Simulation of Unsteady Movement in the Downstream of a Hydroelectric Complex During the Destruction of a Soil Dam

153 reservoirs have been created in the Republic of Belarus. During the period of passing catastrophic floods and high waters along the river, there is a risk of overflowing reservoirs, overflow of water masses through the crest of an earthen dam and flooding of significantly large areas. The destruction of the dam is accompanied by the formation of a breach and the outflow through it of an unsteady flow of water in the form of a breakthrough wave into the downstream. A breakthrough wave and catastrophic flooding of the area are the main destructive factors of hydrodynamic accidents. Calculations to determine parameters of the wave and to assess the possible consequences of flooding are necessary when drawing up operational-and-tactical plans for the prevention and elimination of emergencies in case of accidents at retaining structures, determining the probable damage from flooding of the territory in the downstream of a hydraulic structure as a result of the passage of a breakthrough wave. It is necessary to assess the flooding zone and the hydrodynamic parameters of the flow, viz. the maximum values of the depth and velocity of the flow in the zone of catastrophic flooding, the time from the beginning of the accident to the arrival of a breakthrough wave at the particular point of the terrain, the duration of flooding, the boundaries of the zone of catastrophic flooding, the hydrographic flow rate in the section of the eroded dam and the graph of the fall headwater level. The degree of reliability of predictive calculations is determined by the accuracy of the two applied mathematical models, viz.: 1) erosion of the dam; 2) the movement of the breakout wave. The analysis of the applied mathematical models shows that in all cases the hydrodynamic models based on the oneand two-dimensional equations of Boussinesq – Saint-Venant are used to calculate the movement of the breakthrough wave. Wave parameters, i. e. wave height and speed of its propagation, completely depend on the hydrograph of the discharge in the section of the eroded dam, which, in its turn, is determined by the dynamics of its erosion. The aim of the work is to develop a methodology for calculating the flooding of the downstream as a result of the destruction of a soil dam.

MAPPING RECURRENT FLOODING ZONE ALONG ESTONIAN INLAND WATERS FROM SENTINEL-1 AND -2

In the process of spatial planning in Estonia the local municipalities are required to define the recurrent flooding zone along the inland waters that locate at their territory. Estonia is well known for its large floodplains that are annually covered by water. However, information about the spatial flood extent is scarce. A methodology for mapping the flooded area from Sentinel-1 and -2 imagery was developed and applied on data covering high water seasons in 2016–2019. Statistical information about flooded areas along the inland waters were compared with other available data sources related to wetlands i.e. map of wetlands in Estonian Topographic Database. Results showed that additional information about flood extent and duration retrieved from Sentinel-1 and Sentinel-2 the data can contribute to defining the recurrent flooding zone along the inland waters in process on spatial planning.

Nesting of Morelet’s crocodile, Crocodylus moreletii (Dumeril and Bibron), in Los Tuxtlas, Mexico

We evaluated the nesting by Crocodylus moreletii in Lago de Catemaco, Veracruz, southeastern, Mexico. During the nesting and hatching seasons, we searched for nests along the northern margins of the lake and small associated streams. We investigated egg mortality by weekly monitoring each of the nests found, recording sign of predation (tracks and holes dug into the nest) and the effect of water level fluctuations. We not found differences to nest between inland or flooded zones. However, we found that egg size varied among nests. In nests built inland, predation was the major cause of egg mortality whereas flooding resulted in more deaths of eggs in the flooding zone. Flooding killed 25% of eggs monitored in this study. We suggest that to increase nest success in the Morelet’s crocodile it is necessary to promote conservation of nesting areas around the lake, recently occupied by urban or tourist developments.

A Study on Compatibility of an ASP Scaling Inhibitor with the Oilfield Chemical Agents

Focused on the produced flood of an ASP flooding zone in Daqing oilfield, an applied scaling inhibitor was researched on the compatibility with the oilfield chemical agents. By a series of lab tests, the compatibility with the chemical agents, including polyacrylamide (PAM), surfactant and demulsifier, are clearly exhibited. Based the data, the effect on the produced fluid treatment is discussed. And the injections of the chemical agents are suitably specified.

Application of a linear finite-frequency theory to time-lapse crosswell tomography in ultrasonic and numerical experiments

Time-lapse seismic monitoring is the geophysical discipline whereby multiple data sets recorded at the same location but at different times are used to locate and quantify temporal changes in the elastic parameters of the subsurface. We validate a time-lapse monitoring method by crosswell tomography using two types of wavefield-modeling experiments: (1) a 3D real ultrasonic waveform experiment and (2) 2D synthetic finite-difference wavefield simulations. For both wavefield experiments, a time-lapse structure simulating a fluid sweep in a reservoir layer is applied. The time-lapse tomographic monitoring approach is based on the standard ray theory and a finite-frequency wavefield theory, where the latter takes into account the finite-frequency properties of recorded wavefields. The inverted time-lapse models compiled with either the ray theory or the finite-frequency wavefield theory locate and correctly quantify the flooding zone in the simulated fluid sweep model. Both wavefield theories provide an adequate result because the flooding zone is comparable in size to the Fresnel volume.