 Veins in vascular networks, such as those found in blood vessels or leaf networks, constantly adapt to minimize energy dissipation. Shares stress on vein walls has been proposed as the primary driver of this process, but it does not explain all observed behavior. In fact, scarce spatiotemporal data makes it difficult to understand how these networks function. We have resolved this issue by studying the dynamics of fissure and polycephalums prototypical vascular networks. Our experiments revealed a variety of vein dynamics, including stable, growing, and shrinking veins, with sheer rate playing a limited role. Additionally, we discovered that sheer rate feeds back on vein radius with a delay of one to three minutes. This delay allows us to reconcile the disparate vein fates observed in experiments. Furthermore, we developed a mathematical model to explain vein adaptation within a network and accounted for the observed time delay. This model revealed that vein fate is determined by parameters that integrate the entire network's architecture, resulting from global conservation of fluid volume. Additionally, we observed avalanches of network reorganization events that cause entire clusters of veins to disappear. This article was authored by Sophie Marbach, Noah's Ethan, Leonie Bastin, and others. We are article.tv, links in the description below.