The influence of floating spheres on evaporation suppression under different climatic conditions

<p>Global warming and population growth increase the need for better management of freshwater resources, in particular in arid and semi-arid regions. Due to increased rainfall variability,  reservoirs became a vital management tool that stores the water during rainfall, thus decrease flood risks and supply water during drought periods. However, large amounts of water are lost by evaporation, which markedly affects reservoirs’ function of ensuring water availability. In Egypt, about 20.0% of the country's Nile share (12.1 to 15.4 billion m<sup>3</sup>) are lost annually by evaporation from Lake Nasser. The floating covers, i.e. spheres, shade the water surface and act as a physical barrier that decreases energy flux into the water, thus decrease evaporation. Studies that compare the evaporation suppression efficiency of the floating covers, over different climatic conditions, while considering its impact on the water ecology are limited.</p><p>A field experiment in an outdoor setting (class A-pan) was conducted for nine months (March to November) in two locations that vary in their climatic conditions, i.e. Aswan and Damanhur, representing northern and southern Egypt, respectively. The water surface was covered by white, black, or multicolor spheres, in addition to the control. Daily evaporation rate (ER), water temperature (WT), evaporation suppression efficiency (ESE), were determined. Moreover, the microalgae growth was measured as an indicator of water ecology.  </p><p>Obtained results revealed massive evaporation losses from the uncovered water surface (control) in Aswan location, in which the nine-month average was 2.25 times higher than in Damanhour location. The floating spheres reduced ER in both locations, in particular the white spheres. The ESE in Aswan was less than in Damanhour location. The ESE in Damanhour was 63.38, 58.13, and 54.8%, while in Aswan was 48., 42.5, and 41.6% for white, multicolor and black spheres, respectively. Floating spheres decreased WT in the morning and mid-day, while in the evening the control treatment was the coldest, indicating partial isolation of covered water surface. Irrespective of the spheres’ color, the spheres had no detrimental effect on microalgae growth, indicating enough light penetration and gas exchange through the gaps between spheres.</p><p>In conclusion, the floating spheres is an effective mean for evaporation suppression and its efficiency is dependent on the climate and spheres’ color. The ESE of spheres is lower in environments with lower relative humidity. The white spheres are recommended for evaporation suppression without negative impacts on microalgae growth which could be a viable indicator for the ecology of the water ecosystem. Further studies on larger water reservoirs are needed while considering several aquatic organisms.</p>

Investigation and assessment of ecological water resources in the salt marsh area of a salt lake: A case study of West Taijinar Lake in the Qaidam Basin, China

The water ecology of salt marshes plays a crucial role in climate regulation, industrial production, and flood control. Due to a poor understanding of water ecology and the extensive mining of salt resources, concerns are mounting about declining groundwater levels, shrinking salt marshes, and other problems associated with the simple yet extremely fragile water ecosystem of salt marshes in arid salt lake areas. This study assessed the ecological status of water resources in the downstream salt marsh area of West Taijinar Lake in the Qaidam Basin, China (2010–2018). Using data from a field investigation, the water ecosystem was divided into an ecological pressure subsystem, an environmental quality subsystem, and a socio-economic subsystem according to an analytic hierarchy process. Each subsystem was quantitatively assessed using the ecological footprint model, the single-factor index, and available data for the salt marsh area. The results showed that water resources were always in a surplus state during the study period, whose development and utilization had a safe status. Surface water had low plankton diversity with no evidence of eutrophication, but its Cl- and SO42- concentrations were too high for direct industrial water uses. Groundwater quality was classified into class V because of high salt concentrations, which could be considered for industrial use given the demand of industrial production. The socio-economic efficiency of water resources was high, as distinguished by decreased water consumption per 10,000 yuan GDP and excellent flood resistance. In conclusion, the ecological status of water resources was deemed good in the study area and this could help sustain regional development. However, since the water ecology in this area is mainly controlled by annual precipitation, it would be challenging to deal with the uneven distribution of precipitation and flood events and to make full use of them for groundwater recharge. This study provides insight into the impact of salt lake resource exploration on water ecology, and the results can be useful for the rational utilization of water resources in salt marshes in other arid areas.

STRUCTURAL ORGANIZATION OF HIGH-ALTITUDE LANDSCAPE COMPLEXES OF THE EASTERN SIKHOTE-ALIN CATCHMENT BASIN AS A BASIS FOR GEOECOLOGICAL RESEARCH

The article considers high-altitude landscape complexes of the catchment area of the Eastern Sikhote-Alin and their structural organization as the basis of geoecological research. There are low-mountain, dismembered medium-mountain, massively medium-mountain, goltsovye high-altitude landscape complexes. Structuring and classification are presented for further study of structures as objects of industry indication, including water ecology and the possibility of using high-altitude landscape complexes as areas of development.

Pont Evksinskiy – 2021 : materials of XII All-Russian scientific and applied conference for young scientists on the water systems problems, dedicated to the 150 th anniversary of the Sevastopol Biological Station ‒ A. O. Kovalevsky Institute of Biology of the Southern Seas of RAS, Sevastopol, 20–24 September, 2021

The book includes materials of young scientists from Russia and the Republic of Abkhazia, revealing various aspects of modern marine and freshwater biology. Abstracts highlight the results of scientific research in the field of population dynamics and genetic differentiation of aquatic organisms, the features of their life cycle. The book present works on the influence of abiotic and anthropogenic environmental factors on the physiological status of aquaculture species. A number of works describes the capabilities of modern research methods applied in marine and freshwater biological studies, such as metabarcoding, "frame" and "rake method" for detecting beach debris, NGS sequencing, and satellite monitoring. In addition, the book reveals the features of the functioning of coastal ecosystems. The book is valuable for young scientists in the field of marine and freshwater biology, water ecology, biotechnology, aquaculture, marine ecology and zoology