Modification of flow regimes and habitat degradation are the strongest, most common, and often co-occurring human activities affecting riverine populations. Ongoing efforts to restore peak flow events found under pristine flow regimes could increase advection-driven dispersal for many species. In rivers with extensive habitat loss, increased advection could transport individuals from remnant populations into degraded downstream areas, causing restored flow regimes to decrease persistence of threatened species. To demonstrate such possible ‘washout’ effects across imperiled taxa, we evaluate population growth in spatial models of insect, fish, and mollusc taxa that experience advective dispersal and either long-term habitat loss or temporary drought disturbances. As a case study to quantify advective dispersal in threatened species, we use intensive mark-recapture methods in a Rio Grande population of the endangered mussel Popenaias popeii belonging to the Unionida order, the most threatened faunal taxa worldwide. Our mark-recapture models estimate high levels of annual downstream emigration (16–51%) and immigration from upstream habitats (32–48%) of adult P. popeii, a result consistent with hydrodynamic experiments. Across taxa where such advective dispersal occurs in specific life stages, our population model suggests that washout effects might strongly reduce population recovery under high levels of habitat loss, especially for sessile or shorter lived species. Averting this potential negative consequence of restoring hydrology requires simultaneously restoring or protecting long, contiguous stretches of suitable habitats. In heavily impacted systems, we suggest integrating hydrodynamic studies and field surveys to detect the presence of advective dispersal and prioritize areas for habitat restoration to enhance population persistence.

改变水流方式和栖息地退化是影响河流人口的最强烈，最常见且经常同时发生的人类活动。为恢复在原始流态下发现的峰值流事件而进行的持续努力可能会增加对流驱动的许多物种的扩散。在栖息地大量流失的河流中，对流的增加可能会将个人从残余种群中转移到退化的下游地区，从而导致水流恢复，从而减少了受威胁物种的持久性。为了证明整个濒危类群可能产生的“冲刷”效应，我们在昆虫，鱼类和软体动物类群的空间模型中评估了人口增长，这些模型经历了对流扩散以及长期生境丧失或暂时的干旱干扰。作为量化受威胁物种中对流扩散的案例研究，Popenaias popeii属于Unionida秩序，是世界上受威胁最大的动物群。我们的标记捕获模型估计，成年P. Popeii的年度下游高水平移民（16-51％）和上游生境（32-48％）移民，结果与流体力学实验一致。在特定生命阶段中发生这种对流扩散的整个分类单元中，我们的种群模型表明，在高水平的栖息地丧失下，冲刷效应可能会大大降低种群的恢复，特别是对于无柄或寿命较短的物种。要避免恢复水文学的潜在负面影响，就需要同时恢复或保护合适的栖息地的长而连续的范围。在受到严重影响的系统中，我们建议将水动力研究与野外调查相结合，以检测对流扩散的存在，并优先考虑栖息地恢复的区域，以增强人口的持久性。