A GIS based MCE model for identifying water colour generation potential in UK upland drinking water supply catchments

Water discolouration is one of the key water quality problems faced by UK water companies taking raw water from peatland catchments. A water colour model has been developed using a combined Geographical Information System and Multicriteria Evaluation approach. The model was used to predict water colour production potential based on key land management practices controlling colour production in UK upland catchments. Calibration of the model with historic data collected at water treatment works treating water from upland areas showed that the model was potentially capable of accurately predicting water colour production potential at the catchment scale (c. 90%). Subsequent validation has shown this to be the case. Rotational heather burning and vegetation type (particularly heather) were identified as the two most statistically significant variables influencing water colour generation in the study catchments. It was predicted that colour is generated in particular hotspots and management to improve water quality should, therefore, focus on such areas. Blending of water is also an important process in controlling colour at the catchment scale and at water treatment works, with high colour often being diluted by runoff from land elsewhere in the catchment with lower potential to generate colour.