Chirp Seismic-Reflection data from the John Day Reservoir

A two-week field operation was conducted in the John Day Reservoir on the Columbia River to image the floor of the pool, to measure the distribution and thickness of post-impoundment sediment, and to verify these geophysical data with video photography and bottom sediment samples. The field program was a cooperative effort between the USGS Coastal and Marine Geology Team of the Geologic Division and the USGS Columbia River Research Laboratory of the Biological Resources Division. The data collection was completed aboard the R/V ESTERO during September 13-27, 2000.
The interest in sediment accumulation in the reservoir was two-fold. First, it was unknown how effective this reservoir was as a sediment trap to material that otherwise would have been transported down-river to the estuary and eventually to the ocean. The recent erosion of beaches along the Washington coast has been attributed to a decreased contribution of sediment from the Columbia River to the coastal system due to the damming of the river. Second, sediment accumulation on the floors of reservoirs along the Columbia River has been suggested to be diminishing salmon spawning grounds. The extent of changes in habitat since construction of the John Day Dam, however, had not been documented. Common data sets were needed to address both of these questions, and for these reasons this geophysical and sampling program was undertaken.

For more information on the seismic surveys see http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2000-030-FA

These data are also available via GeoMapApp (http://www.geomapapp.org/) and Virtual Ocean (http://www.virtualocean.org/) earth science exploration and visualization applications.

本研究于哥伦比亚河（Columbia River）约翰·戴水库（John Day Reservoir）开展为期两周的野外作业，旨在对该水库池床进行成像探测、测量蓄水后沉积物的分布与厚度，并通过水下摄影与底质采样验证所获取的地球物理数据。本次野外项目由美国地质调查局（USGS）地质调查部海岸与海洋地质团队，以及美国地质调查局生物资源部哥伦比亚河研究实验室合作完成。数据采集工作于2000年9月13日至27日在“埃斯特罗号”（R/V ESTERO）考察船上完成。

针对该水库沉积物堆积情况的研究关注源于双重动因。其一，该水库作为沉积物截留库的实际效能尚不明确：若无水库截留，这些沉积物本会被输运至下游河口并最终汇入海洋。华盛顿海岸近期出现的海滩侵蚀现象，被归因于哥伦比亚河筑坝后，其向海岸系统输入的沉积物通量显著降低。其二，有研究指出，哥伦比亚河沿岸水库池床的沉积物堆积正不断压缩鲑鱼的产卵栖息地。但自约翰·戴大坝建成以来，该栖息地的变化范围尚未得到系统性记录。为解答上述两个核心科学问题，亟需统一的数据集支撑，本地球物理勘探与采样项目正是基于此目的启动。

如需了解地震勘探的更多细节，请访问：http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2000-030-FA

本数据集还可通过GeoMapApp（http://www.geomapapp.org/）与Virtual Ocean（http://www.virtualocean.org/）两款地球科学探索与可视化应用获取。