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Drained peatlands have peculiar hydrological properties and cause environmental concerns due to carbon dioxide emissions and nutrient fluxes resulting from decomposition of organic matter in peat. As peat degradation is strongly controlled by soil moisture conditions, it is assumed that flexible water management methods, such as controlled drainage, can be used to reduce the environmental impacts of drained peatlands in agriculture. While peat soils have been extensively researched, there is a need for increased understanding about the hydrological responses of peatlands to various water management schemes. Research is needed to quantify these responses, and a promising approach is to exploit simulation models for describing peatland hydrology at field scale. The goal was to calibrate and validate a hydrological model FLUSH to describe the hydrology of an agricultural field block having a shallow peat cover and managed with controlled drainage. FLUSH is a spatially distributed three-dimensional (3D) process model which simulates the hydrology of agricultural fields managed with controlled subsurface drains and open ditches. The soil description of FLUSH includes both soil matrix and macropores accounting preferential flow. Richards equation and Mualem-van Genuchten water retention model are applied for subsurface flow. The modeled field block is located in Ruukki, northwestern Finland, and the study period was from August 2018 to October 2021. Groundwater table depth and drain discharge observations were used for the calibration and validation. The Kling-Gupta efficiencies for the simulated groundwater table depths in soil matrix and macropore domains were 0.50 and 0.47, respectively, during the calibration period, and 0.23 and 0.33 during the validation period. The efficiency values for the simulated drain discharge during the calibration and validation periods were 0.18 and 0.19, respectively. Limiting the modeled area to the block lead to cumulative drain discharges clearly smaller than the observations. The underprediction was improved by extending the modeled area beyond the block, which suggested a presence of a hydrological connection in terms of groundwater flux originating from outside the block. Thus, the surrounding environment can play a role in the hydrology of peatland fields, and this should be considered in water management design. Despite the large difference between observed and simulated cumulative drain discharges, the main hydrological dynamics were captured, and the model formed a useful tool to simulate drainage scenarios in peatlands and to study the role of the surrounding areas on field hydrology.

Nature-based solutions and similar natural water retention measures to manage urban runoff are often implemented by cities in order to reduce runoff peaks, catch pollutants, and improve sustainability. However, the performance of these stormwater management solutions is relatively rarely assessed in detail prior to their construction, or monitored and evaluated following implementation. The objective of this study was to investigate the field-scale performance of road runoff filters with respect to the management of stormwater quantity and quality. This study synthesizes data from two intensive measurement surveys after the construction of sand and biochar-amended road runoff filters. The filters were able to strongly control the runoff volume and shape of the hydrograph. The long-term retention was about half that of the water inflow, and a hydrographic analysis showed the significant but strong event-size-dependent detention of runoff in both the sand and the sand–biochar filters. The biochar amendment in the filter showed no clear hydrological impact. The pollutant attenuation of the implemented road runoff filters was modest in comparison with that observed under controlled conditions. The impact of the biochar layer on the effluent water quality was observed as the levels of phosphorous, organic carbon, K, Ca and Mg in the sand–biochar filter effluent increased in comparison with the sand filter.

Aqueous film-forming foams (AFFFs) containing perfluoro-octane sulfonate (PFOS) were commonly used in fire trainings until the awareness of their toxicity started to increase in the 2000s. ...

Groundwater : : journal of the Association of Ground-Water Scientists and Engineers, a division of the National Ground Water Association (2021). doi:10.1111/gwat.13087, Published by Wiley-Blackwell, Oxford [u.a.]

Decentralized urban runoff management requires detailed information about pollutant sources and pathways. However, scarce data of local water quality compel simplified approaches in water quality modelling. This study investigated the use of constant source concentrations in modelling pollutant loads. The source area contributions of total suspended solids, total phosphorus, total nitrogen, lead, copper and zinc were modelled with SWMM based on literature event mean concentrations (EMCs) for different land cover types and on-site rainfall and discharge data for a residential area in southern Finland. The simulated pollutant loads were compared with loads measured at the catchment outlet. Large differences were evident in the modelled catchment-scale and land cover specific loads, depending on the EMC data source. The simulated loads exceeded the measured loads especially during wet conditions, which was explained by the dilution effect of large stormwater volumes on measured EMCs. In addition, the mismatch was explained by the lack of local data for the source area EMCs and by the unaccountability of the mechanisms affecting loads along the pollutant pathways from source areas to sewer outlet. The spatial simulation of stormwater pollutant loads enabled the assessment of source area contributions at the catchment scale, as well as the pollutant pathways and the total diffuse pollution load. For a single pollutant, one or two important pollutant sources contributed the majority of the catchment load, which provides useful information for stormwater management. However, for a group of pollutants, no single land cover type dominated the pollutant loads, reflecting the challenges in decentralized water quality management in the scale of a residential area. Overall, the results emphasize that the widely used stormwater quality modelling with constant EMCs is uncertain even when on-site water quality and rainfall-runoff data from a catchment outlet are available.

Climate change is projected to result in higher temperatures, higher annual precipitation and more uneven distribution of precipitation in the northern regions. This requires adaptation in agriculture where both excessively wet and dry cycles pose challenges to cropping. Until now, water management in northern agricultural fields has been resting primarily on efficient drainage, but interest towards more flexible measures has increased.This study focuses on the hydrological effects of climate change and controlled drainage operated with subsurface drains and an open collector ditch in an agricultural field. The objective was to computationally estimate how groundwater levels and water balance respond to controlled drainage and open ditch scenarios in climate conditions projected to take place in Finland during this century. A hydrological model FLUSH was used to simulate the hydrology of an experimental field in Sievi, Northern Ostrobothnia, Finland during years 1970–2100. Down-scaled climate projections from EURO-CORDEX (RCP 8.5 and RCP 2.6) were used as meteorological input. The temporal development of the field hydrology and the effects of controlled drainage were examined by dividing the time series into four subsequent time intervals (historical period and three future periods).Two different control scenarios were studied. Drainage intensity was reduced during growing seasons in summers (Jun.–Aug.) and either in autumn (Oct.–Nov.) or from autumn to spring (Oct.–Mar.). During these periods, groundwater table was on average 17–29 cm, 28–30 cm and 36–40 cm higher, respectively, in the control scenarios when compared to conventional subsurface drainage in different study intervals and emission scenarios. The implementation of controlled drainage reduced annual drain discharge by 21–46 mm. The projected temporal evolution of the effects of controlled drainage on groundwater levels and annual drain discharges were not monotonous, but the projected effects were larger during the future periods when compared to the historical period. Controlled drainage effect on groundwater levels was seen during both dry and wet years. Controlled drainage was assessed to be an effective method to control field water processes currently and in the future decades. The open collector ditch lowered groundwater levels within a distance of 115 m from the ditch.

Urbanization modifies the natural water cycle particularly by reducing the water storage capacity. We analysed the storage capacity of three stormwater management designs in south-western Finland to demonstrate how an urban catchment releases stormwater and how storage contributes to flood resilience. The analysis relies on EPA SWMM5.1 simulations of water balance for a seven-month period including two extreme rain events during the summer and autumn. The enhanced storage capacity provided by the designs increased resilience against flooding and released stormwater with slower rates leading to reduced peak flows. Even the design with the least storage (10% LID coverage) was efficient at regulating floods due to controlled flow in a vegetated swale, whereas the design with the highest storage capacity (60% LID coverage) demonstrated the possibility of restoring nearly natural water cycle in urban catchments. The study suggests storage capacity can act as a flood resilience indicator directly linked with the physical catchment characteristics.

The trenchless (T0) and trencher (T1) drainage installation methods are widely applied in Finland. There is an ongoing debate and a lack of science-based information about the performance differences between the methods. The objective was to assess drainage performance differences between T0 and T1 by analyzing groundwater table observations from field sections drained with the two methods. The differences were studied by using statistical analysis over a two-year period after the drainage installation. An experimental field in middle-Finland was divided into four T0 sections and four T1 sections. The groundwater level was manually measured about twice a week from seven locations in each section. Automatic recording was installed in one T0 section and one T1 section. The manual observations formed 56 time series, which were tested between the same-method plots (T0-T0 and T1-T1) and the different-method plots (T0-T1). Automatic data was used to validate the manual observations. In the T0 sections, 60–90% of the groundwater level observations were higher than those in the T1 sections. These observations had an average difference of 0.14–0.25 m. The variation in the groundwater level time series was larger between the T0 sections than between the T1 sections. Statistically significant differences between the same method field sections indicated that other factors also affected the groundwater table (soil type, etc.). However, the differences between T0 and T1 were stronger than those between the same-method sections, and the differences were clearest when the groundwater levels were above the drain depth (1.0 m). In the seasonal time series, the biggest differences were found during the autumn and winter periods. The average differences between T0 and T1 might not be significant in practice, but occasional larger (> 0.4 m) differences may have a short-term influence on field activities and crop growth.

The increasing awareness of the importance of groundwater for ecosystems limits the possibilities for groundwater usage. In Finland, for instance, several projects aiming to establish new groundwater intakes have been stuck in legal processes for more than ten years or even decades. A typical conflict in the legal process relates to potential negative impacts of the project on protected areas, such as Natura 2000 areas, or habitats of endangered species.Managed aquifer recharge (MAR) is one of the solutions to secure the water balance in groundwater dependent ecosystems, or to produce drinking water from artificial instead of natural groundwater. In MAR, surface water is infiltrated into the ground to add water and facilitate increased groundwater extraction in an aquifer. As the surface water quality typically differs from precipitation by a higher content of organic matter, dissolved solids, bacteria and viruses, infiltration of lake water leads to a different groundwater quality compared to natural recharge formed from precipitation.The sustainability of MAR largely depends on an aquifer’s capacity to remove organic matter over the long term. We studied the impact of surface water infiltration on groundwater quality by using a natural lake-aquifer system as a surrogate for MAR. Natural infiltration of lake water to groundwater has been going on for millennia at our research site, providing information over a much longer time span compared to constructed infiltration sites or laboratory tests.The groundwater flow velocity at the site was estimated with a MODFLOW based flow model. The share of lake water infiltrate in the aquifer was estimated from stable oxygen and hydrogen isotopes. Total organic carbon (TOC), dissolved organic carbon, oxygen, iron and manganese concentrations, conductivity and pH were monitored from lake and ground water. According to our measurements, the mean concentration of TOC in lake water was 3.0 mg/L (Jylhä-Ollila et al., 2020). Within the distance of 3 m from the lake bank (retention time 7–15 days), already 46% of TOC was removed. At greater distances along the main flowpath in the aquifer, 80–90% of TOC was removed. Signs of organic matter accumulation in the aquifer were not observed, which is positive in terms of long term sustainability of MAR. Several processes had an impact on oxygen levels in the aquifer, which led to spatial and seasonal changes in the redox conditions and in the iron and manganese concentrations in groundwater. The results showed that an aquifer can remove organic matter from surface water over a long time span, but possible oxygen depletion and iron and manganese release should be taken into account in MAR projects aiming to secure groundwater dependent ecosystems. Jylhä-Ollila, M., Laine-Kaulio, H., Niinikoski-Fuβwinkel, P., Leveinen, J., Koivusalo, H. 2020. Water Quality and Organic Matter Removal in Natural Bank Infiltration at a Boreal Lake in Finland. Hydrogeology Journal, in print.

Thermal infrared sensing of evapotranspiration (E) through surface energy balance (SEB) models is challenging due to uncertainties in determining the aerodynamic conductance (g(A)) and due to inequalities between radiometric (T-R) and aerodynamic temperatures (T-0). We evaluated a novel analytical model, the Surface Temperature Initiated Closure (STIC1.2), that physically integrates T-R observations into a combined Penman-Monteith Shuttleworth-Wallace (PM-SW) framework for directly estimating E, and overcoming the uncertainties associated with T0 and gA determination. An evaluation of STIC1.2 against high temporal frequency SEB flux measurements across an aridity gradient in Australia revealed a systematic error of 10-52% in E from mesic to arid ecosystem, and low systematic error in sensible heat fluxes (H) (12-25%) in all ecosystems. Uncertainty in TR versus moisture availability relationship, stationarity assumption in surface emissivity, and SEB closure corrections in E were predominantly responsible for systematic E errors in arid and semi-arid ecosystems. A discrete correlation (r) of the model errors with observed soil moisture variance (r = 0.33-0.43), evaporative index (r = 0.77-0.90), and climatological dryness (r = 0.60-0.77) explained a strong association between ecohydrological extremes and T-R in determining the error structure of STIC1.2 predicted fluxes. Being independent of any leaf-scale biophysical parameterization, the model might be an important value addition in working group (WG2) of the Australian Energy and Water Exchange (OzEWEX) research initiative which focuses on observations to evaluate and compare biophysical models of energy and water cycle components. Plain Language Summary Evapotranspiration modeling and mapping in arid and semi-arid ecosystems are uncertain due to empirical approximation of surface and atmospheric conductances. Here we demonstrate the performance of a fully analytical model which is independent of any leaf-scale empirical parameterization of the conductances and can be potentially used for continental scale mapping of ecosystem water use as well as water stress using thermal remote sensing satellite data.d

Reducing the strain on water bodies caused by sediment loads released after ditch network maintenance (DNM) is addressed in operational peatland forestry by implementing sediment control structures in ditches. This study evaluates computationally alternative sediment control scenarios in a 5.2 ha deep peat site in eastern Finland. Coupled to a distributed hydrological model, peat erosion and transport in the ditches were simulated for the first year after DNM with 15 scenarios consisting of individual structures (e.g., sedimentation ponds) and their combinations. One scenario represented the prevailing conditions with a V-notch weir at the catchment outlet. All scenarios were evaluated against a baseline scenario in which no structures affected the catchment sediment processes. The results suggested that bed erosion can be efficiently prevented with breaks in cleaning and structures ponding water. It was proven less efficient to trap already eroded material with sedimentation ponds and pits. The structures raising ditch water level had limited effects on water table levels in the strips between ditches, plausibly not impairing tree growth. The process-based modeling presented here provided a yet unexplored approach to comprehensively evaluating alternatives for sediment control, which is highly needed to address the gap between existing scientific knowledge and operational peatland forestry practices.

Funding Information: This work was funded by Ministry of Agriculture and Forestry, Finland; Schlumberger Foundation Faculty for the Future, Academy of Finland (no 326787, WaterWorks2017 ERA-NET Cofund) and Maa- ja vesitekniikan Tuki ry. The study was part of the UrbanStormwaterRisk and EviBAN (Evidence based assessment of NWRM for sustainable water management) projects. Elisa Lähde, a landscape architect, designed the alternative stormwater management designs assessed in this study. The rainfall data for design simulations came from a rain gauge operated by the City of Turku. The streamflow data for rural reference watershed (Savijoki) and semi-urban reference watershed (Kuninkoja) came from monitoring stations maintained by the Finnish Environment Institute (SYKE) and Turku University of Applied Sciences (TUAS), respectively. Funding Information: This work was funded by Ministry of Agriculture and Forestry, Finland; Schlumberger Foundation Faculty for the Future, Academy of Finland (no 326787, WaterWorks2017 ERA-NET Cofund) and Maa- ja vesitekniikan Tuki ry. The study was part of the UrbanStormwaterRisk and EviBAN (Evidence based assessment of NWRM for sustainable water management) projects. Elisa Lähde, a landscape architect, designed the alternative stormwater management designs assessed in this study. The rainfall data for design simulations came from a rain gauge operated by the City of Turku. The streamflow data for rural reference watershed (Savijoki) and semi-urban reference watershed (Kuninkoja) came from monitoring stations maintained by the Finnish Environment Institute (SYKE) and Turku University of Applied Sciences (TUAS), respectively. Publisher Copyright: © 2021 The Author(s) The goal of Low Impact Development (LID) is to restore and maintain the pre-development flow regime. The static storage capacity, which is often used as a parameter in LID designs, provides the maximum capacity of an LID type and is easily quantifiable already at the design phase. However, the static storage approach does not consider the inter-event recovery of storage capacity by infiltration and evapotranspiration. This study investigated dynamic storage capacities of three stormwater management designs with increasing proportions of LID units on a 1.2 ha urban residential block in Southern Finland, to compare their cost-efficiency, as well as their potential in restoring the pre-development flow regime. The cost-efficiency of LID designs was assessed based on their ability to contribute to water losses, and on the additional construction costs required when comparing them to conventional solutions (e.g. asphalt replaced with permeable pavement). The design with a small storage capacity and a large captureratio, i.e., the ratio of contributing area to LID area, was the least efficient albeit its small construction cost. The design with an appropriate balance between the capture ratio and the LID provided storage capacity was the most efficient option. In assessing the potential of stormwater designs in restoring the pre-development flow regime, the sum of infiltration and flow in storm sewer networks was more representative of the catchment total runoff than flow alone. Finally, an extensive simulation of a large set of differently placed LID units proved useful in a priori identification of the most influential units in the treatment train.

The predicted increase in the number of urban flood events can result in substantial monetary losses to society. These costs may be alleviated by preserving ecosystem services, such as urban runoff management. We studied the monetary value of this ecosystem service by applying the replacement cost method in six catchments with varying land-use intensities in two cities in Finland. The economic analysis was based on metric data of urban runoff generation, provided by automatic monitoring stations in the catchments. A hydrological model was applied to estimate evaporation from impervious surfaces, and to simulate runoff in the catchments. Our results suggest that leaving green space unconstructed results in significant monetary savings. The cost of managing runoff correlated with land-use intensity. The ecosystem service value (ESV) was generally higher in catchments with high land-use intensity, low proportion of green space, and high costs of runoff management. Depending on the degree of imperviousness, the ESV ranged from 90,000–270,000 € ha−1. Further, our results suggest that estimates of runoff generation and evaporation are key hydrological factors for assessing ESV. Our study demonstrates how the combination of field data and hydrological and monetary analyses can support regional planning in cold climates.

In this study, HSPF (Hydrologic Simulation Program-FORTRAN) was used to analyze the potential impact of climate change on the streamflow of four major river basins in Ethiopia: Awash, Baro, Genale, and Tekeze. The calibrated and validated HSPF model was forced with daily climate data of 10 CMIP5 (Coupled Model Intercomparison Project phase 5) Global Climate Models (GCMs) for the 1971–2000 control period and the RCP4.5 and RCP8.5 climate projections of 2041–2070 (2050s) and 2071–2100 (2080s). The ensemble median of these 10 GCMs projects the temperature in the four study areas to increase by about 2.3 °C (3.3 °C) in 2050s (2080s), whereas the mean annual precipitation is projected to increase by about 6% (9%) in 2050s (2080s). This results in about 3% (6%) increase in the projected annual streamflow in Awash, Baro, and Tekeze rivers whereas the annual streamflow of Genale river is projected to increase by about 18% (33%) in the 2050s (2080s). However, such projected increase in the mean annual streamflow due to increasing precipitation over Ethiopia contradicts the decreasing trends in mean annual precipitation observed in recent decades. Regional climate models of high resolutions could provide more realistic climate projections for Ethiopia’s complex topography, thus reducing the uncertainties in future streamflow projections.

An open source subcatchment generator program was developed for the Stormwater Management Model (SWMM) to automate tedious stages in the model construction process. The generator divides the investigated area into subcatchments using a uniform computation grid and connects the grid cells together and to the underlying stormwater network. The system was tested by applying it to two small urban catchments with different fractions of impervious surfaces in Helsinki, Finland, using mostly openly available data. The simulated discharge results were compared to measured data and to results obtained from manually built models. The proposed system significantly accelerated the setup of a SWMM modelling project, as the routing between the subcatchments as well as the subcatchment slopes and flow widths were directly derived from the computation grid. Automatically generated and manually constructed SWMM models produced discharge results that differed only slightly from each other.

Subsurface drain trenches are important pathways for water movement from the field surface to subsurface drains in low permeability clayey soils. The hydrological effects of trenches installed with well conducting backfill material and gravel inlet patches are difficult to study with only experimental methods. Computational three-dimensional soil water models provide additional tools to assess spatial processes of such drainage system. The objective was to simulate water flow pathways with 3-D FLUSH model in drain spacing and trench depth scale with two model configurations: (1) the total pore space of soil was treated as a single continuous pore system and (2) the total pore space was divided into mobile soil matrix and macropore systems. Both model configurations were parameterized almost solely with field data without calibration. Data on soil hydraulic properties and drain discharge measurements were available from a clayey subsurface drained agricultural field in southern Finland. The effect of soil hydraulic variability on water flow pathways was assessed by generating computational grids in which the hydraulic properties were sampled randomly from five measured soil sets. Both model configurations were suitable to describe the recorded drain discharge, when model was parameterized in finer scale than drain spacing and the parameterization described highly conductive subdomains such as macropores in a dual-permeability model or the trench in a single pore system model. Models produced similar hourly discharge and water balance results with randomly sampled soil hydraulic properties. The results provide a new view on consequences of soil heterogeneity on subsurface drainage. The practical implication of the results from different drainage scenarios is that gravel trench appears to be important only in soils with a poorly conductive subsoil layers without direct macropore connections to subsurface drains. Solely drain discharge data was not sufficient to determine the differences in water flow pathways between the two model configurations and more output variables, such as groundwater level, should be taken into account in making assessments on the effects of different drainage practices on field drainage capacity. (C) 2016 Elsevier B.V. All rights reserved.

Quantitative analyses of empirical data requirements for hydrological simulations are rare. This study aims to analyze how a multi-objective optimization framework and information content computations aid in quantifying field-scale data worth in drainage studies. The results showed how a 1D numerical model and a differential evolution algorithm performed in describing the field water balance. The choice of the optimization target (subsurface drain discharge and surface runoff) impacted the simulation results more than parameter deviations. While the information content of surface runoff data was higher than that of drain discharge, drain discharge data contained more information on most of the soil parameters. Uncertainties related to groundwater outflow data, which were not used in the optimization, were higher than those of drain discharge and surface runoff. A central weighing optimization scheme with two data types produced the best but still incomplete description of the field hydrology. Despite the modest model performance, the results demonstrated how the choice of empirical data and optimization strategy can lead to uncertainties in drainage simulations and how the uncertainties can be assessed. Practically, a low amount of information and a parameter sensitivity analysis can lead to a biased description of uncertainty related to such hydrological variables which are not used in the optimization. Benefits of the modeling framework were shown when assessing (1) model structure adequacy with the Pareto front analysis, (2) information content of different data types regarding different parameters, and (3) uncertainties related to simulating hydrological variables based on optimization against a given data type. © 2020 Elsevier B.V.

Constructing hydrological models for large urban areas is time consuming and laborious due to the requirements for high-resolution data and fine model detail. An open-source algorithm using adaptive subcatchments is proposed to automate Storm Water Management Model (SWMM) construction. The algorithm merges areas with homogeneous land cover and a common outlet into larger subcatchments, while retaining small-scale details where land cover or topography is more heterogeneous. The method was tested on an 85-ha urban catchment in Helsinki, Finland. A model with adaptive subcatchments reproduced the observed discharge at the catchment outlet with high model-performance indices emphasizing the strength of the proposed method. Computation times of the adaptive model were substantially lower than those of a corresponding model with uniformly sized high-resolution subcatchments. Given that high-resolution land cover and topography data are available, the proposed algorithm provides an advanced method for implementing SWMM models automatically even for large urban catchments without a substantial manual workload. Simultaneously, the high-resolution land cover details of the catchments can be maintained where they matter the most. (c) 2019 American Society of Civil Engineers.

High-latitude conditions in northern Europe are characterised by short growing seasons (May–August) and long dormant seasons. Alternating mild and freezing conditions lead to variable snow accumulation–melt cycles affecting runoff generation, and consequently the loss of nutrients and sediments from agricultural fields. We assessed water balance in two subsurface drained clayey agricultural fields of different slopes (1% and 5%) in southern Finland to discern changes between mild and cold winters. The water balances of the two field sections were produced with a spatially distributed 3D hydrological model. Simulated snow water equivalent (SWE), drain discharge, tillage layer runoff and groundwater outflow from a 7-year period were examined during the dormant seasons (September–April) in relation to the North Atlantic Oscillation (NAO) index, which characterises phases related to mild and cold winters in northern Europe. Mild periods (positive NAO) were associated with more frequent runoff events, which were sustained throughout mild winters with lower SWE and shorter time of snow cover. Understanding and quantifying the water balance through periods of different weather patterns is essential as climate change is projected to increase the occurrence of positive NAO phases challenging the control of nutrient and sediment losses from agricultural fields.

Preferential flowpaths control hydrological connectivity in forested hillslopes. However, current understanding on the nature, extent, and impacts of hydrological connectivity within hillslopes is still limited. Distributed 2-pore domain models of subsurface water flow and solute transport in and between the preferential flowpaths and the soil matrix provide applicable means to investigate the connectivity. We identified possible (dis)connections of preferential flowpaths in a forested hillslope section from dye tracer data and incorporated them in a 3D 2-pore domain model; the model was run and evaluated against ion tracer data. The objectives were to explore hydrological connectivity within the hillslope and quantify its impacts on solute transport. The main control for capturing the internal concentration dynamics of the ion-tracer plume with the model was an explicit description of local disconnections of preferential flowpaths in the form of local reductions in their hydraulic conductivity. Continuous preferential flowpaths were formed by rooting activities, erosion caused by subsurface flow, freezing–thawing cycles, and soil fauna, but they were locally disconnected by, for example, cemented soil material. As a result, the dominant lateral flowpath was tortuous, and tracer transport within this pathway was highly preferential: Compared to earlier models without flowpath disconnections, increase in the average lateral tracer load was 1.7-fold and in the maximum load 7.9-fold. The results indicate that the volume and hydraulic conductivity of the actual, connected preferential flowpaths control, in combination with linkages between preferential flowpaths and soil matrix, pollutant transport in forested hillslopes.

Efficient mitigation of environmental loads from agricultural fields to surface waters requires sufficient knowledge of dominating erosion processes and sediment transport pathways. Computational models are often applied in sediment load assessments but their structure inherently includes assumptions and uncertainties, which can hinder their predictive and explanatory capabilities. In this study, a 3D dual-permeability model was applied with field-scale data from a high-latitude site to investigate sediment balances and structural uncertainties in sediment transport components. The two-year data encompassed hourly records of water flow and sediment concentration composite samples from tillage layer runoff and drain discharge in two adjacent clayey fields with different slopes (1% and 5%). Three model structures with different assumptions of sediment transport pathways were built to test their performance against the data. The simulations demonstrated how different model structures can reproduce the data with varying results on sediment balance. The varying results revealed the importance of flow, erosion, and sediment transport observations from the fields to improve the simulations. Structural uncertainty analysis revealed uncertainties which parameter sensitivity analysis could not describe. Concentration data was shown to include more information about erosion and sediment transport processes than solely the load data. The results suggest that a major part (48–69%) of the detached particles remained in the field and that lateral subsurface transport contributed to load generation (10–21% of total loads) especially in the steeper field. The results demonstrated that the majority (84–87%) of sediment loads occurred via subsurface drain discharge and groundwater outflow with the slope gradient of 1–5%, which suggests that load mitigation measures should also be directed to decrease loads via subsurface transport pathways. The simulations demonstrated how transport processes were controlled not only by water flow but also by soil structure.

Restoration impact of forestry-drained peatlands on runoff water quality and dissolved organic carbon (DOC) and nutrient export was studied. Eight catchments were included: three mesotrophic (one undrained control, two treatments), two ombrotrophic (one drained control, one treatment) and three oligotrophic catchments (one undrained control, two treatments). Three calibration years and four post-restoration years were included in the data from seven catchments, for which runoff was recorded. For one mesotrophic treatment catchment only one year of pre-restoration and two years of post-restoration water quality data is reported. Restoration was done by filling in and damming the ditches. Water samples were collected monthly-biweekly during the snow-free period; runoff was recorded continuously during the same period. Water quality was estimated for winter using ratios derived from external data. Runoff for non-recorded periods were estimated using the FEMMA model. A high impact on DOC, nitrogen (N) and phosphorus (P) was observed in the mesotrophic catchments, and mostly no significant impact in the nutrient-poor catchments. The DOC load from one catchment exceeded 1000kg (restored-ha)-1 in the first year; increase of DOC concentration from 50 to 250mgl-1 was observed in the other mesotrophic treatment catchment. Impact on total nitrogen export of over 30kg (restored-ha)-1 was observed in one fertile catchment during the first year. An impact of over 5kg (restored-ha)-1 on ammonium export was observed in one year in the mesotrophic catchment. Impact on P export from the mesotrophic catchment was nearly 5kg P (restored-ha)-1 in the first year. The results imply that restoration of nutrient-rich forestry-drained peatlands poses significant risk for at least short term elevated loads degrading the water quality in receiving water bodies. Restoration of nutrient-poor peatlands poses a minor risk in comparison. Research is needed regarding the factors behind these risks and how to mitigate them.

Elevated suspended sediment (SS) loads released from peatlands after drainage operations and the resulting negative effect on the ecological status of the receiving water bodies have been widely recognized. Understanding the processes controlling erosion and sediment transport within the ditch network forms a prerequisite for adequate sediment control. While numerous experimental studies have been reported in this field, model based assessments are rare. This study presents a modeling approach to investigate sediment transport in a peatland ditch network. The transport model describes bed erosion, rain-induced bank erosion, floc deposition, and consolidation of the bed. Coupled to a distributed hydrological model, sediment transport was simulated in a 5.2 ha forestry-drained peatland catchment for two years after ditch cleaning. Comparing simulation results to measured SS concentrations suggested that the loose peat material, produced during excavation, contributed markedly to elevated SS concentrations immediately after ditch cleaning. Both snowmelt and summer rainstorms contributed critically to annual loads. Springtime peat erosion during snowmelt was driven by ditch flow whereas during summer rainfalls, bank erosion by raindrop impact was identified as an important process. Relating modeling results to observed spatial topographic changes in the ditch network was challenging and the results were difficult to verify. Nevertheless, the model has potential to identify risk areas for erosion. The results demonstrate that modeling is effective in separating the importance of different processes and complements pure experimental approaches. Modeling results can aid planning and designing efficient sediment control measures and guide the focus of experimental studies. This article is protected by copyright. All rights reserved.

This review article discusses the climate, water resources and historical droughts of Africa, drought indices, vulnerability, impact of global warming and land use for drought-prone regions in West, southern and the Greater Horn of Africa, which have suffered recurrent severe droughts in the past. Recent studies detected warming and drying trends in Africa since the mid 20th century. Based on the Fourth Assessment Report of the Intergovernmental Panel on Climate Change and the Coupled Model Intercomparison Project Phase 5 (CMIP5), both northern and southern Africa are projected to experience drying, such as decreasing precipitation, runoff and soil moisture in the 21st century and could become more vulnerable to the impact of droughts. The daily maximum temperature is projected to increase by up to 8°C (RCP8.5 of CMIP5), precipitation indices such as total wet day precipitation (PRCPTOT) and heavy precipitation days (R10 mm) could decrease, while warm spell duration (WSDI) and consecutive dry days...

Soil tillage is an anthropogenic factor affecting hydrological processes in agricultural fields. To demonstrate a novel method for increasing mechanistic understanding of the tillage impacts, we combined a process-based three-dimensional (3D) hydrological model with terrestrial laser scanning (TLS) data. This study aimed to (1) exploit high-resolution TLS data to estimate soil surface depression storage (SSDS) and roughness after different soil tillage operations (ploughing, harrowing vs direct drilling) on a heavy clay soil, (2) combine the estimates of SSDS and roughness with a 3D hydrological model to demonstrate the potential of the method in analyzing hydrological impacts of tillage, and (3) evaluate the value and uncertainties in coupling spatial microtopographical data and process-based modeling. The SSDS values showed low mean (0.3–2.9 mm) and rare high values (>5 mm) with clearly the highest variation of SSDS and roughness values in the ploughed conditions. These tillage impacts were reflected in the amounts of surface layer runoff (max. increase 23% due to the SSDS and roughness changes) and drain discharge (max. decrease 8%). The impact on other water balance components was negligible, and factors such as drainage methods and terrain slope were shown to have more control on the water balance. The tillage impacts had also a clear effect on peak surface runoff values. Most (99%) of the hydrological changes were caused by the SSDS variation whereas the roughness had a minor role. The simulations showed that tillage-induced long-term changes on soil hydraulic properties (such as conductivity and macroporosity), which were not detected by the TLS data, can have a high impact on surface layer runoff generation, as these tillage-impacts increased runoff by 25%. While the simulations showed how the various hydrological impacts of tillage can be discerned, a more comprehensive assessment would require more data derived from several sites and tillage conditions.

A prerequisite for sustainable peatland forestry is sufficiently low water table (WT) level for profitable tree production. This requires better understanding on controls and feedbacks between tree stand and its evapotranspiration, drainage network condition, climate, and WT levels. This study explores the role of spatial tree stand distribution in the spatiotemporal distribution of WT levels and site water balance. A numerical experiment was conducted by a three-dimensional (3-D) hydrological model (FLUSH) applied to a 0.5 ha peatland forest assuming (1) spatially uniform interception and transpiration, (2) interception and transpiration scaled with spatial distributions of tree crown and root biomass, and (3) the combination of spatially scaled interception and uniform transpiration. Site water balance and WT levels were simulated for two meteorologically contrasting years. Spatial variations in transpiration were found to control WT levels even in a forest with relatively low stand stem volume (&lt, 100 m3/ha). Forest management scenarios demonstrated how stand thinning and reduced drainage efficiency raised WT levels and increased the area and duration of excessively wet conditions having potentially negative economic (reduced tree growth) and environmental (e.g., methane emissions, phosphorus mobilization) consequences. In practice, silvicultural treatment manipulating spatial stand structure should be optimized to avoid emergence of wet spots.

Low impact development (LID) has received significant attention in supplementing urban drainage designs. This study demonstrates the effects of LID-based urban designs on water balance components for an urban catchment. Two LID-based urban designs (A, B) are simulated for short term (E1) and long term (E2) periods and the effects of the various designs on different water balance components are assessed. The goal of the study is to demonstrate the performance of the designs to realize the sponge city concept. For the intensive short event, scenario A with 15% LID is not effective whereas scenario B with 49% LID is highly effective. For the longer period, both scenarios are highly effective in replicating sponge city concept. In addition, the A scenario possesses a potential for producing sponge city concept for rain events for return periods lower than 100 years.

Simple and automatic optimization approaches were used to create Low Impact Development (LID) scenarios for a residential catchment in Espoo, Finland. Ten LID scenarios were simulated with the Storm Water Management Model (SWMM) to evaluate their impact on urban runoff and pollutant load on a catchment scale. Permeable pavements and bioretention cells were located at the asphalted areas in the catchment. A large variability was observed in the simulated load reduction depending on the LID type, location and pollutant. Scenarios with permeable pavements reduced pollutants effectively, but require knowledge about the pollutant sources and pathways. Scenarios with bioretention cells benefitted the most from location optimization due to their smaller spatial footprint and storage capacity compared with permeable pavements.

Roadside filters can be used to treat polluted stormwater. In this study, sand and sand-biochar filters were investigated in full-scale field conditions during three rain events. Stormwater influent and effluent of the filters were sampled with high frequency and up to 29 water quality parameters were determined. The obtained field data was analyzed and used as an input for geochemical modelling. The study showed promising results for both filter types with respect to retention of metals, total suspended solids and total phosphorus. Biochar amendment had clear improvement only for nitrogen removal; some release of organic carbon from biochar filter material was observed. Concentrations of most measured parameters varied considerably during and between the studied events. Geochemical modelling showed that precipitation is one possible removal mechanisms for many pollutants along with sorption and physical filtration.

Tutkimuksessa oli tavoitteena selvittää, miten valunta ja valumavesien pitoisuudet sekä huuhtoumat muuttuvat siirryttäessä tavanomaisesta viljanviljelystä nurmiviljelyyn ja laidunnukseen. Tutkimus toteutettiin seuraamalla Gårdskulla Gårdin tutkimusalueen kahta peltolohkoa Siuntion Kirkkojoen varrella. Alueiden maalaji on savea (HeS, HsS ja AS). Alueen 1 (5.7 ha) keskikaltevuus on noin 1 % ja Alueen 2 (4.7 ha) noin 5 %. Lohkot on salaojitettu 1940-luvulla keskimäärin 16 metrin ojavälillä. Vuosina 2007–2010 koealueilla viljeltiin kevät- ja syysviljoja kivennäislannoitteita ja tavanomaisia muokkausmenetelmiä käyttäen. Syksystä 2011 lähtien Alue 1 on ollut jatkuvasti nurmella ja Alue 2 lihakarjan laitumena keväästä 2011 lähtien. Tuotantosuunnan muutoksen yhteydessä koealueilla siirryttiin luomutuotantoon. Alueilla on mitattu salaoja- ja pintakerrosvaluntaa jatkuvatoimisesti. Valumavesien kokoomanäytteistä on analysoitu seuraavat pitoisuudet: kokonaistyppi, ammoniumtyppi, nitriitti- ja nitraattityppi, kokonaisfosfori, liukoinen epäorgaaninen fosfori (PO4-P) ja kiintoaine. Edelleen jatkuvat mittaukset aloitettiin syksyllä 2007. Tämän tutkimuksen aineisto on vuosilta 2008–2016. Molemmilla koealueilla salaojavalunta muodosti 80–90 % mitatusta valunnasta (salaojat+pintakerros) sekä ennen tuotantosuunnan muutosta että sen jälkeen. Pintakerrosvalunnan mittauksissa oli kuitenkin useana keväänä epävarmuutta, etenkin Alueella 2. Tuotantosuunnan muutos näkyi molemmilla koealueilla kokonaistyppikuorman (s+p) noin 70 % vähenemisenä aikaisemmasta. Typpihuuhtouma nurmelta (Alue 1) oli keskimäärin 5 kg ha-1 ja laidunnurmelta (Alue 2) 7 kg ha-1 vuodessa. Kokonaisfosforikuormissa (ka. 0.44 kg ha-1 a-1) ei ollut eroa nurmen ja viljan välillä. Laidunnurmen fosforikuorma (1.3 kg ha-1 a-1) oli vajaa 70 % viljanviljelyn keskikuormasta. Myös kiintoainekuormat vähenivät siirryttäessä viljanviljelystä nurmiviljelyyn ja laidunnukseen. Nurmiviljelyn keskimääräinen vuotuinen kiintoainekuorma, 740 kg ha-1, oli 90 % viljanviljelyn kuormasta. Laidunalueella vastaavat luvut olivat 710 kg ha-1 ja noin 50 %. Suurin ero oli liukoisen epäorgaanisen fosforin huuhtoumissa. Laidunnurmella pintakerrosvalunnan keskimääräinen kuorma (0.31 kg ha-1 a-1) oli 7-kertainen viljanviljelyvuosiin verrattuna. Salaojavalunnan keskimääräiseen huuhtoumaan (0.40 kg ha-1 a-1) muutos laitumeksi ei vaikuttanut. Eri valuntareittien yhteenlaskettu PO4-P - kuorma (ka. 0.69 kg ha-1 a-1) laidunnurmelta oli viljanviljelyyn nähden 1.6-kertainen. Nurmiviljelystä vastaava kuorma (0.12 kg ha-1 a-1) oli aikaisempaan verrattuna 1.5-kertainen. Kuormituksen kasvu johtui pääosin kohonneista pintakerrosvalunnan pitoisuuksista.Tutkimusta ovat rahoittaneet Salaojituksen Tukisäätiö sr ja hankkeessa mukana olleet laitokset. Vuosina 2007–2013 rahoittajana oli myös maa- ja metsätalousministeriö ja 2011–2013 Maa- ja vesitekniikan tuki ry.

Terrestrial export of dissolved organic carbon (DOC) to watercourses has increased in boreal zone. Effect of decomposing material and soil food webs on the release rate and quality of DOC are poorly known. We quantified carbon (C) release in CO2, and DOC in different molecular weights from the most common organic soils in boreal zone; and explored the effect of soil type and enchytraeid worms on the release rates. Two types of mor and four types of peat were incubated in laboratory with and without enchytraeid worms for 154 days at + 15 A degrees C. Carbon was mostly released as CO2; DOC contributed to 2-9% of C release. The share of DOC was higher in peat than in mor. The release rate of CO2 was three times higher in mor than in highly decomposed peat. Enchytraeids enhanced the release of CO2 by 31-43% and of DOC by 46-77% in mor. High molecular weight fraction dominated the DOC release. Upscaling the laboratory results into catchment level allowed us to conclude that peatlands are the main source of DOC, low molecular weight DOC originates close to watercourse, and that enchytraeids substantially influence DOC leaching to watercourse and ultimately to aquatic CO2 emissions.

Urbanization leads to the replacement of natural areas by impervious surfaces and affects the catchment hydrological cycle with adverse environmental impacts. Low impact development tools (LID) that mimic hydrological processes of natural areas have been developed and applied to mitigate these impacts. Hydrological simulations are one possibility to evaluate the LID performance but the associated small-scale processes require a highly spatially distributed and explicit modeling approach. However, detailed data for model development are often not available for large urban areas, hampering the model parameterization. In this paper we propose a methodology to parameterize a hydrological model to a large, ungauged urban area by maintaining at the same time a detailed surface discretization for direct parameter manipulation for LID simulation and a firm reliance on available data for model conceptualization. Catchment delineation was based on a high-resolution digital elevation model (DEM) and model parameterization relied on a novel model regionalization approach. The impact of automated delineation and model regionalization on simulation results was evaluated for three monitored study catchments (5.87–12.59 ha). The simulated runoff peak was most sensitive to accurate catchment discretization and calibration, while both the runoff volume and the fit of the hydrograph were less affected.

Transport of perfluorooctanoic acid (PFOA) was simulated in the beginning of River Kokemaenjoki in Finland using one-dimensional SOBEK river model. River Kokemaenjoki is used as a raw water source for an artificial groundwater recharge plant, and the raw water intake plant is located near the downstream end of the model application area. Measured surface water and wastewater concentrations were used to determine the PFOA input to the river and to evaluate the simulation results. The maximum computed PFOA concentrations in the river at the location of the raw water intake plant during the simulation period Dec. 1, 2011-Feb. 16, 2014 were 0.92 ng/l and 3.12 ng/l for two alternative modeling scenarios. These concentration values are 2.3% and 7.8%, respectively, of the 40 ng/l guideline threshold value for drinking water. The current annual median and maximum PFOA loads to the river were calculated to be 3.9 kg/year and 10 kg/year respectively. According to the simulation results, the PFOA load would need to rise to a level of 57 kg/year for the 40 ng/l guideline value to be exceeded in river water at the raw water intake plant during a dry season. It is thus unlikely that PFOA concentration in raw water would reach the guideline value without the appearance of new PFOA sources. The communal wastewater treatment plants in the study area caused on average 11% of the total PFOA load. This raises a concern about the origin of the remaining 89% of the PFOA load and the related risk factors.

Accurate quantification of the amount, quality and sources of urban stormwater runoff are a prerequisite for effective stormwater management. The goal of this study was to estimate city-scale stormwater pollutant export, examine the effect of data sources on export estimates, and develop an optimization method for stormwater monitoring. The results were presented for the city of Lahti in southern Finland, where site mean pollutant concentrations (SMCs), annual pollutant loads, and monitoring guidelines for specific land use types were determined for total suspended solids (TSS), nutrients (total nitrogen TN and total phosphorus TP), chemical oxygen demand (COD), and metals (Pb, Zn, Cu, Cr, and Ni). Depending on the data source, differences between estimated pollutant exports ranged from -89% to 215%. Lack of reference data for every urban land use type and differences in land use classification schemes were identified as key factors limiting the accuracy of pollutant load estimation.

Low Impact Development (LID) aims to mitigate the hydrological impacts of urbanization by replication of processes in natural catchments. Green roofs covered with vegetation and pervious substrate are one alternative among a wide range of LID tools. Water retention of green roofs depends on many factors (e.g. local climate), and measurements remain crucial in evaluating their performance. The simulation of green roof retention by a hydrological model is one option to evaluate their potential benefits before implementation. In this paper, we evaluated the ability of the recently introduced LID green roof module of the stormwater management model to replicate runoff from monitored green roof test beds under Nordic climate conditions. A parameter sensitivity analysis was conducted to identify calibration parameters. The model showed an overall acceptable performance, and the results indicated the importance of accurately estimating potential evapotranspiration rates for inter-event periods, which is essential in representing the retention capacity regeneration. Copyright © 2015 John Wiley & Sons, Ltd.