Limnol. Rev., Volume 20, Issue 3 (September 2020) – 5 articles , Pages 109-171

The article concerns changes in the heat reserves of the lakes of Belarus in connection with the emerging trends of global warming. When calculating the heat reserves of lakes the method proposed by the Hydromet service was adopted. This technique allows the heat reserves of lakes to be determined with greater accuracy for subsequent comparison and discovery of spatio-temporal connections. The heat reserves were calculated for five lakes whose temperature regime has been constantly monitored. A quantitative assessment of changes in heat reserves for the period of instrumental observations was obtained. It was found that the average range of fluctuations in the gradients of heat reserves of lakes for the Belarusian Lake District ranges from 2.71 × 10¹⁵ J in May to 54.56 × 10¹⁵ J in August; for Belarusian Polesie—from 2.78 to 4.17 × 10¹⁵ J, respectively. The cyclicity of fluctuations in the heat reserves of lakes of Belarus was revealed and found to be short-period (3–5 years) and long-period (10–11 years) cycles. Full article

The study on a small lowland river was conducted in order to determine changes in water quality under external loading (inflow of treated wastewater, runoff from agricultural areas) and the location of a dam reservoir in its course. The 21 km long River Pogona (Greater Poland, Poland) is a small tributary of the Obra Canal in Kościan. In 2004, in its valley, the Jeżewo Reservoir, with an area of 78 ha, was utilized to supply the flow in the Obra Canal during the dry season and to irrigate agricultural areas. The river is also a receiver of treated sewage from the sewage treatment plant in Karolewo. The research, carried out in 2017 at six sampling stations in its course, showed that the discharge of treated wastewater resulted in an increase in conductivity, concentration of ammonium nitrogen, nitrites and total nitrogen in the waters of the River Pogona. On the other hand, the location of the Jeżewo Reservoir in its course contributed to an increase in water temperature, pH, dissolved oxygen, chlorophyll-a and nitrite concentration in the outflowing river. The results showed that the inflow of treated wastewater from the sewage treatment plant, surface runoff from the catchment area and the Jeżewo Reservoir formed in its course, influenced seasonal and spatial changes in the water quality of the River Pogona. Full article

Wetlands are areas where water is the primary factor controlling the environment, associated plant and animal life. The present study has been conducted to investigate the environmental variables of water and to make a quantitative analysis of aquatic macrophytes. Five lakes, i.e., Tamor, Beeshazar, Kingfisher, Athaieshazar and Chepang of the Chitwan National Park were studied during the post-monsoon season. Four different sites were studied for each lake. 12 replica of water samples were collected from each site of the lakes and environmental variables of water i.e., pH, temperature, dissolved oxygen, total alkalinity, conductivity, total hardness, nitrate, inorganic phosphorus, total solid matter and free CO₂ were analyzed. Macrophyte floras were collected during field sampling with the help of a 1 m × 1 m light wooden quadrat and herbaria were prepared following the standard technique. Altogether 10 quadrats (five paired quadrats) were plotted in each site of the study area. Data obtained from water analysis and macrophytes were analyzed by SPSS statistics 20 and CANACO version 4.5. Higher values of nitrate and inorganic phosphorus were found in Beeshazar Lake and Tamor Lake, i.e., 4.41 ± 0.52 mg dm^–3 and 2.93 ± 0.29 mg dm^–3, respectively. In most of the lakes, macrophyte species, mostly Eichhornia crassipes was found to be dominant in terms of the importance value index (IVI), whereas in Tamor Lake, Spirodela polyrhiza was dominant. All the studied lakes were in the hypereutrophic category on the basis of nitrate and phosphorus concentration. Runoff of polluted water with agricultural fertilizers, pesticides and untreated industrial discharge as well as domestic wastes from the Khageri canal and excessive growth of invasive macrophytes are major threats to the studied lakes. The luxuriant growth of invasive macrophytes like Eichhornia crassipes also revealed the productive nature of the lakes and they can be taken as ecological indicators of organic pollution. Full article

Not so long ago, due to the great shortage of irrigation water, Egypt on the national level, began to mix (in a certain percentage) raw agricultural drainage water with fresh irrigation water. This mix was for enhancing its quality to be compatible with the proper specifications and standards of irrigation water, for using it safely in the irrigation process, to compensate for the severe shortage of available quantities of irrigation water. In some regions, and local farms, to save their crops farmers were forced to use the drainage water available in the nearby area drains for irrigation due to the problem of insufficient water in the distributary canals. Such use of raw drainage water can cause great harm and has a negative impact on the environment generally, especially on aquatic and agricultural life. Therefore, in this study we aim to introduce an efficient, simple, cheap mobile treatment unit. This new introduced treatment unit can be used locally on farms to solve the problem of insufficient quantities of irrigation water, and also in some cases where the irrigation water, for various reasons, does not reach the ends of some irrigation canals thus causing a serious problem for farmers. The new introduced treatment unit, using some environmentally friendly cheap materials in certain tested quantities and doses, through three designed cylindrical filtration containers connected with each other respectively, succeeded in converting raw contaminated drainage agricultural water into safe water that can be safely and directly used in the irrigation process. Full article

Wadi El Rayan is located in Egypt in the Sahara ecoregion the Palearctic ecozone (the world’s largest hot desert). The total area of Wadi El Rayan is 1759 km². The aim of this work was to study the ecosystems, compare species composition, species richness and species diversity of the study sites in the Wadi El Rayan protected area and the distributions of plants in the different landform. The field observations found that there is a low diversity and number of plant species around the lakes, in particular a decline in vegetation cover in accordance with a dramatic decrease in the water level in the lakes compared to earlier studies. The reduction of water levels due to decreased water supply is considered the main threat facing ecosystems and biodiversity in the lake area which requires a continuous survey of flora and measures to be implemented to conserve the natural vegetation in the area. Based on investigations of the spontaneous flora of Wadi El Rayan in 2018, 18 taxa of vascular plants were recorded. This inventory was compared with published records of investigations made in 1998, 2002 and 2014. A total of 18 vascular plant species belonging to 14 families were recorded in the wetland and desert ecosystems around the lakes of Wadi El Rayan. The vegetation mainly consists of sparsely distributed xerophytic and halophytic plants except in the wetland ecosystem around the lakes where it is characterized by some hydrophytic and halophytic plants. The family with the highest number of species was Poaceae followed by Zygophyllaceae. The results showed that a higher number of species was recorded from the Lower Lake (13 species) than the Upper Lake (10 species) and (5 species) for the connecting channel. The most frequently recorded species were Phragmites australis, Tamarix nilotica, Juncus rigidus and Alhagi graecorum: the first two species were the most successful species as they grow in a variety of ecosystems and habitats. Full article