Modelling spatial patterns of erosion in the West Usambara Mountains of Tanzania

Prompt location of sources and sinks of sediment within a catchment would allow more effective Soil and Water Conservation (SWC) planning. Distributed erosion models are valuable tools for watershed planning, but the quality of spatially distributed model predictions is seriously hampered by the natural complexity and spatial heterogeneity of the landscape system, coupled with limited spatio-temporal datasets of sufficient accuracy. This study aimed at developing a semi-empirical, spatially distributed erosion model to locate sources of sediment within a catchment in data scarce environments. In the experimental catchment of Kwalei, in the West Usambara Mountains of Tanzania, the spatial distribution of erosion and erosion factors was observed during two rainy seasons. In the catchment, overland flow was of dynamic Hortonian type: it was triggered by short and intense showers, but as it moved downward, it quickly reinfiltrated. These observations and measurements at the catchment outlet were used to build a hydrologic model to predict event-based overland flow depth that accounted for rainfall characteristics, land use, field topology, and reinfiltration length, i.e. the average travel distance of overland flow. The hydrologic model was coupled with the sediment phase of the Morgan, Morgan and Finney model to estimate field erosion rates. The best model simulations predicted correctly around 75 % of erosion pattern, but the uncertainty of model prediction due to sediment transport parameterisation was high: 10 % of fields were either classified as subject to severe or slight erosion depending on the sediment transport parameters. Analysis of the spatial patterns of erosion and erosion factors showed that in the Kwalei catchment the location of severely eroded areas was correlated to crust and vegetation cover, but the spatial extent of erosion depended upon the overland flow travel distance. Moreover, the spatial scale of the distribution of some farmers¿ indicators of erosion, i.e. signs that farmers use to assess erosion in their fields, was very close to that of eroded areas and overland flow distribution. Farmers¿ indicators of erosion were used to build a classification tree to predict the distribution of erosion. The resulting Farmers¿ Indicator Tree was the best among several erosion models tested in the area in predicting the spatial pattern of erosion. These findings open up possibilities to integrate more effectively farmers' knowledge into distributed modelling of hydrology and erosio

Comparison of landscape approaches to define spatial patterns of hillslope-scale sediment delivery ratio

A sediment delivery ratio (SDR) is that fraction of gross erosion that is transported from a given catchment in a given time interval. In essence, a SDR is a scaling factor that relates sediment availability and deposition at different spatial scales. In this paper, we focus on hillslope-scale SDR, i.e. the ratio of sediment produced from hillslopes to that delivered to the stream network. Factors that affect hillslope water movement, and thus entrainment or deposition of sediments, ultimately affecting the SDR, include upslope area, climate, topography, and soil cover. In erosion models, SDR is usually treated as a constant parameter. However, the use of spatially variable SDRs could improve the spatial prediction of the critical sources of sediment, i.e. identification of those areas directly affecting stream water quality. Such information would improve prioritisation of natural resource management effort and investment. Recent literature has described several landscape approaches to represent SDR variability in space, some of which account only for topography, whilst others consider topography and soil cover characteristics. The aim of this study was to evaluate four landscape approaches for their ability to depict spatial patterns of SDR in the Avon-Richardson catchment in the semi-arid Wimmera region (Victoria, South-east Australia). Erosion was assessed using a semi-distributed model (CatchMODS) with disaggregation based in subcatchments of around 40 km2 area. Hillslope gross erosion was assessed with a RUSLE approach. By applying the four landscape approaches using DEM and estimates of land use cover, four landscape index subcatchment distributions were calculated. These were normalised into standard distributions. Then, a sigmoid function was used to transform the standardised indices into SDR-index distributions ranging from zero to one. Finally, subcatchment SDRs were estimated as the product of the SDR-index by a whole-of-catchment SDR value that was estimated by calibration against sediment loads measured at five gauging stations of the study area. The major sources of hillslope erosion were modelled to be located in the southern hilly areas of the catchment. However, a topographic convergence approach predicted as well important contribution of hillslope-erosion sediment loads coming from the eastern flatter cropping land. The introduction of landscape-variable SDRs improved the overall goodness-of-fit of modelled versus observed sediment loads at five gauging stations located in the catchment for only the topographic convergence approach. However, the limited number of observations (11), the location of some gauging stations downstream of active gully erosion, and the lack of gauging stations monitoring the north-eastern part of the catchment hindered the assessment of which spatial distribution of hillslope erosion best represented the real catchment conditions. Further research is needed to define the relationship between landscape indices and SDR; and to evaluate the spatial distribution of erosion against more complete field evidence

Modelling nutrient pollution in the Danube River Basin: a comparative study of SWAT, MONERIS and GREEN models

The Water Framework Directive requires the development and implementation of river basin management plans for improving the ecological status of freshwater bodies throughout Europe. The scientific community supports this process by developing decision-support tools for identifying the principal sources of water pollution. Models, however, are imperfect representations of the real world, and are conditioned by structural uncertainty, implicit in the description of biophysical processes, and data uncertainty, as well as in the various restrictions of the environmental data the models were developed. Hence, decision makers must plan management actions on the basis of the best available, however still incomplete, knowledge. The comparison of independent assessments may offer insights that are useful for decision-making, e.g. for identifying knowledge gaps, identifying data uncertainties, consolidating investigation results, and increasing stakeholders’ acceptance. The Danube River is the second largest and most international river of Europe. Its basin covers approximately 803,000 km2 of Central and South-Eastern Europe and is shared by 19 countries. Within the context of fostering scientific collaboration in the Danube region and under the auspices of the International Commission for the Danube River Protection (ICPDR), three independent model (SWAT, MONERIS and GREEN) were compared with the objective of reaching a shared appraisal of nutrient pressures and drivers in the Danube Basin. Annual water discharge (Flow, m3/s) as well as annual loads of total nitrogen (TN, ton/y) and total phosphorus (TP, ton/y) were compared at the outlet of 18 ICPDR regions for the decade 2000-2009. For each region, mean annual values, correlation, standard deviation, and root mean square error of model simulations were analysed. Good water discharge simulations across the basin confirmed that hydrology was correctly represented in all models. The nutrients comparison revealed for some assessment regions the need for a spatially and temporarily intensified monitoring especially for TN. Concerning TP, SWAT and MONERIS had comparable long mean annual TP loads, but differed for amplitude and phases; while GREEN generally overestimated TP loads. Despite differences in model approaches and considered input data, the three assessments were coherent, and all three models may be confidently used for river basin management of the region.JRC.H.1-Water Resource

Identifying efficient Nitrate reduction strategies in the Upper Danube

Nitrogen losses in the form of Nitrate (N-NO3) from point and diffuse sources of pollution are recognized to be the leading cause of water body impairment throughout Europe. Implementation of conservation programs is perceived as being crucial for restoring and protecting the good ecological status of freshwater bodies. The success of conservation programs depends on the efficient identification of management solutions with respect to the envisaged environmental and economic objectives. This is a complex task, especially considering that costs and effectiveness of conservation strategies depend on their locations. We applied a multi-objective, spatially explicit analysis tool, the R-SWAT-DM framework, to search for efficient, spatially-targeted solution of Nitrate abatement in the Upper Danube Basin. The Soil Water Assessment Tool (SWAT) model served as the nonpoint source pollution estimator for current conditions as well as for scenarios with modified agricultural practices and waste water treatment upgrading. A spatially explicit optimization analysis that considered point and diffuse sources of Nitrate was performed to search for strategies that could achieve largest pollution abatement at minimum cost. The set of optimal spatial conservation strategies identified in the Basin indicated that it could be possible to reduce Nitrate loads by more than 50% while simultaneously provide a higher income

A decision support tool (R-SWAT-DS) for integrated watershed management

Best management practices (BMPs) can be used effectively to reduce nutrient and sediment loads generated from point sources or non-point sources to receiving water bodies. Methodologies for optimal, cost effective BMP selection and placement are needed to assist watershed management planners and stakeholders. We developed a modeling-optimization framework that can be used to find cost-effective solutions of BMP placement to attain nutrient load reduction targets. The framework integrates the Soil and Water Assessment Tool (SWAT) watershed model, spatial representation of BMPs, an economic component, and multi-objective optimization routines in the R environment. The framework can be used to launch individual or iterative BMPs simulations, or search for optimal strategies. Advanced plotting, mapping and statistical analysis functionalities that facilitate the interpretation and assessment of the results are included

Assessment of the effectiveness of reported Water Framework Directive Programmes of Measures - Part II – development of a system of Europe-wide Pressure Indicators

The EC DG JRC is using in-house models and other information to build indicators of pressures on water bodies, in the context of the 2nd river basin management plan (RBMP) implementation assessment (Water Framework Directive (WFD) 60/2000/EC, art. 18) and review of the WFD (art. 19). These indicators are meant to provide a picture of major water pressures at the European scale. The main reason to develop a set of independent pressure indicators is the need to evaluate and monitor the effectiveness of the EU water policies at broad. If the indicators are realistic, the models used for their computation can be used also as tools to simulate scenarios with changing pressures, as a result of policies or other drivers (such as climate changes, implementation of measures or EU sectorial policies). The EC DG ENV is steering the development of an integrated hydro-economic modelling platform in support to the evaluation of policies, with the broadest possible involvement of the EU Member States, and collaborates with DG JRC by leading a large study on the economics of water in Europe also in order to supplement JRC’s biophysical models and indicators with additional economic evidence about the costs and benefits of reducing pressures and improving the conditions of freshwater and marine ecosystems. Another question is whether the pressures are evaluated consistently throughout the European Union. The JRC indicators could be used to benchmark pressure and status reported by the Member States at a different scale. In fact, if JRC indicators are sufficiently reliable, it is expected that overall trends will be consistent with the pressures reported by the Member States. At the same time, JRC indicators do not take into account local conditions in specific water bodies, and should not be compared to reported pressures and status at water body level. The aim of benchmarking is to understand the reasons for assessment discrepancies, primarily for verification purposes. In particular, discrepancies should not be considered per se as evidence of non-compliance in the implementation of the WFD by Member States. particularly, if a given river basin is flagged by Member State reports to suffer from a given pressure, but this is not found in the JRC pressure indicators, the knowledge available at the Commission is likely inadequate for that river basin. The benchmarking process with reported pressures/status in itself could prompt the Commission to seek an explanation for the discrepancies, and eventually to update the indicators, with the overall goal of a coherent and shared vision of pressures at the European and river basin district scales. DG ENV encourages Member States to provide feedback to DG JRC on the indicators and the underpinning models, so that the European scale picture of water pressures they provide can be improved to a sufficient level of realism and representativeness, and can be consequently used as a basis for European water policy evaluation and development. As a first opportunity for this process, the JRC organised a workshop in Ispra on 11-12 May 2016 with the aim to collect feedback from experts on the proposed methodologies and indicators. The JRC pressure indicators are updated over time, as new knowledge is available at the European level. Therefore the benchmarking of local and European assessments is supposed to be a continuous process. The reviews by experts in the Member States should not add to the administrative burden related to the WFD, but should be conducted with the modalities of scientific peer reviews. It will be necessary to pay significant attention to the way the results are communicated, so to clarify the content of the indicators and avert risks of misinterpretation. The review of the indicators will serve also this purpose. This document summarizes the JRC indicators, the state of play with their update and further development, and the outcomes of the workshop held in Ispra on May 11-12, 2016.JRC.D.2-Water and Marine Resource

The potential of water reuse for agricultural irrigation in the EU: A Hydro-Economic Analysis

Policy context Water reuse has been identified by the European Commission as a relevant solution to be further promoted in the EU to address water scarcity. This opportunity was highlighted again in the context of the EU action plan for a Circular Economy (COM(2015) 614 final). In, particular the Commission committed to table a legislative proposal setting minimum quality requirements for water reuse. This initiative has been included in the Commission Work Programme 2017. In order to support the decisions to be taken on the matter, the costs and benefits of water reuse need to be clearly identified and quantified to the best possible extent. Key conclusions/Main findings In this study we estimate the distribution of costs of reclaiming and transporting treated wastewater for reuse in agricultural irrigation across Europe. We consider treatment costs as well as the costs associated to the water transport infrastructure and to energy for pumping. The study highlights a high variability of costs depending on the relative position of irrigated agricultural land with respect to the wastewater treatment plants. Treatment costs alone may be minor, about 8 €cents/m3, compared to the other costs, with typical total costs exceeding 50 €cents/m3. However, when treatment requirements become more stringent, treatment costs may surge up to about 0.3 €/m3, causing total costs to shift consistently. The energy requirements for pumping of reclaimed water from wastewater treatment plants to agricultural land follow a distribution with a median of about 0.5 kWh/m3 and an interquartile range of another 0.5 kWh/m3, which seems slightly higher than reported in representative cases of irrigation with conventional water sources. The total volumes of water that can be in principle reused for irrigation are significant, and may contribute to the reduction of water stress by 10% or more in regions where irrigation is an important component of demand. Water reuse may also contribute, in a less apparent and more uncertain way, to nutrient pollution mitigation. While the treatment and energy costs are mostly compatible with the market value of the crops produced thanks to irrigation, the total costs may exceed the capacity of farmers to pay. This indicates that (1) reuse is most suitable where irrigation infrastructure already exists and the necessary additional investments are minor, and (2) the cost of water reuse should be considered in a broader context. This context should be extended to include, on the one side, the whole value chain supplied by agriculture and, on the other side, the process of river basin management where reuse may represent a measure with important co-benefits. Related and future JRC work This work is part of the broader “Water-Energy-Food-Ecosystems Nexus” project of the JRC. Water reuse is regarded as a relevant water resource management option, and this report provides the basis for an assessment of strategic priorities for water reuse in Europe.JRC.D.2-Water and Marine Resource

The hillslope length impact on SWAT streamflow prediction in large basins

The objective of this study was to assess the impact of hillslope length on Soil and Water Assessment Tool (SWAT) streamflow predictions in large basins using three methods for hillslope length calculation (the SWAT method, L1; a 3D analysis method, L2; a constant value, L3) combined with two DEMs (pixel size of 25 and 100 m), for a total of six DEML configurations that were tested in the Upper Danube (132000 km(2)). The delineation of subbasins and HRUs were kept unchanged in all configurations, thus isolating the DEM impact on streamflow from that of subbasins delineation. The configurations were independently calibrated in 98 gauged stations located in headwater subbasins (period 1995 similar to 2006), and validated in 150 gauged stations (period 1995 similar to 2009). The analysis of streamflow prediction was extended to its components (surface runoff, lateral flow and baseflow) using performance criteria and residual analysis, and the comparison of different components of water yield was pursued. Calibration and validation showed that all configurations simulated monthly streamflow acceptably (PBIAS < 25% for more than 70% of 150 gauged stations). DEM pixel size had negligible effect of streamflow and its components. The default hillslope length (L1) resulted in large overestimations of lateral flow. L2 resulted in the best performance as well as L3 method. Given that L2 method takes into account the topographic convergence of flow, the configuration of DEM100 and L2 is recommended for SWAT application in large basins in order to obtain reliable streamflow predictions

Estimation of domestic and industrial waste emissions to European waters in the 2010s

Estimation of domestic and industrial emissions to the European fresh and marine waters is needed for assessing current ecological status of water bodies and providing inputs to conceptual models of pollutant transport and fate. Regulatory efforts of the European Commission, particularly Urban Waste Water Directive (UWWWD) and Water Framework Directive (WFD) prompted investments in waste treatment, and as a result point source emissions to water bodies have declined. In order to account for these improvements, domestic and industrial emission assessments were to be updated for conditions valid in the 2010s. The aim of this study was to assess the quantity and location of domestic and industrial waste emissions of pollutants in European waters for the 2010s. Specifically, the pollutants considered in this study were total Nitrogen (N), total Phosphorous (P), and organic pollution as measured by 5-days Biochemical Oxygen Demand (BOD). The spatial resolution and extent of the analysis corresponded to the CCM2 River and Catchment Database for Europe. Pollutants were estimated in terms of mean annual average load (t/y) released in the CCM2 catchments. The reference period for the assessment was set to 2014-2015, although in some cases a longer time period was considered. The assessment of pollutant loads to waters from domestic and industrial emissions made full use of available European databases created in response to EU regulations. A method was developed to exploit the European datasets and fill in content gaps through alternative sources of information (REP approach). The European datasets allowed pinpointing waste emissions to a much higher spatial and conceptual resolution than before, although some knowledge gaps remained, affecting especially emissions from domestic waste of isolated dwellings, small agglomerations, and industries. Outside EU28, Switzerland and Norway, domestic and industrial emissions were assessed based on population density and national statistics of shares of population served by sewerage treatment and level of WWTP treatments (POP approach). The comparison between Population Equivalent generated in agglomerations and reported in the UWWTD database with country resident population allowed estimating an equivalence of 1.23 PE per inhabitant, meaning that on average in Europe the contribution of small industries, commercial activities and tourism can be considered about 23% of generated load. This information was used to assess population unreported in the UWWTD database because belonging to small isolated dwellings. Estimates of total emissions due to domestic waste with REP approach with those from POP approach for 30 countries covered by both methods were in good agreement, with Pearson’s correlation coefficient of 0.95 for Nitrogen, 0.94 for Phosphorous and 0.71 for BOD. Yet, important differences emerged when separating emissions by treatment type or pathway, e.g. looking at disconnected, connected not treated or connected and treated shares of domestic waste. The comparison highlighted inconsistencies between the European database and national statistics and it was noted that for some countries national statistics were scant or inconsistent. Thus, while total emissions are comparable, care should be taken when considering each population share independently. Finally, total pollutant emissions for Europe in 2010s were obtained by merging all available data, using the REP approach and the POP approach estimates to fill in knowledge gaps. In EU28, annual emissions to water from domestic and industrial waste for the 2010s were estimated at 777.6 kt/y of Nitrogen, 126.6 kt/y of Phosphorous and 2,190 kt/y of BOD. The majority of domestic waste is treated in WWTPs, with high adoption rates of tertiary treatment and Phosphorus removal technology, lowering emissions of domestic waste per capita. EU28 IND emissions accounted for 11.3% of N, 6.7% of P and 33.7% of BOD emissions. Emissions from population disconnected to sewerage systems or treated with IAS (for which only primary treatment was assumed) accounted for 11.2% of Nitrogen, 14.6% of Phosphorous and 19.5% BOD emissions to the environment. However only a part of these emissions would eventually reach freshwater systems, as environmental abatement (not considered in this study) would further reduce them. Conversely, connected not treated population contributed 6.2% of Nitrogen, 7.2% of Phosphorous, and 14.4% of BOD directly discharged to freshwater bodies. Tackling these sources of domestic waste and upgrading primary treatment facilities may further reduce pollution loads discharged in freshwater systems and ultimately to the seas.JRC.D.2-Water and Marine Resource

Measuring, modelling and managing gully erosion at large scales: A state of the art

Soil erosion is generally recognized as the dominant process of land degradation. The formation and expansion of gullies is often a highly significant process of soil erosion. However, our ability to assess and simulate gully erosion and its impacts remains very limited. This is especially so at regional to continental scales. As a result, gullying is often overlooked in policies and land and catchment management strategies. Nevertheless, significant progress has been made over the past decades. Based on a review of >590 scientific articles and policy documents, we provide a state-of-the-art on our ability to monitor, model and manage gully erosion at regional to continental scales. In this review we discuss the relevance and need of assessing gully erosion at regional to continental scales (Section 1); current methods to monitor gully erosion as well as pitfalls and opportunities to apply them at larger scales (section 2); field-based gully erosion research conducted in Europe and European Russia (section 3); model approaches to simulate gully erosion and its contribution to catchment sediment yields at large scales (section 4); data products that can be used for such simulations (section 5); and currently existing policy tools and needs to address the problem of gully erosion (section 6). Section 7 formulates a series of recommendations for further research and policy development, based on this review. While several of these sections have a strong focus on Europe, most of our findings and recommendations are of global significance.info:eu-repo/semantics/publishedVersio