w regime, including periods of no or low flow, is a dominant factor controlling macroinvertebrate community structure in stream ecosystems. Within non-perennial streams, flow cessation and/or drying often results in communities that are a nested subset of nearby perennial systems, characterized by dominance of desiccant-resistant specialists or species that can reestablish quickly. We examined how flow variability alters diversity of macroinvertebrates across three reaches within a headwater stream network in Alabama, USA. We predicted that the structure of its local communities would vary as a result of the severity of drying, method of re-establishment, and the degree of isolation from perennial refugia. We sampled each of the three reaches four times seasonally from 2021-2022 by collecting both riffle (n=4) and pool (n=4) samples within each reach. We identified invertebrate samples to the lowest possible taxonomic resolution and measured lengths of individuals to quantify invertebrate biomass. We characterized flow using continuous level-loggers along each reach, as well as environmental characteristics on each sampling occasion, including wetted width, substrate type, and depth. Our sampling encompassed a flow-contraction event in late October 2022, which resulted in a significant shift in the communities in non-perennial reaches. Within pool samples, we observed no difference in richness across space, but overall, pools had lower richness when compared to riffles. Despite richness in riffles initially being comparable across space, they showed a significant decline in richness with flow recession (e.g., Acerpenna, Hydropsyche, Dubiraphia were lost). Future analysis will include quantifying changes in biomass over time, as well as functional trait shifts, which will better highlight the degree to which different taxa are able to respond to reductions in flow. Examining macroinvertebrate communities within specific habitats that are differentially affected by changes in flow allows for an increased understanding of community resilience and how future flow fluctuations will alter headwater stream biodiversity.