Evaluation of Methods for Determining the Drinking Wellhead Protection Area Using Numerical Model (Case study: Birjand plain)

Determining the protective area of the well is one of the important parts of the groundwater protection policies in order to prevent the health and environmental hazards. In this research, while introducing calculated constant radius method, KLF and Wyssling analytical methods and numerical modeling were used as the most common methods for protective area of the wellin order to compare these methods using data from 6 rings of rural drinking water in Birjand Plain. The results of the study show that the protective area plotted by the calculated constant radius method does not include a significant part of the protective space plotted by the numerical model in the upstream section of the well. In addition, boundaries plotted by Wyssling and KLF analytical methods are narrow and stretched in terms of appearance compared with the boundary of numerical model, and do not cover a significant portion of the numerical modellateral distances and the calculated upstream protective area is always wider than upstream protective area in the numerical model. The best overlapping of calculated constant radius and analytic Wyssling and KLF methods with numerical boundaries occurs with the efficiency percentage of respectively 67.12%, 64.35% and 60.03% for duration of one year. As the travel time increases, their overlapping with the numerical model is reduced. In general, the numerical model is the most accurate method for drawing the protection area of the well, but the use of simpler methods such as constant radius and analytical techniques will have acceptable accuracy in the absence of data, time, capital, and sufficient expertise.