Document Type : Original Article
Authors
1 Assistant Professor, Department of Civil Engineering, Dez.C., Islamic Azad University, Dezful, Iran
2 Department of Civil Engineering, Dez.C., Islamic Azad University, Dezful, Iran
3 Department of Physics, Dez.C., Islamic Azad University, Dezful, Iran
Abstract
This study critically evaluates Regulation 747, Iran's guideline for determining the quantitative protection zone of water wells, highlighting its conceptual flaws. The regulation erroneously equates the radius of influence with the quantitative protection zone, though these are distinct concepts. To assess the regulation's methods, a well in an unconfined aquifer was simulated using Modflow under two scenarios: 1) a simplified scenario matching the regulation's assumptions, and 2) a more realistic scenario. Results showed that in the first scenario, the cone of depression never stabilized, while in the second, it stabilized after a long period; in both cases, the final radius of influence encompassed the entire aquifer. The findings reveal that misinterpretation of minor water level changes as steady-state conditions (as in Regulation 747) is incorrect for two reasons: first, protection zones must be established prior to drilling, and second, minor changes do not indicate stability. The study concludes that Regulation 747 provides an unreliable estimate of the radius of influence and that using it as a quantitative protection zone is invalid. Instead, a circular protection area is proposed, where the annual pumping volume equals a percentage of the annual recharge within that area. Thus, the safe distance between two wells should be the sum of their protection radii.
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