The sensor nodes of wireless sensor networks are placed in observation areas and transmit data to the observer by using multi-hop communication between nodes. Because these nodes are small and have a limited power supply, they must save power in order to prolong the network's lifetime. We propose HGAF (Hierarchical Geographic Adaptive Fidelity) to give a layered structure to GAF (Geographic Adaptive Fidelity), a power saving technique using location information in sensor networks. Simulation results reveal that HGAF outperforms GAF in terms of the number of survived nodes and packet delivery ratio when the node density is high. The lifetime of dense and randomly distributed sensor networks with HGAF is about 200% as long as ones with GAF.