Uwe Grünewald

Water resources management in river catchments influenced by lignite mining

Abstract Open-pit lignite mining is a dominant economic sector in several parts of Germany. The various German lignite mining districts are characterized by specific geological, geographical, hydrological and other conditions leading to different technological solutions, ecological consequences and social impacts in the regions concerned. Generally, the effects for the regional groundwater and surface water resources are substantial. High pumping rates of mining water over many years and the need for restoration of more or less original hydrological conditions state serious problems to the regional water resources management regarding quantity and quality of groundwater and surface water. With the drastic decline of lignite mining in the former GDR after 1989, reliable management tools and methods are required to minimize negative consequences for water quantity and quality conditions. Special efforts are undertaken in the affected catchment areas of the Spree and Schwarze Elster Rivers in the Lower Lusatian lignite mining district.

The year-long unprecedented European heat and drought of 1540 – a worst case

The heat waves of 2003 in Western Europe and 2010 in Russia, commonly labelled as rare climatic anomalies outside of previous experience, are often taken as harbingers of more frequent extremes in the global warming-influenced future. However, a recent reconstruction of spring–summer temperatures for WE resulted in the likelihood of significantly higher temperatures in 1540. In order to check the plausibility of this result we investigated the severity of the 1540 drought by putting forward the argument of the known soil desiccation-temperature feedback. Based on more than 300 first-hand documentary weather report sources originating from an area of 2 to 3 million km2, we show that Europe was affected by an unprecedented 11-month-long Megadrought. The estimated number of precipitation days and precipitation amount for Central and Western Europe in 1540 is significantly lower than the 100-year minima of the instrumental measurement period for spring, summer and autumn. This result is supported by independent documentary evidence about extremely low river flows and Europe-wide wild-, forest- and settlement fires. We found that an event of this severity cannot be simulated by state-of-the-art climate models.

Trends in water demand and water availability for power plants—scenario analyses for the German capital Berlin

The availability of electric power is an important prerequisite for the development or maintenance of high living standards. Global change, including socio-economic change and climate change, is a challenge for those who have to deal with the long-term management of thermoelectric power plants. Power plants have lifetimes of several decades. Their water demand changes with climate parameters in the short and medium term. In the long term, the water demand will change as old units are retired and new generating units are built. The present paper analyses the effects of global change and options for adapting to water shortages for power plants in the German capital Berlin in the short and long term. The interconnection between power plants, i.e. water demand, and water resources management, i.e. water availability, is described. Using different models, scenarios of socio-economic and climate change are analysed. One finding is that by changing the cooling system of power plants from a once-through system to a closed-circuit cooling system the vulnerability of power plants can be reduced considerably. Such modified cooling systems also are much more robust with respect to the effects of climate change and declining streamflows due to human activities in the basin under study. Notwithstanding the possible adaptations analysed for power plants in Berlin, increased economic costs are expected due to declining streamflows and higher water temperatures.

Adaptation strategies to global change for water resources management in the Spree river Catchment, Germany

Abstract Computer models for long‐term simulations of water resources management strategies are used in the analysis of water availability problems in river basins. Such models can also be used for the examination of global change impacts, which are characterised by changed natural water yield and water demand due to climate and socio‐economic changes. Already existing water quantity and water quality problems in the catchments of the river Spree and the river Schwarze Elster were analysed in the context of global change. The main water quantity issues are caused by the future development of the mining industry and climate change. The effects of these future developments were analysed using the long‐term water resources management model WBalMo. Subsequently, adaptation strategies were defined in co‐operation with the relevant stakeholders and their effects analysed with the same model. The results show that continuation of the existing water resources management strategy will not be able to compensate for the impacts of global change. However, a changed management strategy might compensate the impacts for some users.

Tree-rings and people – different views on the 1540 Megadrought. Reply to Büntgen et al. 2015

Buntgen et al. (2015; hereinafter B15) present the result of new research which question the results of Wetter et al. 2014, (hereinafter W14) and Wetter et al. (2013, hereinafter W13)regarding European climate in 1540. B15 conclude from tree-ring evidence that the results based on documentary data of W14 probably overstated the intensity and duration of the 1540 drought event. W14 termed it Megadrought because of its extreme duration and spatial extent compared to other drought events in central Europe, although they note that the term is generally used for decadal rather than for single-year droughts (Seneviratne et al. 2012). We take the opportunity to recall the following issues. Firstly, when dealing with drought the complexity of this phenomenon should be kept in mind. Meteorological drought defined as a large negative precipitation anomaly during a certain period can trigger agricultural, hydrological, groundwater and socioeconomic droughts. Lloyd-Hughes (2013] and references cited herein) concluded that any workable objective definition of drought does not exist. To quantify droughts, various indices based on precipitation, temperature and evapotranspiration are used such as the Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI), Z-index and PDSI. Their calculation depends on different periods (seasons, combination of months) and so different indices may classify the same drought episode differently (e.g. Brazdil et al.2014).

Potential impacts of climate change and regional anthropogenic activities in Central European mesoscale catchments.

Abstract The Soil and Water Integrated Model (SWIM) was used to assess potential climate and land-use change impacts in the Central European catchments of Schwarze Elster, Spree and Lusatian Neisse which are heavily influenced by opencast lignite mining. To account for potential climate change, scenarios of two statistical regional climate models, STAR and WettReg, were used. Regional anthropogenic change was considered in terms of increasing cultivation of energy crops (oilseed rape, silage maize, sunflower and sorghum) and decreasing mining activities (decreasing groundwater depression cone). In the climate scenarios, decreased natural discharge, by up to 60% in the long-term average, was simulated. In simulations with climate scenarios and oilseed rape, this effect is halved; the other energy crops have a small additional impact on discharge. The decreasing groundwater depression cone slightly compensates for climate change impacts. Overall, potential impacts of regional anthropogenic activities are secondary to those of climate change. Editor Z.W. Kundzewicz; Guest editor M. White

Nutzung von Standortuntersuchungen zur verbesserten Quantifizierung des regionalen Wasserhaushalts der Lausitz (Teilprojekt 9)

Fur Prognosen der Wiederherstellung des durch den Braunkohletagebau stark beeinflussten Wasserhaushalts der Lausitzer Region sind u. a. Aussagen uber die Grundwasserneubildung in hoher raumlicher und zeitlicher Auflosung notwendig. Neben rekultivierten Flachen bleiben auch grose, sich selbst uberlassene, Kippenareale ohne wesentliche Vegetation erhalten, deren Beitrag zur Grundwasserneubildung weitgehend unbekannt ist. Die vorgestellten Untersuchungen wurden in einem solchen Bereich der Tagebaukippe Schlabendorf-Nord durchgefuhrt. Die mehrjahrigen kontinuierlichen Gelandemessungen fuhrten zur schrittweisen Prozesserkennung.

Trend analysis for integrated regional climate change impact assessments in the Lusatian river catchments (north-eastern Germany)

Trend analysis on observations and model-based climate change simulations are two commonly used methods for climate change detection and impact analysis. Here we propose an integrated assessment and interpretation of climate change impacts as a prerequisite for stakeholder outreach and planning of suitable climate change adaptation measures. The assessment includes (i) identifying trends in meteorological and hydrological observations and their nature, (ii) analysing the relation between the meteorological drivers and generated run-off as an integrated catchment response and (iii) analysing how hitherto changes agree with the simulations by regional climate models (RCMs). The Lusatian river catchments of Spree and Schwarze Elster, characterised by high anthropogenic impact (e.g. mining activities) and low natural water yield, serve as study areas. The results of this study suggest that increases in observed temperature and potential evapotranspiration are robust while observed precipitation remained nearly unchanged (1963–2006). The RCMs agree on simulating a temperature increase but simulate opposing trends for precipitation for both past (1963–2006) and future (2018–2060) periods, the latter inducing differences in the hydrological response (actual evapotranspiration and run-off). For stakeholder outreach, we communicated a range of potential future climates and identified the statistical RCMs (STAR, WettReg) as warm and dry scenarios, and the dynamical RCMs (REMO, CCLM) as wet scenarios. Ultimately, the combined analysis of trends in observations and simulation models can be beneficial for stakeholder outreach and may increase their willingness to plan and implement suitable climate change adaptation strategies which are urgently needed within the Lusatian river catchments.

Klimawandel und Wasserhaushalt

Die kostengunstige Deckung des Wasserbedarfs der Nutzer bei gleichzeitiger Erhaltung der Okosystemfunktionen von Gewassern stellt eine stetig zu erfullende Aufgabe der Wasserwirtschaft dar. Eine nachhaltige Bewirtschaftung hoch beanspruchter Wasserressourcen-Systeme ist dabei nur mOglich, wenn fortlaufend solche Methoden und Verfahren evaluiert und weiterentwickelt werden, die Veranderungen und Anpassungen des Wasserwirtschaftssystems erlauben. Es gilt, Wasserdargebot und Wasserbedarf durch dargebotsund/ oder bedarfsorientierte Einflussnahmen unter minimalen Kosten bzw. bei maximaler Nachhaltigkeit in ubereinstimmung zu bringen (Grunewald 2008a; Abb. 2-1).

Potential impacts of climate change on natural and managed discharges of the Rivers Spree, Schwarze Elster and Lusatian Neisse, Central Europe

The water balance of the Rivers Spree, Schwarze Elster and Lusatian Neisse is profoundly disturbed due to large-scale open-cast lignite mining activities and water management. Together with continental climate conditions this affects water resources and water users in the region. Driven by scenarios of the regional climate model STAR which assume increasing temperature and decreasing precipitation, two hydrological models, the Soil and Water Integrated Model SWIM and the catchment model EGMO simulate declining natural discharges in the region. Thus, decreasing managed discharges are simulated with the long term water management model WBalMo. The refinement of the simulation time step of WBalMo from months to weeks improves the consideration of climate variability and is also associated with higher simulated managed discharges in early summer. Management scenarios in terms of a reduced outlet capacity of a mining lake reservoir result in higher releases from other reservoirs and slightly reduced summer discharges in downstream river sections.