Snizeni zakladniho odtoku kvuli evapotranspiraci povrchove a podzemni vody z mokradu v povodi Libechovky: porovnani mereni a vypoctu Oudinovou metodou

This study is focused on the base flow decrease due to surface water and groundwater evapotranspiration (ET) in wetlands of the Liběchovka catchment. Evapotranspiration in wetlands can significantly affect stream discharge, and its influence will probably still increase in the future due to the global rise of temperatures caused by climate change.

The study site is located in the upper part of Liběchovka catchment (Fig. 1). This wetland hosts a small stream supplied by rather steady groundwater inflow, representing the favourable site for detection of the effect of ET. V notch weir and two piezometers were used to monitor stream discharge and wetland water table in 30 minute periods (Fig. 2). Diurnal periodical oscillations of water flow and water table caused by ET were observed (Fig. 3). They occurred in the summer part of the year, especially on sunny days without rain. The amplitude of water table level oscillation was increasing with increasing temperature (Fig. 4). Calculation showed that evapotranspiration reduced the water flow, on average, by 15 % on the warm sunny days. The maximum daily reduction was up to 32 %.

Direct measurements were compared with the potential ET calculated using the Oudin’s method (Oudin 2005). The ET from the measurement was 45 % of the potential ET calculated by Oudin’s method.

In the next step, the Oudin’s method was used to calculate the potential ET of all wetlands in Liběchovka catchment upstream from the Želízy village, where gauging station of ČHMÚ is situated. The original discharge not reduced by the wetland ET was defined as the sum of the wetland potential ET and the mean annual measured discharge. Due to the ET from wetlands (years 2015–2020), the discharge was reduced on average by 13 %. If only the summer months of July and August were considered, it was reduced, on average, by 26 % and by 39 % in the driest day recorded in this period.

To estimate the role of groundwater abstraction on the Liběchovka stream during the period of 2015–2020, the sum of measured stream discharge, groundwater abstraction and wetland ET was calculated. From this sum, 71.5 % represented the directly measured water flow, 18.2 % was the groundwater abstraction, and 10.3 % was the wetland ET (Fig. 8).

References

BOND, B. J. – JONES, J. A. – MOORE, G. – PHILLIPS, N. – POST, D. – McDONNELL, J. J. (2002): The zone of vegetation influence on baseflow revealed by diel patterns of streamflow and vegetation water use in a headwater basin. Hydrological Processes, 16(8), 1671–1677.

BRUTHANS, J. – KADLECOVÁ, R. – SLAVÍK, M. – KRÁLOVÁ, M. – FRYČ, T. – ČURDA, J. (2020): Příčina prudkého snížení průtoků některých vodních toků ve středních Čechách v léte 2019 a extrémně nízkých specifických odtoků: vliv evapotranspirace z příbřežní zóny toku a ploch s mělkou hladinou podzemní vody. Geoscience Research Reports 53: 47–54.

ČHMÚ (2022): Průměrná denní teplota vzduchu, denní úhrn srážek a denní úhrn doby trvání slunečního svitu [online]. Citováno 5. 3 2022, z https://www.chmi.cz/historicka-data/ pocasi/denni-data/Denni-data-dle-z.-123-1998-Sb#.

ČÚZK (2022a): Základní mapa 1 : 10 000 (ZM 10) [online]. Citováno 12. 3 2022, z https://geoportal.cuzk.cz/ (S(1rrwqvbhvmcmwksyycxa0d3o))/Default.aspx?mode= TextMeta&side=wms.verejne&metadataID=CZ-CUZK-WMS- ZM10-P&metadataXSL=metadata.sluzba&head_tab=sekce-03- gp&menu=3115.

ČÚZK (2022b): Ortofoto [online]. Citováno 5. 3 2022, z https: //geoportal.cuzk.cz/(S(wmisol4y4ucc3tdfzalc5cwn))/ Default.aspx?menu=3121&mode=TextMeta&side=wms. verejne&metadataID=CZ-CUZK-WMS-ORTOFOTO- P&metadataXSL=metadata.sluzba.

ČÚZK (2023): Základní mapa 1: 100 000 (ZM 100) [online]. Citováno 9. 3 2023, z https://geoportal.cuzk.cz/(S(ue0hdwrb fe0roybbabvjabme))/Default.aspx?menu=31171&mode=Te xtMeta&side=wms.verejne&metadataID=CZ-CUZK-WMS- ZM100-P&metadataXSL=metadata.sluzba.

Graham, C. B. – Barnard, H. R. – Kavanagh, K. l. – McNamara, J. P. (2013): Catchment scale controls the temporal connection of transpiration and diel fluctuations in streamflow. – Hydrol. Processes 27, 18, 2541–2556.

Gribovszki, Z. – Kalicz, P. – Szilágyi, J. – Kucsara, M. (2008): Riparian zone evapotranspiration estimation from diurnal groundwater level fluctuations. – J. Hydrol. 349, 1–2, 6–17.

Horáček, S. – Kašpárek, L., ed. (2011): Možnosti zmírnění současných důsledků klimatické změny zlepšením akumulační schopnosti v povodí Rakovnického potoka. – VÚV TGM. Praha.

ISVS – VODA (2022): Odběry podzemních vod. [online]. Citováno 14. 4. 2022, z https://voda.gov.cz/?page=odbery-podzemnich-vod-mapa.

Kůrková, I. et al. (2016): Rebilance zásob podzemních vod. Záv. zpráva, příl. č. 2/35: Stanovení zásob podzemních vod, hydrogeologický rajon 4522 – Křída Liběchovky a Pšovky – Čes. geol. služba. Praha. Dostupné z http://www.geology.cz/extranet/vav/prirodni-zdroje/podzemni-vody/rebilance#.

Moore, G. W. – Jones, J. A. – Bond, B. J. (2011): How soil moisture mediates the influence of transpiration on streamflow at hourly to interannual scales in a forested catchment. – Hydrol. Processes, 25, 24, 3701–3710.

Oudin, l. – Hervieu, F. – Michel, C. – Perrin, Cc. – Andréassian, V. – Anctil, F. – Loumagne, C. (2005): Which potential evapo-transpiration input for a lumped rainfall-runoff model? Part 2 – Towards a simple and efficient potential evapotranspiration model for rainfall-runoff modelling. – J. Hydrol. 303, 1–4, 290–306.

Pátek, K. (2022): Metody stanovení evapotranspirace v mokřadech a spotřeba podzemní vody evapotranspirací mokřadů v povodí Liběchovky a Pšovky. – Bakal. práce, Úst. hydrogeol., inž. geol. a užité geofyz., PřF UK. Praha.

White, W. N. (1932). A method of estimating ground-water supplies based on discharge by plants and evaporation from oil: Results of investigations in Escalante Valley, Utah. – Wat. Supply Pap. 659.