groundwater
• Well loss
• Aquifer loss
• Well efficiency
• Transmissivity

A groundwater investigation was performed to characterize hydrogeological conditions and well performance in a shallow alluvial aquifer using well logs, step-drawdown tests, and hydrogeochemical data. Results from three single-well step-drawdown tests conducted in three recently drilled boreholes located west of the Qena area in Upper Egypt and were analyzed by the Rorabaugh (1953) graphical method. A total of 47 groundwater wells were sampled and analyzed to detect the main hydrochemical facies associated geochemical processes. Results of the step-drawdown tests indicated well losses between 1.5% and 27.7% (14.2% avg.) and aquifer losses of between 723% and 98.5% (85.8% avg.), reflective of high well efficiencies. Specific capacity values varied from 183.4 m(3)/day/m to 278.4 m(3)/day/m while well efficiency values varied from 72.3% to 98.5%, indicating that the wells had been properly designed and developed. Estimated aquifer transmissivity ranges from 1103.7 m(2)/day to 1459.7 m(2)/day (1314.9 m(2)/day avg.), indicating high yields and water accessibility to the wells. Results indicated laminar flow at the aquifer/well-face contact with negligible turbulent flow. Gibbs and various scatter ionic ratios plots of the geochemical data indicate that water-rock interaction followed by evaporation are the most dominant processes controlling groundwater composition, while a Piper plot reflects mixing with irrigation-return flows subject to evapotranspiration. The approach demonstrates the practical applications of the single well step-drawdown tests for estimating of the safe and sustained well yields for future groundwater extraction.

• 出版日期2018-2