Erik P. Querner

Eco-Hydrological Functioning of the Biebrza Wetlands: Lessons for the Conservation and Restoration of Deteriorated Wetlands

Human activities have led to the loss of a large proportion of biodiversity in riverine wetlands in western Europe (Van Urk 1984; Cirujano et al. 1996). In the second half of the twentieth century, many floodplains, fens, and riparian woodlands were cultivated for agricultural purposes. In addition, the remain- ing riverine wetlands lost species due to the impact of human activities (Rich and Woodruff 1996; McCollin et al. 2000). Recently, policy has become more focused on conservation of the remaining wetlands and on rehabilitation of disturbed rivers and floodplains (Jongman 1998). The management and reha- bilitation of wetlands is difficult without adequate knowledge of the hydrolog- ical and ecological processes responsible for the functioning and biodiversity of undisturbed wetlands.

Surface water sanitation and biomass production in a large constructed wetland in the Netherlands

In Western-Europe, agricultural practices have contributed to environmental problems such as eutrophication of surface and ground water, flooding, drought and desiccation of surrounding natural habitats. Solutions that reduce the impact of these problems are urgently needed. Common reed (Phragmites australis) is capable of sanitizing surface water and may function as green energy source because of its high productivity. Here, the results of an experiment in a constructed wetland in the Netherlands are presented where two different sanitation treatments were compared. Depending on the residence time and volume per unit area, reed is capable to reduce the total amount of nitrogen in the water with average efficiencies from 32 to 47% and the total amount of phosphorous with 27–45%. Although biomass production still varies largely between different parts of the constructed wetland, a rapid increase in biomass was observed since planting. Constructed wetlands with reed provide opportunities to improve water quality and reed produces enough biomass to serve as green energy source. Moreover, these wetlands also function as a flood water reservoir and are possibly advantageous for biodiversity. The optimal moment of reed harvesting depends on the goal of the owner. This moment should be chosen wisely, as it may have consequences for reed filter regeneration, biomass production, biodiversity, methane emission and water sanitation efficiency.

Flood generation and classification of a semi-arid intermittent flow watershed: Evrotas river

Hourly water level measurements were used to investigate the flood characteristics of a semi-arid river in Greece, the Evrotas. Flood events are analysed with respect to flood magnitude and occurrence and the performance of Curve Number approach over a period of 2007–2011. A distributed model, Soil and Water Assessment Tool, is used to simulate the historic floods (1970–2010) from the available rainfall data, and the performance of the model assessed. A new flood classification method was suggested the Peaks-Duration Over Threshold method that defines three flood types: ‘usual’, ‘ecological’ and ‘hazardous’. We classify the basin according to the flood type for the most serious past simulated flood events. The proportion of hazardous floods in the main stream is estimated to be 5–7% with a lower figure in tributaries. Flood Status Frequency Graphs and radar plots are used to show the seasonality of simulated floods. In the Evrotas, the seasonality pattern of hazardous flood is in agreement with other studies in Greece and differs from other major European floods. The classification in terms of flood types in combination with flood type seasonality is identified as an important tool in flood management and restoration.

Possibilities to restore natural water regime in the Žuvintas Lake and surrounding wetlands ‐ modelling analysis approach

Abstract The Žuvintas Lake, located in southern Lithuania in the basin of the Dovine River is one of the biggest lakes and the oldest natural reserves of the country. However, the changes in the hydrology of the Dovine River basin, caused by large‐scale melioration and water management works carried out in the 20th century, have resulted in significant alteration of hydrological regime and decrease in biodiversity of the Žuvintas Lake and surrounding wetlands. In order to prevent the ongoing deterioration of the Lake and wetlands solutions have to be found. Therefore, various scenarios have been analysed to evaluate the impact of water management alternatives. For these scenarios the physically‐based distributed parameter model SIMGRO was used. The results have shown that natural water regime in the Žuvintas Lake is hardly reversible. However, the replacement of sluice‐gates implemented at the outlet of the Žuvintas Lake by overflow weir as well as the blocking of drainage ditches and the removal of scrub...

Hydrological effects of water management measures in the Dovinė River basin, Lithuania

Abstract Lake Žuvintas, located in southern Lithuania in the Dovinė River basin, is one of the largest lakes and oldest nature reserves in the country. However, changes in the hydrology of the Dovinė River basin, caused by large-scale land reclamation and water management works carried out in the 20th century, have resulted in a significant decrease in the biodiversity of the lake and surrounding wetlands. In order to halt the ongoing deterioration of the lake and wetlands, solutions have to be found at the basin level. Using the SIMGRO model, various measures were therefore analysed to evaluate their impact on the water management in the Dovinė River basin. The results show that it is impossible to fully restore the water dynamics and flow pattern in the Dovinė River to their original state. However, a good measure for improving the hydrological conditions is to block drainage ditches and remove bushes and trees from the wetlands.

Water management measures analysed for Dutch basins to reduce flooding

Water management measures analysed for Dutch basins to reduce flooding Flooding in the northern part of The Netherlands has caused serious economic threats to densely populated areas. Therefore a project has been carried out in a pilot area to assess the retention of water in two river basins as a way to reduce flooding. The physically-based groundwater and surface water model SIMGRO was used to model the hydrology of the basins. The model was calibrated using discharges and groundwater levels. Scenarios of measures to assess the possibility of retaining water in the basin were then defined and tested. The first measure was the retention of higher discharges using culverts or gates in the upstream part of the basin. The second measure was to make the streams shallower and thereby, increase flood plain storage. The last measure was flood water storage in a designated area in the downstream part of one basin. The analysis indicates that holding water in the upstream parts of the basins proved to be feasible and can result in significant reductions of peak flows. Analiza sposobów gospodarki wodnej zmierzających do ograniczenia powodzi na przykładzie zlewni holenderskich Powodzie w północnej części Holandii stwarzają poważne zagrożenie ekonomiczne dla gęsto zaludnionych obszarów. Dlatego też na obszarze pilotowym podjęto badania, mające na celu ocenę retencji wody jako sposobu ograniczenia powodzi w dwóch zlewniach rzecznych. Warunki hydrologiczne zlewni zobrazowano wykorzystując model SIMGRO w odniesieniu do wód podziemnych i powierzchniowych. Model kalibrowano za pomocą odpływów i poziomów wód gruntowych. Następnie zdefiniowano i testowano różne warianty sposobów oceny możliwości retencjonowania wody w zlewni. Pierwszym sposobem była retencja dużych przepływów wody za pomocą przepustów i zastawek w górnej części zlewni. Drugi sposób polegał na wypłycaniu cieków i zwiększeniu pojemności tarasów zalewowych. Ostatnim sposobem było przetrzymywanie wód powodziowych na specjalnie przeznaczonych do tego terenach w dolnej części jednej ze zlewni. Wyniki analizy dowodzą, że zatrzymywanie wody w górnej części zlewni było wykonalne i mogło spowodować znaczące zmniejszenie fali powodziowej.

Hydrological analysis for meeting climate change effects and European Water Framework Directive targets

Hydrological analysis for meeting climate change effects and European Water Framework Directive targets The very wet conditions of recent years in Europe have made it clear that measures will have to be taken in this century to prevent flooding. The question is how to manage groundwater in order to reduce the anticipated increased hydrological risk. Furthermore the surface water quality in the Netherlands is insufficient to meet the standards of the Water Framework Directive. The required improvements are difficult to reach, because the diffuse loads of nutrients from agricultural land can not be easily reduced. This demands for innovative solutions with respect to improve the surface water quality. In this pilot study the focus is on the purification in reed fields and use it as well to reduce the effects of the anticipated climate change. An experimental evidence on a practical scale is lacking and therefore in the woodland area of Lankheet in the eastern part of the Netherlands, 3 ha has been planted with reeds to purify the river water. The aim of the study is further to store the purified water in the groundwater in order to reduce climate change effects. For the hydrological situation a scenario study was set up, using a regional hydrological model to simulate the groundwater flow together with the water flow in a network of water courses. The analysis will give knowledge on the multifunctional use of such a system. Analiza hydrologiczna w obliczu skutków zmian klimatu i wymogów europejskiej Ramowej Dyrektywy Wodnej Bardzo wilgotne ostatnie lata w Europie uświadomiły nam, że w bieżącym stuleciu należy podjąć kroki w celu zapobiegania powodziom. Pytanie, jak gospodarować wodami gruntowymi, aby zredukować przewidywany wzrost ryzyka hydrologicznego, pozostaje otwarte. Ponadto, jakość wód powierzchniowych w Holandii nie spełnia wymogów Ramowej Dyrektywy Wodnej. Trudno osiągnąć wymaganą poprawę, ponieważ niełatwo ograniczyć rozproszone ładunki pierwiastków biogennych z terenów rolniczych. Sytuacja ta wymaga innowacyjnych rozwiązań w odniesieniu do jakości wód powierzchniowych. Przedstawione badania koncentrują się na oczyszczaniu wód w trzcinowisku i jednoczesnym wykorzystaniu go do ograniczenia skutków przewidywanych zmian klimatycznych. Z powodu braku eksperymentalnych danych w skali praktycznej, obsadzono trzciną 3 ha leśnego terenu w Lankheet we wschodniej Holandii. Celem tego projektu było następnie przetrzymanie oczyszczonych w ten sposób wód w wodach podziemnych celem ograniczenia skutków zmian klimatycznych. Dla takiej sytuacji hydrologicznej ustalono scenariusz badawczy z wykorzystaniem regionalnego modelu hydrologicznego, symulującego przepływ wód gruntowych w powiązaniu z przepływem wody w sieci cieków. Analiza wyników dostarczy danych do poznania wielofunkcyjnego wykorzystania takich systemów.

Simulating streamflow variability and aquatic states in temporary streams using a coupled groundwater-surface water model

Abstract In order to apply the EU Water Framework Directive for temporary streams, it is important to quantify the space–time development of different aquatic states. We report on research on the development of aquatic states for temporary streams in the Evrotas basin, Greece. The SIMGRO regional hydrological model was used in a GIS framework to generate flow time series for the Evrotas River and all major tributaries. Five flow phases were distinguished: flood conditions, riffles, connected pools, isolated pools and dry bed conditions. Thresholds based on local hydraulic characteristics were identified per stream reach and flow phase, enabling the frequency of flow phases per month and the average frequencies for all streams to be derived. Three historical scenarios within the 20th century, marking periods of major changes in water management, were investigated. Additionally, a climate scenario for the 2050s was analysed. Simulations revealed that low flows are now much lower, mainly because more groundwater is abstracted for irrigation. The consequence is that stretches of the river fall dry during several months, causing the ecological status to deteriorate. Editor Z.W. Kundzewicz Associate editor X. Chen

The analysis of the impact of small retention on water resources in the catchment

Abstract The aim of this study was to analyse the impact of selected small water retention measures on surface and groundwater level in river basins. The study was limited to the analysis of measures like small water reservoirs, restoration of bogs and reconstruction of drainage systems in the river valleys. A few study cases were described. Dutch SIMGRO numerical model describing the regional surface water and groundwater flow has been used for simulation modelling of different cases. The result of the study has shown that small retention measures are a good and effective method to increase the ability to retain water in the small river basins. Construction of small water reservoirs and weirs on ditches and creeks and restoration of drained bogs can limit the fast outflow of precipitation and melting water from the catchment. The study has proved that the small water retention measures can be helpful for flood protection and in decreasing of drought threats in small river basins. Omówiono wpływ wybranych działań małej retencji na ograniczenie zagrożeń powodowanych suszą lub powodzią. Na podstawie badań modelowych oceniono wpływ małych zbiorników wodnych i piętrzeń wody w sieci rowów na odpływ rzeczny oraz poziom zwierciadła wód gruntowych. Zwiększenie potencjalnej zdolności retencyjnej zlewni rzecznej może być osiągnięte różnymi metodami. Skuteczna jest budowa małych zbiorników wodnych oraz budowli piętrzących wodę i ograniczających szybki odpływ wód opadowych i roztopowych. Renaturyzacja obszarów bagiennych poprzez likwidację systemu odwadniającego, a również hamowanie odpływu wody w dużych zlewniach nie wywiera istotnego wpływu na reżim hydrologiczny zlewni. Może natomiast znacznie poprawić warunki wodne niezbędne do zachowania walorów przyrodniczych cennych obszarów mokradłowych. Wskazana jest modernizacja istniejących systemów melioracji dolinowych w celu umożliwienia racjonalnego gospodarowania miejscowymi zasobami wody. Przynosi to korzyści rolnictwu, jak również środowisku przyrodniczemu, w tym ochronie zasobów wody. Przedstawione wyniki badań wpisują się we współczesny trend unowocześnienia i reorganizacji zasad gospodarowania wodą, szczególnie na terenach rolniczych, ale również na obszarach zurbanizowanych. Cechą charakterystyczną tego trendu jest retencjonowanie wody na obszarach powstawania zasobów wody. Zatrzymywanie wody z opadów atmosferycznych, topnienia śniegu w zlewni, w tym na terenach rolniczych, leśnych i zurbanizowanych, jest podstawowym elementem ograniczania skutków suszy i ochrony przed zwiększaniem się maksymalnych przepływów powodziowych.

Modelling of Groundwater Fluctuations in the Area Between the Narew and Suprasl Rivers

The main goal of this paper is to explore by hydrological modelling the groundwater system on both sides of the watershed boundary between the rivers Narew and Supraśl, North-East Poland and the influence of two nearby peat mines. An integrated model of the area was set up using the SIMGRO program. The aim of the model simulations was to estimate the historic hydrological situation of the area. The current groundwater levels were simulated as well as scenarios were investigated, which were based on blocking all drainage canals in the area of the two peat mines. The research proves that the watershed boundary between the Narew and the Suprasl River corresponds to the division of groundwater basins. Significant influences of the peat mines on groundwater levels are noticeable only in the close surroundings of the mines.