Energy and resources saving is of significance to sustainable development. In the past decades, heat integrated water allocation networks (HIWANs) have been applied to generate effective strategies for water and energy management in chemical process industries, where large amounts of water and energy are consumed. In this paper, a graphical approach for the synthesis of heat exchanger networks (HENs) in HIWANs has been proposed to reveal the new insights into T-H/H-F diagrams and fully exploit the HEN structure possibilities. Current conceptual design methods for HENs in HIWANs by the original separate systems (T-H diagram) and the matching composite curve (H-F diagram) only generate two special kinds of HEN structures: series and parallel structures. A transformation method is proposed to generate HENs with different structures based on these two tools. Both simplex series or parallel structures and hybrid structures can be obtained via the transformation procedures. Two examples are illustrated to demonstrate the operability of the proposed procedures.