Abstract: An improved continuous, smooth, porous, rigid surface is supported by an array of shaped, porous, support blocks mounted on an impervious planar foundation and surrounded by bi-functional containment walls to form a gravity filtration and drainage apparatus. The particular shape of the support blocks in contact with the foundation creates a plurality of parallel flumes, the center-lines of which align with the slope, if any, of the plane to facilitate drainage to contiguous drainage ditches. Accessibility of these drainage flumes at both ends of the overall structure provide for inspection, flushing, and purging of the overlying filter surface to assure functionality by simplified maintenance procedures. The drainage apparatus can be attached to an impervious evaporation surface, on which residual solids harvested from the surface of the drainage apparatus are deposited and periodically manipulated for further accelerated dewatering by evaporation.