Predicting long-term recovery of a strongly acidified stream using MAGIC and climate models (Litavka, Czech Republic) D. W. Hardekopf, J. Horecký, J. Kopá?ek, E. Stuchlík To cite this version: D. W. Hardekopf, J. Horecký, J. Kopá?ek, E. Stuchlík. Predicting long-term recovery of a strongly acidified stream using MAGIC and climate models (Litavka, Czech Republic). Hydrology andEarth System Sciences Discussions, European Geosciences Union, 2008, 12 (2), pp.479-490. hal-00305150 HAL Id: hal-00305150 https://hal.archives-ouvertes.fr/hal-00305150 Submitted on 5 Mar 2008 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Hydrol. Earth Syst. Sci., 12, 479–490, 2008 www.hydrol-earth-syst-sci.net/12/479/2008/ Hydrology and © Author(s) 2008. This work is licensed Earth System under a Creative Commons License. Sciences Predicting long-term recovery of a strongly acidified stream using MAGIC and climate models (Litavka, Czech Republic) D. W. Hardekopf1, J. Horecky´1, J. Kopa´cekˇ 2, and E. Stuchl´ık1 1Institute for Environmental Studies, Faculty of Science, Charles University in Prague, Benatsk´ a´ 2, 12801, Prague 2, Czech Republic 2Hydrobiological Institute, Academy of Sciences of the Czech Republic, and Faculty of Biological Sciences, University of South Bohemia, Na Sadk´ ach´ 7, 37005, Ceskˇ e´ Budejovice,ˇ Czech Republic Received: 1 December 2006 – Published in Hydrol. Earth Syst. Sci. Discuss.: 11 September 2007 Revised: 18 January 2008 – Accepted: 5 February 2008 – Published: 5 March 2008 Abstract. Two branches forming the headwaters of a stream (Moldan and Schnoor, 1992; Fott et al., 1994). Large re- in the Czech Republic were studied. Both streams have sim- ductions in S and N inputs in the 1980s and 1990s have re- ilar catchment characteristics and historical deposition; how- sulted in significant reversal of acidification in some of these ever one is rain-fed and strongly affected by acid atmospheric fresh waters (Vesely´ et al., 2002). Dynamic models have deposition, the other spring-fed and only moderately acidi- been successfully applied to many catchments in the region fied. The MAGIC model was used to reconstruct past stream (Majer et al., 2003; Hruskaˇ and Kram,´ 2003; Kopa´cekˇ et al., water and soil chemistry of the rain-fed branch, and predict 2004a) and have proven to be robust in predicting changes future recovery up to 2050 under current proposed emissions in soil and water chemistry in response to the decreased de- levels. A future increase in air temperature calculated by a re- position. Future predictions based on expected atmospheric gional climate model was then used to derive climate-related emission reductions required under European Union agree- scenarios to test possible factors affecting chemical recov- ments (Gothenburg Protocol – UN-ECE, 1999), however, ery up to 2100. Macroinvertebrates were sampled from both show that recovery of these ecosystems is complicated by branches, and differences in stream chemistry were reflected continued leaching of sulphate (SO4), and in some cases ni- in the community structures. According to modelled fore- trate (NO3), from soils exposed to long-term deposition of casts, recovery of the rain-fed branch will be gradual and these compounds (Kopa´cekˇ et al., 2002; Hruskaˇ et al., 2002). limited, and continued high levels of sulphate release from Although acidification in the former Czechoslovakia was first the soils will continue to dominate stream water chemistry, recognized in the more intensively studied border mountain while scenarios related to a predicted increase in tempera- areas (Fott et al., 1987), a study on the distribution of acid- ture will have little impact. The likelihood of colonization ification in the Czech Republic (Vesely´ and Majer, 1996) of species from the spring-fed branch was evaluated consid- showed that the Brdy Mountain region in the central part of ering the predicted extent of chemical recovery. The results the country was among the most anthropogenically acidified suggest that the possibility of colonization of species from areas. The headwater region of one of the streams originat- the spring-fed branch to the rain-fed will be limited to only ing in these mountains, the Litavka River, consists of two the acid-tolerant stonefly, caddisfly and dipteran taxa in the branches in the first two kilometres. Both streams have sim- modelled period. ilar catchment characteristics and historical exposure to acid atmospheric deposition. One branch, however, is rain-fed and strongly acidified, with current pH around 4.1 and high 1 Introduction levels of reactive aluminium (AlR, sensu Driscoll, 1984). The other branch is spring-fed, and currently has an aver- Acidification of surface waters in sensitive regions due to age pH of 5.6, with low concentrations of AlR. The MAGIC extremely high emissions of sulphur (S) and nitrogen (N) model was applied to the rain-fed catchment to reconstruct compounds has been well documented in Central Europe historical soil and stream water chemistry, and to predict the possibility of the chemical recovery of this ecosystem. The Correspondence to: D. W. Hardekopf benthic macroinvertebrate communities from both branches ([email protected]) Published by Copernicus Publications on behalf of the European Geosciences Union. 480 D. W. Hardekopf et al.: Predicting long-term recovery of a strongly acidified stream 1 km Fig. 1. Map of the Czech Republic, showing the location of the Brdy Mountains and the Litavka River. The rain-fed and spring-fed branches are indicated. The star indicates the location of regular monitoring of the rain-fed branch, and the catchment is outlined. were studied, and the likelihood of colonization of species Vesely´ and Majer, 1996). The headwater of the Litavka from the spring-fed branch to the rain-fed was evaluated con- River, in the south-west part of the mountains, is composed sidering the predicted extent of this chemical recovery. of two small branches in the first approximately two kilo- Recently, the question has arisen of how predicted pat- metres. One branch is rain-fed, while the other has its main terns of global climate change might affect the course of re- source in a small spring. The rain-fed branch of the Litavka covery in sensitive ecosystems such as the Litavka. “Con- has a catchment lying at 695–843 m a.s.l. (49◦42′17′′ N, founding factors” (Wright and Jenkins, 2001) related to 13◦50′56′′ E; area 1.85 km2), and the adjacent spring-fed climate-related changes in temperature and precipitation are catchment is separated by just a small ridge. The bedrock predicted to influence the outcome of surface water re- of both branches is typical for most of the Brdy Mountains, covery. Some of these factors are changes in dissolved and consists of Cambrian sandstone, conglomerates, and organic carbon (DOC) (Freeman et al., 2001; Evans et quartzites. Acidic poor brown cambisolic soils cover both al., 2005), temperature related weathering (Sommaruga- catchments, and peat bogs occur in many areas. Much of the Wograth¨ et al., 1997), increased NO3 leaching at higher tem- original forest in the area was composed of beech with oc- peratures (Wright, 1998), and increased or more variable pre- casional fir, but was replaced by spruce monocultures, most cipitation and runoff. Though levels of acid deposition typ- likely starting before the middle of the 19th century. The ically drive acidification models, Wright et al. (2006) tested vegetation is currently dominated by Norway spruce (Picea the sensitivity of MAGIC to temperature-related parame- abies) which covers approximately 90% of the catchments, ters, such as weathering, organic decomposition, uptake of most of which are 80–90 years old; occasionally beech (Fa- base cations and nitrogen (through forest growth), precipita- gus sp.) oak (Quercus sp.) and hazel (Corylus sp.) are found tion, and production of organic acids through decomposition. in upper parts. The median stream flow of the rain fed-branch They found that in inland forested sites, including two sites in is 1.0 l s−1, though this fluctuates widely during the year the Czech Republic, increases in DOC, forest growth, and or- depending on rainfall and snow cover, ranging from non- ganic decomposition had particular relevance in affecting the flowing to extreme flood events of over 1200 l s−1. The flow future recovery of soil and water chemistry from acidifica- rate of the spring-fed branch is similar, but has lower seasonal tion. Future air temperature calculated by a regional climate variation because of the underground source of much of the model was used to derive scenarios for changes in some of water. Thus, both catchments have almost identical charac- these factors up to the year 2100. We then incorporated these teristics and exposure to deposition, and differ primarily in scenarios into the MAGIC model using forecast sequences the hydraulic regime of the streams. The two branches con- using the methods described in Wright et al. (2006). Our aim verge less than 1 km below the sampling sites, and then lead was to examine how these climate-related changes might im- into a small reservoir (Fig. 1). At the beginning of the 19th pact the course of future recovery of the ecosystem. century the streams supported brown trout (Salmo trutta – Cˇ aka,´ 1998). Currently, the reservoir supports a native pop- ulation of minnow (Phoxinus phoxinus), though introduced 2 Site description perch (Perca fluviatilis) is having a large impact on its pop- ulation (Fischer, 2005).