Fluvial Dynamics Research Group - RIUS, University of Lleida, Lleida, E-25198 Catalonia, Spain.
Department of Geography, Prehistory and Archaeology, University of the Basque Country, 01006 Vitoria-Gasteiz, Spain.
Sci Total Environ. 2015 Mar 1;508:101-14. doi: 10.1016/j.scitotenv.2014.10.058. Epub 2014 Dec 1.
River regulation by dams modifies flow regimes, interrupts the transfer of sediment through channel networks, and alters downstream bed dynamics, altogether affecting channel form and processes. So far, most studies on the geomorphic impacts of dams are restricted to single rivers, or even single river stretches. In this paper we analyse the geomorphic status of 74 river sites distributed across four large basins in the Iberian Peninsula (i.e. 47 sites located downstream of dams). For this purpose, we combine field data with hydrological data available from water agencies, and analyse historical (1970) and current aerial photographs. In particular, we have developed a Geomorphic Status (GS) index that allows us to assess the physical structure of a given channel reach and its change through time. The GS encompasses a determination of changes in sedimentary units, sediment availability, bar stability and channel flow capacity. Sites are statistically grouped in four clusters based on contrasted physical and climate characteristics. Results emphasise that regulation changes river's flow regime with a generalized reduction of the magnitude and frequency of floods (thus flow competence). This, in addition to the decrease downstream sediment supply, results in the loss of active bars as they are encroached by vegetation, to the point that only reaches with little or no regulation maintain exposed sedimentary deposits. The GS of regulated river reaches is negatively correlated with magnitude of the impoundment (regulation). Heavily impacted reaches present channel stabilization and, in contrast to the hydrological response, the distance and number of tributaries do not reverse the geomorphic impact of the dams. Stabilization limits river dynamics and may contribute to the environmental degradation of the fluvial ecosystem. Overall, results describe the degree of geomorphological alteration experienced by representative Iberian rivers mostly because of regulation, challenging the successful long-term implementation of river basin management programmes.
河流调水工程改变了水流模式，阻断了泥沙在河道网络中的输送，并改变了下游河床的动力特性，这些都对河道形态和过程产生了影响。到目前为止，大多数关于大坝地貌影响的研究都局限于单一河流，甚至是单一的河流河段。在本文中，我们分析了分布在伊比利亚半岛四个大流域的 74 个河流站点的地貌状况（即 47 个位于大坝下游的站点）。为此，我们结合了野外数据和水务局提供的水文数据，并分析了历史（1970 年）和当前的航空照片。特别是，我们开发了一个地貌状况（GS）指数，用于评估给定河道的物理结构及其随时间的变化。GS 包括确定沉积单元、沉积物供应、沙洲稳定性和河道水流能力的变化。根据对比明显的物理和气候特征，站点被分为四个聚类进行统计分组。结果强调，河流调水改变了水流模式，导致洪水的幅度和频率普遍减少（从而降低了水流能力）。此外，下游泥沙供应减少，导致活跃沙洲因植被侵占而消失，只有那些几乎没有或没有调水的河道才保留暴露的沉积层。受调控的河道的 GS 与水库规模（调水）呈负相关。受严重影响的河道呈现出河道稳定化的趋势，与水文响应相反，支流的距离和数量并不能扭转大坝对地貌的影响。河道稳定化限制了河道的动力特性，可能导致河流生态系统的环境退化。总体而言，研究结果描述了由于调水而导致的具有代表性的伊比利亚河流经历的地貌改变程度，这对河流流域管理计划的长期成功实施提出了挑战。
