Significance of organic matter in the process of aggregation of suspended sediments in retention reservoirs.

It is crucial to have a comprehensive understanding of the process by which suspended sediment (SS) in water is aggregated and deposited to ensure the proper use and management of storage reservoirs. The present study was an investigation into the varied granulometric composition of accumulated sediment, as well as an examination of the amounts of organic matter present and its origins. This study aimed to determine what underpins the process of aggregation of sediment suspended in reservoir water. The results of the study, as also analysed using multivariate statistics, reveal a process of sediment aggregation dependent not only on the amount of organic matter but also on its origin. Greater production of autochthonous organic matter was shown to be associated with an intensified process of suspended sediment flocculation, confirming that the metabolism of a reservoirs' aquatic organisms influences the granulometric composition of suspended sediment.

Trophic degradation predispositions and intensity in a high-flow, silted reservoir.

The objective of the work was to demonstrate the relationship between the natural environmental characteristics of a reservoir and its catchment and severity of trophic degradation. The shallow, highly-silted Rzeszów Reservoir (SE Poland) was the object of study. The impact on degradation of internal supply from accumulated bottom sediments was also assessed, using water and sediment sampled in 2013 and 2014. A high value for trophic state was identified for the reservoir on the basis of TSI indexes, while assessed natural resilience to degradation and analysis of the catchment as a supplier of biogenic and organic matter both indicate high susceptibility to cultural eutrophication. Obtained values for equilibrium phosphate concentrations under anoxic conditions (EPC-0) point to the possibility of a more intensive process of internal supply in phosphorus. However, the presence of sediments poor in organic matter suggest no major threat of ongoing eutrophication. Desludging and/or dredging are likely to entail elimination from the ecosystem of a large part of the pollutants accumulated in sediments, as well as the internal supply of phosphate to the water column. However, as external sources are responsible for the advanced degradation of Rzeszów Reservoir, any attempts at reclamation within the water will fail to yield persistent effects if appropriate protective procedures in the catchment are not implemented.

A new concept for risk analysis relating to the degradation of water reservoirs.

This paper presents a proposal for a procedure by which to analyse the risk of reservoirs being degraded. The body of water assessed for its susceptibility to degradation in line with the proposed procedure is Myczkowce Reservoir, SE Poland. This reservoir has a maximum capacity of ten million m3 and helps provide hydropower, by serving as a surge tank located above the main Solina Reservoir. On the basis of an assessment of its morphometric and hydrological parameters, Myczkowce Reservoir was assigned to the low-resilience category where risk of degradation was concerned. The primary factors responsible for that are limited capacity in relation to shoreline length, a lack of thermal stratification, and a high value for the Schindler index. These and other environmental parameters provided for Myczkowce's assignment to the category of susceptible to the impact of matter supplied by its catchment, with this reflecting the instantaneous nature of the basin, high values for the Ohle coefficient, average catchment slope, and the lack of a septic system. The designated risk level supported Myczkowce's assignment to a category characterised by an "unacceptable" risk of degradation. The proposed method taking two parameters (resilience and susceptibility) into account represents the first universal method for assessing reservoirs without reference to risks such as drought, flooding, or lack of water supply for human consumption. The risk depends only on the reservoir and catchment parameters.

The influence of environmental factors on the carbon dioxide flux across the water-air interface of reservoirs in south-eastern Poland.

Studies concerning the emission of carbon dioxide (CO2) were carried out in 2009-2012 for six reservoirs located in four provinces of south-eastern Poland. The CO2 flux across the water-air interface was measured using the "static chamber" method. The measured fluxes of CO2 (FCO2) ranged from -30.64 to 183.78mmol/m2/day, and the average values varied in the range from -3.52 to 82.11mmol/m2/day. In most of the cases, emission of CO2 to the atmosphere was observed. The obtained values of CO2 fluxes were comparable to values typical for other temperate reservoirs. Analysis of the influence of selected environmental factors on the FCO2 showed that it depends on parameters characterizing both the sediments and surface water. The CO2 flux at the water-air interface was positively correlated with parameters of bottom sediments such as porosity, content of organic carbon and total nitrogen; and negatively with pH value and δ13C of organic carbon. In the case of the parameters characterizing surface water, positive dependences on the concentrations of nitrate and total nitrogen, and negative relationships with water temperature and chlorophyll a concentrations, were found.

The qualitative and quantitative analysis of the coupled C, N, P and Si retention in complex of water reservoirs.

The Solina-Myczkowce complex of reservoirs (SMCR) accounts about 15 % of the water storage in Poland. On the base of historical (2004-2006 years) data, the mass balance of nitrogen, phosphorus, total organic carbon and dissolved silicon were calculated. Large, natural affluents were the main source of the biogenic compounds in the studied ecosystem, delivering 90 % of TOC, 87 % of TN and 81 % of TP and DSi load. Moreover, results show that SMCR is an important sink for all the analysed biogenic elements. About 15-30 % of external loads were retained in the reservoir mainly in upper Solina. Due to the intensive processes of primary production, inorganic forms of nitrogen and phosphorus were mainly retained. Internal production of organic matter lead to an amount of the organic matter deposited in the sediments greater than was anticipated on the basis of the mass balance calculations. A constant load of dissolved silicon originating only from natural sources did not contribute to supplement deficits of Si present in the body of water in the reservoirs, promoting disturbances in N:C:P:Si ratios and another growth condition for other types of algae.