During hydrological research in a Chilean swamp forest, we noted a pattern of higher streamflows close to midday and lower ones close to midnight, the opposite of an evapotranspiration (Et)-driven cycle. We analyzed this diurnal streamflow signal (DSS), which appeared mid-spring (in the growing season). The end of this DSS coincided with a sustained rain event in autumn, which deeply affected stream and meteorological variables. A survey along the stream revealed that the DSS maximum and minimum values appeared 6 and 4 hours earlier, respectively, at headwaters located in the mountain forests/ plantations than at the control point in the swamp forest. Et in the swamp forest was higher in the morning and in the late afternoon, but this process could not influence the groundwater stage. Trees in the mountain headwaters reached their maximum Ets in the early morning and/or close to midday. Our results suggest that the DSS is a wave that moves from forests high in the mountains towards lowland areas, where Et is decoupled from the DSS. This signal delay seems to convert the link between streamflow and Et in an apparent, but spurious positive relationship. It also highlights the role of landscape heterogeneity in shaping hydrological processes.
This paper contains the method and results of calculation evapotranspiration and its structure - transpiration and evaporation from traditionally tilled and mulched soil. The data considered indicate that in the arid regions of territory under study the evapotranspiration when soil is mulched does not change significantly and only the relation between the transpiration and soil evaporation changes. In the wet regions, evapotranspiration decreases when the soil is mulched which can result in a certain disturbance of the natural structure of the hydrological cycle and possible overmoistening soils.
The paper introduces the Special Section on the Hydrology of the Carpathians in this issue. It is the result of an initiative of the Department of Land and Water Resources Management of the Slovak University of Technology in Bratislava, the Institute of Hydraulic Engineering and Water Resources Management of the TU Vienna and the Institute of Geomatics and Civil Engineering of the University of Sopron to allow young hydrologists in the Carpathian Basin (and from outside) to present their research and re-network on the emerging topics of the hydrology of the Carpathians at the HydroCarpath Conferences since 2012.
We apply the Linear Storage Model (LSM) to simulate the influence of the evapotranspiration on discharges. High resolution discharge data from two small catchments in the Czech Republic, the Teply Brook and the Starosuchdolsky Brook catchment are used. The results show the runoff process is simpler in a deeper valley of the Starosuchdolsky catchment where the soil zone is deeper and the valley bottom recharges runoff even during very dry periods. Two-soil zone model is adequate to simulate the diurnal runoff variability. Three-soil zone model is needed in the Teply Brook catchment due to the absence of water transport in the most-upper soil zone. Time delays between minimum and maximum discharge during the day reach up to about 20 hours. Evapotranspiration and hydraulic resistances are as high as 14% of catchment daily runoff in the urbanized Starosuchdolsky Brook catchment and 25% of catchment daily runoff in the forested, less impacted Teply Brook catchment.
Providing information on the impacts of climate change on hydrological processes is becoming ever more critical. Modelling and evaluating the expected changes of the water resources over different spatial and time scales can be useful in several fields, e.g. agriculture, forestry and water management. Previously a Budyko-type spatially distributed long-term climate-runoff model was developed for Hungary. This research includes the validation of the model using historical precipitation and streamflow measurements for three nested sub-catchments of the Zala River Basin (Hungary), an essential runoff contributing region to Lake Balaton (the largest shallow lake in Central Europe). The differences between the calculated (from water balance) and the estimated (by the model) mean annual evapotranspiration varied between 0.4% and 3.6% in the validation periods in the sub-catchments examined. Predictions of the main components of the water balance (evapotranspiration and runoff) for the Zala Basin are also presented in this study using precipitation and temperature results of 12 regional climate model simulations (A1B scenario) as input data. According to the projections, the mean annual temperature will be higher from period to period (2011–2040, 2041–2070, 2071–2100), while the change of the annual precipitation sum is not significant. The mean annual evapotranspiration rate is expected to increase slightly during the 21st century, while for runoff a substantial decrease can be anticipated which may exceed 40% by 2071–2100 relative to the reference period (1981–2010). As a result of this predicted reduction, the runoff from the Zala Basin may not be enough to balance the increased evaporation rate of Lake Balaton, transforming it into a closed lake without outflow.
Water resources are usually treated as potential resources, directly exploitable by human population on the Earth. Among them, surface water and groundwater can be effectively managed for operational use. Soil water which belongs to the class of subsurface water represents the major volume of terrestrial water resources. The concept of soil water resources as a water source for biosphere was introduced recently by Budagovsky (1985) and is related to the fact, that the soil water is the most important factor of the existence and development of terrestrial vegetation. As a measure of soil water resources, Budagovsky proposed the evapotranspiration rate from the land surface during the frostless period representing the sum of water evaporation by soil and transpiration from stomata of the leaves of terrestrial plants. The primary importance of soil water is in its role as a source of water for biosphere, for the first stage of trophic chain on the Earth. In this review, the role of soil water in biotic and abiotic cycle on the Earth is discussed. Possible directions of the future study of soil water resources in relation to the environment are proposed. and Za zdroje vody na Zemi sa považujú spravidla tie potenciálne zdroje, ktoré môžu byť využité ľudstvom priamo. Priamo môžu byť využité povrchové a podzemné vody. Najväčší objem vody súše na Zemi je reprezentovaný vodami podpovrchovými. Budagovskij (1985) navrhol koncepciu pôdnych vôd ako zdroja vody pre biosféru; táto koncepcia je založená na skutočnosti, že pôdne vody sú najvýznamnejším zdrojom vody pre suchozemskú vegetáciu. Ako mieru zdrojov pôdnej vody Budagovskij navrhol evapotranspiráciu z pevniny počas bezmrazového obdobia, ako súčet výparu z pôdy a transpirácie cez prieduchy suchozemských rastlín. Najvýznamnejšou úlohou vody v pôde je to, že je zdrojom vody pre biosféru, pre prvú časť trofického reťazca na Zemi. Táto práca pojednáva o úlohe vody v pôde v biotickom a abiotickom cykle na Zemi. Sú naznačené tiež možné smery výskumu zdrojov vody v pôde v kontexte k biosfére.
The present article demonstrates the impact of water content in the soil profile on the formation of rain-water outflow below the soil profile. The example of the soil water regime during the vegetation season is applied to show two alternative types of soil water movement: the diffusion type flow (DTF) in drier soils and the instability-driven flow (IDF) in soils with a higher soil moisture content. This responds to two phases of soil water regime alternation - the percolation phase (IDF is taking place) and the accumulation phase (DTF is taking place). In the course of the percolation phase, the infiltrating rain water flows through the soil without causing any considerable increment of water content in the soil profile. During the accumulation phase rain water accumulates in the soil, without practically flowing through the soil profile. The soil profile functions like a reservoir filled with rain water and emptied by the withdrawal of water for plant transpiration. and Príspěvek ukazuje, jak aktuální zásoba půdní vody rozhoduje o tvorbě odtoku srážkové vody z půdy do podloží. Na příkladu vodního režimu půdy ve vegetační sezóne je vyvozeno, že střídavě dochází ke dvěma odlišným typům proudění vody v půdě: proudění difuzního typu DTF v pude sušší a nestabilitou hnané proudění (perkolační) IDF v půdě vlhčí. Tomu odpovídá střídání dvou fází vodního režimu půd - fáze perkolační (probíhá IDF) a fáze akumulační (probíhá DTF). V perkolační fázi infiltrující srážková voda půdou protéká, aniž by se v ní významně akumulovala. V akumulační fázi se srážková voda v půdě zadržuje, téměř neodtéká do podloží. Půda se chová jako nádrž, která se zaplnuje srážkovou vodou a prázdní odběrem vody na transpiraci rostlin.
Basic information about the evapotranspiration and its components is presented. System of equations describing the transport of water and energy in the soil - plant continuum is analyzed. The system of five differential equations with five unknowns is proposed, describing transport of heat and water vapour within the plant canopy, including exchange processes among the leaves and the atmosphere, vertical transport of the heat, water vapour and the energy balance. and Príspevok obsahuje základné informácie o evapotranspirácii a jej zložkách, výpare a transpirácii. Proces prenosu vody a energie v systéme pôda - porast je opísaný systémom piatich diferenciálnych rovníc kvantifikujúcich prenos vodnej pary a tepla medzi listami a atmosférou, ktoré umožnujú výpočet charakteristík vertikálneho prenosu vody a tepla v poraste a tiež bilanciu energie v tomto systéme.
Evaporation of water from the soil is described and quantified. Formation of the soil dry surface layer is quantitatively described, as a process resulting from the difference between the evaporation and upward soil water flux to the soil evaporating level. The results of evaporation analysis are generalized even for the case of water evaporation from the soil under canopy and interaction between evaporation rate and canopy transpiration is accounted for. Relationships describing evapotranspiration increase due to evaporation of the water intercepted by canopy are presented. Indirect methods of evapotranspiration estimation are discussed, based on the measured temperature profiles and of the air humidity, as well as of the net radiation and the soil heat fluxes. and Príspevok obsahuje kvantitatívny opis výparu vody z pôdy a bilanciu energie počas vyparovania, charakterizovanú rovnicou obsahujúcou turbulentný tok tepla a skupenské teplo vyparovania. Je opísaný proces tvorby suchej vrstvy na povrchu pôdy počas výparu; jeho tvorba závisí od rozdielu medzi rýchlosťou výparu a prítokom vody k horizontu výparu zo spodnej vrstvy pôdy.Výsledky analýzy možno použiť aj na kvantifikáciu výparu z pôdy pod porastom. Uvádzajú sa vzťahy na výpočet zvýšenia rýchlosti evapotranspirácie, spôsobenej intercepciou. Práca obsahuje analýzu nepriamych metód výpočtu evapotranspirácie, ktoré sú založené na meraní profilov teploty a vlhkosti vzduchu nad vyparujúcim povrchom, ako aj radiačnej bilancie a tokov tepla v pôde.
Wetlands are sensitive ecosystems with groundwater table close to the soil surface and they are characteristics with specific biotops, corresponding to the continuous and high soil water content. The National Natural Reserve (NNR) Kláštorské lúky is one of those types of ecosystems in the catchment of Turiec River, Central Slovakia. Social changes in Slovakia led to the management changes of this reserve, and its consequence is replacement of original plants by invasive ones, particularly by weeds. Another unfavourable phenomenon is continuous decrease of groundwater table level, probably as a part of global changes. This work is focusing on evaluation of possible influence of changes in canopy properties due to wetland management on evapotranspiration and its structure, on soil water content changes and on changes of groundwater table level at this area. and Mokrade sú citlivé ekosystémy charakteristické výskytom hladiny podzemnej vody v blízkosti terénu alebo aj na jeho povrchu. Významným mokradným systémom je aj národná prírodná rezervácia (NPR) Kláštorské lúky, ležiaca v povodí rieky Turiec. Zmena vo vlastníckych vzťahoch spôsobila aj zmenu obhospodarovania mokrade a vzácne travinno-bylinné porasty sú postupne nahrádzané spoločenstvami inváznymi, najmä tŕstím. Ďalším nepriaznivým javom, ku ktorému došlo v poslednom období v NPR, je pokles hladiny podzemnej vody (HPV). Táto práca je zameraná na zistenie možného vplyvu manažmentu na evapotranspiráciu a jej štruktúru, na zmeny chodov HPV a na zmeny obsahu vody vo vrchnej vrstve pôdy, spôsobené nahradením pôvodného porastu trávy inváznym porastom - tŕstím.