Preface 3th Workshop "Large-scale Hydrological Modelling – Hydrological Modelling for the Assessment of Ecosystem Services and Landscape Functions", 25–27 November 2009, Dresden

No abstract available

A modeling framework to assess water and nitrate balances in the Western Bug river basin, Ukraine

The objective of this study was to assess the utility of the eco-hydrological SWAT model (Soil and Water Assessment Tool, Arnold et al., 1998) for representing water balance and nitrate fluxes given limited input and calibration data. The investigated catchment is located in Western Ukraine with an area of approximately 2616 km². Land use is currently dominated by agriculture with significant areas of pasture, and has undergone a high degree of changes in land-use and agricultural practice since the end of the Soviet Union. Model application produced a fitted water balance (calibration: <i>R</i>² = 0.52, NS = 0.46; validation: <i>R</i>² = 0.47, NS = 0.51) and plausible ranges and dynamics of nitrate in stream loadings. Groundwater parameters were found to be highly sensitive. The results indicate that SWAT is an appropriate tool for water resource investigations in the Western Bug catchment, and can provide a useful tool for further eco-hydrologic research in the region (i.e. diffuse pollution impacts)

Time series analysis of the long-term hydrologic impacts of afforestation in the Agueda watershed of north-central Portugal

The north-central region of Portugal has undergone significant land cover change since the early 1900s, with large-scale replacement of natural vegetation types with plantation forests. This transition consisted of an initial conversion primarily to Pinus pinaster, followed by a secondary transition to Eucalyptus globulus. This land cover change is likely to have altered the hydrologic functioning of this region; however, these potential impacts are not fully understood. To contribute to a better understanding of the potential hydrologic impacts of this land cover change, this study examines the temporal trends in 75 years of data from the Águeda watershed (part of the Vouga Basin) over the period of 1936–2010. A number of hydrometeorological variables were analyzed using a combined Thiel–Sen/Mann–Kendall trend-testing approach, to assess the magnitude and significance of patterns in the observed data. These trend tests indicated that there have been no significant reductions in streamflow over either the entire test period, or during sub-record periods, despite the large-scale afforestation which has occurred. This lack of change in streamflow is attributed to the specific characteristics of the watershed and land cover change. By contrast, a number of significant trends were found for baseflow index, with positive trends in the early data record (primarily during Pinus pinaster afforestation), followed by negative trends later in the data record (primarily during Eucalyptus globulus afforestation). These trends are attributed to land use and vegetation impacts on streamflow generating processes, both due to species differences and to alterations in soil properties (i.e., infiltration capacity, soil water repellency). These results highlight the importance of considering both vegetation types/dynamics and watershed characteristic when assessing hydrologic impacts, in particular with respect to soil properties

Analysis and Model-Based Assessment of Water Quality under Data Scarcity Conditions in two rural Watersheds

Pollution of surface and groundwater, due to improper land management, has become a major problem worldwide. Integrated watershed modelling provides a tool for the understanding of the processes governing water and matter transport at different scales within the watershed. The Soil Water Assessment Tool (SWAT) has been successfully utilized for the combined modelling of water fluxes and quality within a large range of scales and environmental conditions across the world. For suitable assessments integrated watershed models require large data sets of measured information for both model parameterization as for model calibration and validation. Data scarcity represents a serious limitation to the use of hydrologic models for supporting decision making processes, and may lead unsupported statements, poor statistics, misrepresentations, and, ultimately, to inappropriate measures for integrated water resources management efforts. In particular, the importance of spatially distributed soil information is often overlooked. In this thesis the eco-hydrological SWAT model was been applied to assess the water balance and diffuse pollution loadings of two rivers within a rural context at the mesoscale watershed level: 1) the Western Bug River, Ukraine, 2) the Águeda River, Portugal. Both watersheds in focus serve as examples for areas where the amount and quality of the measured data hinders a strait forward hydrologic modelling assessment. The Dobrotvir watershed (Western Bug River, Ukriane) is an example of such a region. In the former Soviet Union, soil classification primarily focused on soils of agricultural importance, whereas, forested, urban, industrial, and shallow soil territories were left underrepresented in the classification systems and resulting soil maps. Similarly the forest-dominated Águeda watershed in North-Central Portugal is a second example of a region with serious soil data availability limitations. Through the use of pedotransfer functions (PTFs) and the construction of soil-landscape models the data gaps could be successfully diminished, allowing a subsequent integrated watershed modelling approach. A valuable tool for the data gap closure was the fuzzy logic Soil Land Inference Model (SoLIM) which, combined with information from several soil surveys, was used to create improved maps. In the Dobrotvir watershed the fuzzy approach was used to close the gaps of the existing soil map, while in the Águeda watershed a new soil properties map, based upon the effective soil depths of the landscape, was constructed. While the water balance simulation in both study areas was successful, a calibration parameter ensemble approach was tested for the Águeda watershed. In the common modelling practice the individual best simulation and best parameter set is considered, the tested approach involved merging individual model outputs from numerous acceptable parameter sets, tackling the problematic of parameter equifinality. This procedure was tested for both original soil map and the newly derived soil map with differentiation of soil properties. It was noticeable that a better model set-up, with a better representation of the soil spatial distribution, was reflected in tighter model output spreads and narrower parameter distances. A further challenge was the calibration of water quality parameters, namely nitrate-N in the Dobrotvir watershed and sediment loads in the Águeda watershed. The limited amount of water quality observations were handled by assessing and by process verification at the smallest modelling unit, the hydrological response unit (HRU). The ruling hydrological processes could be depicted by combining own measured data and modelling outputs. The management scenario simulations showed the anticipated response to changes in management and reflected the rational spatial variation within the watershed reasonably well. The impacts of the different intervention options were evaluated on water balance, nitrate-N export and sediment yield at the watershed, sub-watershed and, when feasible, HRU level. This thesis covers two regional case studies with particular data limitations and specific processes of water and matter fluxes. Still, data reliability is a problem across the globe. This thesis demonstrates how relevant it is to tackle shortages of spatially differentiated soil information. The considered approaches contribute toward more reliable model predictions. Furthermore, the tested methods are transferable to other regions with differing landscape and climate conditions with similar problems of data scarcity, particularly soil spatially differentiated information

Soil Water Repellency Dynamics in Pine and Eucalypt Plantations in Portugal – A High-resolution Time Series

During the 20th century, afforestation resulted in plantations of Pine and Eucalypt becoming the main crops in north-central Portugal with associated and well-known soil water repellency (SWR). The aim of this study was to improve the insights in the temporal dynamics and abrupt transitions in water repellency of the topsoil and the mechanism that determine the behaviour of SWR. Topsoil water repellency was monitored in the Caramulo Mountains (north-central Portugal) between July 2011 and June 2012. The intensity of SWR was measured in situ at soil depths of 0, 2.5 and 7.5 cm using the ‘molarity of an ethanol droplet’ test. Volumetric soil moisture content was monitored in situ using a Decagon ECH2O EC-5 probe. SWR behaviour broadly followed five alternating dry and wet periods during the 12-month period, with more pronounced differences in the Pine site than in the Eucalypt site. SWR under Eucalypt was substantially more temporally dynamic than under Pine, with double the number of moderate and large SWR changes at the 7.5 cm depth. Soil moisture content and antecedent rainfall were better correlated to SWR under Pine than under Eucalypt, although in both cases insufficient to predict the temporal variations

Water Use of Hybrid Poplar (Populus deltoides Bart. ex Marsh × P. nigra L. “AF2”) Growing Across Contrasting Site and Groundwater Conditions in Western Slovakia

The water use by short rotation coppices (SRC) has been a focus of ongoing research in the last decades. Nevertheless, investigations that consider site factors and present long-term monitoring of the components of the water balance are rare. This research quantified the tree-based transpiration in the 4th growing season of uncoppiced 1st rotational hybrid poplar stands (Populus deltoides Bart. ex Marsh × P. nigra L. “AF2”) in western Slovakia. The aim of the study was to determine the influence of meteorological and soil-related site conditions on transpiration rates. Three experimental plots were located in the Morava River floodplains, on loamy sand-textured soils with different groundwater accessibilities: higher, low, and fluctuating groundwater level. We measured sap flow (Heat Ratio Method), volumetric water content, matric potential, groundwater level, and meteorological variables throughout the growing season in 2019. The results indicated that transpiration in the three sites was almost constant during that period, which was characterized by distinct conditions. The average cumulative transpiration at the site with a higher groundwater level (1105 mm) was larger than at the site with a lower groundwater level (632 mm) and the site with fluctuating groundwater (863 mm). A principal component analysis (PCA) and correlation analysis identified that the contribution of meteorological and soil-related site variables to transpiration differed among the sites. Soil water availability and groundwater accessibility are critical variables for the water use of poplar SRC. We concluded that the combination of site conditions needs to be reconsidered for the expansion of sustainable short rotation plantations in Europe

Monitoring of sap flow in hybrid poplar (Populus deltoides Bart. Ex Marsh x P.nigra L. "AF2") across contrasting sites and groundwater conditions, Kopcany, western Slowakia, 2019-2021

This dataset contains measurements of sap flow from the study area of the project Dendromass4Europe. Three poplar SRC stands were selected according to a gradient of groundwater accessibility: S5-N (higher groundwater level), S4-D (low groundwater level), and S2-F (fluctuating groundwater level). On each of the selected sites four trees were selected according to the tree diameter at breast height distribution.The aim of the study was to quantify the water use of clone "AF2" on sites with contrasting groundwater conditions. For the sap measurements a SFM1 sap device (Heat Ratio Method) was used at 20-minutes resolution in 2019 and 30-minutes resolution in 2021. In 2019 the sensors were installed in April and the measurements were conducted throughout the growing season until end of September. In 2021, measurements started in July and concluded in September. No measurements were conducted in growing season 2020

Monitoring of soil variables across contrasting site and groundwater conditions in Kopcany, western Slowakia, 2018-2022

This dataset contains measurements of soil moisture, soil matric potential, soil temperature, groundwater depth, and throughfall from the study area of the project Dendromass4Europe. Three poplar SRC stands were selected according to a gradient of groundwater accessibility: S5-N (higher groundwater level), S4-D (low groundwater level), and S2-F (fluctuating groundwater level). On each of the selected sites one soil profile was excavated and prepared for the installation of soil sensors. The aim of the study was to determine the influence of meteorological and soil-related site conditions on tree transpiration rates in poplar SRC stands. Soil moisture was measured with frequency domain reflectometry (FDR) sensors, with 51 mm rods. Soil matric potential and soil temperature were measured with Tensiomark sensors of a length of 125 mm, with a ceramic head. The soil profiles were excavated on May 2018 and sensors were installed as follows: four pairs of sensors of soil moisture and matric potential at 0.3 m soil depth, three pairs at 0.6 m soil depth, and two pairs at 0.9 m soil depth. In the horizontal plane, the distance between sensors was 0.15 m; the distance between pairs was 0.3 m. At the site with fluctuating groundwater level (S2-F), at 0.9 m soil depth, high gravel content prevented the installation of matric potential sensors. On each site, a groundwater well was excavated at a distance of three meters from the soil pit. The fluctuations in groundwater level were recorded with a KELLER pressure sensor. Throughfall collectors were built at 1 m height above ground. The measurements started in June 2018 (in the case of fluctuations of groundwater level: December 2018) with a resolution of 15 minutes until middle of March 2020 (16.03.2020) and after that with a resolution of 60 minutes until end of May 2022 (31.05.2022)

Monitoring of sap velocity in hybrid poplar (Populus deltoides Bart. Ex Marsh x P.nigra L. "AF2") across contrasting sites and groundwater conditions, Kopcany, western Slowakia, 2019-2021

This dataset contains measurements of sap velocity and sap flow from the study area of the project Dendromass4Europe. Three poplar SRC stands were selected according to a gradient of groundwater accessibility: S5-N (higher groundwater level), S4-D (low groundwater level), and S2-F (fluctuating groundwater level). On each of the selected sites four trees were selected according to the tree diameter at breast height distribution.The aim of the study was to quantify the water use of clone "AF2" on sites with contrasting groundwater conditions. For the sap measurements a SFM1 sap device (Heat Ratio Method) was used at 20-minutes resolution in 2019 and 30-minutes resolution in 2021. In 2019 the sensors were installed in April and the measurements were conducted throughout the growing season until end of September. In 2021, measurements started in July and concluded in September. No measurements were conducted in growing season 2020