Search Results (19)

The provision of food in pre-Inca/Inca cultures (1000 BC–≈1532 AD) in environments near Lake Titikaka (approximately 4000 m above sea level) was possible through an agricultural technique called “Waru-Waru”, which consists of filling the space (volume) between rows of land containing plants that are cultivated (a series of earth platforms surrounded by water canals) with water, using water as thermal energy storage to store energy during the day and to regulate the temperature of the soil and crop atmosphere at night. The problem is that these cultures left no evidence in written documents that have been preserved to this day indicating the mathematical models, the physics involved, and the experimental part they performed for the research, development, and innovation of the “Waru-Waru” technique. From a review of the existing literature, there is (1) bibliography that is devoted to descriptive research (about the geometry, dimensions, and shapes of the crop fields (and more based on archaeological remains that have survived to the present day) and (2) studies presenting complex mathematical models with many physical parameters measured only with recently developed instrumentation. The research objectives of this paper are as follows: (1) develop a mathematical model that uses finite differences in fluid mechanics, thermodynamics, and heat transfer to explain the experimental and theory principles of this pre-Inca/Inca technique; (2) the proposed mathematical model must be in accordance with the mathematical calculation tools available in pre-Inca/Inca cultures (yupana and quipu), which are mainly based on arithmetic operations such as addition, subtraction, and multiplication; (3) develop a mathematical model in a sequence of steps aimed at determining the best geometric form for thermal energy storage and plant cultivation and that has a simple design (easy to transmit between farmers); (4) consider the assumptions necessary for the development of the mathematical model from the point of view of research on the geometry of earth platforms and water channels and their implantation in each cultivation area; (5) transmit knowledge of the construction and maintenance of “Waru-Waru” agricultural technology to farmers who have cultivated these fields since pre-Hispanic times. The main conclusion is that, in the mathematical model developed, algebraic mathematical expressions based on addition and multiplication are obtained to predict and explain the evolution of soil and water temperatures in a specific crop field using crop field characterization parameters for which their values are experimentally determined in the crop area where a “Waru-Waru” is to be built. Therefore, the storage of thermal energy in water allows crops to survive nights with low temperatures, and indirectly, it allows the interpretation that the Inca culture possessed knowledge of mathematics (addition, subtraction, multiplication, finite differences, approximation methods, and the like), physics (fluids, thermodynamics, and heat transfer), and experimentation, with priority given to agricultural techniques (and in general, as observed in all archaeological evidence) that are in-depth, exact, practical, lasting, and easy to transmit. Understanding this sustainable energy storage technique can be useful in the current circumstances of global warming and climate change within the same growing areas and/or in similar climatic and environmental scenarios. This technique can help in reducing the use of fossil or traditional fuels and infrastructure (greenhouses) that generate heat, expanding the agricultural frontier. Full article

Known as the “white oil”, lithium is a key raw material to support strategic emerging industries and future industrial development. Zabuye Salt Lake is the only one in Tibet, China that has so far realized the industrialization of lithium extraction from the salt lake brine. The green and low-cost lithium extraction technology by using the salinity-gradient solar pond (SGSP) adopted has always been paid much attention by lithium-related practitioners and researchers. In order to improve the lithium yield and grade of a single crystallization pond, the cross-year brine mixing method can be used to increase the initial temperature and CO₃²⁻ concentration of the raw brine for making the SGSP. The premise is to ensure that the summer brine with low Li⁺ and high CO₃²⁻ prepared in the previous year could be stored safely for overwintering with a minimal change in brine composition, for use in brine mixing in February and March of the next year, which can be realized by using the SGSP. In this paper, two experiments of brine storage for overwintering were carried out in the Zabuye mining area, Tibet in 2020 and 2021 by using the large-scale SGSP with an area of nearly 4000 m². The results show that during the operation of the SGSP in winter, the brine temperature in the lower convective zone (LCZ) can still rise to more than 20 °C and remain relatively stable, indicating that the coverage of surface ice layer not only has an effect of heat preservation and insulation on the SGSP, but also plays a positive role in the thermal storage capacity of the SGSP. The vertical distributions of brine temperature, density and salinity in the pond showed the ideal gradient curves increasing from top to bottom, and the concentrations of Li⁺ and CO₃²⁻ in the brine only decreased slightly. The structure of the salinity-gradient layer tended to stabilize faster when the brine filling depth was larger, but the boundary between the upper convective zone (UCZ) and the non-convective zone (NCZ) was relatively blurred. It is completely feasible to store the brine for overwintering by using the SGSP in the Zabuye mining area, and the experimental results could be directly scalable to larger industrial applications. It can not only provide high-quality raw brine for cross-year brine mixing, but also reduce the pressure of brine production, and a small amount of lithium mixed salt collected is helpful to increase the output of a single crystallization pond. Additionally, the potential challenges of maintaining the SGSP system during extreme winter conditions are described, and effective measures and suggestions are proposed to make the technology feasible in diverse climates. Full article

Human activities, global warming, frequent extreme weather events, and changes in atmospheric composition affect the solar radiation reaching the Earth’s surface, affect mass and heat transfer at the air–water interface, and induce oscillations in wind-driven internal waves. This leads to changes in the spatiotemporal characteristics of thermal stratification in lakes, altering lake circulation patterns and vertical mass transfer. However, thermal stratification structures are often overlooked. The intensification of lake thermal stratification due to warming may lead to increased release of bottom pollutants, spreading through the dynamic behavior of the thermocline to the epilimnion. Moreover, the increased heat storage is beneficial for the growth and development of certain phytoplankton, resulting in rapid transitions of the original steady state of lakes. Consequently, water quality deterioration, ecological degradation, and declining biodiversity may occur. Conventional surface water monitoring may not provide comprehensive, accurate, and timely assessments. Model simulations can better predict future thermal stratification behaviors, reducing financial burdens, providing more refined assessments, and thus preventing subsequent environmental issues. Full article

Water, soil, and heat are strategic supporting elements for human survival and social development. The degree of matching between human-land-water-heat elements directly influences the sustainable development of a region. However, the current evaluation of the matching of human-land-water-heat elements overlooks the influence of elevation factors on the matching results, especially evident in mountainous areas. Taking the Yunnan Plateau with distinctive mountainous features as the research subject, divided into 11 elevation ranges, the Lorenz Gini coefficient, asymmetry coefficient, matching distance, and imbalance index are used to assess the spatial matching and balance of human-land-water-heat elements. A projection tracing model is employed to analyze its water resource carrying capacity. Analyses revealed that the Gini coefficient of monthly precipitation from the 1950s to 2022 on the Yunnan Plateau increases with increasing latitude, whereas the correlation with elevation is notably lower. The asymmetry coefficient increases gradually from west to east with change in longitude. The mismatch of the human–land–water–heat system in regions at different elevations is in the order 1800–2000 m > 2000–2200 m > 1400–1600 m > 800 m > other areas. The matching of the human–land–water–heat system in different wet–dry years and seasons also fluctuates with elevation, resulting in serious seasonal drought and water shortage problems in mountainous areas with elevations of 1200–1600, 1800–2000 m, and >2600 m. The spatial equilibrium of temperature and precipitation in regions of different elevations is best, followed by that of cultivated land, while that of the population is the worst. The Gini coefficients for different water cycle processes of precipitation, surface runoff, and regulating storage capacity for water supply continue to increase. Specifically, the Gini coefficient of industrial water supply is the highest, reaching 0.576, and that of agricultural irrigation is the lowest (0.424). Through artificial regulation of lake and reservoir water, seasonal changes in the demand for agricultural irrigation water are offset to achieve a demand–supply balance and matching of land and water resources. The water resource capacity of different elevation ranges is evenly underloaded. However, the potential of the water resource capacity varies obviously with elevation in the order 2000–2200 m < 1800–2000 m < 1600–8000 m < 1400–1600 m < other areas. It appears that the greater the human–land–water–heat system mismatch, the smaller the regional potential of the water resource capacity. Full article

A thermal system in the very deep Lake Tazawa (maximum depth, 423 m) was investigated by estimating the heat budget. In the heat budget estimate, the net heat input at the lake’s surface and the heat input by river inflow and groundwater inflow were considered. Then, the heat loss by snowfall onto the lake’s surface was taken into account. Meanwhile, the lake water temperature was monitored at 0.2 m to the bottom by mooring temperature loggers for more than two years. The heat storage change of the lake from the loggers was calibrated by frequent vertical measurements of water temperature at every 0.1 m pitch by a profiler with high accuracy (±0.01 °C). The heat storage change (W/m²) obtained by the temperature loggers reasonably accorded to that from the heat budget estimate. In the heat budget, the net heat input at lake surface dominated the heat storage change, but significant heat loss by river inflow sporadically occurred, caused by the relatively large discharge from a reservoir in the upper region. How deeply the vertical water circulation in the lake occurs in winter was judged according to the differences between water temperatures at 0.2 m depth and at the bottom and between vertical profiles of dissolved oxygen over winter. It is strongly suggested that the whole water circulation process does not occur every winter, and if it does, it is very weak. A consistent increase in the water temperature at the bottom is probably due to the conservation of geothermal heat by high frequency of incomplete vertical water circulation. Full article

Raised-field agricultural systems have received attention from scholars involved in the analysis of prehistoric agricultural intensification in the New World. This paper discusses the function of raised fields associated with the Tiwanaku society (500–1100 CE) located on the southern rim of Lake Titicaca in Bolivia. The overnight internal heat storage capacity of Tiwanaku raised-field berms located at the high-altitude (~3810 masl) Bolivian altiplano is analyzed through ANSYS (version 4.2B) finite difference methods to provide an understanding of ancient agricultural engineers’ knowledge regarding how to protect crops from nightly subzero freezing temperatures and water saturation. The present analysis concludes that enhanced berm heat storage capacity derived from solar radiation into multi-layered moist berm agricultural soils, together with radiative heating of berm-surrounding swale water (swale water depth determined from excavation into the groundwater aquifer), was an essential Tiwanaku design element of raised-field agriculture to protect crops from freezing damage during both wet and dry seasons. This paper reports the ANSYS temperature distribution results derived from a raised-field berm swale computer model of ancient excavated raised fields in the form of a 24 h heat input and cooling cycle, which indicates the presence of an internal berm heat storage effect designed to protect crops from freezing damage. The calculations performed use specific hydrological and climatological conditions characteristic of the littoral and near-shore environment of Lake Titicaca. The use of the ANSYS finite element code to investigate the source of internal berm heat storage protecting crops from freezing temperatures, compared to the field test results from experimental use of reconstructed ancient, raised fields, provides an understanding of the technologies developed by Tiwanaku agricultural engineers to increase raised-field agricultural production. Full article

A large number of different-sized lakes exist in the inland area of the Tibetan Plateau (TP), which are examples of the important connection between the atmosphere and hydrosphere through the analysis of lake surface convergence and evaporation processes. The evaporation level changes that occur in middle–large-sized lakes (surface area > 50 km²) in the area directly influence the regional mass and energy balance values, atmospheric boundary layer heat and humidity structures, and weather processes occurring in the lower-reach areas. The studies conducted in the literature at present, concerning lake evaporation processes, generally overlook the differences in lake heat storage behavior due to the reduced amount of data in the literature concerning lake bathymetry. According to the in situ bathymetric data obtained for 68 middle–large-sized lakes in the inner basin of the TP, in this study, we calculated their heat storage (G) change values by using the different vertical-depth water-temperature-change integral method, and we established a regression equation for the heat storage and lake surface net radiation values for 68 lakes. The evaporation rates of 134 middle–large-sized lakes larger than 50 km² in the inland are of the TP were calculated by obtaining the G regression result and adopting it into the Penman model, as well as estimating the evaporation losses of theses 134 lakes from 2002 to 2018. The result shows that the annual average evaporation rate for these lakes is 927.39 mm/year, with an insignificant upward trend (0.10 mm/year). This method achieved good accuracy compared with the Bowen ratio method, which estimates the evaporation rate during the ice-free season, with a high correlation coefficient (R) value of 0.95 and least root mean square error (RMSE) value of 61 mm. The annual mean evaporation rate can be divided into the southern and northern lake groups along a 34°N line with a difference of 314.41 mm/year. The annual average evaporation volume of these lakes was 25.02 km³ and showed an upward trend of 0.35 km³/year. Among them, the annual average evaporation volume contribution ratio of level-1 lakes (50 km² ≤ lake’s area < 100 km², 61 lakes) was 14.04%, showing an upward trend, and the contribution of level-3 lakes (lake’s area ≥ 500 km², 10 lakes) was 41.50%, showing a downward trend. There were no obvious changes in the level-2 lakes (100 km² ≤ lake’s area < 500 km², 63 lakes), which maintained at the same level in approximately 44.46%. Air temperature is the most important factor affecting the evaporation rate of lakes, while the lake surface area is the main factor affecting lake evaporation volume. Our study, considering the actual lake heat storage value, provides a useful reference for further improving lake water budget balance values and watershed hydrologic features in the inland closed lakes located in the TP. Full article

Lake stratification and mixing processes can influence gas and energy transport in the water column and water–atmosphere interactions, thus impacting limnology and local climate. Featuring the largest high-elevation inland lake zone in the world, comprehensive and comparative studies on the evolution of lake stratification and mixing and their driving forces are still quite limited. Here, using valuable temperature chain measurements in four large lakes (Nam Co, Dagze Co, Bangong Co, and Paiku Co) and a “small lake” adjacent to Nam Co, our objectives are to investigate the seasonal and diurnal variations of epilimnion depth (E_p, the most important layer in stratification and mixing process) and to analyze the driving force differences between “small lake” and Nam Co. Results indicate that E_p estimated by the methods of the absolute density difference (<0.1 kg m⁻³) from the surface and the Lake-Analyzer were quite similar, with the former being more reliable and widely applicable. The stratification and mixing in the four large lakes showed a dimictic pattern, with obvious spring and autumn turnovers. Additionally, the stratification form during heat storage periods, with E_p quickly locating at depths of approximately 10–15 m, and, after that, increasing gradually to the lake bottom. Additionally, the diurnal variation in E_p can be evidenced both in the large and small lakes when temperature measurements above 3 m depth are included. For Nam Co, the dominant influencing factors for the seasonal variation of E_p were the heat budget components (turbulent heat fluxes and radiation components), while wind speed only had a relatively weak positive correlation (r = 0.23). In the “small lake”, radiation components and wind speed show high negative (r = −0.43 to −0.59) and positive (r = 0.46) correlation, with rare correlations for turbulent heat flux. These reported characteristics have significance for lake process modeling and evaluation in these high-elevation lakes. Full article

Exploring how the hydrological and thermal conditions of a volcanic lake change in response to volcanic activity is important to identify the signs of a volcanic eruption. A water cycle system and a geothermal process in a crater lake, Okama, in the active Zao Volcano, Japan, were explored by estimating the hydrological and chemical budgets of the lake, and analyzing the time series of lake water temperature, respectively. In 2021, the lake level consistently increased by snowmelt plus rainfall in May–June, and then stayed nearly constant in the rainfall season of July–September. The hydrological budget estimated during the increasing lake level indicated that the net groundwater inflow is at any time positive. This suggests that the groundwater inflow to the lake is controlled by the water percolation into volcanic debris from the melting of snow that remained in the catchment. Solving the simultaneous equation from the hydrological and chemical budgets evaluated the groundwater inflow, G_in, at 0.012–0.040 m³/s, and the groundwater outflow, G_out, at 0.012–0.027 m³/s in May–September 2021. By adding the 2020 values of G_in and G_out evaluated at the relatively high lake level, it was found that G_in and G_out exhibit highly negative and positive correlations (R² = 0.661 and 0.848; p < 0.01) with the lake level, respectively. In the completely ice-covered season of 15 December 2021–28 February 2022, the lake water temperature increased between the bottom and 15 m above the bottom at the deepest point, which reflects the geothermal heat input at the bottom. The heat storage change during the increasing water temperature was evaluated at a range of −0.4–5.5 W/m² as the 10-day moving average heat flux. By accumulating the daily heat storage change for the calculated period, the water temperature averaged over the heated layer increased from 1.08 to 1.56 °C. The small temperature increase reflects a stagnant state of volcanic activity in the Zao Volcano. The present study could be useful to investigate how an active volcano responds to water percolation and geothermal heat. Full article

A lake’s water quality and its ecosystem structure are mainly determined by heat storage change through its energy budget, dissolved oxygen, nutrients and primary productivity. A one-dimensional water quality model for lakes was used to estimate temperature, dissolved oxygen, phytoplankton (as chlorophyll-α), and inorganic and organic phosphorus. Evaporation, energy budget and surface water temperature were also computed. The results of the mathematical model simulation are presented and evaluated. Data from Lake Volvi in Central Macedonia (in northern Greece) for three successive years (2013 to 2015) were used to calibrate and recalibrate the model. The model results of water temperature, dissolved oxygen and primary productivity (Chlα) were compared with measurements for the years 2013 to 2015. The comparison showed that the predicted values of these parameters were all in good agreement with the measurements. The simulation results of water quality parameters generally exhibited the same seasonal dynamic and inter-annual variations as the measured data. The simulation results of the model application provided important information on changes in the physical, chemical and biological variables of the lake. The water temperature and heat fluxes at the water–atmosphere interface are crucial variables related to climate changes. Full article

Antarctic basal water storage variation (BWSV) refers to mass changes of basal water beneath the Antarctic ice sheet (AIS). Identifying these variations is critical for understanding Antarctic basal hydrology variations and basal heat conduction, yet they are rarely accessible due to a lack of direct observation. This paper proposes a layered gravity density forward/inversion iteration method to investigate Antarctic BWSV based on multi-source satellite observations and relevant models. During 2003–2009, BWSV increased at an average rate of 43 ± 23 Gt/yr, which accounts for 29% of the previously documented total mass loss rate (−76 ± 20 Gt/yr) of AIS. Major uncertainty arises from satellite gravimetry, satellite altimetry, the glacial isostatic adjustment (GIA) model, and the modelled basal melting rate. We find that increases in basal water mainly occurred in regions with widespread active subglacial lakes, such as the Rockefeller Plateau, Siple Coast, Institute Ice Stream regions, and marginal regions of East Antarctic Ice Sheet (EAIS), which indicates the increased water storage in these active subglacial lakes, despite the frequent water drainage events. The Amundsen Sea coast experienced a significant loss during the same period, which is attributed to the basal meltwater discharging into the Amundsen Sea through basal channels. Full article

In order to investigate the characteristics of the condensate absorption capacity in an exposed sandy bottom when water recedes, the characteristics of condensate variation, condensate formation time, condensate volume, and its absorption capacity were investigated in July 2021, using a micro-osmometer. The research area was the artificial water-retention layer and bare ground of the exposed sandy bottom, formed under the influence of the warming-wetting trend that occurs when water recedes in the salt-lake area of the Qinghai-Tibet Plateau, as well as two conditions: underpass and under sealed. According to the results, the time of condensation generation during the observation period in the salt-lake area of Hoh Xil begins at about 0:00 and ends at about 10:00 The artificial water-retention layer had little influence on the condensation generation time, and the trend of the condensation rate is the same. The unidirectional condensation of water in near-surface air is significantly better under artificial water-retention layer conditions than under bare ground conditions, with condensation occurring three times more frequently than under bare ground conditions. The amount of water condensation in the lower part of the soil under artificial aquifer conditions is 2.588 times greater than that in the near-ground air, while the amount of water condensation in the lower part of the soil under bare ground conditions is 1.783 times greater than that in the near-ground air. The total amount of bi-directional condensation under artificial water-retention layer conditions is slightly less than that in bare ground conditions, while the total amount of unidirectional condensation under artificial water-retention layer conditions is significantly higher, indicating that the artificial water-retention layer contributes to the absorption of water from near-surface air. Due to the presence of permafrost in the Qinghai-Tibet Plateau region, the zero-flux surface transport of evanescent heat in the salt-lake area of Hoh Xil lies approximately within 30 cm from the surface to the ground. The analogous humidity coefficient characterizes the condensate absorption capacity coefficient as the storage capacity of condensate in the surface layer of the soil in a certain area, providing strong evidence that the condensate absorption capacity is higher under the artificial water-retention layer conditions than in bare ground, regardless of whether the condensation is bi-directional or unidirectional. The results of this study can provide a theoretical basis for condensate absorption capacity and vegetation restoration in the bare ecologically degraded areas of the lake bottom. Full article

We present an approach for the calibration of simplified evaporation model parameters based on the optimization of parameters against the most complex model for evaporation estimation, i.e., the Penman–Monteith equation. This model computes the evaporation from several input quantities, such as air temperature, wind speed, heat storage, net radiation etc. However, sometimes all these values are not available, therefore we must use simplified models. Our interest in free water surface evaporation is given by the need for ongoing hydric reclamation of the former Ležáky–Most quarry, i.e., the ongoing restoration of the land that has been mined to a natural and economically usable state. For emerging pit lakes, the prediction of evaporation and the level of water plays a crucial role. We examine the methodology on several popular models and standard statistical measures. The presented approach can be applied in a general model calibration process subject to any theoretical or measured evaporation. Full article

To study the vertical water temperature structure and thermodynamic characteristics of tropical lake-like reservoirs, a water temperature model was developed by a vertical one-dimensional numerical model for Songtao Reservoir in Hainan Province, China. The model was verified by the measured water temperature data, and sensitivity analysis of key model parameters was carried out. The results show that water temperature simulated by the model in Songtao Reservoir agreed with the observations quite well, and the model is feasible for water temperature simulations in large reservoirs in tropical zones. The sensitivity of vertical water temperature structure to different model parameters varied. For example, the extinction coefficient greatly affected surface water temperature, which is important for the formation and development of the surface water temperature hybrid layer. The vertical mixing coefficient significantly influenced the inflection point position and thickness of the thermocline. The vertical water temperature structure in Songtao Reservoir was stratified. Reservoir surface water temperature varied from 19.4 °C to 33.8 °C throughout a year. The hypolimnion mainly appeared in elevation below 150 m, where the water temperature is basically maintained at 19 °C throughout the year. This study also found that the surface water temperature of Songtao Reservoir in the tropical zone was higher than the air temperature throughout a year, with an annual average of 3.5 °C higher than that of air temperature. The preliminary analysis found out that the higher surface water temperature may be caused by the strong air temperature and solar radiation in tropical zones, in addition to the enhanced capacity of heat absorption and heat storage due to the slow water flow in the reservoir. Full article

β-Cyclocitral, specifically produced by Microcystis, is one of the volatile organic compounds (VOCs) derived from cyanobacteria and has a lytic activity. It is postulated that β-cyclocitral is a key compound for regulating the occurrence of cyanobacteria and related microorganisms in an aquatic environment. β-Cyclocitral is sensitively detected when a high density of the cells is achieved from late summer to autumn. Moreover, it is expected to be involved in changes in the species composition of cyanobacteria in a lake. Although several analysis methods for β-cyclocitral have already been reported, β-cyclocitral could be detected using only solid phase micro-extraction (SPME), whereas it could not be found at all using the solvent extraction method in a previous study. In this study, we investigated why β-cyclocitral was detected using only SPME GC/MS. Particularly, three operations in SPME, i.e., extraction temperature, sample stirring rate, and the effect of salt, were examined for the production of β-cyclocitral. Among these, heating (60 °C) was critical for the β-cyclocitral formation. Furthermore, acidification with a 1-h storage was more effective than heating when comparing the obtained amounts. The present results indicated that β-cyclocitral did not exist as the intact form in cells, because it was formed by heating or acidification of the resulting intermediates during the analysis by SPME. The obtained results would be helpful to understand the formation and role of β-cyclocitral in an aquatic environment. Full article