4.8.3.3. Open Area of Well-Screen For head loss through the well screen to be minimum, Peterson et al. (18) have suggested that the value of the parameter CcApL/D should be greater than 0.53. Here, Cc is the coefficient of contraction for the openings, Ap the ratio of the open area to the total surface area of the screen, L the screen length, and D is the diameter of well screen. Theoretical studies conducted at the UP Irrigation Research Institute have shown that the parameter CcCvApL/D should be greater than 1.77. Here, Cv is the coefficient of velocity. A factor of safety of 2.5 is further recommended by Sharma and Chawla (16). This means that CcCvApL/D should be greater than 4.42.