Huang from Meso to Macro Scale Dynamic Water Quality Modelling.Pdf
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Ecological Modelling 220 (2009) 2543–2558 Contents lists available at ScienceDirect Ecological Modelling journal homepage: www.elsevier.com/locate/ecolmodel From meso- to macro-scale dynamic water quality modelling for the assessment of land use change scenarios Shaochun Huang ∗, Cornelia Hesse, Valentina Krysanova, Fred Hattermann Potsdam Institute for Climate Impact Research, P.O. Box 601203, Telegrafenberg, 14412 Potsdam, Germany article info abstract Article history: The implementation of the European Water Framework Directive requires reliable tools to predict the Received 23 January 2009 water quality situations in streams caused by planned land use changes at the scale of large regional Received in revised form 5 June 2009 river basins. This paper presents the results of modelling the in-stream nitrogen load and concentra- Accepted 19 June 2009 tion within the macro-scale basin of the Saale river (24,167 km2) using a semi-distributed process-based Available online 21 July 2009 ecohydrological dynamic model SWIM (Soil and Water Integrated Model). The simulated load and con- centration at the last gauge of the basin show that SWIM is capable to provide a satisfactory result for Keywords: a large basin. The uncertainty analysis indicates the importance of realistic input data for agricultural Water quality modelling SWIM management, and that the calibration of parameters can compensate the uncertainty in the input data to Meso-scale river basin a certain extent. A hypothesis about the distributed nutrient retention parameters for macro-scale basins Macro-scale river basin was tested aimed in improvement of the simulation results at the intermediate gauges and the outlet. To Uncertainty analysis verify the hypothesis, the retention parameters were firstly proved to have a reasonable representation Retention parameters of the denitrification conditions in six meso-scale catchments. The area of the Saale region was classified Land use change scenarios depending on denitrification conditions in soil and groundwater into three classes (poor, neutral and good), and the distributed parameters were applied. However, the hypothesis about the usefulness of distributed retention parameters for macro-scale basins was not confirmed. Since the agricultural man- agement is different in the sub-regions of the Saale basin, land use change scenarios were evaluated for two meso-scale subbasins of the Saale. The scenario results show that the optimal agricultural land use and management are essential for the reduction in nutrient load and improvement of water quality to meet the objectives of the European Water Framework Directive and in view of the regional development plans for future. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Water quality models could provide an important and valu- able support for the assessment and analysis of pollution loads The increasing input of nutrients in rivers induced or caused in river basins and possible measures to improve water quality, by point sources (sewage treatment plants, industrial enterprises and therefore they could be a useful instrument for fulfilling the and municipal wastewater) and diffuse sources (agricultural land, requirements of the Water Framework Directive. Hence, various atmosphere) often leads to pollution and degradation of water qual- water quality models for the basin scale were developed and tested ity and can cause ecological changes in freshwater. As the discharge in the last decades (Arheimer and Brandt, 1998; Whitehead et al., of polluted wastewater has been notably reduced by wastewater 1998; Bicknell et al., 1997; Arnold et al., 1998; Krysanova et al., treatment in the recent decades, agriculture is generally perceived 1998). These models vary in the level of complexity, from statistical as the main source of nutrient input to rivers in Europe (De Wit et and conceptual models based on statistical and empirical relation- al., 2002). In recognition of the importance of water quality prob- ships to process-based and physically based models derived from lem and the need for integrated management in river basins, the physical and physicochemical laws and including also some equa- European Water Framework Directive (WFD) was adopted in 2000, tions based on empirical knowledge. Due to the lack of description aiming to restore the “good ecological status” at the scale of large of important physical processes, the simplified conceptual models river systems until 2015 (EC, 2000). have limited applicability, and are not appropriate for simulation of some essential spatially distributed processes. The physically based models are by definition fully distributed accounting for spatial variations in all variables. However, these models are often con- ∗ Corresponding author. Tel.: +49 331 288 2406. sidered too complex without a guarantee of better performance E-mail address: [email protected] (S. Huang). (Beven, 1989; Beven, 1996). The requirement of large amount of 0304-3800/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.ecolmodel.2009.06.043 2544 S. Huang et al. / Ecological Modelling 220 (2009) 2543–2558 Fig. 1. An overview of processes included in SWIM. input data and computation resources for such models is also a very similar model result using various parameter combinations particulate concern, especially for large basin simulations (Lunn (problem of equifinality) (Oreskes et al., 1994). There are already et al., 1996). This indicates that using the process-based models many published studies on uncertainty in water quality modelling (Krysanova et al., 2005a) of intermediate complexity for the basin- related to physical data such as rainfall (Bertoni, 2001), spatial data scale water quality assessment may be sufficient and even more such as land use maps (Payraudeau et al., 2004), and parameters promising. Numerous studies have proven that the process-based (Abbaspour et al., 2007; Hattermann et al., 2006). The uncertainty models are spatially explicit and sufficiently adequate to represent analysis allows to find the most important factors controlling the major hydrological, biogeochemical and vegetation growth pro- model behaviour, and to represent the modelling results in a more cesses at the catchment scale (Arnold and Allen, 1996; Chaplot et reliable way. al., 2004; Krysanova et al., 2005b; Stewart et al., 2006; Hattermann Recent studies on land use change impacts have demonstrated et al., 2006). The models SWAT (Arnold et al., 1998), HSPF (Bicknell that the process-based water quality models are effective tools to et al., 1997), SWIM (Krysanova et al., 1998) and DWSM (Borah et al., simulate the hypothetic land use scenarios. They are helpful to 2004) belong to the process-based modelling tools for river basins. either evaluate the long-term impacts of implementation of the However, in the most of the published studies the validation is per- current management practices (Santhi et al., 2005), or to investi- formed using the catchment outlet data only, which provides no gate the optimal solutions in order to reduce the nutrients loads in information on how they perform spatially (Cherry et al., 2008). rivers (Zammit et al., 2005; Hesse et al., 2008 and Volk et al., 2008). Besides, most of the current catchment scale studies with However, these studies did not account for some new tendencies dynamic process-based models focus on micro-scale and small in land use, like the influence of introducing energy plants on the catchments ranging from 1 to 100 km2 (Du et al., 2006; Chaplot et water quality aspect in the future. In this study the land use scenar- al., 2004; Eisele et al., 2001 and Bogena et al., 2003) and meso-scale ios are based on various measures of controlling nutrient emissions, basins with the drainage area from 100 to 5000 km2 (Abbaspour et and include the potential agricultural practice changes due to the al., 2007; Saleh et al., 2000 and Volk et al., 2008). The process-based development of the energy market. modelling at the macro-scale is very rare in literature, where the Hence, the objectives of the study were: statistical and conceptual riverine load models are usually applied. One example is by Even et al. (2007), who simulated water quality conditions in the Seine River basin (78650 km2) using four coupled deterministic models with satisfactory seasonal results at differ- - to test the applicability of the process-based ecohydrological ent stations. Since the WFD requires the assessment on large river model SWIM for simulating nitrogen dynamics in a macro-scale basin scale, more efforts are needed on improving the capabilities basin considering the outlet and intermediate gauges as valida- of describing nutrient fluxes in large basins. tion points, As all necessary input data, such as crop rotations and fertiliza- - to investigate the uncertainties related to input data and tion schedule, and parameters of the current process-based models parametrization, usually cannot be precisely defined at the basin scale, there are - to test the hypothesis about the usefulness of distributed reten- considerable uncertainties in the water quality modelling. More- tion parameters for nitrogen simulation in a macro-scale basin, over, the process-based water quality models often confront the and to establish ranges of retention parameters depending on the problem of over-parameterization, which results in the equal or catchment characteristics, and S. Huang et al. / Ecological Modelling 220 (2009) 2543–2558 2545 - to evaluate impacts