Markus Venohr

Managing aquatic ecosystems and water resources under multiple stress--an introduction to the MARS project.

Water resources globally are affected by a complex mixture of stressors resulting from a range of drivers, including urban and agricultural land use, hydropower generation and climate change. Understanding how stressors interfere and impact upon ecological status and ecosystem services is essential for developing effective River Basin Management Plans and shaping future environmental policy. This paper details the nature of these problems for Europes water resources and the need to find solutions at a range of spatial scales. In terms of the latter, we describe the aims and approaches of the EU-funded project MARS (Managing Aquatic ecosystems and water Resources under multiple Stress) and the conceptual and analytical framework that it is adopting to provide this knowledge, understanding and tools needed to address multiple stressors. MARS is operating at three scales: At the water body scale, the mechanistic understanding of stressor interactions and their impact upon water resources, ecological status and ecosystem services will be examined through multi-factorial experiments and the analysis of long time-series. At the river basin scale, modelling and empirical approaches will be adopted to characterise relationships between multiple stressors and ecological responses, functions, services and water resources. The effects of future land use and mitigation scenarios in 16 European river basins will be assessed. At the European scale, large-scale spatial analysis will be carried out to identify the relationships amongst stress intensity, ecological status and service provision, with a special focus on large transboundary rivers, lakes and fish. The project will support managers and policy makers in the practical implementation of the Water Framework Directive (WFD), of related legislation and of the Blueprint to Safeguard Europes Water Resources by advising the 3rd River Basin Management Planning cycle, the revision of the WFD and by developing new tools for diagnosing and predicting multiple stressors.

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. The results of the nutrient load partitioning show a variation in the computed average annual nitrogen and phosphorus loss from agricultural land within the 17 catchments between 19.1-34.6 kg N ha(-1) and 0.12-1.67 kg P ha(-1). All the applied nutrient models show that the catchment specific variation (range and standard deviation) in the model results is lowest when simulating the net nutrient load and becomes increasingly higher for simulation of the gross nutrient loss from agricultural land and highest for the simulations of the gross nutrient loss from other diffuse sources in the core catchments. The average coefficient of variation for the model simulations of gross P loss from agricultural land is nearly twice as high (67%) as for the model simulations of gross N loss from agricultural land (40%). The variation involved in model simulations of net nutrient load and gross nutrient losses in European catchments was due to regional factors and the presence or absence of large lakes within the catchment.

Integrated water resources management in central Asia: nutrient and heavy metal emissions and their relevance for the Kharaa River Basin, Mongolia

Within the framework of Integrated Water Resources Management (IWRM) the nutrient and heavy metal levels within the Kharaa river basin were investigated. By the application of the MONERIS model, which quantifies nutrient emissions into river basins, various point and diffuse pathways, as well as nutrient load in rivers, could be analysed. Despite seasonal variations and inputs of point sources (e.g. Wastewater Treatment Plant Darkhan) the nutrient concentrations in most of the subbasins are on a moderate level. This shows evidence for a nutrient limited ecosystem as well as dilution effects. However, in the middle and lower reaches heavy metal concentrations of arsenic and mercury, which are linked to mining activities in many cases, are a point of concern. Thus measures are necessary to protect the valuable chemical and ecological status of the Kharaa River and its tributaries. As a result of the growing economic pressure Mongolia will enhance the agricultural production by irrigation. Until 2015 about 60% of the agricultural land shall be irrigated. In addition the gold mining activities shall increase by 20% a year. Both sectors have a high demand for water quantity and quality. The model MONERIS allows the assessment of measures which are inevitable to protect the water quality under shrinking water availability.

Managing the world’s most international river: the Danube River Basin

Transboundary river-basin management is a challenging task emerging from lack of on-site expert knowledge, high administrative and socioeconomic complexity, various stakeholder interests, and difficulties enforcing international and national law. Therefore, an efficient ‘science–policy interface’ is a crucial ingredient for the successful development and implementation of adequate management strategies. The Danube River Basin (DRB) drains areas of 19 countries with different cultural, political, and environmental legacies. The European Water Framework Directive (WFD) has provided the guiding legal instrument for DRB management since 2000, supported by several multilateral agreements. The International Commission for the Protection of the Danube River (ICPDR) is responsible for the implementation of the WFD in the DRB. It stimulates management-oriented research and coordinates the various activities of the contracting parties and observers, including those of many NGOs and stakeholders. The development of the first DRB Management Plan in 2009 constituted a milestone of cooperation among scientific, political, and public organisations. Key stressors and pressures have been identified, a new basin-wide monitoring network has been established, and numerous conservation and restoration sites have been designated. A major challenge in DRB management will be to establish synergies among the competing interests of navigation, hydropower production, flood protection and nature conservation. This paper examines the strengths and weaknesses of DRB science–policy interactions and outlines future strategies for sustainable development of the DRB as a template for transboundary river basin management.

The degree of phosphorus saturation of agricultural soils in Germany: Current and future risk of diffuse P loss and implications for soil P management in Europe

Decades of intensive agricultural production with excessive application of P fertilizer have resulted in the accumulation of P in soils, threatening water bodies in most industrialized countries with eutrophication. In our study, we elucidated the risk of P loss of German agricultural soils by transforming provided monitoring data of plant-available P determined by the calcium-acetate-lactate (PCAL) and double-lactate method (PDL) into the degree of phosphorus saturation (DPS). As water-soluble phosphorus (WSP) is correlated to DPS, we derived a pedotransfer function (PTF) between PCAL and WSP for different soil types. Considering all soils together resulted in WSP=0.1918×PCAL (R2=0.80, n=54). Subsequently, risk parameters DPS and EPC0 were calculated from PCAL and PDL monitoring data (n>337,000) by using the determined PTF and soil type-independent correlations with WSP, as published in an earlier study. Calculated DPS values from monitoring data indicated high risks of dissolved P loss for >76% of German arable soils. Recent suggestions by the Association of German Agricultural Analytical and Research Institutes (VDLUFA) to reduce recommended PCAL levels are crucial for the reduction of P loss risks in the future. The accuracy of predicted DPS and EPC0 values by CAL and other methods used in Europe to estimate plant-available P is limited by the soil type-dependency of these methods. Consequently, we recommend considering WSP as an agri-environmental soil P test across Europe. Our results indicate that a WSP level in soils can be defined that constitutes a reasonable compromise between the securing of agronomic production and the fulfillment of environmental goals.

Modelling nutrient emissions and the impact of nutrient reduction measures in the Weser river basin, Germany

To implement the European Water Framework Directive (WFD) into German law, measures have to be taken to reduce the unacceptably high nutrient input into rivers. To identify the most effective measures, the sources and pathways of nutrient emissions into rivers have to be quantified. Therefore, the MONERIS model is applied, which quantifies nutrients emissions into river basins, via various point and diffuse pathways, as well as nutrient load in rivers. Most nitrogen emissions come from groundwater flow (43%), tile drainages (30%), and point sources (12%), whereas most phosphorus emissions come from groundwater flow (31%), point sources (23%), erosion (13%) and overland flow (12%). Because of their great distance from the river basin outlet, the southern sub-basins Werra and Fulda-Diemel have an 8% reduction in their nitrogen loads and a 15% and 16% reduction in their phosphorus loads, respectively. This reduction is due to retention in the main part of the river Weser. For the choice of the most effective measures, the different retention in the river is relevant.

Estimation of the degree of soil P saturation from Brazilian Mehlich-1 P data and field investigations on P losses from agricultural sites in Minas Gerais

The degree of phosphorus saturation (DPS) of agricultural soils is studied worldwide for risk assessment of phosphorus (P) losses. In previous studies, DPS could be reliably estimated from water-soluble P (WSP) for European and Brazilian soils. In the present study, we correlated measured WSP and Mehlich-1 P (M1P) from soils of Minas Gerais (MG) and Pernambuco (PE) (R(2) = 0.94, n = 59) to create a DPS map from monitoring data. The resulting DPS map showed high spatial variability and low values of DPS (54 ± 22%, mean and standard deviation; n = 1,827). Measured soil DPS values amounted to 63 ± 14% and resulted in relatively low dissolved P concentrations measured in a surface runoff study in MG. However, fertilizer grains on the soil surface led to high WSP values (>30 mg/kg) indicating high risks of dissolved P losses. We suppose that small Oxisol particles with Fe and Al hydroxides sorbed most of the dissolved fertilizer P in runoff so that P was mainly exported in particulate form. In soils with lower contents of P sorption and binding partners, e.g. Entisols in PE, this effect may be less dominant. Consequently, superficial fertilizer effects have to be considered in addition to DPS in risk assessment of P losses from agricultural areas in Brazil.

Modelling nitrogen retention in floodplains with different degrees of degradation for three large rivers in Germany

Floodplains perform a variety of ecosystem functions and services - more than many other ecosystems. One of these ecosystem services is the reduction in nitrogen (N) loads and a subsequent improvement to the water quality. Since diffuse and also point nitrogen sources continue to cause a variety of problems in rivers and floodplains, inundated floodplains could act as net sinks for N and are therefore of great importance throughout Germany and Europe. This study analyses the effects of riparian floodplains on N-retention on the landscape scale for three large river systems with different degrees of degradation. Two approaches, differing in terms of the complexity of their respective input data and methods, were applied under wet and dry conditions. Whereas the proxy-based approach considers proxy values for N-retention, the model-based approach accounts for event-driven dynamic input data such as the extent of the inundated floodplain and incoming loads. Comparing the results of the two approaches it can be observed that floodplains of the near-natural river can retain up to 4% of the river load under wet conditions. During such conditions N-retention in floodplains is similar to that of rivers. For the two other floodplains, the results of the two approaches were quite different, showing lower N-retention capacities. However, for these floodplains as well, both approaches are suitable for calculating measurable N-retention rates, which is an important result because it also suggests that even degraded floodplains still preserve this particular ecosystem function and therefore still contribute to improving the quality of river water.

Evaluating riparian solutions to multiple stressor problems in river ecosystems — A conceptual study

Rivers are among the most sensitive of all ecosystems to the effects of global change, but options to prevent, mitigate or restore ecosystem damage are still inadequately understood. Riparian buffers are widely advocated as a cost-effective option to manage impacts, but empirical evidence is yet to identify ideal riparian features (e.g. width, length and density) which enhance ecological integrity and protect ecosystem services in the face of catchment-scale stressors. Here, we use an extensive literature review to synthesise evidence on riparian buffer and catchment management effects on instream environmental conditions (e.g. nutrients, fine sediments, organic matter), river organisms and ecosystem functions. We offer a conceptual model of the mechanisms through which catchment or riparian management might impact streams either positively or negatively. The model distinguishes scale-independent benefits (shade, thermal damping, organic matter and large wood inputs) that arise from riparian buffer management at any scale from scale-dependent benefits (nutrient or fine sediment retention) that reflect stressor conditions at broader (sub-catchment to catchment) scales. The latter require concerted management efforts over equally large domains of scale (e.g. riparian buffers combined with nutrient restrictions). The evidence of the relationships between riparian configuration (width, length, zonation, density) and scale-independent benefits is consistent, suggesting a high certainty of the effects. In contrast, scale-dependent effects as well as the biological responses to riparian management are more uncertain, suggesting that ongoing diffuse pollution (nutrients, sediments), but also sources of variability (e.g. hydrology, climate) at broader scales may interfere with the effects of local riparian management. Without concerted management across relevant scales, full biological recovery of damaged lotic ecosystems is unlikely. There is, nevertheless, sufficient evidence that the benefits of riparian buffers outweigh potential adverse effects, in particular if located in the upstream part of the stream network. This supports the use of riparian restoration as a no-regrets management option to improve and sustain lotic ecosystem functioning and biodiversity.

Phosphorus saturation and superficial fertilizer application as key parameters to assess the risk of diffuse phosphorus losses from agricultural soils in Brazil

In Brazil, a steady increase in phosphorus (P) fertilizer application and agricultural intensification has been reported for recent decades. The concomitant P accumulation in soils potentially threatens surface water bodies with eutrophication through diffuse P losses. Here, we demonstrated the applicability of a soil type-independent approach for estimating the degree of P saturation (DPS; a risk parameter of P loss) by a standard method of water-soluble phosphorus (WSP) for two major soil types (Oxisols, Entisols) of the São Francisco catchment in Brazil. Subsequently, soil Mehlich-1P (M1P) levels recommended by Brazilian agricultural institutions were transformed into DPS values. Recommended M1P values for optimal agronomic production corresponded to DPS values below critical thresholds of high risks of P losses (DPS=80%) for major crops of the catchment. Higher risks of reaching critical DPS values due to P accumulation were found for Entisols due to their total sorption capacities being only half those of Oxisols. For complementary information on soil mineralogy and its influence on P sorption and P binding forms, Fourier transformation infrared (FTIR) spectroscopic analyses were executed. FTIR analyses suggested the occurrence of the clay minerals palygorskite and sepiolite in some of the analyzed Entisols and the formation of crandallite as the soil specific P binding form in the investigated Oxisols. Palygorskite and sepiolite can enhance P solubility and hence the risk of P losses. In contrast, the reshaping of superphosphate grains into crandallite may explain the chemical processes leading to previously observed low dissolved P concentrations in surface runoff from Oxisols. To prevent high risk of P losses, we recommend avoiding superficial fertilizer application and establishing environmental thresholds for soil M1P based on DPS. These measures could help to prevent eutrophication of naturally oligotrophic surface waters, and subsequent adverse effects on biodiversity and ecosystem function.