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Summary: A model system that overcomes the separation of rural and urban areas for an integrated immission based modelling of catchments with complex land use is presented. To account for both the sewer system dynamic processes and the dynamics of single events in the runoff processes from rural areas, the model operates on a high temporal resolution and in continuous mode. The basic system structure and the rural areas are represented by means of a semi-distributed rainfall-runoff and pollution load model that allows for a user-specified spatial resolution. For each urbanized area within the catchment an urban hydrological pollution load model is used. This allows for a detailed assessment of the urban drainage structure even for multiple settlements within one catchment. Pollutant transport, mixing, and transformation processes within the receiving water body are modelled to account for accumulating and long-term effects. The model concept was applied to a real world case study. It was found that the consideration of all impacts is essential for an immission based approach. It can be concluded that a realistic description of the water body status can only be achieved by means of a detailed representation of both flow and mass transport processes in urban and rural parts of the catchment as well as the receiving water body in a high temporal and spatial resolution. [Copyright &y& Elsevier]

Summary: Watershed losses of phosphorus (P) have been a topic of concern for water resource managers over recent decades. To evaluate environmental policies or before implementing mitigation options at the watershed (catchment area) scale, stakeholders often need to analyze the patterns of point and diffuse sources of phosphorus. This information is often not easy to obtain in field conditions. Several statistical modeling approaches have been developed in recent years to respond to this basic operational demand. Point and diffuse sources are often evaluated from power functions established between phosphorus concentration and water discharge. Such models do not explicitly account for in-stream processes which control P concentrations in the hydrographic network and differentiate the P export dynamics of the various forms and inputs of P. To identify the phosphorus sources and evaluate their change in response to environmental policies, we developed a simple and loaded-oriented model (POPEYE – PhOsPhorus, Evaluation of the efficiencY of Environmental policy measures) that computes retention, settling and re-suspension rates of fine and coarse P fractions and their relation to P concentration of bed sediments. The model is calibrated to a long-term database (25years), and describes the weekly water and chemical fluxes of a tributary of Lac Léman (Lake Geneva, Venoge river watershed, 240km2). It adequately predicts observed values of fine and particulate phosphorus and reflects the gradual decrease of point and diffuse inputs over the studied period due to agricultural and sewage treatment policies implemented for the control of lake pollution. [ABSTRACT FROM AUTHOR]

Summary: This paper assesses the impact and quantifies the relative contribution of stormwater runoff (diffuse pollution sources) and point pollution sources on the quality of receiving water in the urban catchment of Orange. The study results were employed to develop management strategies to control stormwater pollution at the catchment level. The Orange urban catchment has experienced moderate to high levels of pollution in terms of nutrients (P and N), suspended solids (SS), heavy metals, fecal coliforms, and, to a lesser extent, salinity (TDS). Treated sewage effluent (point source) contributed, on average, 5% SS, 29% total nitrogen (TN) and 41% total phosphorous (TP). The nutrient yield per unit area was 2–31-folds higher than those reported for other Australian urban catchments. The overall contribution of the urban sources accounted for 93% and 94% of the TP and TN mass loads, respectively. In contrast, stormwater pollution in coastal urban catchments, that have similar population and land use, is dominated by rural diffuse sources contributing 81–99% of nutrient mass loads. This striking difference is attributed largely to the position of the catchment with respect to the hydrological system. Orange urban catchment is situated at the headwater of its river system and as such rural runoff into the urban part of the catchment was limited. The coastal catchments, on the other hand, are located at the end of their river systems and thus rural inflow into the urban area is substantially higher than those in upland catchments. This comparative assessment may suggest that the relative impact, per capita, of urban stormwater pollution on the receiving water is more significant in the upland catchments than in the coastal catchments. A stormwater management plan (SMP), consisting of structural and non-structural strategies, was developed to control stormwater pollution and enhance the quality of receiving water. [Copyright &y& Elsevier]

Summary: Sources of nutrients and suspended solids (SS) are diverse in origin and dynamic with respect to their transport pathways and delivery to surface and groundwaters. Three broad source groups can be identified based on their hydrological and compositional characteristics. Consented discharges from point sources are generally continuous and highly concentrated relative to receiving waters while non-point (diffuse) sources are generally more dilute with SS and phosphorus in particular tending to have a high transport dependence upon hydrological (storm) events. A third group with properties that are intermediate include overflows from septic systems, seepages from farmyards or road/track runoff. This grouping automatically introduces a strong temporal and spatial variability in the relative contribution individual group sources make to the total quantity of nutrients and SS delivered to freshwaters. This spatial or temporal variability in either effluent volumes or composition is generally not considered when predicting impacts, which can be highly significant in headwater streams. Complete compositional data for individual sources (especially the intermediary group) are also often lacking when apportioning source contributions in catchments, being simply lumped into average export coefficients. Better definition of intermediary sources would help to more accurately define the relative contribution of different sources and enable cost-effective river basin management planning as required under the Water Framework Directive. [Copyright &y& Elsevier]

Abstract: Nonpoint source and point source nutrient loads (N, PO4-P, COD) to the Ebro River in its central sector were estimated using hydrogeological and socioeconomical data. Their impacts on eutrophication and nutrient dynamics in the river were analyzed through a review of the public administration''s historical data and the interpretation of two sampling profiles in September 02 (low flows season) and April 03 (high flows season). A marked seasonality was found in nutrient concentrations, nutrient loads and eutrophication indicators (O2, Turbidity), appearing symptoms of eutrophication during the summer related to both NPS and PS Nutrient loads within the study area. Agricultural NPS account for 64% of NO3 loads generated within the study area while urban and industrial PS are responsible of 88% PO4-P and 71% COD loads. Biological reactions within the river ecosystem (including denitrification in the most eutrophic branches) were found to be a key factor in nutrient content and dynamics. Improvements in urban and industrial wastewater treatment facilities, land use planning and restoration of river-side wetlands, seem to be adequate policies for the improvement of the nutrient water quality in the studied sector of the Ebro River. Flow and temperature seasonality related to Mediterranean fluvial regime imposes significant limitations to nutrient PS in order to accomplish the combined approach proposed in European Water Framework Directive (WFD), based upon Emission Limit Values (ELV) and Environmental Quality Standards (EQS). [Copyright &y& Elsevier]

Human activities may cause enhanced loads of total N (TN) and total P (TP) in running waters, which may have a serious impact on their ecological quality. Likely sources for N and P are industries, dwellings and agriculture. A GIS based model is proposed to analyse which of these sources cause the main problems. Simulated concentrations were compared with standards for TN and TP representing natural conditions in running water. The model was applied on the strongly disturbed catchment of the river Dommel (Belgium/The Netherlands). It was taken into account that river sediments may act as a sink for nutrients.Flows from point sources and dwellings were taken from databases. Diffuse sources were assumed to be a percentage of the anthropogenic input, defined as the nutrient input on the soil minus crop yield. A regression analysis on ten headwaters without point sources suggests that 5.5% of anthropogenic N and 0.02% of anthropogenic P has leached to the river network. Applying the model for all tributaries of the Dommel yielded a good fit between observed and simulated TN and TP loads (R2 of 0.88 and 0.95, respectively).All analysed tributaries exceed the standards for TN and TP. Analysis suggests that point sources are -overall- the main contributor to nutrient fluxes, although they affect few tributaries only. Most intermediate and small tributaries are affected by diffuse flows from agricultural pastures (24.2 kg TN ha−1 yr−1; 0.82 kg TP ha−1 yr−1). It can be argued that reduction of point sources may help to minimise the magnitude of the nutrient fluxes on the catchment scale, reduction of diffuse sources may help to restore a good water quality on the scale of individual tributaries. [Copyright &y& Elsevier]