SCIMAP is based on the identification of locations of critical source areas (Heathwaite et al. 2005). within the landscape. These locations are based on the areas that are most likely to have a source of the pollutant of interest and have an active connection. Within the SCIMAP approach, the most appropriate information on the sources and connections needs to be selected by the user to capture the area of interest. In the standard version of SCIMAP, the sources are related to land cover as a proxy for land use and management and this approach is follows the same basis as Export Coefficient models such as Johnes (1996). The connectivity predictions are based on the Network Index (Lane et al. 2004) which traces each individual flowpath across the landscape to determine how wet the landscape must be to both generate runoff and connect to the river channel. The standard approach utilises the topographic wetness index (Beven and Kirkby 1979) to make spatial predictions of soil moisture but these maps can be based on observations or physically based hydrological model simulation output (Lane et al. 2009). It is important to ensure that the assumptions embedded within the predictions of patterns of soil moisture, connectivity and source risks match with the environment under study.


Beven, K. J. and Kirkby, M. J. 1979: A physically based, variable contributing area model of basin hydrology, Hydrolological Sciences Bulletin, 24, 43–69,.

Heathwaite, AL, Quinn, PF and Hewett, CJM 2005:Modelling and managing critical source areas of diffuse pollution from agricultural land using flow connectivity simulation; Journal of Hydrology 304 (1-4) 446-461   DOI: 10.1016/j.jhysrol.2004.07.043

Johnes, P. J. (1996) Evaluation and management of the impact of land use change on the nitrogen and phosphorus load delivered to surface waters: the export coefficient modelling approach. Journal of Hydrology, 183. 323-349

Lane, S. N., Brookes, C. J., Kirkby, M. J. & Holden, J. 2004: A network-index-based version of TOPMODEL for use with high-resolution digital topographic data. Hydrol. Process., 18: 191–201. doi: 10.1002/hyp.5208

Lane, S.N., Reaney, S.M. & Heathwaite, A.L. 2009: Representation of landscape hydrological connectivity using a topographically driven surface flow index. Water Resources Research.;45:W08423.


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