Science gateways, also known as advanced web portals, virtual research environments and more, have changed the face of research and scholarship over the last two decades. Scholars world-wide leverage science gateways for a wide variety of individual research endeavors spanning diverse scientific fields. Evaluating the value of a given gateway to its constituent community is critical in obtaining the financial and human resources to sustain gateway operations. Accordingly, those who run gateways must routinely measure and communicate impact. Just as gateways are varied, their success metrics vary as well. In this survey paper, a variety of different gateways briefly share their approaches.
