Evaluation of overland flow modelling hypotheses with a multi-objective calibration using discharge and sediment data.

Conceptual hydrological models can move towards process-oriented modelling when addressing broader issues than discharge modelling alone. For instance, water quality modelling generally requires understanding of both pathways and travel times which might not be easily identified because observations at the outlet aggregate all processes at the catchment scale. In this study we tested if adding a second kind of observation, specifically sediment data, can help distinguish overland flow from total discharge.

Hydrological impacts of a wildfire in a Boreal region: The Västmanland fire 2014 (Sweden).

The largest forest wildfire in Swedish modern history burnt 14,000 ha of Boreal forest in the Västmanland County (south-central Sweden) during the summer of 2014. Here, we assess the impacts of this wildfire on the hydrological regime during the three years after it happened. In the empirical experiment carried out, four catchments (two burnt and two non-burnt nearby) with similar character and climate and with mean area of 20 km were compared.

Future socioeconomic conditions may have a larger impact than climate change on nutrient loads to the Baltic Sea.

The Baltic Sea is suffering from eutrophication caused by nutrient discharges from land to sea, and these loads might change in a changing climate. We show that the impact from climate change by mid-century is probably less than the direct impact of changing socioeconomic factors such as land use, agricultural practices, atmospheric deposition, and wastewater emissions. We compare results from dynamic modelling of nutrient loads to the Baltic Sea under projections of climate change and scenarios for shared socioeconomic pathways.

Changing climate both increases and decreases European river floods.

Climate change has led to concerns about increasing river floods resulting from the greater water-holding capacity of a warmer atmosphere. These concerns are reinforced by evidence of increasing economic losses associated with flooding in many parts of the world, including Europe. Any changes in river floods would have lasting implications for the design of flood protection measures and flood risk zoning.

Changing climate shifts timing of European floods.

A warming climate is expected to have an impact on the magnitude and timing of river floods; however, no consistent large-scale climate change signal in observed flood magnitudes has been identified so far. We analyzed the timing of river floods in Europe over the past five decades, using a pan-European database from 4262 observational hydrometric stations, and found clear patterns of change in flood timing. Warmer temperatures have led to earlier spring snowmelt floods throughout northeastern Europe; delayed winter storms associated with polar warming have led to later winter floods around the North Sea and some sectors of the Mediterranean coast; and earlier soil moisture maxima have led to earlier winter floods in western Europe.

Regulation of snow-fed rivers affects flow regimes more than climate change.

River flow is mainly controlled by climate, physiography and regulations, but their relative importance over large landmasses is poorly understood. Here we show from computational modelling that hydropower regulation is a key driver of flow regime change in snow-dominated regions and is more important than future climate changes. This implies that climate adaptation needs to include regulation schemes.

Ensemble modeling of the Baltic Sea ecosystem to provide scenarios for management.

We present a multi-model ensemble study for the Baltic Sea, and investigate the combined impact of changing climate, external nutrient supply, and fisheries on the marine ecosystem. The applied regional climate system model contains state-of-the-art component models for the atmosphere, sea ice, ocean, land surface, terrestrial and marine biogeochemistry, and marine food-web. Time-dependent scenario simulations for the period 1960-2100 are performed and uncertainties of future projections are estimated.

Climate change impact on riverine nutrient load and land-based remedial measures of the Baltic sea action plan.

To reduce eutrophication of the Baltic Sea, all nine surrounding countries have agreed upon reduction targets in the HELCOM Baltic Sea Action Plan (BSAP). Yet, monitoring sites and model concepts for decision support are few. To provide one more tool for analysis of water and nutrient fluxes in the Baltic Sea basin, the HYPE model has been applied to the region (called Balt-HYPE).

Nitrogen and phosphorus retention in surface waters: an inter-comparison of predictions by catchment models of different complexity.

Nitrogen and phosphorus retention estimates in streams and standing water bodies were compared for four European catchments by a series of catchment-scale modelling tools of different complexity, ranging from a simple, equilibrium input-output type to dynamic, physical-based models: source apportionment, MONERIS, EveNFlow, TRK, SWAT, and NL-CAT. The four catchments represent diverse climate, hydrology, and nutrient loads from diffuse and point sources in Norway, the UK, Italy, and the Czech Republic. The models' retention values varied largely, with tendencies towards higher scatters for phosphorus than for nitrogen, and for catchments with lakes (Vansjø-Hobøl, Zelivka) compared to mostly or entirely lakeless catchments (Ouse or Enza, respectively).

Ensemble modelling of nutrient loads and nutrient load partitioning in 17 European catchments.

An ensemble of nutrient models was applied in 17 European catchments to analyse the variation that appears after simulation of net nutrient loads and partitioning of nutrient loads at catchment scale. Eight models for N and five models for P were applied in three core catchments covering European-wide gradients in climate, topography, soil types and land use (Vansjø-Hobøl (Norway), Ouse (Yorkshire, UK) and Enza (Italy)). Moreover, each of the models was applied in 3-14 other EUROHARP catchments in order to inter-compare the outcome of the nutrient load partitioning at a wider European scale.

Evaluation of diffuse pollution model applications in EUROHARP catchments with limited data.

The application of diffuse pollution models included in EUROHARP encompassed varying levels of parameterisation and approaches to the preparation of input data depending on the model and modelling team involved. Modellers consistently faced important decisions in relation to data interpretation, especially in those catchments with unfamiliar physical or climatic characteristics, where catchment conditions were beyond the range for which a particular model was originally developed, or where only limited input data were available. In addition to a broad discussion of data issues, this paper compares the performance of the four sub-annual output models tested in EUROHARP (EveNFlow, NL-CAT, SWAT and TRK) in three test catchments without the modelling teams having sight of measured flow and nitrate concentration data.

Evaluation of the difference of eight model applications to assess diffuse annual nutrient losses from agricultural land.

The capability of eight nutrient models to predict annual nutrient losses (nitrogen and phosphorus) at catchment scale have been studied in the EUROHARP project. The methodologies involved in these models differ profoundly in their complexity, level of process representation and data requirements. This evaluation is focused on model performance in three core catchments: the Vansjø-Hobøl (Norway), the Ouse (Yorkshire, UK) and the Enza (Italy).

Subannual models for catchment management: evaluating model performance on three European catchments.

Models' abilities to predict nutrient losses at subannual timesteps is highly significant for evaluating policy measures, as it enables trends and the frequency of exceedance of water quality thresholds to be predicted. Subannual predictions also permit assessments of seasonality in nutrient concentrations, which are necessary to determine susceptibility to eutrophic conditions and the impact of management practices on water quality. Predictions of subannual concentrations are pertinent to EC Directives, whereas load estimates are relevant to the 50% target reduction in nutrient loading to the maritime area under OSPAR.

Description of nine nutrient loss models: capabilities and suitability based on their characteristics.

In EUROHARP, an EC Framework V project, which started in 2002 with 21 partners in 17 countries across Europe, a detailed intercomparison of contemporary catchment-scale modelling approaches was undertaken to characterise the relative importance of point and diffuse pollution of nutrients in surface freshwater systems. The study focused on the scientific evaluation of different modelling approaches, which were validated on three core catchments (the Ouse, UK; the Vansjo-Hobøl, Norway; and the Enza, Italy), and the application of each tool to three additional, randomly chosen catchments across Europe. The tools involved differ profoundly in their complexity, level of process representation and data requirements.

How participatory can participatory modeling be? Degrees of influence of stakeholder and expert perspectives in six dimensions of participatory modeling.

The authors are involved in a project aiming at the development of a methodology for participatory modeling as a tool for public participation in water resource management. In this paper, some examples of different degrees of stakeholder influence in six key dimensions of participatory modeling are identified and discussed. Arnstein's (A ladder of citizen participation.

Using catchment models to establish measure plans according to the Water Framework Directive.

A participatory modelling process (DEMO) has been developed and applied in a 350 km2 catchment in southern Sweden. The overall goal is to improve the dialogues between experts and local stakeholders by using numerical models as a platform for discussions. The study is focused on reducing nutrient load and on the development of a locally established measure plan, which is requested by the European Water Framework Directive.

Climate change impact on water quality: model results from southern Sweden.

Starting from six regional climate change scenarios, nitrogen leaching from arable-soil, water discharge, and nitrogen retention was modeled in the Rönneå catchment. Additionally, biological response was modeled in the eutrophic Lake Ringsjön. The results are compared with similar studies on other catchments.

Modeling the impact of potential wetlands on phosphorus retention in a Swedish catchment.

In southern Sweden, wetlands are constructed to remove nitrogen (N) in agricultural catchments. The possible effects of such wetlands on riverine phosphorus (P) were also estimated using input-output data from three well-monitored wetlands. This was done to formulate a simple model for removal of P that is dependent on inflow characteristics.

Parameter precision in the HBV-NP model and impacts on nitrogen scenario simulations in the Rönneå river, southern Sweden.

The HBV-NP model is a newly developed water quality model that describes the turnover and fluxes of both nitrogen and phosphorous. It is based on the conceptual precipitation/runoff HBV model. The HBV-NP model was applied for simulation of nitrogen for the Rönneå catchment in southern Sweden.

Estimating catchment nutrient flow with the HBV-NP model: sensitivity to input data.

The dynamic catchment model HBV-N has been further developed by adding routines for phosphorus transport and is now called the HBV-NP model. The model was shown to satisfactorily simulate nutrient dynamics in the Rönneå catchment (1,900 km2). Its sensitivity to input data was tested, and results demonstrated the increased sensitivity to the selection of input data on a subcatchment scale when compared with the catchment scale.

Integrated catchment modeling for nutrient reduction: scenarios showing impacts, potential, and cost of measures.

A hydrological-based model (HBV-NP) was applied to a catchment (1900 km2) in the southern part of Sweden. Careful characterization of the present load situation and the potential for improved treatment or reduced soil leaching were analyzed. Several scenarios were modeled to find strategies to reach the Swedish environmental goals of reducing anthropogenic nitrogen load by 30% and phosphorus load by 20%.

Nitrogen retention in a river system and the effects of river morphology and lakes.

The mean annual transfer (loss and retention) of nitrogen in a river system was estimated using a conceptual approach based on water surface area and runoff. Two different approaches for the calculation of water surface area were applied to determine riverine nitrogen retention in four European catchments, ranging between 860-14,000 km2 in area, and differing considerably in the proportion and distribution of surface waters, specific runoff and specific nutrient emissions. The transfer rate was estimated sequentially as either the mean value for the total catchment, on a sub-catchment scale, or considering the distribution of water surface area within a sub-catchment.

Modelling diffuse nutrient flow in eutrophication control scenarios.

The Swedish Water Management Research Programme (VASTRA) focuses on the development and demonstration of tools for more efficient eutrophication control when implementing the EU water framework directive in Sweden. During the first half of the programme, models for nitrogen flow were developed, and at present, similar models for phosphorus are under construction (e.g.