Characterization of aquatic environments in the De Ondas River, Bahian Cerrado

This work sought to characterize the types of environments present in the De Ondas River, with the aim of obtaining information on their structural complexity and supporting public policies for water resource management that will allow the shared water use and will protect the biodiversity of the river basin. The De Ondas River watershed is located in the Cerrado Region, in the western part of Bahia State, and covers an area of 5.559 km². In order to perform the characterization, two stretches were demarcated, one in the upper part of the basin and another in the lower. Afterwards, a topobathymetric survey was conducted, and characterizations of the bottom and of hydraulic properties were done for both the rainy and dry seasons. The topobathymetric survey in the upper course showed altitudes ranging from 699.82 m to 714.06, whereas in the lower course these varied from 439.45 m to 446.91 m. Bathymetric profiles allowed the visualization of the structure and distribution of the bottom of the channel environments. The granulometric analysis of the higher part of the basin showed that sand was predominant (88.94%), while in the lower part boulders (76.9%) and cobble (23.1%) predominated. In the higher part of the basin, the water flow varied from 5.20 m³s-1 (dry period) to 9.07 m³s-1 (rainy period); and in the lower part, from 25.73 m³s-1 (dry period) to 66.44 m³s-1 (rainy period). The complexity of the environments of these stretches favors biological diversity in the river, resulting in different environments that aid aquatic species in adapting to the channel structure. The study of the physical characteristics of the De Ondas River produced a great amount of information regarding the micro-environments of the stretches examined, and will support studies related to aquatic biota and water resource management.本研究旨在刻画当达斯河（De Ondas River）流域内各类生境的特征，以期获取其结构复杂度相关数据，并为水资源管理公共政策制定提供支撑，以实现水资源共享利用，同时保护该流域的生物多样性。当达斯河流域位于巴伊亚州（Bahia State）西部的塞拉多地区（Cerrado Region），流域面积达5.559 km²。为完成该生境刻画工作，研究人员划定了两处河段，分别位于流域上游与下游。随后开展了地形水深测量（topobathymetric survey），并针对雨季与旱季两个时段，分别对河床底质与水力特性进行了表征分析。上游河段的地形水深测量结果显示，海拔范围为699.82米至714.06米，而下游河段的海拔则介于439.45米至446.91米之间。水深剖面可直观呈现河道生境的底部结构与分布特征。流域上游的粒度分析（granulometric analysis）结果表明，沉积物以砂粒为主（占比88.94%）；而下游河段则以巨砾（76.9%）与砾石（23.1%）占优。流域上游的水流速率在旱季为5.20 m³·s⁻¹，雨季增至9.07 m³·s⁻¹；下游河段的水流速率则从旱季的25.73 m³·s⁻¹升至雨季的66.44 m³·s⁻¹。上述河段的生境复杂度有利于提升河流生物多样性，形成了多样化的生境类型，可助力水生生物适应河道结构。本研究对当达斯河物理特性的调查，获取了大量关于所研究河段微生境的相关数据，将为水生生物群落及水资源管理相关研究提供有力支撑。