ZANCO Journal of Pure and Applied Sciences The official scientific journal of Salahaddin University-Erbil https://zancojournals.su.edu.krd/index.php/JPAS ISSN (print ):2218-0230, ISSN (online): 2412-3986, DOI: http://dx.doi.org/10.21271/zjpas RESEARCH PAPER Comparison between Theim and Theis Equations in Analysis of Pumping Tests Dana Khider Mawlood Department of Civil Engineering, College of Engineering, Salahaddin University - Erbil, Kurdistan Region, Iraq. A B S T R A C T: The presented study is tried to analyze the main difference between the application of Theim (1906) and Thies (1935) equations for steady and non- steady conditions to determine the property of layer such as (Transmissivity , Specific yield and storativity). Thies and Theim methods can be applied for pumping test, using a single well testing lead to well losses and aquifer losses, the results of property layer need further adjustment therefore, advisable to have observation well in order to avoid losses (such as well losses and aquifer losses), however, by applying Theim equation, the property of layer was restricted just for Transmissivity since the application is for equilibrium condition. The benefit is performed to evaluate the capacity of an aquifer to meet municipal or industrial water requirement and hydraulic characteristics reflect the potential of an aquifer for water development. KEY WORDS: Steady-state condition, transient flow condition, equilibrium, non-equilibrium equation. DOI: http://dx.doi.org/10.21271/ZJPAS.31.2.6. ZJPAS (2019) , 31(2);41-47 . INTRODUCTION : Globally groundwater is the main source of water supply because most of the countries depend on the groundwater for their purposes such as irrigation, drinking water, and industrial. One of the main purposes of the pumping test is to predict the specific capacity of the well, it is the proportion of pumping rate to drawdown in the well, also, it is the associated with the hydraulic flow properties, the specific capacity of the well is precious number that can be utilized to estimate the volume of water abstracted in the well, and it has a major function for design of well and estimating radius of influence. Appropriate management of ground-water resources imposes an accurate evaluation of the parameters (hydraulic properties) that governor the movement and storage of water. Aquifer tests, implemented by pumping a well at aconstant rate and monitoring the resulting variations in hydraulic head in the aquifer, it was the most normally used method for determination of aquifer hydraulic properties (Moench et al., 2000). The test data were analyzed through many methods according to the situation of each locations. The first scientist was Theim in 1906 that developed a method for both confined and unconfined aquifer according to the Dupuit assumptions in 1863, who governed the equation for flow in water table aquifer for steady state (equilibrium conditions). It is evident from the Thiem equation that the drawdown varies with the logarithm of the distance from the pumping well. Thiem equation can be used to compute constant pumping rate (Q), steady drawdown (s 1 or s 2 ) or distance of the point of observation from the * Corresponding Author: Dana Khider Mawlood E-mail: dana.mawlood@su.edu.krd Article History: Received: 12/11/2018 Accepted: 02/04/2019 Published: 23/04/2019