Day-ahead energy production in small hydropower plants: uncertainty-aware forecasts through effective coupling of knowledge and data

Motivated by the challenges induced by the so-called Target Model and the associated changes to the current structure of the energy market, we revisit the problem of day-ahead prediction of power production from Small Hydropower Plants (SHPPs) without storage capacity. Using as an example a typical run-of-river SHPP in Western Greece, we test alternative forecasting schemes (from regression-based to machine learning) that take advantage of different levels of information. In this respect, we investigate whether it is preferable to use as predictor the known energy production of previous days, or to predict the day-ahead inflows and next estimate the resulting energy production via simulation. Our analyses indicate that the second approach becomes clearly more advantageous when the expert's knowledge about the hydrological regime and the technical characteristics of the SHPP is incorporated within the model training procedure. Beyond these, we also focus on the predictive uncertainty that characterize such forecasts, with overarching objective to move beyond the standard, yet risky, point forecasting methods, providing a single expected value of power production. Finally, we discuss the use of the proposed forecasting procedure under uncertainty in the real-world electricity market.

Impacts of Climate Change and Variability on Precipitation and Maximum Flows in Devil’s Creek, Tacna, Peru

Global projections of climate change indicate negative impacts on hydrological systems, with significant changes in precipitation and temperature in many parts of the world. As a result, floods and droughts are expected. This article discusses the potential effects of climate change and variability on the maximum precipitation, temperature, and hydrological regime in Devil’s Creek, Tacna, Peru. The outputs of precipitation and daily temperature of fifteen regional climate models were used for the RCP4.5 and RCP8.5 emission scenarios. The methodology used includes the bias correction and downscaling of meteorological variables using the quintiles mapping technique, hydrological modeling, the evaluation of two emission scenarios, and its effect on the maximum flows of the stream. The results of the multi-model ensemble show that the maximum annual precipitation will probably increase by more than 30% for the RCP4.5 and RCP8.5 scenarios for the 2021–2050 period relative to the 1981–2005 period. Likewise, as expected, the maximum flows could increase by 220% and 154% for the RCP4.5 scenarios for the 2021–2050 and 2051–2080 terms, respectively, and 234% and 484% for the RCP8.5 scenarios and for the 2021–2050 and 2051–2080 terms, respectively, concerning the recorded historical value, increasing the probability of flood events and damage in populations located downstream.

Dynamics of plankton biocenoses under water level fluctuations in steppe lakes

Barun-Torey and Zun-Torey lakes are located in the arid steppe zone of the Central (Inner) Asia, Eastern Siberia, Russia. The Torey lakes are characterizes unstable hydrological regime. The water level variation is explained by the periodic filling and drying of the lakes due to cyclical climatic changes in humidity and temperature. We conducted our studies various water level phases of the climatic cycle: from high water level (1999, 2003) to drying out and the initial filling phase (2007, 2011, 2014, 2016, 2018, and 2020). The aim of this paper is to present long-term research results on changes in the plankton biocenoses of the Torey lakes during a climate cycle, the drying and initial filling of basins. Succession of plankton dominant species is in the direction of: diatoms+green algae and rotifers+crustaceans → green algae and crustaceans → green algae+cyanobacteria and crustaceans → no planktonic algae and invertebrates → cyanobacteria+diatoms+green algae and rotifers+cladocerans+copepods.

Impact of Climate Change on the Hydrological Regime of the Yarkant River Basin, China: An Assessment Using Three SSP Scenarios of CMIP6 GCMs

Quantification of the impacts of climate change on streamflow and other hydrological parameters is of high importance and remains a challenge in arid areas. This study applied a modified distributed hydrological model (HEC-HMS) to the Yarkant River basin, China to assess hydrological changes under future climate change scenarios. Climate change was assessed based on six CMIP6 general circulation models (GCMs), three shared socio-economic pathways (SSP126, SSP245, SSP370), and several bias correction methods, whereas hydrological regime changes were assessed over two timeframes, referred to as the near future (2021–2049) and the far future (2071–2099). Results demonstrate that the DM (distribution mapping) and LOCI (local intensity scaling) bias correction methods most closely fit the projections of temperature and precipitation, respectively. The climate projections predicted a rise in temperature of 1.72–1.79 °C under the three SSP scenarios for the near future, and 3.76–6.22 °C under the three SSPs for the far future. Precipitation increased by 10.79–12% in the near future, and by 14.82–29.07% during the far future. It is very likely that streamflow will increase during both the near future (10.62–19.2%) and far future (36.69–70.4%) under all three scenarios. The increase in direct flow will be greater than baseflow. Summer and winter streamflow will increase the most, while the increase in streamflow was projected to reach a maximum during June and July over the near future. Over the far future, runoff reached a peak in May and June. The timing of peak streamflow will change from August to July in comparison to historical records. Both high- and low-flow magnitudes during March, April, and May (MAM) as well as June, July, and August (JJA) will increase by varying degrees, whereas the frequency of low flows will decrease during both MAM and JJA. High flow frequency in JJA was projected to decrease. Overall, our results reveal that the hydrological regime of the Yarkant River is likely to change and will be characterized by larger seasonal uncertainty and more frequent extreme events due to significant warming over the two periods. These changes should be seriously considered during policy development.

Application of Remote Sensing and GIS Techniques for the Analysis of Lake Water Fluctuations: A Case Study of Ugii Lake, Mongolia

Ugii Lake is a freshwater lake located in the steppe region of Mongolia and is an important breeding and staging area for a wide variety of waterfowl. Remote sensing and geographic information system techniques were used to estimate fluctuations in the surface area and water balance of Ugii Lake. To estimate the changes in lake water balance, lake water fluctuations should be analyzed using the most accurate methods. A different water extraction technique was applied, and the results were compared with field surveys conducted in May, July, and September 2020. The lake surface area using both NDWI and MNDWI-1 showed a strong, positive correlation (R=0.93, R=0.94, p < 0.01) with the water level of Ugii Lake. A topographic map of Ugii Lake was provided by the project (P2018-3568) conducted in August 2019 and used to estimate the volume of Ugii Lake in ArcGIS 10.1. This result was consistent with that of a previous study by JICA in 2005. Finally, the water balance of Ugii Lake was estimated, and the results proved that the influence of both surface and groundwater on Ugii Lake are valuable parameters, which are completely dependent on hydrological regime changes mostly due to local climate change in steppe regions. This study provides valuable insight into the most suitable water extraction methods for lakes in semi-arid steppe regions in Mongolia.

Commercial exploitation of Kуiv reservoir as a fishery water body (a review)

Purpose. To analyze an array of special scientific literature and summarize the obtained information on the commercial exploitation of the Kуiv reservoir as a fishery water body. To review main abiotic conditions of the reservoir, which exist and form the specificity of its commercial use by the fishery industry of Ukraine. To highlight the historical course of their impact on the fish fauna of the Kyiv Reservoir and general forecasts for its future transformations. Findings. An overview of scientific publications devoted to the specifics of commercial exploitation of the Kуiv reservoir as a fishery water body from the moment of its creation to the present day were presented. In particular, following was analyzed: hydrological regime, color and chemical composition of water, oxygen regime, accumulation of heavy metals, formation of bottom sediments and landscape. In addition, the radioecological situation in the reservoir was anazyed, both general and in three most significant areas for fisheries — in bottom sediments, macrophytes, and fish fauna. The literature data on the specificity of the above-mentioned abiotic factors in this reservoir, which form the hydro-ecological feature of this reservoir, were generalized. The main directions of their influence on the ichthyofauna of the Kуiv reservoir, which affect the possibility of its commercial exploitation, were described. The share of anthropogenic origin in the composition of the above-mentioned abiotic factors and the consequences of its impact were highlighted. The perspective ways of further development of the Kiev reservoir as a fishery water body of strategic importance for Ukraine were shown. Practical Value. The review may be useful for scientists, PhD students, students, government authorities, and private entrepreneurs involved in research process or exploatation of aquatic living resources in internal water bodies, primarily in the Kуiv reservoir. Keywords: Kуiv reservoir, fishery water body, hydrological regime, water chemical composition, water oxygen regime, heavy metals, bottom sediments, landscape formation, radioecological situation.

Vulnerability of the Ancient Peat Plateaus in Western Siberia

Based on the data of the plant macrofossil and palynological composition of the peat deposits, the evolution and current state of polygonal peatlands were analyzed at the southern limit of continuous permafrost in the Pur-Taz interfluve. Paleoreconstruction shows that peat accumulation began in the Early Holocene, about 9814 cal. year BP, in the Late Pre-Boreal (PB-2), at a rate of 1 to 1.5 mm year−1. Intensive peat accumulation continued in the Boreal and early Atlantic. The geocryological complex of polygonal peatlands has remained a stable bog system despite the predicted warming and increasing humidity. However, a rather rapid upper permafrost degradation and irreversible changes in the bog systems of polygonal peatlands occur with anthropogenic disturbances, in particular, a change in the natural hydrological regime under construction of linear objects.

SAMARA CITY UNDERGROUND URBANIZATION DEVELOPMENT AND ITS CONSEQUENCES

Nowadays the area of cities is almost everywhere increasing - the territory urbanization is developing. At the same time, due to lack of land resources, the underground space development intensifi es, and the underground construction volume increases, i.e., underground urbanization takes place. This process has undoubtedly positive results, as it can help solve territorial, transport, environmental and other problems of cities while preserving the unique appearance of buildings in the historical centers of cities. At the same time, some engineering and geological processes may be activated as a negative underground urbanization result. The article deals with underground urbanization history in Samara and defi nes its main stages. More than one million people live in Samara city, subway line was built, there are subway objects of industrial and defense importance (bunkers) reaching considerable depth. Active underground construction can lead to geological processes strengthening (weathering, karst formation, suff osia, etc.), change of strength properties of rocks, violation of natural hydrological regime of the territory. The territory of Samara has an inhomogeneous geological structure and complex engineering and geological construction conditions. Seven engineering-geological districts have been identifi ed and studied, on the territory where underground construction development can lead to diff erent, including negative, consequences.

The Influence of Intra-Day Non-Uniformity of Operation of Large Hydroelectric Powerplants on the Performance Stability of Water Intakes Located in Their Upper Pools

The creation of reservoirs in water streams leads to significant changes in the hydrological regime of water bodies: it allows smoothing the peaks of maximum water discharge during a flood period and regulating low-water flow. The creation of reservoirs with significant storage capacity makes it possible to solve a wide range of water-management problems, including the use of falling water energy for hydropower purposes, and maintenance of the uninterrupted water supply and navigation. Since constructed dams are usually operated by hydropower companies, the regulatory regime for the discharge of water into the lower pool is often determined by the daily electricity consumption regime. Intra-day variations in the volume of water discharges through hydroelectric power stations generate multidirectional streams in the upper pool, which can affect the operation of other water withdrawal systems. This paper considers the effect of intraday variations in water discharges into the lower pool on the dynamic and physical properties of the water mass in the region of the location of drinking water-intake heads of Perm city and the quality of the withdrawn water.