MONERIS Model Research Articles

Base Flow Index Estimation on Gauged and Ungauged Catchments in Hungary Using Digital Filter, Multiple Linear Regression and Artificial Neural Networks

A country scale analysis of diffuse source nutrient emissions have been undertaken previously on small catchments level using the MONERIS model, which needed a proper estimation of surface and subsurface runoff differentiation to support or contradict its own water budget based method. As reliable, country scale base flow estimation has not been available for the country at the time of the study, this knowledge gap has been tried to be filled by the current work. This has been done using multiple methods. Digital filter have been applied on continuous river discharge data on gauged catchments in order to determine base flow indices (BFI). Using multiple linear regression (MLR) and artificial neural networks (ANN), climatic, soil and land use properties of the catchments have been used to extend base flow indices to ungauged catchments. MLR brought acceptable results (adjusted r2 values around 0.7), however it proved to be sensitive of the selection of catchments used for validation, and therefore a mean of prediction by thirty different regression equation was used for the estimation. ANN was less sensitive for the change of the variables included and the number of nodes used for the learning. The results are comparable with the MLR method and show good agreement in most of the areas, however in some part of the country the two approach show significant differences in the predicted BFI values.

Differences in emission of nitrogen and phosphorus into the Vistula and Oder basins in 1995–2008 — Natural and anthropogenic causes (MONERIS model)

The aim of the modeling studies (MONERIS) was to estimate annual source apportioned nitrogen (N) and phosphorus (P) emissions into the Vistula and Oder basins in 1995–2008, thus, during the transition period in Poland, characterized by changes in both agricultural sector and handling of point source pollution. N and P emissions into both basins showed declining tendencies. Between the sub-periods 1995–2002 and 2003–2008, the overall N emission into the Vistula and Oder basins decreased by 16–17% (i.e. by ca. 26,900 tons in the Vistula and by ca. 18,000 tons in the Oder basin); P emission declined by 23% in the Vistula and by 32% in the Oder basins (i.e. by ca. 3400 tons in the Vistula and by ca. 2200 tons in the Oder basin). The temporal patterns of N and P emission into the Vistula and Oder basins, as well as the percentage contribution of N and P pathways (particularly: overland flow, tile drainage, groundwater, waste water treatment plants) showed great differences between the basins. Natural (type of bedrock, soil type, lake area) and anthropogenic (regionally and temporarily different type and intensity of agricultural activity, spatially different structural changes in agriculture during the transition period, regionally and temporarily different investment in waste water treatment plans) factors were found to be responsible for the differences, and the relationships are extensively discussed in the paper. In 1995–2008, 70% of N emission into both river basins was via groundwater and tile drainage, with the former playing more important role in the Vistula basin, and the latter playing more important role in the Oder basin; contribution of N emission from point sources was comparable in both rivers and it reached 11–12%. In 1995–2008, point sources, erosion, overland flow, and urban systems were found the most important P pathways in both basins, with a higher percentage contribution of point sources in the Oder basin.

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.

Groundwater protection and diffuse nitrogen emissions to surface waters – which catchment areas have to be considered?

Two Austrian case study regions within the Danube basin have been selected for detailed investigations of groundwater and surface water quality at the catchment scale. Water balance calculations have been performed using the conceptual continuous time SWAT 2000 model to characterise catchment hydrology and to identify individual runoff components contributing to river discharge. Nitrogen emission calculations have been performed using the empirical emission model MONERIS to relate individual runoff components to specific nitrogen emissions and for the quantification of total nitrogen emissions to surface waters. Calculated total nitrogen emissions to surface waters using the MONERIS model were significantly influenced by hydrological conditions. For both catchments the groundwater could be identified as major emission pathway of nitrogen emissions to the surface waters. Since most of the nitrogen is emitted by groundwater to the surface water, denitrification in groundwater is of considerable importance reducing nitrogen levels in groundwater along the flow path towards the surface water. An approach was adopted for the grid-oriented estimation of diffuse nitrogen emissions based on calculated groundwater residence time distributions. Denitrification in groundwater was considered using a half life time approach. It could be shown that more than 90% of the total diffuse nitrogen emissions were contributed by areas with low groundwater residence times and short distances to the surface water. Thus, managing diffuse nitrogen emissions the location of catchment areas has to be considered as well as hydrological and hydrogeological conditions, which significantly influence denitrification in the groundwater and reduce nitrogen levels in groundwater on the flow path towards the surface water.

Phosphorus losses at the catchment scale within Europe: an overview

AbstractQuantifying P losses to surface waters at different scales and partitioning of the loads into P losses from point sources and diffuse sources are significant future challenges for river basin managers. The agricultural share of P losses to surface waters is, in many river basins, increasing and therefore becoming more important to quantify and analyse. The importance of phosphorus losses from agricultural land was analysed using monitoring data and two different models for 35 micro‐catchments (<30 km2) in the Nordic–Baltic region of Europe, 17 European macro‐catchments (250–11 000 km2) and 10 large European river basins (>50 000 km2). Average annual phosphorus loss from agricultural land in the micro‐catchments varied from 0.1 to 4.7 kg P ha−1 and showed no relationship with the short‐term P surplus on agricultural land. The average annual total P loss from agricultural land showed equally large variation in the 17 macro‐catchments (0.1–6.0 kg P ha−1), but the range was less for the 10 larger river basins (0.09–2.0 kg P ha−1). The annual P loss from the 35 micro‐catchments was greatest in the micro‐catchments characterized by soil erosion and a high proportion of surface run‐off as in the Norwegian catchments. The same pattern was true for the 17 macro‐catchments where the model‐simulated total P loss from agricultural land was greatest in the catchments in northern and southern parts of Europe. The main diffuse pathways for total P loads in the 17 macro‐catchments were simulated with the MONERIS model. On average, soil erosion and surface run‐off was estimated to have contributed 53% (4.1–81%), groundwater 14% (0.2–41.7%) and tile drainage water 3% (0–14.0%).

Comparative study of two watershed scale models to calculate diffuse phosphorus pollution

The aim of this study was to compare and assess models having different principles to calculate diffuse phosphorus emissions on a selected watershed. The empirical MONERIS model and the physically based SWAT model were evaluated for comparative purposes. The approaches were applied for a sub-basin of the Hungarian Zala River watershed for five years. The calculated river loads were checked by the measured values at the catchment outlet. Due to the dissimilar results of water balance and erosion calculations, a highly different phosphorus emission was computed. It was also concluded that in the case of transport-limited watersheds, the SWAT model calculates phosphorus river loads slightly inaccurately, since it does not include the description of fate of inorganic phosphorus interacting with sediment during the channel transport. When these processes are taken into account, modeling results fit better the measured loads. The MONERIS model calculates acceptable river load by assuming very intensive in-stream retention. Additionally, the empirical method can be useful for long-term investigations as a decisions support tool for preliminary design. However, for detailed emission assessment and scenario development the physically based approach seems to be more appropriate.

Point and diffuse nutrient emissions and loads in the transboundary Danube River Basin. I. A modelling approach

Nutrient emissions by point and diffuse sources were estimated for the Danube River Basin on the basis of a harmonized and integrated database at the sub-catchment level by application of the MONERIS model. The estimation of nutrient emissions was carried out for the period 1998-2000 for 388 sub-catchments as well as the thirteen countries each responsible for more than 1 % of the total area of the Danube River Basin. A total of 756 kt a -1 nitrogen (N) and 68 kt a -1 phosphorus (P) are emitted by the different pathways. 77 % of N-emissions and 53 % of P-emissions were due to diffuse sources. The dominant pathway is groundwater for N-emissions and point source discharges for P-emissions with 48% and 47 %, respectively. The regionalized analysis facilitates the identification of spatial hot spots for the individual emission pathways. This analysis allows one to deduce specific measures for the reduction of nutrient emissions in the river system of the Danube and the Black Sea. Background nutrient emissions were calculated to approx. 6.5 kt a -1 P and 61 kt a -1 N. Consequently, the human impact is about 10 times higher than the background for P and 12 times higher for N, and 54 and 35% of the total N and P-emissions were due to agricultural activities. Urban settlements are responsible for 50% (P) and 22% (N) of the total emissions. The total nutrient loads of the Danube into the Black Sea were estimated to 22.5 kt a -1 for total P, 396 kt a -1 for dissolved inorganic N, and 468 kt a -1 for total N. The comparison of calculated and observed loads shows that the mean load deviation for the investigated sub-catchments of the Danube River Basin was 21 % for dissolved inorganic N (93 stations) and 32 % for P (65 stations).

Lessons learned from investigations on case study level for modelling of nutrient emissions in the Danube basin

In the framework of the project daNUbs (Nutrient Management in the Danube Basin and its Impact on the Black Sea) the MONERIS emission model is used for the basin wide calculation of nutrient (nitrogen and phosphorus) emissions in the Danube Basin. The MONERIS model was developed and successfully applied for German river catchments. Based on investigations in selected test regions (case studies) the daNUbs approach is to check the applicability of the MONERIS emission model for the specific conditions of the Danube Basin in more detail than is possible with a basin wide application. Six case studies with areas of 400-3,500 km2 and several subcatchments have been selected in order to represent different conditions along the Danube Basin. In this study region intensive data collection and enhanced monitoring has been performed in order to raise the database significantly above the generally available data. Water balance as well as nutrient balance calculations have been performed with the MONERIS model as well as with other approaches. Results are compared to each other and to data from monitoring. Results up till now showed the applicability and sensitivity of the MONERIS approach in different conditions of the Danube Basin (e.g. emissions via groundwater). They indicated that the nitrogen retention in the catchments is well described with the MONERIS model.

Groundwater-borne nitrate intakes into surface waters in Germany

The nitrogen loads entering the surface waters in Germany via the groundwater path were quantified. For this purpose, the results of a nitrogen balance model (Bach et al., 2000), which considers the most important N-inputs to the soil (manure, inorganic fertiliser, atmospheric deposition) and N-removals from the soil through crop harvest, were combined with the groundwater residence time/denitrification model WEKU (Kunkel and Wendland, 1997; Wendland et al., 2001). The modelled groundwater-borne nitrogen inputs into surface waters were validated using results from the MONERIS model (Behrendt et al., 2000) concerning riverine nitrogen retention, nitrogen inputs from point sources as well as nitrogen inputs through direct run-off (drainage etc.). In the vicinity of surface waters and in solid rock areas, the groundwater borne nitrogen inputs into surface waters are considerably high compared to the inputs into the aquifer due to predominantly unfavourable de-nitrification conditions and short residence times of groundwater. In the North German lowlands, however, the groundwater-borne nitrate inputs into surface waters are considerably low compared to the inputs into the aquifer. There, the residence time of groundwater in the aquifer is high and the groundwater is predominantly oxygen free and contains pyrite and/or organic carbon compounds, allowing a halving of the nitrate loads in the groundwater within a period of 1 to 4 years (see Wendland and Kunkel, 1999).