Hydropower reservoir sediment and water quality assessment

Abstract

Purpose Finer sediment particles (silt and clay) transported by rivers carry the major part of nutrient loads by absorption; thus, sediment settling can remove nutrients from the water column. The purpose of this paper is to analyze the relation between reservoir sedimentation and water quality by assessing the reservoir sedimentation process and the sediments’ characteristics. Design/methodology/approach Bathymetric surveys from 2004 to 2014 were analyzed to assess the sedimentation process. Core samples provided information on a layer-by-layer basis of the sediment deposits, and water samples near the surface and near the bottom provided information on sediment concentration, and adsorbed and dissolved nutrients. Findings The upstream region of a reservoir is already silted. From 2004 to 2014, the delta evoluted approximately 500 m downstream and the deposits were mainly composed of clay. An area of approximately 1,000 m between the delta and the dam should still be able to continue allowing sediment deposition in the coming years. Most of the nutrients were absorbed into the sediment particles, except for the nitrogen measured in the dry season. Research limitations/implications Although analyses of the full cycle of the nutrients were not carried out, the constant sediment trapping of finer sediments and the high rate of absorbed nutrients in the suspended sediment support the hypothesis that the reservoir has removed nutrients from aqueous media by adsorption into sediments. Practical implications In the studied case, reservoir sedimentation has led to better water quality downstream. Originality/value It is shown in this study that reservoir sedimentation may have positive effects on river water quality.

Prediction of Reservoir Sediment Quality Based on Erosion Processes in Watershed Using Mathematical Modelling

“…Pimentel and Burgess [21] summarized, that a ton of fertile topsoil averages 1 to 6 kg of nitrogen, 1 to 3 kg of phosphorus, and 2 to 30 kg of potassium, whereas the topsoil on the eroded land has an average nitrogen content of only 0.1 to 0.5 kg per ton. As reported in literature [22,23], sediments act as an efficient trap for both nutrients (nitrogen and phosphorus). For example, sediments from Gulf of Finland trap 20-50% of P and 40-65% of N in the Neva estuary and in the open Gulf, and up to 100% in the Neva Bay are buried within the accumulating sediment.…”

“…The rest is released to the overlying water [22]. Similarly, [23] showed that finer sediment particles (silt and clay) transported by rivers carry the major part of nutrient loads by absorption and thus, sediment settling can remove nutrients from the water column. On the other hand, the sediment accumulation in Iron Gate reservoir (Romania) on the Danube River corresponded to 5% of total nitrogen and 12% of total phosphorus of the incoming loading [24].…”

Statistical Assessment of Water Quality Issues in Hongze Lake, China, Related to the Operation of a Water Diversion Project

“…Then, the water velocity in outlets of the Huai River and Hongze Lake were relatively high in the dry season, which accelerates the movements of nitrogen and phosphorus [37,38]. Moreover, the silt transported by rivers can also absorb major nutrient salts [39]. At the same time, the rich biological groups in the intersection area of the river and lake can play an effective role in the removal of nutrient salts.…”

Compuestos nitrogenados en los sedimentos del estero San Camilo: Guayas, Ecuador y su relación con actividades antrópicas adyacentes

“…En su proceso biológico el amonio se oxida a nitrito y luego a nitrato, este proceso junto con la degradación de la materia orgánica, provoca disminución en las concentraciones de niveles de oxígeno disuelto producto del exceso de nutrientes en cuerpos de agua (Aranda, 2004;Guieysse y Norvill, 2014). Por ello, es importante el muestreo en sedimentos, considerando que funcionan como reservorio de nutrientes en estuarios y costas, y su tiempo de residencia es mayor que en el agua (Hayn et al, 2014;Estigoni et al, 2017). Además, los nutrientes concentrados en los sedimentos, se infiltran hasta llegar a los acuíferos (Lin y Dushoff, 2004).…”