Hydrometeorological Parameters Research Articles

Analysis and assasment method of the Chirchik river flow for water supply and water use

The scientific work is devoted to studying hydroecological problems and methods for assessing the transformation of river water on the example of the Chirchik River, which flows through large industrial centers of the Republic of Uzbekistan and the territory of its capital, Tashkent. Investigations of quantitative and qualitative transformation of river water runoff were carried out using the interpolation method. The main task is to describe the method of interpolation of hydrometeorological data of the territories; For such system, the center in this work adopted a material point that characterizes the movement of the whole system; for this research, such as the hydrometeorological parameters of the territory. The data of the hydrometeorological service of the Republic of Uzbekistan were used when interpolating climatic parameters, which are the main determining factors in the formation and transformation of the river flow of Chirchik. In the proposed interpolation method, a combined system is created, consisting of a landscape-natural component, a system representing a moving mass with a single center. The meteorological parameters of the territory are taken as elements of the mass system, which have their centers of change-movement. The performed test calculations showed that the difference in meteorological parameters affects the position of their centers; each parameter: atmospheric pressure, precipitation, humidity, and temperature, etc., has its center.

Impact of Hydro-Climatic Changes on Coastal Dunes Landscape According to Normalized Difference Vegetation Index (The Case Study of Curonian Spit)

Coastal dunes are recognized as one of the most threatened ecosystems, the formation of which mainly depends on two opposite processes—sand dunes overgrowth and formation of open dunes. The application of cost-effective remote sensing methods permits monitoring the interaction of these two processes over a large area and long periods of time. Therefore in this study we assessed the links between hydro-meteorological parameters and the normalized difference vegetation index (NDVI) in Curonian spit coastal dunes landscape-a creation of human and nature integrity situated in the South eastern part of the Baltic Sea. Time series of NDVI (2000–2019) were obtained from the moderate resolution imaging spectro-radiometer and compared with hydro-meteorological parameters in three different ecosystems—forest, herbaceous and open sands. Moderate and strong positive correlation between NDVI and average wind speed was detected in non-forested ecosystems. Moderate positive correlation was detected between NDVI and the Baltic sea water level in all three analyzed ecosystems. Moderate positive correlation between NDVI and air temperature was found in forest ecosystem. This confirms that NDVI could be treated as an appropriate indicator, showing the interaction of coastal dunes overgrowth and formation of open dunes, and could be applied in its management that should be reconsidered under nowadays climate change.

Evaluation and Quantification of the Effects of Climate and Vegetation Cover Change on Karst Water Sources: Case Studies of Two Springs in South-Western Slovenia

Karst aquifers hold important water resources such as regional water budgets and freshwater supply. Due to highly dynamic hydrological processes in comparison to other less permeable systems, they are particularly susceptible to environmental changes. However, little research directly characterizes the impacts of climate and vegetation cover changes on karst water sources. In this study, we aimed to evaluate individual long-term impacts and impacts of sudden large-scale forest disturbances on changes in groundwater recharge and in spring discharge. The work is based on temporal analysis of forest cover and a comparison of trend analysis of hydro-meteorological parameters. To investigate and evaluate vegetation cover change impacts on groundwater recharge, we used a soil water balance model and compared estimated actual daily values of effective precipitation to its fictional estimation disregarding the vegetation cover change. The applied methodology enabled quantification of the impacts of climate and vegetation cover change on selected karst water sources. The study suggests that the vegetation cover can have a significant impact on the spring recharge. Large-scale disturbances that occurred in a short-term mitigated the effects expected from the trend analysis of hydro-meteorological parameters. In the long-term, in addition to climate changes, the multi-decadal natural vegetation overgrowth significantly contributed to the reduction in the spring’s discharge values, especially in the warm season when water demand is higher. Therefore, the results are of key importance for developing proper water management and environmental policies.

Hydrological Extremes in the Canadian Prairies in the Last Decade due to the ENSO Teleconnection—A Comparative Case Study Using WRF

In the Prairie provinces of Alberta, Saskatchewan, and Manitoba, agricultural production depends on winter and spring precipitation. There is large interannual variability related to the teleconnection between the regional hydroclimate and El Niño and La Niña in the Tropical Pacific. A modeling experiment was conducted to simulate climatic and hydrological parameters in the Canadian Prairie region during strong El Niño and La Niña events of the last decade in 2015–2016 and 2010–2011, respectively. The National Center for Atmospheric Research (NCAR) Weather Research and Forecasting (WRF) model was employed to perform two sets of sensitivity experiments with a nested domain at 10 km resolution using the European Centre for Medium-Range Weather Forecasts Reanalysis (ERA) interim data as the lateral boundary forcing. Analysis of the hourly model output provides a detailed simulation of the drier winter, with less soil moisture in the following spring, during the 2015–2016 El Niño and a wet winter during the La Niña of 2010–2011. The high-resolution WRF simulation of these recent weather events agrees well with observations from weather stations and water gauges. Therefore, we were able to take advantage of the WRF model to simulate recent weather with high spatial and temporal resolution and thus study the changes in hydrometeorological parameters across the Prairie during the two extreme hydrological events of the last decade.

A synergy of linear model and wavelet analysis towards space-time characterization of aerosol optical depth (AOD) during pre-monsoon season (2007–2016) over Indian sub-continent

The pre-monsoon aerosol concentration plays a significant role in modifying precipitation amount over the Indian sub-continent. A large variety of aerosol from different sources produces a complex radiative and climate response through the interaction with the hydrometeorological parameters. In this study, we analyzed the space-time dynamics of aerosol optical depth (AOD) in relation to the meteorological and surface parameters over Indian sub-continent during pre-monsoon season from 2007 to 2016. The level-3 daily aerosol products from Moderate Resolution Imaging Spectroradiometer (MODIS) and Multi-angle Imaging Spectroradiometer (MISR) were used. The IMD gridded rainfall and temperature, ECMWF derived RH and wind velocity, and GLADS derived soil moisture data were also used at daily time scale. For the space-time model, the Mann-Kendall trend test and a pixel-based multiple linear regression were used, while, wavelet transformation was used on these daily observations for analyzing periodicities of AOD. The time-series average shows moderate to high AOD (0.4–0.8), including a consistent positive anomaly in the Indo-Gangetic basin (IGP) in north India. A significant inter-annual variation is also observed both in MODIS and MISR datasets. The trend statistics shows an increasing trend of aerosol concentration in the eastern and southern India. The linear regression shows a variable response of AOD with changing magnitude of meteorological factors. However, a substantial spatial coverage of significantly decreased AOD is observed with increasing soil moisture content (β < −0.04). The wavelet analysis manifests the abundances of 32–128 days of cycle with a periodic interjection of 8–32 days of cycle suggesting occurrence of fine and coarse mode aerosols events, respectively. The coherency of time series AOD and other covariates shows varying leading and lagging dynamics in these two principal periodicities. The findings, however, evidenced a notable difference in the space-time patterns of AOD in MODIS and MISR datasets. The analyzed AOD cycles are coincided with the Madden-Julian-Oscillation (MJO) that recurs every 30–60 days interval. The findings also support the theoretical proposition of elevated heat pump theory (EHP) driven by fine mode aerosols for occurring pre-monsoon and monsoon precipitation over the Indian sub-continent. The analyzed periodicity of AOD can provide useful insights in studying the short/long term variability of precipitation over polluted environments during the pre-monsoon season.

Spatiotemporal Analysis of Water Resources in the Haridwar Region of Uttarakhand, India

Watershed management plays a dynamic role in water resource engineering. Estimating surface runoff is an essential process of hydrology, since understanding the fundamental relationship between rainfall and runoff is useful for sustainable water resource management. To facilitate the assessment of this process, the Natural Resource Conservation Service-Curve Number (NRCS-CN) and Geographic Information Systems (GIS) were integrated. Furthermore, land use and soil maps were incorporated to estimate the temporal variability in surface runoff potential. The present study was performed on the Haridwar city, Uttarakhand, India for the years 1995, 2010 and 2018. In a context of climate change, the spatiotemporal analysis of hydro meteorological parameters is essential for estimating water availability. The study suggested that runoff increased approximately 48% from 1995 to 2010 and decreased nearly 71% from 2010 to 2018. In turn, the weighted curve number was found to be 69.24, 70.96 and 71.24 for 1995, 2010 and 2018, respectively. Additionally, a validation process with an annual water yield model was carried out to understand spatiotemporal variations and similarities. The study recommends adopting water harvesting techniques and strategies to fulfill regional water demands, since effective and sustainable approaches like these may assist in the simultaneous mitigation of disasters such as floods and droughts.

Perspectives of land evaluation of floodplains under conditions of aridification based on the assessment of ecosystem services

Global climate change has discernible impacts on the quality of the landscapes of Hungary. Only a dynamic and spatially differentiated land evaluation methodology can properly reflect these changes. The provision level, rate oftransformation and spatial distribution of ecosystem services (ESs) are fundamental properties of landscapes and have to be integral parts of an up-to-date land evaluation. For agricultural land capability assessment soil fertility is a major supporting ES, directly associated with climate change through greenhouse gas emissions and carbon sequestration as regulationg services. Since for Hungary aridification is the most severe consequence of climate change, water-related ESs, such as water retention and storage on and below the surface as well as control of floods, water pollution and soil erosion, are of increasing importance. The productivity of agricultural crops is enhanced by more atmospheric CO2 but restricted by higher drought susceptibility. The value of floodplain landscapes, i.e. their agroecological, nature conservation, tourism (aesthetic) and other potentials, however, will be increasingly controlled by their water supply, which is characterized by hydrometeorological parameters. Case studies are presented for the estimation of the value of two water-related regulating ESs (water retention and groundwater recharge capacities) in the floodplains of the Kapos and Drava rivers, Southwest Hungary. It is predictable that in the future land evaluation techniques based on the FAO framework will be more dynamic and integrated with the monetary valuation of ESs. The latter task, however, still involves numerous methodological problems to solve.

Samoorganizuyushchiyesya karty atmosfernoy tsirkulyatsii i mezhgodovaya izmenchivost' gidrometeorologicheskikh poley v Arktike

The article suggests the use of a nonlinear method of data analysis based on a neural network – an algorithm of Kohonen self-organizing maps for the task of typing the atmospheric surface circulation in the Arctic. Based on the construction of self-organizing surface pressure maps, the seasonal and interannual variability of atmospheric circulation in the Arctic for the period 1979–2018 is studied. Several modes were distinguished: cyclonic, two anticyclonic, and three mixed types. Indices of seasonal and annual repeatability of self-organizing atmospheric pressure maps are introduced, which allow us to study the temporal variability of atmospheric circulation modes and a composite method is proposed for calculating connected maps of other hydrometeorological parameters. The regimes of variability of the area of sea ice distribution and sea surface temperature depending on the type of atmospheric circulation are highlighted. Depending on the type of wind regime, there is a change in the area of sea ice distribution due to the variability of the flows of warm Atlantic waters into the Arctic Ocean. The characteristic types of sea surface temperature variability in the Barents Sea are identified, which are modulated by cyclonic / anticyclonic regimes of atmospheric circulation in the region and are an indicator of heat advection by the Atlantic waters. The interrelation is established of the repeatability index of self-organizing atmospheric pressure maps characterizing the types of atmospheric circulation with the variability of the Arctic Oscillation Index. The revealed regularities of the change in the types of cyclonic-anticyclonic atmospheric circulation are manifested in the interannual variability of the introduced repeatability index of selforganizing atmospheric pressure maps, which is a development of the Arctic Oscillation Index, improves understanding of the atmospheric climate circulation regimes in the Arctic.

ДОЛГОПЕРИОДНАЯ ИЗМЕНЧИВОСТЬ ГИДРОМЕТЕОРОЛОГИЧЕСКИХ ПАРАМЕТРОВ В АКВАТОРИИ КАСПИЙСКОГО МОРЯ. ЧАСТЬ 2: АНАЛИЗ

The second part of the paper presents a phenomenological analysis of the relationships of long-term variability of various hydrometeorological parameters in the Caspian Sea in the period 1948–2017. It is shown that under annual averaging the North-Eastern wind regime prevails over the sea basin, but the major portion of heat advection into the region is provided by zonal (Eastern) transport. Periods of warming/cooling are associated with a weakening/ strengthening of the Eastern transport. The time lag between the change of dynamic and thermal (as well as humidity) regimes is about 10–12 years. Specific humidity is positively correlated with air temperature and decreases/increases during periods of cooling/warming. In contrast, relative humidity and precipitation rates are negatively correlated with air temperature. Periods of intensification of Eastern transport (and, consequently, cooling) over the Caspian Sea coincide with a situation when the NAO index decreases to negative or zero values, and the EAWR index is significantly positive. Easing of the Eastern transport (and warming) occurs during a period of sharp strengthening of the NAO at strongly negative values of the EAWR index.

Statistical hydrology for evaluating peatland water table sensitivity to simple environmental variables and climate changes application to the mid-latitude/altitude Frasne peatland (Jura Mountains, France)

Peatlands are habitats for a range of fragile flora and fauna species. Their eco-physicochemical characteristics make them as outstanding global carbon and water storage systems. These ecosystems occupy 3% of the worldwide emerged land surface but represent 30% of the global organic soil carbon and 10% of the global fresh water volumes. In such systems, carbon speciation depends to a large extent on specific redox conditions which are mainly governed by the depth of the water table. Hence, understanding their hydrological variability, that conditions both their ecological and biogeochemical functions, is crucial for their management, especially when anticipating their future evolution under climate change. This study illustrates how long-term monitoring of basic hydro-meteorological parameters combined with statistical modeling can be used as a tool to evaluate i) the horizontal (type of peat), ii) vertical (acrotelm/catotelm continuum) and iii) future hydrological variability. Using cross-correlations between meteorological data (precipitation, potential evapotranspiration) and water table depth (WTD), we primarily highlight the spatial heterogeneity of hydrological reactivity across the Sphagnum-dominated Frasne peatland (French Jura Mountain). Then, a multiple linear regression model allows performing hydrological projections until 2100, according to regionalized IPCC RCP4.5 and 8.5 scenarios. Although WTD remains stable during the first half of 21th century, seasonal trends beyond 2050 show lower WTD in winter and markedly greater WTD in summer. In particular, after 2050, more frequent droughts in summer and autumn should occur, increasing WTD. These projections are completed with risk evaluations for peatland droughts until 2100 that appear to be increasing especially for transition seasons, i.e. May–June and September–October. Comparing these trends with previous evaluations of phenol concentrations in water throughout the vegetative period, considered as a proxy of plant functioning intensity, highlights that these hydrological modifications during transitional seasons could be a great ecological perturbation, especially by affecting Sphagnum metabolism.

Перспективы развития безэкипажных судов в Российской Федерации

The article considers the actuality of crewless shipping. The development of technical means in the marine shipbuilding industry has been pointed out. The statistical data on accidents at sea are given; as a result of the data analysis, there have been identified the main causes &#x0D; of the accidents: non-compliance with generally accepted methods of controlling a vessel, ignoring the specific hydrometeorological parameters of the navigation and mooring areas, non-compliance with safety and technical operation rules, navigation errors, etc. The human factor has been stated to remain the main and most frequent cause of accidents at sea. The types of accidents at sea are considered in detail (damage to ship devices and mechanisms, ship's hull, loss of life, bulk, explosion, fire, loss of a towed object, winding on a screw, grounding, serious bodily harm, collision, loss of stability, buoyancy, collision with a submerged object). The advantages of using a crewless vessel are substantiated, as well as the prospects associated with the introduction of such vessels: reduction in accident rate due to the exclusion of the human factor, lower negative and harmful effects on the environment, increased reliability of transportation due to changes in the structure &#x0D; of vessels, increased economic efficiency due to the uselessness of crew support, etc. There has been given an example of creating a project for the e-Navigation test area executed by Kronstadt in 2016. The test water area includes all e-Navigation coverage areas, combines 13 ports, training centers, over 300 sea vessels, several ship traffic control systems into a single electronic space. Within the framework of the project, developers introduce and test new equipment, conduct training for the crews. The conclusions have been made about possibility for the Russian Federation of accelerating the introduction of new technologies in the global market of shipping companies, increasing competitiveness and reducing dependence on foreign technologies

Water balance assessment using remote sensing, Wet-Spass model, CN-SCS, and GIS for water resources management in Saïss Plain (Morocco)

Saiss plain contains an important aquifer. This complex groundwater system plays an important socio-economic role. Managing the groundwater resources requests a good understanding of resources availability and human needs satisfaction. These two components are estimated to get annual water balance of Saiss aquifer. Resources availability depends on meteorological parameters (rainfall, wind speed, temperature, etc.), soil types, topography, water table, and land use. Previous studies do not consider all of these parameters in assessing the water resources availability in this region. In this study, we have identified the relationship between all Saiss hydro-meteorological parameters and we have organized all data in Geographic Information System (GIS) to assess inputs of the water balance. Meteorological and hydrological data and landuse/landcover maps obtained from Landsat imageries classification were used in Wet-Spass (water and energy transfer between soil, plants, and atmosphere under quasi-steady state) model and Soil Conservation Service Curve Number (CN-SCS) method to assess annual runoff, potential evapotranspiration, interception, actual evapotranspiration, and natural recharge of shallow aquifer of Saiss plain. The results of the water balance calculation indicate significant fluctuations in the aquifer recharge: 280 Mm3 (1987) and 418 Mm3 (2018). The annual direct runoff increased from 344 Mm3 (1987) to 638 Mm3 (2018).

A Review on the Decadal Irrigation System of Shali Water Reservoir

Irrigation is a prime factor for agriculture, fishing and afforestation in two water scant districts namely Bankura and Purulia of West Bengal province in India. To fulfill such purposes, Shali reservoir was erected on the Shali River near Bhairabpur village of Gangajalghati block at Bankura district in 1978. After the four decades of construction it was found that only a few studies were conducted by previous researchers on Shali reservoir. In these four decades many things like population, climate, soil type, reservoir life, hydro-meteorological parameters like rainfall pattern, evaporation rates etc., people’s behavior on water utilizations, river morphology -have been changed over periods. Therefore it is most needed to bring together all those previous researches for finding out the new need of any further detail research on Shali reservoir. This paper aims to coalesce all those researches in a succinct manner for the benefit of the people of Gangajalghati block in Bankura.

Late Quaternary and Modern Evolution of Permafrost Coasts at Beliy Island, Kara Sea

Baranskaya, A.V.; Novikova, A.V.; Shabanova, N.; Romanenko, F., and Ogorodov, S., 2020. Late Quaternary and modern evolution of permafrost coasts at Beliy Island, Kara Sea. In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 356–361. Coconut Creek (Florida), ISSN 0749-0208.The low coasts of Beliy Island, Kara Sea, composed of perennially frozen sands and silts with peat are extremely vulnerable to all changes in sea level and climate conditions in the Arctic. The complex Holocene history of the island is reflected in sediments outcropping in its coastal bluffs. Modern erosion leads to destruction of these bluffs, continuing to change the topography of the island.To reconstruct Late Quaternary history, coastal exposures were investigated. They generally consist of three units: the lower clays and sands with plant debris, parallel and rippled lamination formed in shallow marine conditions in MIS 3. The middle sandy unit with allochtonuous peat lenses was deposited in the mid-Holocene (5 to 8 ka BP) in coastal conditions. The upper peats, sandy loams and silts accumulated in continental conditions after 5 ka.To estimate modern coastal erosion rates, multitemporal satellite imagery (1969-2016) was used. The western coast retreated at higher average rates than the eastern coast (1.9±0.2 m/y and 1.2±0.2 m/y, respectively). Extreme rates during 47 years were higher from the eastern side (4.6 m/y compared to 3.1 m/y in the west). Both mean and extreme erosion rates are higher than the known erosion intensity of the Kara Sea coastal dynamics monitoring sites, evidencing considerable vulnerability of the low coasts to erosion in the changing climate. Evolution of the hydrometeorological parameters affecting coastal erosion in the XX-XXI century was estimated. High average retreat rates must have happened in the 2000s-2010s as a result of both temperature and wave energy increase providing unprecedent environmental forcing of coastal dynamics.

Spatiotemporal Variability of Coastal Retreat Rates at Western Yamal Peninsula, Russia, based on Remotely Sensed Data

Belova, N.G.; Novikova, A.V.; Günther, F., and Shabanova, N.N., 2020. Spatiotemporal variability of coastal retreat rates at Western Yamal Peninsula, Russia, based on remotely sensed data. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 367–371. Coconut Creek (Florida), ISSN 0749-0208.The work aims at estimating coastal retreat at Western Yamal from 1972 to 2016, when significant climate change occurred in the Arctic. One fourth of the Kara Sea coasts are collapsing cliffs composed of permafrost, i.e. thermoabrasional coasts. Although these coasts are bounded by sea ice for most of the year, they retreat with rates comparable to those of temperate latitudes, but only during the short ice-free period. Permafrost cliffs are not only eroded by waves; they also get destroyed by melting of the ground ice bounding the sediments (thermo-denudation). Arctic coasts are sensitive to climate change, as rising summer air temperatures lead to deeper thawing of frozen sediments, and longer ice-free periods extend the time of the wave impact on the coast. At Western Yamal, in the area of Kharasavey gas condensate field, the average long-term coastal retreat rate is 1.3 m/yr (1972-2016) for 5.9 km of the coastline, reaching mean annual rates of 3 m/yr in some areas. The greatest retreat rates are typical for coastal segments composed of permafrost with high ice content. Based on the analysis of multitemporal aerial and space images, the coastal retreat rates for four time periods between 1972 and 2016 were estimated. The retreat rates were brought into context with data on sediment composition and type (grain size, ice content, presence of massive ice), reconstructed evolution of hydrometeorological parameters and the history of economic development of Kharasavey area. Unlike other Kara Sea sites of coastal dynamics' monitoring, the strongest coastal retreat rates at Kharasavey were observed earlier in 1977-1988, when the hydrometeorological stress was low, implying vulnerability of the coasts to significant anthropogenic impact at the beginning of the gas field development.

Flood Inundation Mapping and Impact Assessment Using Multi-Temporal Optical and SAR Satellite Data: a Case Study of 2017 Flood in Darbhanga District, Bihar, India

Flooding is a recurrent hazard in east Gangetic plains, largely on account of natural factors that pose risks to life and property. Bagmati and Burhi Gandak rivers draining parts of North Bihar causes substantial flooding owing to higher rainfall. This comprehensive study was carried out to map near real-time flood inundation using multi-temporal Sentinel-1A (SAR) and Moderate-resolution Imaging Spectroradiometer Near Real-Time (MODIS NRT) flood data (Optical and 3-day composite) over Darbhanga district of North Bihar during August and September 2017. Floodwater pixels were extracted using the binarization technique, wherein the threshold was applied as −22.5, −23.4, −23.8 and − 22.7 over VH polarization image. The key results revealed that during peak flooding stage (23rd August), 13% of areas were submerged based on SAR data, whereas overestimation by >20% was estimated using MODIS data. As shown in the composite flood inundated map, the inundated patches are quite similar in both the optical and SAR based data. Notably, there were higher flood patches observed in the central, northern, and western parts of the district due to the presence of more water channels in those regions. Our findings suggested that agriculture patches of ~392 sq.km area were inundated due to flood followed by vegetation clutters (16.07 sq.km) and urban (8.46 sq.km). These results indicated the impact of floodwater on agriculture and urban patches. These findings are crucial for policymakers to assess flood impacts. It can be inferred that flood prognosis using SAR data will lead to spatial accuracy and can be improved when coupling with various hydro-meteorological parameters and hydrological models.

Recent Advances in Real-Time Pluvial Flash Flood Forecasting

Recent years have witnessed considerable developments in multiple fields with the potential to enhance our capability of forecasting pluvial flash floods, one of the most costly environmental hazards in terms of both property damage and loss of life. This work provides a summary and description of recent advances related to insights on atmospheric conditions that precede extreme rainfall events, to the development of monitoring systems of relevant hydrometeorological parameters, and to the operational adoption of weather and hydrological models towards the prediction of flash floods. With the exponential increase of available data and computational power, most of the efforts are being directed towards the improvement of multi-source data blending and assimilation techniques, as well as assembling approaches for uncertainty estimation. For urban environments, in which the need for high-resolution simulations demands computationally expensive systems, query-based approaches have been explored for the timely retrieval of pre-simulated flood inundation forecasts. Within the concept of the Internet of Things, the extensive deployment of low-cost sensors opens opportunities from the perspective of denser monitoring capabilities. However, different environmental conditions and uneven distribution of data and resources usually leads to the adoption of site-specific solutions for flash flood forecasting in the context of early warning systems.

Changes in the hydrological characteristics of Cauvery river draining the eastern side of southern Western Ghats, India

ABSTRACTThe changes in land use and regional climate together with human interventions affect the hydrological processes, resulting in the spatial and temporal alterations of surface and subsurface flow processes. Both climate and land surface change have adverse implications on the natural hydrological system in terms of variation in the run-off regime, surface storage, evapotranspiration, subsurface flow and infiltration, thereby affecting the hydrology of the river basin as a whole. Even though several studies worldwide have attempted to address the influence of climate change, land-use change and human activities on the hydrology of river basins, either as a whole or limited to a few components of the hydrological cycle, limited attention has been given to study the hydrological changes in the river basins of arid and semi-arid tropics, which are essentially fed by precipitation. The objective of the study is to analyse the changes in hydrological characteristics of the Cauvery river basin, a semi-arid river basin in South India. The changes in the hydrology of the Cauvery river basin are studied by analysing the trends in hydro-meteorological parameters using Mann-Kendall trend tests and Sen’s estimator of the slope. The results showed that the changes in the volume of rainfall and the number of rainy days significantly affect the overall hydrological regime of the river basin. The analysis of annual and seasonal rainfall over the Cauvery river basin showed a decreasing trend in the middle Cauvery basin. A declining trend in the number of rainfall events was also observed in the middle Cauvery region. The effect of decreasing trend in the volume of rainfall and number of rainy days is evident from the decreasing trends in the streamflow of the main channel and tributaries of the Cauvery river. The regions of increase in evapotranspiration showed a significant correlation with the regions which exhibited a decline in groundwater level.

CALCULATION ACCURACY OF EVAPORATION AT DIFFERENT AVERAGING PERIODS BY OBSERVATION DATA IN THE SOUTHERNBALTIC

The evaporation or moisture flow in the boundary layer is one of important components in the ocean-atmosphere interaction system. The most commonly used formulas for calculating evaporation include standard hydrometeorological parameters — atmospheric pressure, wind speed, drop of humidity, and height, at which measurements are made, and the exchange rate of moisture, which also depends on these parameters. The correct method is to calculate moisture flow based on current or hourly parameter values and then average the flow values for the required period: day, month or year. In the absence of current data of observation parameters, flow values should be calculated based on averaged parameter values. In this case, the calculated values of evaporation strongly depend on the method and the averaging period. Using the example of rather long observation series (2002—2016) at stations in the Southern Baltic, a quantitative assessment of the effect of averaging on the calculated values of the moisture flow both for direct calculation from the current observation data and for averaged data is made. The probable explanations are given for a significant variation in the calculated values of evaporation in the Baltic Sea by different authors. The coefficients for the correction of evaporation values obtained from the averaged values of hydrometeorological parameters are calculated. It is shown that averaging the parameters per day is acceptable with almost no loss of accuracy (error no more than 2-4 %). Averaging the values of hydrometeorological parameters over the period of a month leads to an underestimation of the calculated evaporation values by 20-30 %. When averaging over a period of about a year, the error increases to 30-35 %. The conclusions and correction coefficients are valid for calculations of evaporation in the Baltic Sea and can be used in other areas of middle and high latitudes, where the evaporation values do not differ by orders of magnitude (tropics, equator, zones of significant variability of environmental parameters).

ДОЛГОПЕРИОДНАЯ ИЗМЕНЧИВОСТЬ ГИДРОМЕТЕОРОЛОГИЧЕСКИХ ПАРАМЕТРОВ В АКВАТОРИИ КАСПИЙСКОГО МОРЯ. ЧАСТЬ 1: ОПИСАНИЕ ДАННЫХ

NSEP/NCAR reanalysis data for the period of 1948–2017 were used for description of the long-term variability of the hydro-meteorological parameters in the Caspian Sea (surface air temperature, sea surface temperature, wind, relative and specific humidity, precipitation rate, precipitable water). Linear trends and polynomial approximations of these parameters are presented. The latter show the nonlinear nature and periodicity of the parameters’ variability. Three time spans of 10–25 years duration with multidirectional trends of hydrometeorological parameters have been identified. The switch of wind regimes occurred 10–12 years earlier than the change of thermal and humidity regimes, which suggests the leading role of the long-term variations of the large-scale atmospheric forcing in the variability of hydrometeorological parameters in the Caspian Sea.