Modified Strongly Implicit Procedure for groundwater flow analysis

A Modified Strongly Implicit Procedure (MSIP) to solve two dimensional groundwater flow problems in non-rectangular regions is presented. At present while using SIP, such problems are solved over a superscribed rectangular computational region with zero transmissivities for nodes outside the region of interest. This leads to wastage in computer storage and time. The MSIP is developed to handle non-rectangular regions directly without such dummy nodes. It is found that except for four types of boundary nodes, the same equations as in the normal SIP are applicable. The relationships for the special types of boundary nodes for row computations are presented. The method is tested on two test problems and compared with other finite difference methods, and MSIP is found to be the best. The MSIP will be particularly advantageous in regions with non-rectangular boundaries and where a number of parameters have to be stored for each node.