one skilled in the art will thus recognize that the substantially impermeable man made barrier may be formed in a number of shapes including arcs ovals irregularly shaped one sided two sided three sided and up to n sided depending upon the topography and property boundaries and other site specific considerations fig6 shows a top view of an irregularly shaped bank sided porosity storage reservoir of the present invention shown with bedrock depth contours and fig7 shows a cross section of the same embodiment of the bank sided porosity storage reservoir referring now to fig6 and 7 basin 60 comprises a riverbed 61 that flows along the top of alluvial deposits 73 e g sand and gravel formed within a floodplain that extends to either side of the riverbed 61 an underground bank sided porosity reservoir 64 is preferably formed on a first side with a substantially impermeable man made barrier 68 hereinafter referred to as simm barrier 68 such as a slurry wall formed in an irregular shape and bounded on a second side by utilizing the native soil 66 and bedrock 72 basin 60 is seen in cross section along line 6 a 6 a u2032 in fig7 bank sided porosity reservoir 64 capitalizes on a scour region 700 formed by the river path thousands of years ago where the flow of the river scoured out a depression in bedrock 72 various contour lines are is shown in fig6 indicating the depth below the surface.