Browsing by Subject "hydrology"

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  • Bhattacharjee, Joy; Rabbil, Mehedi; Fazel, Nasim; Darabi, Hamid; Choubin, Bahram; Khan, Md. Motiur Rahman; Marttila, Hannu; Haghighi, Ali Torabi (Elsevier, 2021)
    Science of the Total Environment 797 (2021), 149034
    Lake water level fluctuation is a function of hydro-meteorological components, namely input, and output to the system. The combination of these components from in-situ and remote sensing sources has been used in this study to define multiple scenarios, which are the major explanatory pathways to assess lake water levels. The goal is to analyze each scenario through the application of the water balance equation to simulate lake water levels. The largest lake in Iran, Lake Urmia, has been selected in this study as it needs a great deal of attention in terms of water management issues. We ran a monthly water balance simulation of nineteen scenarios for Lake Urmia from 2003 to 2007 by applying different combinations of data, including observed and remotely sensed water level, flow, evaporation, and rainfall. We used readily available water level data from Hydrosat, Hydroweb, and DAHITI platforms; evapotranspiration from MODIS and rainfall from TRMM. The analysis suggests that the consideration of field data in the algorithm as the initial water level can reproduce the fluctuation of Lake Urmia water level in the best way. The scenario that combines in-situ meteorological components is the closest match to the observed water level of Lake Urmia. Almost all scenarios showed good dynamics with the field water level, but we found that nine out of nineteen scenarios did not vary significantly in terms of dynamics. The results also reveal that, even without any field data, the proposed scenario, which consists entirely of remote sensing components, is capable of estimating water level fluctuation in a lake. The analysis also explains the necessity of using proper data sources to act on water regulations and managerial decisions to understand the temporal phenomenon not only for Lake Urmia but also for other lakes in semi-arid regions.
  • Shu, Song; Liu, Hongxing; Beck, Richard A.; Frappart, Frédéric; Korhonen, Johanna; Lan, Minxuan; Xu, Min; Yang, Bo; Huang, Yan (Copernicus Publications / European Geosciences Union, 2021)
    Hydrology and Earth System Sciences Discussions 25:3
    A total of 13 satellite missions have been launched since 1985, with different types of radar altimeters on board. This study intends to make a comprehensive evaluation of historic and currently operational satellite radar altimetry missions for lake water level retrieval over the same set of lakes and to develop a strategy for constructing consistent long-term water level records for inland lakes at global scale. The lake water level estimates produced by different retracking algorithms (retrackers) of the satellite missions were compared with the gauge measurements over 12 lakes in four countries. The performance of each retracker was assessed in terms of the data missing rate, the correlation coefficient r, the bias, and the root mean square error (RMSE) between the altimetry-derived lake water level estimates and the concurrent gauge measurements. The results show that the model-free retrackers (e.g., OCOG/Ice-1/Ice) outperform the model-based retrackers for most of the missions, particularly over small lakes. Among the satellite altimetry missions, Sentinel-3 gave the best results, followed by SARAL. ENVISAT has slightly better lake water level estimates than Jason-1 and Jason-2, but its data missing rate is higher. For small lakes, ERS-1 and ERS-2 missions provided more accurate lake water level estimates than the TOPEX/Poseidon mission. In contrast, for large lakes, TOPEX/Poseidon is a better option due to its lower data missing rate and shorter repeat cycle. GeoSat and GeoSat Follow-On (GFO) both have an extremely high data missing rate of lake water level estimates. Although several contemporary radar altimetry missions provide more accurate lake level estimates than GFO, GeoSat was the sole radar altimetry mission, between 1985 and 1990, that provided the lake water level estimates. With a full consideration of the performance and the operational duration, the best strategy for constructing long-term lake water level records should be a two-step bias correction and normalization procedure. In the first step, use Jason-2 as the initial reference to estimate the systematic biases with TOPEX/Poseidon, Jason-1, and Jason-3 and then normalize them to form a consistent TOPEX/Poseidon–Jason series. Then, use the TOPEX/Poseidon–Jason series as the reference to estimate and remove systematic biases with other radar altimetry missions to construct consistent long-term lake water level series for ungauged lakes.
  • Menberu, Meseret Walle; Marttila, Hannu; Ronkanen, Anna-Kaisa; Haghighi, Ali Torabi; Kløve, Bjørn (American Geophysical Union, 2021)
    Water Resources Research 57, e2020WR028624
    Undisturbed peatlands are effective carbon sinks and provide a variety of ecosystem services. However, anthropogenic disturbances, especially land drainage, strongly alter peat soil properties and jeopardize the benefits of peatlands. The effects of disturbances should therefore be assessed and predicted. To support accurate modeling, this study determined the physical and hydraulic properties of intact and disturbed peat samples collected from 59 sites (in total 3,073 samples) in Finland and Norway. The bulk density (BD), porosity, and specific yield (Sy) values obtained indicated that the top layer (0–30 cm depth) at agricultural and peat extraction sites was most affected by land use change. The BD in the top layer at agricultural, peat extraction, and forestry sites was 441%, 140%, and 92% higher, respectively, than that of intact peatlands. Porosity decreased with increased BD, but not linearly. Agricultural and peat extraction sites had the lowest saturated hydraulic conductivity, Sy, and porosity, and the highest BD of the land use options studied. The van Genuchten-Mualem (vGM) soil water retention curve (SWRC) and hydraulic conductivity (K) models proved to be applicable for the peat soils tested, providing values of SWRC, K, and vGM-parameters (α and n) for peat layers (top, middle and bottom) under different land uses. A decrease in peat soil water content of ≥10% reduced the unsaturated K values by two orders of magnitude. This unique data set can be used to improve hydrological modeling in peat-dominated catchments and for fuller integration of peat soils into large-scale hydrological models.
  • Ahonen, Veronica (Helsingin yliopisto, 2019)
    Permafrost peatlands have the capacity to store significant amounts of carbon, and thus they act as important controllers of the climate. Approximately 14% of the world’s soil organic carbon pool is stored in permafrost peatlands, which are sensitive to climatic fluctuations due to their location in the high latitudes of the subarctic zone. Permafrost peatlands also act as a habitat for a large number of moisture-sensitive organisms, such as bryophytes and testate amoebae, which can be used to study how the hydrology of peatlands has changed and will continue to change throughout time, giving us an opportunity to predict the future of peatlands under a changing climate. In this Master’s Thesis I examined the testate amoebae composition and used these species as indicators to study hydrological fluctuations from three subarctic permafrost peatland cores extracted from Taavavuoma and Abisko in northern Sweden. The species compositions were combined with radiocarbon (14C) and lead (210Pb) dates to reconstruct the past water table levels for the late Holocene, spanning four climatic periods. The reconstructions were then compared to past studies on testate amoebae to understand how permafrost peatlands and their species assemblages respond to changes in the hydrology of the active layer of the peat. Out of the study sites only the Taavavuoma cores spanned the Dark Age Cold Period (DACP) and Medieval Climate Anomaly (MCA). Species compositions in both cores indicated fluctuating water tables during the DACP, but during the MCA the results began to contradict with one site showing a wetter, and the other a drier MCA. Two out of three study sites indicated a wetter Little Ice Age and a drier Post-Industrial Warming, supporting past studies indicating similar results, whereas one study site gave opposite results. The results indicated large variability in testate amoebae assemblages throughout time, indicating that the hydrology of peatlands can change very abruptly and vary considerably even on a local scale. Modelling is however complicated by the poorly known ecology of testate amoebae, which is why a multi-proxy approach is essential to reliably predict the future fate of permafrost peatlands.
  • Heikurainen, Leo (Suomen metsätieteellinen seura, 1963)
  • Bechtold, M.; De Lannoy, G. J. M.; Koster, R. D.; Reichle, R. H.; Mahanama, S. P.; Bleuten, W.; Bourgault, M. A.; Brümmer, C.; Burdun,; Desai, A. R.; Devito, K.; Grünwald, T.; Grygoruk, M.; Humphreys, E. R.; Klatt, J.; Kurbatova, J.; Lohila, A.; Munir, T. M.; Nilsson, M. B.; Price, J. S.; Röhl, M.; Schneider, A.; Tiemeyer, B. (2019)
    Peatlands are poorly represented in global Earth system modeling frameworks. Here we add a peatland-specific land surface hydrology module (PEAT-CLSM) to the Catchment Land Surface Model (CLSM) of the NASA Goddard Earth Observing System (GEOS) framework. The amended TOPMODEL approach of the original CLSM that uses topography characteristics to model catchment processes is discarded, and a peatland-specific model concept is realized in its place. To facilitate its utilization in operational GEOS efforts, PEAT-CLSM uses the basic structure of CLSM and the same global input data. Parameters used in PEAT-CLSM are based on literature data. A suite of CLSM and PEAT-CLSM simulations for peatland areas between 40 degrees N and 75 degrees N is presented and evaluated against a newly compiled data set of groundwater table depth and eddy covariance observations of latent and sensible heat fluxes in natural and seminatural peatlands. CLSM's simulated groundwater tables are too deep and variable, whereas PEAT-CLSM simulates a mean groundwater table depth of -0.20 m (snow-free unfrozen period) with moderate temporal fluctuations (standard deviation of 0.10 m), in significantly better agreement with in situ observations. Relative to an operational CLSM version that simply includes peat as a soil class, the temporal correlation coefficient is increased on average by 0.16 and reaches 0.64 for bogs and 0.66 for fens when driven with global atmospheric forcing data. In PEAT-CLSM, runoff is increased on average by 38% and evapotranspiration is reduced by 19%. The evapotranspiration reduction constitutes a significant improvement relative to eddy covariance measurements.
  • Leppäranta, Matti; Luttinen, Arto; Arvola, Lauri (2020)
    Shallow Antarctic surface lakes belong to the most extreme aquatic environments on the Earth. In Vestfjella, proglacial surface lakes and ponds are characterized by a 2-5 month long period with liquid water and depths <2 m. We give a detailed description of nine seasonal lakes and ponds situating at three nunataqs (Basen, Plogen and Fossilryggen) in western Dronning Maud Land. Their physical and geochemical properties are provided based on observations in four summers. Three main 'lake categories' were found: 1) supraglacial lakes, 2) epiglacial ponds and 3) nunataq ponds. Category 3 lakes can be divided into two subgroups with regards to whether the meltwater source is glacial or just seasonal snow patches. Supraglacial lakes are ultra-oligotrophic (electrical conductivity <10 mu S cm(-1), pH <7), while in epiglacial ponds the concentrations of dissolved and suspended matter and trophic status vary over a wide range (electrical conductivity 20-110 mu S cm(-1), pH 6-9). In nunataq ponds, the maxima were an electrical conductivity of 1042 mu S cm(-1)and a pH of 10.1, and water temperature may have wide diurnal and day-to-day fluctuations (maximum 9.3 degrees C) because snowfall, snow drift and sublimation influence the net solar irradiance.
  • Kurimo, Heikki (Suomen metsätieteellinen seura, 1984)
  • Yan, Dongjun (Helsingfors universitet, 2009)
    Industrial plantations of eucalyptus are sharply increasing in Asia. Although supplying raw material for the pulp and paper industry, easing deforestation on native forests and increasing carbon sequestration to help counter global warming, there are several concerns about the environmental effects of industrial eucalyptus plantations. These concerns include invasiveness of eucalyptus and loss of biodiversity, loss of land for food production, loss of soil fertility due to short rotation times and biomass removal, and excessive water-use and reduced catchment water yields. With protagonists on both sides, there is a need to research and examine the environmental effects of industrial eucalyptus plantations in southern China. We modelled and mapped the spatial distribution of water balance components across a small (752 ha) catchment in Guangxi province in relation to land-use, including industrial and local community plantations of eucalyptus and agriculture. Studies about the spatial distribution of water-use by eucalyptus across the landscape are few. WATBAL, a water balance model with a monthly time step, was parameterized and used to derive water balance components for 180 selected locations in the catchment. From the model output, continuous (predictive) surfaces for monthly (long-term average) potential (PET) and actual evapotranspiration (AET), evapotranspiration deficit (PET- AET), surface runoff and drainage below rooting zone were generated using GIS (ArcGIS 9.2). Averaged across the catchment, annual (October- September) actual evapotranspiration accounted for 77 %, surface runoff for 15 % and drainage below rooting zone for 8 % of rainfall. Differences between land-use types were relatively small, but areas of highest actual evapotranspiration and lowest surface runoff were associated with the oldest (6-7 years old) forested areas, including pure and mixed eucalyptus industrial plantations and local community, coppiced plantations on the slopes. The areas with the lowest actual evapotranspiration were associated with agricultural crops in the bottom of the catchment. The clear dominance of actual evapotranspiration in the water balance of all land-use types reflects the dominating role of the evaporative potential of the climate, with land-use cover, soil and topography factors playing secondary roles. While water-use was the highest for the forested areas, eucalyptus per se did not use more water than mixed plantations or those of the local community. Tree cover in general reduced surface runoff and therefore would reduce the risk of erosion. Using our modelling and mapping approach, we were able to assess the water-use and other components of the water balance of eucalyptus plantations and other land use types for this catchment. The study showed the importance of having suitable and adequate ground truth data in order to derive reliable and useful interpolation surfaces using ArcGIS.
  • Marttila, Hannu; Lohila, Annalea; Ala-Aho, Pertti; Noor, Kashif; Welker, Jeffrey M.; Croghan, Danny; Mustonen, Kaisa; Meriö, Leo-Juhani; Autio, Anna; Muhic, Filip; Bailey, Hannah; Aurela, Mika; Vuorenmaa, Jussi; Penttilä, Timo; Hyöky, Valtteri; Klein, Eric; Kuzmin, Anton; Korpelainen, Pasi; Kumpula, Timo; Rauhala, Anssi; Kløve, Bjørn (2021)
    Subarctic ecohydrological processes are changing rapidly, but detailed and integrated ecohydrological investigations are not as widespread as necessary. We introduce an integrated research catchment site (Pallas) for atmosphere, ecosystems, and ecohydrology studies in subarctic conditions in Finland that can be used for a new set of comparative catchment investigations. The Pallas site provides unique observational data and high-intensity field measurement datasets over long periods. The infrastructure for atmosphere- to landscape-scale research in ecosystem processes in a subarctic landscape has recently been complemented with detailed ecohydrological measurements. We identify three dominant processes in subarctic ecohydrology: (a) strong seasonality drives ecohydrological regimes, (b) limited dynamic storage causes rapid stream response to water inputs (snowmelt and intensive storms), and (c) hydrological state of the system regulates catchment-scale dissolved carbon dynamics and greenhouse (GHG) fluxes. Surface water and groundwater interactions play an important role in regulating catchment-scale carbon balances and ecosystem respiration within subarctic peatlands, particularly their spatial variability in the landscape. Based on our observations from Pallas, we highlight key research gaps in subarctic ecohydrology and propose several ways forward. We also demonstrate that the Pallas catchment meets the need for sustaining and pushing the boundaries of critical long-term integrated ecohydrological research in high-latitude environments.
  • Kurimo, Heikki (Suomen metsätieteellinen seura, 1983)
  • Ala-Aho, Pertti Otto Antero; Autio, Anna Katarzyna; Bhattacharjee, Joy; Isokangas, Elina Henriikka; Kujala, Katharina; Marttila, Hannu Juhani; Menberu, Meseret; Meriö, Jyrki Leo-Juhani; Postila, Heini Tuulia; Rauhala, Anssi Ilmari; Ronkanen, Anna-Kaisa; Rossi, Pekka Matias; Saari, Markus Tapani; Torabi Haghighi, Ali; Kløve, Björn (IOP Publishing Ltd, 2021)
    Environmental Research Letters 16: 4
    The influence of seasonally frozen ground (SFG) on water, energy, and solute fluxes is important in cold climate regions. The hydrological role of permafrost is now being actively researched, but the influence of SFG has received less attention. Intuitively, SFG restricts (snowmelt) infiltration, thereby enhancing surface runoff and decreasing soil water replenishment and groundwater recharge. However, the reported hydrological effects of SFG remain contradictory and appear to be highly site- and event-specific. There is a clear knowledge gap concerning under what physiographical and climate conditions SFG is more likely to influence hydrological fluxes. We addressed this knowledge gap by systematically reviewing published work examining the role of SFG in hydrological partitioning. We collected data on environmental variables influencing the SFG regime across different climates, land covers, and measurement scales, along with the main conclusion about the SFG influence on the studied hydrological flux. The compiled dataset allowed us to draw conclusions that extended beyond individual site investigations. Our key findings were: (a) an obvious hydrological influence of SFG at small-scale, but a more variable hydrological response with increasing scale of measurement, and (b) indication that cold climate with deep snow and forest land cover may be related to reduced importance of SFG in hydrological partitioning. It is thus increasingly important to understand the hydrological repercussions of SFG in a warming climate, where permafrost is transitioning to seasonally frozen conditions.
  • Ala-Aho, P; Autio, A; Bhattacharjee, J; Isokangas, E; Kujala, K; Marttila, H; Menberu, M; Meriö, L-J; Postila, H; Rauhala, A; Ronkanen, A-K; Rossi, P. M.; Saari, M; Torabi Haghighi, A; Kløve, B (Institute of Physics and IOP Publishing, 2021)
    Research Letters 16: 043008
    The influence of seasonally frozen ground (SFG) on water, energy, and solute fluxes is important in cold climate regions. The hydrological role of permafrost is now being actively researched, but the influence of SFG has received less attention. Intuitively, SFG restricts (snowmelt) infiltration, thereby enhancing surface runoff and decreasing soil water replenishment and groundwater recharge. However, the reported hydrological effects of SFG remain contradictory and appear to be highly site- and event-specific. There is a clear knowledge gap concerning under what physiographical and climate conditions SFG is more likely to influence hydrological fluxes. We addressed this knowledge gap by systematically reviewing published work examining the role of SFG in hydrological partitioning. We collected data on environmental variables influencing the SFG regime across different climates, land covers, and measurement scales, along with the main conclusion about the SFG influence on the studied hydrological flux. The compiled dataset allowed us to draw conclusions that extended beyond individual site investigations. Our key findings were: (a) an obvious hydrological influence of SFG at small-scale, but a more variable hydrological response with increasing scale of measurement, and (b) indication that cold climate with deep snow and forest land cover may be related to reduced importance of SFG in hydrological partitioning. It is thus increasingly important to understand the hydrological repercussions of SFG in a warming climate, where permafrost is transitioning to seasonally frozen conditions.