Quantity and Quality Integrated Catchment Modeling under Climate Change with use of Soil and Water Assessment Tool Model Ekaterini Varanou 1 ; Eleni Gkouvatsou 2 ; Evangelos Baltas 3 ; and Maria Mimikou 4 Abstract: This paper focuses on the regional impact of climate change on several critical water quantity and quality issues. The study area is the Ali Efenti Basin in central Greece. The soil and water assessment tool daily step conceptual model has been applied to simulate the water cycle and the nitrogen transport within the catchment. The outputs of six general circulation models have been used to perturb the time series of precipitation and temperature. For all of the scenarios a decrease in streamflow is observed and there is an increase in the magnitude of floods for certain return periods. Changes in surface water runoff influence nitrogen losses, resulting in an annual reduction of the nitrogen flux to the water body. DOI: 10.1061/ASCE1084-069920027:3228 CE Database keywords: Catchments; Climatic changes; Water quality; Floods; Nitrogen. Introduction Many scientific sources are predicting global warming and cli- mate change due to a variety of factors Arnell 1998; Hulme et al. 1999. One of the major concerns is the assessment of the poten- tial impacts on several critical water resources quantity and qual- ity indicators, such as surface runoff, flood magnitude and asso- ciated risk, and nutrients. The European Union EU Environment and Climate Research Program sponsored a series of relevant studies. This paper presents part of the results of two EU funded projects, namely the climate hydrochemistry and economics of surface-water systems CHESS project and the European river flood occurrence and total risk assessment EUROTAS project, funded by the fourth FP-DGXII 1997–2000. The study area is a subbasin of the Pinios River catchment, situated in the central part of Greece. It suffers from frequent and hazardous storms, and consequent flash floods, which the natural capacity of the river is inadequate to pass downstream for a large part of its length. This is mainly due to the topography of the river network, which varies from narrow passes to wide floodplains. The Pinios River and its tributaries are sources of both irriga- tion and water supply. According to data provided by the Ministry of the Environment, Physical Planning and Public Works 1998, the water quality of the river network is, in general, adequate for these purposes. However, nitrate nitrogen concentrations exceed- ing 12 mg/L were observed during the summer months of 1990, providing inadequate water quality for the water supply. A recent report University 1999 included the catchment in the vulnerable zones due to nitrate contamination, as nitrate concentrations ex- ceeding 50 mg/L were detected in the groundwater. These inci- dents in correlation with the intensive cultivation of the agricul- tural areas and the considerable irrigation water needs signify the importance of the water and nutrient transport modeling in the catchment. A conceptual daily step model, the soil and water assessment tool SWAT, has been applied to simulate the water cycle and nitrogen fluxes. In the study area other models have been applied as well in order to estimate the hydrological effects of climate change Mimikou et al. 2000. SWAT has some major advan- tages. It is a daily step model that allows for a more detailed simulation of the water cycle. It was developed to assess the long-term impacts of land use and management in large and com- plex watersheds, and thus provides a more holistic approach to water and nutrient yields. The results of six climate change experiments have been used to perturb precipitation and temperature time series. Simulated, climatically changed monthly flows indicate a decrease of water yield for almost the entire year. Simulations in a daily time step give strong indications of increased flood magnitude in a climati- cally altered future Knox 1993. Although the impact of climate change on water yield is well documented in the literature Mim- ikou et al. 1991a,b; Mimikou and Kouvopoulos 1991; Mimikou 1 Research Engineer, Dept. of Civil Engineering, Div. of Water Re- sources, Hydraulic and Maritime Engineering, Laboratory of Hydrology and Water Resources Management, National Technical Univ. of Athens, 5, Iroon Polytechniou, 157 73 Athens, Greece. E-mail: varanou@chi.civil.ntua.gr 2 Research Engineer, Dept. of Civil Engineering, Div. of Water Re- sources, Hydraulic and Maritime Engineering, Laboratory of Hydrology and Water Resources Management, National Technical Univ. of Athens, 5, Iroon Polytechniou, 157 73 Athens, Greece. 3 Research Engineer, Dept. of Civil Engineering, Div. of Water Re- sources, Hydraulic and Maritime Engineering, Laboratory of Hydrology and Water Resources Management, National Technical Univ. of Athens, 5, Iroon Polytechniou, 157 73 Athens, Greece. 4 Professor, Dept. of Civil Engineering, Div. of Water Resources, Hy- draulic and Maritime Engineering, Laboratory of Hydrology and Water Resources Management, National Technical Univ. of Athens, 5, Iroon Polytechniou, 157 73 Athens, Greece. Note. Discussion open until October 1, 2002. Separate discussions must be submitted for individual papers. To extend the closing date by one month, a written request must be filed with the ASCE Managing Editor. The manuscript for this paper was submitted for review and pos- sible publication on August 8, 2000; approved on October 4, 2001. This paper is part of the Journal of Hydrologic Engineering, Vol. 7, No. 3, May 1, 2002. ©ASCE, ISSN 1084-0699/2002/3-228 –244/$8.00+$.50 per page. 228 / JOURNAL OF HYDROLOGIC ENGINEERING / MAY/JUNE 2002 J. Hydrol. Eng. 2002.7:228-244. Downloaded from ascelibrary.org by Indian Institute of Technology, Delhi on 09/10/13. Copyright ASCE. For personal use only; all rights reserved.